Merge pull request 'next' (#50 ) from next into main

Reviewed-on: #50
2026-09-26 15:27:29 +02:00
41 changed files with 2004 additions and 4932 deletions
@@ -0,0 +1,5 @@
 {
    "worktree": {
        "bgIsolation": "none"
    }
 }
@@ -1,79 +1,7 @@
-# .dockerignore does NOT use .gitignore semantics. Docker matches with
+.git
 # moby/patternmatcher: filepath.Match plus `**`, so `*` does not cross
 # `/` and an unprefixed pattern is anchored at the context root. Every
 # depth-independent pattern therefore needs `**/`, or `config/.env` and
 # `certs/server.key` still ship while this file reads as solved. Only
 # genuinely root-anchored entries go unprefixed. Never transplant these
 # into .gitignore, where `**/` is wrong.
 #
 # Matching is case-sensitive, so secrets use character ranges rather
 # than an ALL-CAPS twin, which would still miss `Server.Key`.
 #
 # Extend with this repo's own host-built artifacts, written anchored:
 # `/myapp`, never `**/myapp`, which also matches `cmd/myapp/` and
 # deletes the package directory from the context.
 # .git is sent without its config. Without a VERSION build argument the
 # stage that compiles runs `git describe --tags --always` on .git, which
 # does not need .git/config; that file can hold a credential, such as a
 # password in a remote URL or the token the CI checkout step stores there.
 # Each submodule keeps a config with the same exposure in its git directory
 # under .git/modules/, nested again for a submodule's own submodules, or in
 # its own .git directory when it keeps one.
 # KNOWN GAP: a submodule whose name has a `config` segment (`config`,
 # `deploy/config`, `config/lib`) loses its whole git directory, because
 # `**/.git/modules/**/config` also matches that segment's directory
 # under .git/modules/. Go's version stamping then fails the build;
 # nothing leaks. Name such a submodule without that segment:
 # `git submodule add --name`.
 **/.git/config
 **/.git/modules/**/config
 # Agent scratch: one full checkout of the repo per in-flight agent.
 # Anchored because it occurs once where agents run at the repo root.
 # KNOWN GAP: a repo running agents in subdirectories still ships
 # `services/api/.claude/` and must add its own anchored entry.
 .claude
-
+.DS_Store
-# Environment files. `*.env` covers bare `.env` and the `prod.env`
+sfdupes
-# convention. Re-include a committed template with a negation if the
+*.log
-# build needs one: `!docs/example.env`.
+*.out
-**/*.[eE][nN][vV]
+*.test
 **/.[eE][nN][vV].*
 **/.[eE][nN][vV][rR][cC]
 # Private keys and the bundles carrying them. Public certificates
 # (*.crt, *.cer) are deliberately absent: they are legitimate inputs.
 **/*.[pP][eE][mM]
 **/*.[kK][eE][yY]
 **/*.[pP]12
 **/*.[pP][fF][xX]
 **/[iI][dD]_[rR][sS][aA]
 **/[iI][dD]_[dD][sS][aA]
 **/[iI][dD]_[eE][cC][dD][sS][aA]
 **/[iI][dD]_[eE][cC][dD][sS][aA]_[sS][kK]
 **/[iI][dD]_[eE][dD]25519
 **/[iI][dD]_[eE][dD]25519_[sS][kK]
 # Dependencies: restored inside the image, never copied in.
 **/node_modules
 # OS metadata.
 **/.DS_Store
 **/Thumbs.db
 # Editor state: never a build input, and it churns COPY.
 **/*.swp
 **/*.swo
 **/*~
 **/*.bak
 **/.idea
 **/.vscode
 **/*.sublime-*
 # This repository's host-built artifacts: the binary `make build` writes,
 # and test binaries, coverage output and logs.
 /sfdupes
 /*.test
 /*.out
 /*.log
@@ -13,6 +13,3 @@ indent_style = tab
 [*.go]
 indent_style = tab
 # This repository's own sections, such as one for another language it
 # uses, go below this comment, and a re-vendor keeps them.
@@ -1,20 +1,9 @@
 name: check
 on: [push]
 # Free the shared runner: a new push cancels only the same branch's older run.
 concurrency:
    group: ${{ github.workflow }}-${{ github.ref }}
    cancel-in-progress: true
 jobs:
    check:
        runs-on: ubuntu-latest
        # Free the shared runner from a hung build.
        timeout-minutes: 20
        steps:
            # actions/checkout v4.2.2, 2026-02-22
            - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
              # script/cibuild needs no token, so none is left in .git/config.
              with:
                  persist-credentials: false
                  # All history and tags, so git describe finds the version tag.
                  fetch-depth: 0
            - run: script/cibuild
@@ -11,50 +11,25 @@ Thumbs.db
 .vscode/
 *.sublime-*
 # Agent scratch (worktrees of this repo, created and destroyed by
 # in-flight tooling). Unanchored: .gitignore patterns already match at
 # every depth, so no prefix is wanted here. This is not a .dockerignore
 # entry and must not be given a `**/` prefix on the way into one.
 .claude/
 # Node
 node_modules/
-# Secrets. Unanchored like every entry above, so each matches at every
+# Environment / secrets
-# depth. Matching is case-sensitive on Linux, so names use character
+.env
-# ranges rather than a lowercase form that misses `Server.Key`.
+.env.*
 *.pem
 *.key
-# Environment files. `*.env` covers bare `.env` and the `prod.env`
+# Go build artifacts
 # convention. Only the templates `example.env` and `sample.env` are
 # re-included below. A repository that commits any other template adds
 # its own negation at the end of this file, for example `!.env.example`.
 *.[eE][nN][vV]
 .[eE][nN][vV].*
 .[eE][nN][vV][rR][cC]
 !example.env
 !sample.env
 # Private keys and the bundles carrying them.
 *.[pP][eE][mM]
 *.[kK][eE][yY]
 *.[pP]12
 *.[pP][fF][xX]
 [iI][dD]_[rR][sS][aA]
 [iI][dD]_[dD][sS][aA]
 [iI][dD]_[eE][cC][dD][sS][aA]
 [iI][dD]_[eE][cC][dD][sS][aA]_[sS][kK]
 [iI][dD]_[eE][dD]25519
 [iI][dD]_[eE][dD]25519_[sS][kK]
 # This repository's own entries, such as its build outputs, go below
 # this comment, and a re-vendor keeps them. Anchor a binary built at the
 # root: `/myapp`, never `myapp`, which also ignores `cmd/myapp/`.
 /sfdupes
 *.log
 *.out
 *.test
 *.out
 *.log
-# A scan database lists every path it scanned.
+# Local scan data
 *.sqlite
 *.sqlite-shm
 *.sqlite-wal
 # Agent worktrees
 .claude/worktrees/
@@ -10,23 +10,14 @@ run:
 linters:
  default: all
  enable:
    # Successor to the deprecated gomodguard. Named explicitly, rather than
    # left to `default: all`, because it carries the module policy below.
    - gomodguard_v2
  disable:
    # Genuinely incompatible with project patterns
    - exhaustruct      # Requires all struct fields
-    - exhaustruct_v5   # Requires all struct fields (successor to exhaustruct)
+    - depguard         # Dependency allow/block lists
    - godot            # Requires comments to end with periods
    - wsl              # Deprecated, replaced by wsl_v5
    - wrapcheck        # Too verbose for internal packages
    - varnamelen       # Short names like db, id are idiomatic Go
    # Deprecated: the warning is attached to the old name, so it is
    # silenced by disabling that name, not by enabling the successor.
    - wsl              # Deprecated, replaced by wsl_v5
    - gomodguard       # Deprecated, replaced by gomodguard_v2
    # Misses findings at random in v2.14.0; back once a pinned release fixes it
    - canonicalheader
  settings:
    lll:
      line-length: 88
@@ -37,64 +28,6 @@ linters:
      max-complexity: 15
    dupl:
      threshold: 100
    depguard:
      # Test-support code must not be compiled into the shipped binary. A
      # test-support package exists to hand a test privileges the program
      # itself must never have, so a file that is not a test must not import
      # one. Test files, and the files inside a package whose directory name
      # ends in `test`, are where that code belongs, and are exempt.
      #
      # The deny list below is the one part of this file a repository is
      # expected to extend, and the only part it may. depguard matches an
      # import path against a list of prefixes, so it cannot be told "any path
      # whose last segment ends in test"; a repository's own test-support
      # packages have to be named here one at a time, by full import path,
      # under a module path that differs from repository to repository. Add
      # them; change nothing else.
      rules:
        test-support:
          list-mode: lax
          files:
            - "$all"
            - "!$test"
            - "!**/*test/**"
          deny:
            - pkg: net/http/httptest
              desc: >-
                Test-support code belongs in test files and in packages whose
                directory name ends in test, not in the shipped binary.
    # Only decisions already recorded in the Go package defaults are
    # listed here. Every entry matches the module path exactly.
    gomodguard_v2:
      blocked:
        - module: github.com/rs/zerolog
          recommendations:
            - log/slog
          reason: "Structured logging is stdlib log/slog."
        # One entry per pre-fork module path, because the later releases
        # are separate paths. A prefix match would be shorter but would
        # also reach github.com/go-redis/redismock, the test double for
        # the successor these entries recommend.
        - module: github.com/go-redis/redis
          recommendations:
            - github.com/redis/go-redis/v9
          reason: "Pre-fork module; use the maintained go-redis v9."
        - module: github.com/go-redis/redis/v7
          recommendations:
            - github.com/redis/go-redis/v9
          reason: "Pre-fork module; use the maintained go-redis v9."
        - module: github.com/go-redis/redis/v8
          recommendations:
            - github.com/redis/go-redis/v9
          reason: "Pre-fork module; use the maintained go-redis v9."
        - module: github.com/sergi/go-diff
          recommendations:
            - github.com/aymanbagabas/go-udiff
          reason: "No unified diff output; use go-udiff."
        - module: github.com/hexops/gotextdiff
          recommendations:
            - github.com/aymanbagabas/go-udiff
          reason: "Unmaintained fork; use go-udiff."
 issues:
  max-issues-per-linter: 0
@@ -1,2 +0,0 @@
 node_modules/
 yarn.lock
@@ -1,4 +0,0 @@
 {
    "tabWidth": 4,
    "proseWrap": "always"
 }
@@ -1,75 +1,116 @@
-# Lint phase, built alone by script/lint. The tools are invoked directly
+# Lint stage — fast feedback on formatting and lint issues
-# rather than through `make lint`, which runs docker itself and so cannot
+# golangci/golangci-lint:v2.12.2, 2026-08-07
-# run inside a build step.
+FROM golangci/golangci-lint@sha256:5cceeef04e53efe1470638d4b4b4f5ceefd574955ab3941b2d9a68a8c9ad5240 AS lint
 # golangci/golangci-lint:v2.14.0, 2026-10-07
 FROM golangci/golangci-lint@sha256:ad862ba6b3798cbe0fd9fd7408d498fd74fbd2623a92406b2fd3898faf0bf98f AS lint
 WORKDIR /src
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
-# The gofmt half of `make fmt-check`. gofmt's output is assigned to a
+# Cache-buster for the gate layers, and only for them. Docker
-# variable first so that its own exit status, as when it cannot parse a
+# invalidates COPY only when the copied content changes, so on an
-# file, still fails the step.
+# unchanged tree the gates below would be served from cache and the
-RUN files="$(gofmt -s -l .)" && \
+# build would exit 0 having run nothing. script/cibuild and
-    if [ -n "$files" ]; then \
+# script/docker pass a fresh CHECK_EPOCH on every invocation.
        echo "gofmt: files not formatted:" >&2; echo "$files" >&2; exit 1; \
    fi
 # Validates .golangci.yml against the schema the pinned binary embeds.
 RUN golangci-lint config verify --config .golangci.yml
 RUN golangci-lint run --config .golangci.yml ./...
 # Test phase, built alone by script/test. -race needs cgo and so a C
 # compiler, which the Debian Go image ships and the alpine one does not.
 #
-# The tests run as nobody: several of them make a file unreadable and
+# Two properties this depends on. ARG is per-stage, so the build stage
-# expect reading it to fail, and root reads it anyway. nobody has no home
+# below declares it again; one declaration here would leave that
-# directory, so HOME is /tmp, where Go puts its build cache.
+# stage's gate cacheable. And each gate RUN must reference the value,
-# golang:1.25-trixie, 2026-10-04
+# because BuildKit hashes the expanded command: a declared but
-FROM golang@sha256:2c4c60ef415fbfa5e90300722293bef36c5e63fae17570ce18f580af933dbd73 AS test
+# unreferenced ARG invalidates nothing.
-USER nobody
+#
-ENV HOME=/tmp
+# It sits below the dependency layers deliberately. Everything above it
-WORKDIR /src
+# (the pinned base image, go mod download) keeps its cache; only the
-COPY go.mod go.sum ./
+# gates go cold.
-RUN go mod download
+ARG CHECK_EPOCH
 COPY . .
 RUN go test -timeout 90s -race -cover ./... || \
    { echo "--- Rerunning with -v for details ---"; \
      go test -timeout 90s -race -v ./...; exit 1; }
-# Build stage. Nothing is wanted from either phase above; the copies are
+# The linter is invoked directly here, not through `make lint`. That
-# what make BuildKit build them first, so this stage cannot run unless
+# target now runs `docker build -f Dockerfile.lint`, and a docker build
-# lint and test passed.
+# cannot run a docker build: routing the gate through make would mean
 # nesting docker inside this image. Same reason `make check` is gone
 # from the build stage below. `make fmt-check` stays as it is — it is a
 # gate, not the aggregate, and it shells out to nothing.
 RUN echo "gate fmt-check, epoch ${CHECK_EPOCH}" && make fmt-check
 # The FROM above and the one in Dockerfile.lint pin the same linter
 # twice, and nothing else keeps them in sync; this fails the build when
 # they disagree. See the script for why it restates neither pin.
 RUN echo "gate lint-image-pin, epoch ${CHECK_EPOCH}" && \
    script/verify-lint-image-pin
 # Same config-schema check Dockerfile.lint runs, kept here so this build
 # gates on exactly what script/lint gates on. It validates against a
 # schema the pinned binary embeds, so it needs no network.
 RUN echo "gate config verify, epoch ${CHECK_EPOCH}" && \
    golangci-lint config verify --config .golangci.yml
 RUN echo "gate lint, epoch ${CHECK_EPOCH}" && \
    golangci-lint run --config .golangci.yml ./...
 # Build stage
 # golang:1.25-alpine, 2026-07-23
 FROM golang@sha256:56961d79ea8129efddcc0b8643fd8a5416b4e6228cfd477e3fd61deb2672c587 AS builder
-COPY --from=lint /src/go.sum /dev/null
+
-COPY --from=test /src/go.sum /dev/null
+# We never build or run as root. Create an unprivileged user and point
-RUN apk add --no-cache git make
+# HOME and the Go caches at its home so go build and go test can write
-# A tar-stream context keeps the sender's file owners, which git refuses.
+# their caches when we drop to it below. $GOPATH/bin is deliberately not
-RUN git config --system --add safe.directory /src
+# on PATH: script/bootstrap no longer `go install`s anything (the linter
 # runs from a pinned image, never from a host install), so nothing lands
 # there and adding it would only widen what this image resolves.
 RUN adduser -D -u 1000 builder
 ENV HOME=/home/builder
 ENV GOPATH=/home/builder/go
 ENV GOCACHE=/home/builder/.cache/go-build
 WORKDIR /src
 # No-op file copy whose only purpose is the build-graph edge: it is what
 # makes this stage depend on the lint stage, and so what forces BuildKit
 # to finish fmt-check, the pin guard and lint before compilation and
 # tests start. Remove it and the fail-fast design dies silently — the
 # build stops gating on lint and still exits 0. It replaces a copy of
 # the linter binary itself, which is no longer wanted here: nothing in
 # this stage runs the linter, because `make lint` is now a docker build
 # and a docker build cannot run inside one.
 COPY --from=lint /src/go.sum /dev/null
 # Install development prerequisites the same way a developer does,
 # rather than duplicating the installs inline. Only script/ and the
 # dependency manifests are copied first, nothing else, so this layer
 # stays cached until the scripts or the dependencies change — bootstrap
 # ends in `go mod download`, which is why there is no separate
 # invocation of it here.
 COPY script/ script/
 COPY go.mod go.sum ./
-RUN go mod download
+RUN script/bootstrap
 COPY . .
-# The version stamped into the binary: the VERSION build argument when
+# Hand the sources and caches to the unprivileged user, then drop root
-# one is given, otherwise `git describe --tags --always` of the .git in
+# before running any checks or builds.
-# the build context. A context that carries .git and still yields no
+RUN chown -R builder:builder /src /home/builder
-# version fails the build; with neither, as from a source tarball, it is
+USER builder
 # "dev". `make build` rather than `go build`, so the image and a host
 # build share one compile recipe, cgo disabled included.
 ARG VERSION
 RUN version="${VERSION:-$(git describe --tags --always || echo dev)}"; \
    if [ -e .git ] && { [ -z "$version" ] || [ "$version" = dev ] || \
        [ "$version" = unknown ]; }; then \
        echo "no version could be derived although the build context carries .git" >&2; \
        exit 1; \
    fi; \
    make build VERSION="$version"
-# Runtime stage, and the last one: a plain `docker build .` builds this
+# Fail the build unless the branch is green. Runs as non-root so the
-# stage's chain and nothing else.
+# permission-denied test paths are exercised legitimately (root would
 # bypass the chmod(0) the tests rely on).
 #
 # The gates are the individual targets, not `make check`: that aggregate
 # runs `script/lint`, which is now a docker build, and nothing inside an
 # image build may shell out to docker. Lint is not skipped by this — it
 # ran in the lint stage above, which this stage's COPY --from makes a
 # prerequisite. `make`, not the scripts directly, because the Makefile's
 # `export CGO_ENABLED = 0` applies only to what it invokes.
 #
 # Second per-stage declaration of the gate cache-buster; see the lint
 # stage above for why one is not enough. It is placed after USER so the
 # drop to the unprivileged user still happens before the checks run.
 ARG CHECK_EPOCH
 RUN echo "gate test, epoch ${CHECK_EPOCH}" && make test
 RUN echo "gate fmt-check, epoch ${CHECK_EPOCH}" && make fmt-check
 RUN make build
 # Runtime stage
 # alpine:3.22, 2026-07-23
 FROM alpine@sha256:14358309a308569c32bdc37e2e0e9694be33a9d99e68afb0f5ff33cc1f695dce
@@ -0,0 +1,59 @@
 # Lint-only image: this is how the linter runs, everywhere. The repo is
 # COPYed into the pinned golangci-lint image and the linter runs as a
 # build step, so a successful build IS a clean lint. golangci-lint is
 # never installed on a host — one toolchain, pinned by digest, identical
 # on a laptop and in CI — and this works even when the docker daemon is
 # remote and bind mounts are impossible.
 #
 # script/lint builds this file. It is a separate image from the lint
 # stage of the main Dockerfile because script/lint must not depend on
 # the rest of that build; the two FROM lines are kept identical by
 # script/verify-lint-image-pin, run as a gate below.
 # golangci/golangci-lint:v2.12.2, 2026-08-07
 FROM golangci/golangci-lint@sha256:5cceeef04e53efe1470638d4b4b4f5ceefd574955ab3941b2d9a68a8c9ad5240
 WORKDIR /src
 # Dependency layers first, so they stay cached across lint runs.
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
 # Cache-buster for the gate layers, and only for them. Caching of the
 # lint run is waived by ruling: COPY is invalidated only by changed
 # content, so on an unchanged tree the gates below would be served from
 # cache and this build would exit 0 in under a second having run no
 # linter at all. That exact false green has bitten this repo twice
 # already (#32, #39). script/lint passes a fresh value on every
 # invocation.
 #
 # Each gate RUN must reference the value, because BuildKit hashes the
 # expanded command and not the ARG declaration: a declared but
 # unreferenced ARG invalidates nothing. The ARG sits below the
 # dependency layers deliberately — everything above it keeps its cache,
 # only the gates go cold.
 ARG CHECK_EPOCH
 # The linter version is pinned in two places, here and in the main
 # Dockerfile's lint stage. Nothing else keeps them in sync, so a
 # half-applied bump is a build failure; see the script.
 RUN echo "gate lint-image-pin, epoch ${CHECK_EPOCH}" && \
    script/verify-lint-image-pin
 # Validates .golangci.yml against golangci-lint's JSON schema. The
 # concern about this step was that it fetches that schema over a live,
 # unpinned HTTPS call; measured on the pinned image, it does not. The
 # binary carries the schema for its own version, so under
 # `--network none` this both passes on a valid config and still rejects
 # an invalid one with the jsonschema error. That holds for the gate
 # steps generally — none of them makes a network call — but not for
 # this build as a whole: `go mod download` above needs the network on a
 # cold cache, and under `--network none` a first build fails there
 # before reaching any gate. That layer stays cached, so only a warm
 # cache lints offline, until go.mod or go.sum changes.
 RUN echo "gate config verify, epoch ${CHECK_EPOCH}" && \
    golangci-lint config verify --config .golangci.yml
 RUN echo "gate lint, epoch ${CHECK_EPOCH}" && \
    golangci-lint run --config .golangci.yml ./...
@@ -1,6 +1,6 @@
 ---
 title: Repository Policies
-last_modified: 2026-10-07
+last_modified: 2026-07-06
 ---
 This document covers repository structure, tooling, and workflow standards. Code
@@ -60,28 +60,17 @@ style conventions are in separate documents:
  prerequisite since nvm requires bash. yarn is then pinned via
  `corepack prepare yarn@<version> --activate`. Never install "latest" or "lts";
  always exact versions. `script/cibuild` runs the CI build: it changes to the
-  repo root, runs `script/bootstrap`, runs `script/check`, and builds the image
+  repo root and runs `docker build .`; the Gitea workflow calls it. Four further
-  with the version; the Gitea workflow calls it. **`script/cibuild` runs
+  scripts are our own extensions to the standard: `script/check` runs
-  `script/bootstrap` first**, because the workflow checks out the repo and runs
+  `script/test`, `script/lint`, and `script/fmt-check`; `script/precommit` is
-  nothing else, while `script/fmt-check` runs the formatter on the host: on a
+  what the git pre-commit hook runs, and it calls `script/check`;
-  pristine checkout with nothing installed the run dies there, after the
+  `script/install-precommit` installs the git pre-commit hook (the `make hooks`
-  containerised gates have passed. **The bootstrap alone is not enough**:
+  target shims to it); and `script/projectname` (literally that filename) simply
-  `script/bootstrap` installs node and yarn under nvm and leaves neither on the
+  outputs the project's name. Scripts that need the name call
-  `PATH` of the shell that called it, so a bare `yarn` still exits 127. The host
+  `script/projectname` — e.g. `script/docker` assembles its image tag from it —
-  entrypoints that need yarn — `script/fmt` and `script/fmt-check` — therefore
+  so those scripts stay byte-identical across all repos. Repo-type-specific
-  source nvm for the pinned node version before invoking it, exactly as
+  pre-commit extras (e.g. `go mod tidy` verification in Go repos) belong in
-  `script/bootstrap`'s own install step does. A runner carrying nothing but
+  `script/precommit`, not in the hook itself. Model scripts are at
  docker and git then gets through `script/check`. Four further scripts are our
  own extensions to the standard: `script/check` runs `script/test`,
  `script/lint` and `script/fmt-check`; `script/precommit` is what the git
  pre-commit hook runs, and it calls `script/check`; `script/install-precommit`
  installs the git pre-commit hook (the `make hooks` target shims to it); and
  `script/projectname` (literally that filename) simply outputs the project's
  name. Scripts that need the name call `script/projectname` — e.g.
  `script/docker` assembles its image tag from it — so those scripts stay
  byte-identical across all repos. Repo-type-specific pre-commit extras (e.g.
  `go mod tidy` verification in Go repos) belong in `script/precommit`, not in
  the hook itself. Model scripts are at
  `https://git.eeqj.de/sneak/prompts/raw/branch/main/script/<name>`. The README
  must document the provided scripts in an **Entrypoints** section (see the
  README requirements below).
@@ -100,222 +89,87 @@ style conventions are in separate documents:
  contributor should be able to understand the entire development workflow by
  reading the Makefile.
- Every repo should have a `Dockerfile`, and it carries the repo's gates: a
+- Every repo should have a `Dockerfile`. All Dockerfiles must run `make check`
-  `lint` phase and a `test` phase, with the final stage depending on both so the
+  as a build step so the build fails if the branch is not green. For non-server
-  image cannot be built unless they pass. For non-server repos the final stage
+  repos, the Dockerfile should bring up a development environment and run
-  brings up a development environment; for server repos it is the runtime image.
+  `make check`. For server repos, `make check` should run as an early build
-  The gate phases and the build stage start from their pinned base images and
+  stage before the final image is assembled. Dockerfiles install development
-  install what those images lack either inline, as the canonical Go `Dockerfile`
+  prerequisites by running `script/bootstrap` rather than duplicating installs
-  below does for `git`, or by running `script/bootstrap`, as the `prompts`
+  inline; COPY `script/` and the dependency manifests (`package.json` +
-  repo's own `Dockerfile` does for its yarn packages. The development
+  `yarn.lock`, `go.mod` + `go.sum`, etc.) before running it so the bootstrap
-  environment stage installs development prerequisites by running
+  layer stays cached until dependencies change.
  `script/bootstrap` rather than duplicating its installs inline. A stage that
  runs `script/bootstrap` COPYs `script/` and the dependency manifests
  (`package.json` + `yarn.lock`, `go.mod` + `go.sum`, etc.) before running it.
- **Linting and testing run in Docker, as phases of the `Dockerfile`.** There is
+- **Dockerfiles must use a separate lint stage for fail-fast feedback.** Go
-  no separate lint file. `script/lint` and `script/test` each build one phase
+  repos use a multistage build where linting runs in an independent stage based
-  and nothing else:
+  on the `golangci/golangci-lint` image (pinned by hash). This stage runs
  `make fmt-check` and `make lint` before the full build begins. The build stage
  then declares an explicit dependency on the lint stage via
  `COPY --from=lint /src/go.sum /dev/null`, which forces BuildKit to complete
  linting before proceeding to compilation and tests. This ensures lint failures
  surface in seconds rather than minutes, without blocking on dependency
  download or compilation in the build stage.
-    ```sh
+    The standard pattern for a Go repo Dockerfile is:
    docker build --no-cache --target lint --output type=cacheonly .
    docker build --no-cache --target test --output type=cacheonly .
    ```
    **A stage that is not the last one in the file is built only when the final
    stage's chain depends on it, or when `--target` names it.** That is why the
    two gates are always invoked by name here, and why the final stage carries a
    `COPY --from=` of a harmless file from each of them: without that edge a
    plain `docker build .` builds the last stage alone and exits 0 having linted
    and tested nothing.
    **The gate builds write no image.** With `--output type=cacheonly` the phase
    runs and a failing step fails the build, but the result is not exported.
    Nothing uses those images, and writing one out is slow: a Go test phase's
    image holds the toolchain and every compiled package. A build given neither
    `--output` nor `-t` writes an untagged image and leaves it dangling, on
    every developer host and every CI runner. `script/cibuild` and
    `script/docker` build the image that ships and tag it, so each build
    replaces the previous image; each assigns the tag on its own line before the
    build, so `set -e` stops it where `script/projectname` fails.
    Inside a phase the tool is invoked directly — `golangci-lint`, `go test`,
    `eslint`, `prettier` — never through `make lint` or `script/test`, which are
    themselves a `docker build` and would recurse into a daemon that does not
    exist in a build step. Formatting is the exception and stays on the host:
    `script/fmt` writes the working tree, and `script/fmt-check` is its
    read-only twin.
    **No lint verdict may come from a host invocation of the linter.** On a
    shared host golangci-lint reads a result cache keyed on file content rather
    than location, so a second checkout of the same content is served the first
    one's findings, and a host-global lock in `$TMPDIR` makes concurrent runs
    exit non-zero with `parallel golangci-lint is running` — a status a caller
    cannot tell from real findings. Both have produced wrong verdicts in this
    org, in both directions. A container has its own cache, its own `TMPDIR` and
    a digest-pinned binary, so neither is reachable.
 - **Any build that runs checks is built with `--no-cache`.** Docker invalidates
  a `COPY` layer only when the copied content changes, so on an unchanged tree
  the check `RUN` is served from cache, nothing executes, and the build still
  exits 0. Every `docker build` in `script/` therefore passes `--no-cache`:
  `script/lint`, `script/test`, `script/cibuild` and `script/docker` are the
  four, and there is no fifth — `script/check` runs the two gate phases and
  `script/fmt-check`, and builds no image of its own. A bare `docker build .` is
  not evidence that anything ran: a sub-second build reporting success is a
  cache hit, not a result. Never invalidate by pruning — `docker builder prune`
  and friends destroy a build cache shared with every other build on the host.
  When a check is added or changed, prove it works by planting a defect it must
  catch and watching the run fail on it, then revert the defect. A green run
  alone shows neither that the check ran nor that it covers what it should.
 - **The gate phases are separate stages, and the build stage depends on both.**
  The lint phase is based on the `golangci/golangci-lint` image (pinned by
  hash), so lint failures surface in seconds rather than after a full compile,
  and the test phase is based on the Debian Go image. The canonical Go repo
  `Dockerfile`:
    ```dockerfile
-    # Lint phase
+    # Lint stage — fast feedback on formatting and lint issues
    # golangci/golangci-lint:v2.x.x, YYYY-MM-DD
    FROM golangci/golangci-lint@sha256:... AS lint
    WORKDIR /src
    COPY go.mod go.sum ./
    RUN go mod download
    COPY . .
-    RUN golangci-lint run --config .golangci.yml ./...
+    RUN make fmt-check
    RUN make lint
-    # Test phase. -race needs cgo and so a C compiler, which the Debian Go
+    # Build stage
    # image ships and the alpine one does not.
    # golang:1.x, YYYY-MM-DD
    FROM golang@sha256:... AS test
    WORKDIR /src
    COPY go.mod go.sum ./
    RUN go mod download
    COPY . .
    RUN go test -timeout 90s -race -cover ./... || \
        { echo "--- Rerunning with -v for details ---"; \
          go test -timeout 90s -race -v ./...; exit 1; }
    # Build stage. Nothing is wanted from either phase above; the copies
    # are what make BuildKit build them first, so this stage cannot run
    # unless lint and test passed.
    # golang:1.x-alpine, YYYY-MM-DD
    FROM golang@sha256:... AS builder
    COPY --from=lint /src/go.sum /dev/null
    COPY --from=test /src/go.sum /dev/null
    RUN apk add --no-cache git
    # A tar-stream context keeps the sender's file owners, which git refuses.
    RUN git config --system --add safe.directory /src
    WORKDIR /src
    # Force BuildKit to run the lint stage before proceeding
    COPY --from=lint /src/go.sum /dev/null
    COPY go.mod go.sum ./
    RUN go mod download
    COPY . .
    RUN make test
-    # The VERSION build arg when one is given, otherwise
+    ARG VERSION=dev
-    # `git describe --tags --always` on the .git in the build context. With
+    RUN CGO_ENABLED=0 go build -trimpath \
    # .git present, a version that is still empty, dev or unknown fails the
    # build: git is missing or could not read the checkout.
    ARG VERSION
    RUN VERSION="${VERSION:-$(git describe --tags --always)}"; \
        if [ -e .git ]; then \
            case "$VERSION" in ""|dev|unknown) \
                echo "version is '$VERSION' although .git is present" >&2; \
                exit 1 ;; \
            esac; \
        fi; \
        CGO_ENABLED=0 go build -trimpath \
        -ldflags="-s -w -X main.Version=${VERSION}" \
        -o /app ./cmd/app/
-    # Runtime stage, and the last one
+    # Runtime stage
    FROM alpine@sha256:...
    COPY --from=builder /app /usr/local/bin/app
    ENTRYPOINT ["app"]
    ```
    Key points:
-    - The lint phase uses the `golangci/golangci-lint` image directly (it has
+    - The lint stage uses the `golangci/golangci-lint` image directly (it
-      both Go and the linter), so nothing needs installing.
+      includes both Go and the linter), so there is no need to install the
-    - `COPY --from=<phase> /src/go.sum /dev/null` is a no-op copy whose only
+      linter separately.
-      purpose is the ordering edge. BuildKit runs stages in parallel by default,
+    - `COPY --from=lint /src/go.sum /dev/null` is a no-op file copy that creates
-      and a stage nothing depends on is not built at all, so without these two
+      a stage dependency. BuildKit runs stages in parallel by default; without
-      lines a red gate would not fail the build.
+      this line, the build stage would not wait for lint to finish and a lint
-    - Keep the runtime stage last, and if you add a stage after it, give it the
+      failure might not fail the overall build.
      same two copies. A plain `docker build .` builds the last stage's chain
      and nothing else.
    - If the project uses `//go:embed` directives that reference build artifacts
-      (e.g. a web frontend compiled in a separate stage), the lint phase must
+      (e.g. a web frontend compiled in a separate stage), the lint stage must
      create placeholder files so the embed directives resolve. Example:
      `RUN mkdir -p web/dist && touch web/dist/index.html web/dist/style.css`.
-    - If the project requires CGO or system libraries for linting, install them
+      The lint stage should not depend on the actual build output — it exists to
-      in the lint phase. The `golangci/golangci-lint` image is Debian-based and
+      fail fast.
-      has no `apk`, so install with `apt-get` under the Debian package name
+    - If the project requires CGO or system libraries for linting (e.g.
-      (`libvips-dev`, where alpine says `vips-dev`), and delete the package
+      `vips-dev`), install them in the lint stage with `apk add`.
-      lists in the same `RUN`, so the layer does not keep them:
+    - The build stage runs `make test` after compilation setup. Tests run in the
-
+      build stage, not the lint stage, because they may require compiled
-        ```dockerfile
+      artifacts or heavier dependencies.
        RUN apt-get update \
            && apt-get install -y --no-install-recommends libvips-dev \
            && rm -rf /var/lib/apt/lists/*
        ```
    - `.dockerignore` lets `.git` into the build context. It keeps out every git
      `config` at any depth (`**/.git/config`, `**/.git/modules/**/config`): the
      repository's own, each submodule's under `.git/modules/`, and that of a
      submodule keeping its own `.git` directory. `git describe` does not need
      them, and each can hold a credential: a password in a remote URL, or the
      token the CI checkout step stores there. A submodule whose name has a
      `config` segment (`config`, `deploy/config`, `config/lib`) loses its whole
      git directory to `**/.git/modules/**/config`, and Go's version stamping
      then fails the build: give it a name without that segment
      (`git submodule add --name`). The stage that compiles has `git` (the
      Debian Go image has it; an alpine one needs `apk add --no-cache git`) and
      takes the version from the `VERSION` build argument when one is given,
      otherwise from `git describe --tags --always`. That gives the tag on a
      tagged commit; on a later commit, the tag, the number of commits since it
      and the short commit (`v1.2.3-4-gabc1234`); and the short commit when no
      tag is reachable. The stage that compiles also marks its working directory
      safe for git (`git config --system --add safe.directory /src`): a context
      sent as a tar stream keeps the sender's file owners, and git refuses a
      checkout owned by another user, so the version would come out empty.
      `ARG VERSION` has no default, and the build fails if the context carries
      `.git` and the version still comes out empty, `dev` or `unknown`. A plain
      `docker build .` with no build arguments must succeed; a Dockerfile that
      refuses an empty build argument drops that refusal and keeps the argument.
      A checkout whose `.git` is a file (a linked worktree, or a repository
      checked out as a submodule) is the exception: that file points to a git
      directory outside the build context, so the build cannot read the version
      and a plain `docker build .` fails; pass the version with
      `--build-arg VERSION=...`, as `script/docker` and `script/cibuild` already
      do.
 - Every repo should have a Gitea Actions workflow (`.gitea/workflows/`) that
-  runs `script/cibuild` on push, and checks out the repo as its only other step,
+  runs `script/cibuild` (which runs `docker build .`) on push. Since the
-  with `persist-credentials: false`: `script/cibuild` needs no token, and
+  Dockerfile already runs `make check`, a successful build implies all checks
-  without it the checkout leaves the job's token in `.git/config` for every
+  pass.
  later step. The checkout step also sets `fetch-depth: 0`, which fetches the
  tags `git describe` needs: by default it clones shallow with no tags, and a
  tagged repository's CI build would stamp a bare short commit id. The
  workflow's `concurrency` block groups runs by workflow and branch
  (`${{ github.workflow }}-${{ github.ref }}`) with `cancel-in-progress: true`,
  so a new push cancels the older run on the same branch, queued or running, and
  no other: runs for replaced commits do not hold up the shared runner.
  `script/cibuild` bootstraps, runs the gate phases, and then builds the image,
  so a successful run means every check passed; a bare `docker build .` does not
  carry the same guarantee, because its gate phases may come from the cache. The
  image build is uncached and so runs the gate phases a second time. That is the
  price of the rule above, and it is worth paying: the image that ships is built
  from a run of its own gates rather than from a cache entry. The `check` job
  sets `timeout-minutes: 20`, so a hung build frees the shared runner after 20
  minutes. That allows for the three Docker builds described above (the test
  phase, the lint phase, then the image), each held to the 5-minute Docker build
  limit below, plus the bootstrap. A separate workflow limited to `main` by a
  `branches` list under `on: push` cannot be checked by review: to try a change
  to it, add the feature branch to that list and push, then remove the branch
  from the list again before merging. Keep any job in it that publishes behind
  `if: github.ref_name == 'main'`, so the run from the feature branch publishes
  nothing.
 - Use platform-standard formatters: `black` for Python, `prettier` for
  JS/CSS/Markdown/HTML, `go fmt` for Go. Always use default configuration with
@@ -335,21 +189,14 @@ style conventions are in separate documents:
  module under test to verify it compiles/parses. There is no excuse for
  `make test` to be a no-op.
- `make test` must complete in under 60 seconds. That is the hard cap, and a
+- `make test` must complete in under 20 seconds. Add a 30-second timeout in the
-  suite that exceeds it fails. Under 20 seconds is the target. A suite between
+  Makefile.
  20 and 60 seconds is still green, but the overage must be filed as an
  improvement bug against that repo. Add a 90-second timeout to the test
  invocation (`go test -timeout 90s`). The backstop deliberately sits above the
  hard cap so that it catches a genuinely hung test rather than a merely slow
  one.
- **The test command should use the conditional verbose rerun pattern.** Run
+- **`make test` should use the conditional verbose rerun pattern.** Run tests
-  tests without `-v` (verbose) first. If tests fail, automatically rerun with
+  without `-v` (verbose) first. If tests fail, automatically rerun with `-v` to
-  `-v` to show full output. This keeps CI logs and `docker build` output clean
+  show full output. This keeps CI logs and `docker build` output clean on
-  on success (just package/suite summaries) while providing full diagnostic
+  success (just package/suite summaries) while providing full diagnostic detail
-  detail on failure (every test case, every assertion). The command lives in the
+  on failure (every test case, every assertion). The general shell pattern:
  `test` phase of the `Dockerfile`, since `script/test` builds that phase; the
  Makefile form below is the same pattern for any repo-local invocation:
    ```makefile
    test:
@@ -362,26 +209,11 @@ style conventions are in separate documents:
    ```makefile
    test:
-    	@go test -count=1 -timeout 90s -race -cover ./... || \
+    	@go test -timeout 30s -race -cover ./... || \
    		{ echo "--- Rerunning with -v for details ---"; \
-    		  go test -count=1 -timeout 90s -race -v ./...; exit 1; }
+    		  go test -timeout 30s -race -v ./...; exit 1; }
    ```
    `-count=1` is required on both invocations: it defeats Go's test _result_
    cache, so neither run can report a stored pass in place of running the
    tests. It leaves the build cache alone, so it costs the runtime of the suite
    and no recompilation.
    That cache is Go's own, separate from Docker's layer cache. Go stores a
    passing result in its cache directory (`GOCACHE`), and when the same tests
    run again on unchanged code it prints that result, marked `(cached)`,
    without running them. That matters on a developer's machine, where this
    target runs and the directory lasts from one run to the next. The `test`
    phase of the `Dockerfile` needs no `-count=1`: its base image holds no
    result for this repo's tests and nothing before its `go test` step runs a
    test, so there is nothing to replay. `--no-cache` (above) is what makes that
    step run on an unchanged tree.
    Python example:
    ```makefile
@@ -407,89 +239,10 @@ style conventions are in separate documents:
  must be in `.gitignore`. No exceptions.
 - `.gitignore` should be comprehensive from the start: OS files (`.DS_Store`),
-  editor files (`.swp`, `*~`), in-repo agent scratch directories (`.claude/`),
+  editor files (`.swp`, `*~`), language build artifacts, and `node_modules/`.
-  `node_modules/`, and the repo's own build outputs. Fetch the standard
+  Fetch the standard `.gitignore` from
  `.gitignore` from
  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitignore` when setting up
-  a new repo. A repo's `.gitignore` is the standard file followed by the repo's
+  a new repo.
  own entries, such as its binaries; a re-vendor replaces the standard part and
  keeps those entries. These patterns are written to `.gitignore`'s own
  semantics, in which an unanchored pattern already matches at every depth; they
  are not a `.dockerignore` and must not be transplanted into one unmodified.
 - **`.dockerignore` does not use `.gitignore` semantics, and copying patterns
  across unmodified leaves secrets in the build context.** Docker matches with
  `moby/patternmatcher`: `filepath.Match` semantics plus a `**` extension, so
  `*` does not cross `/` and a pattern without a leading `**/` is anchored at
  the build-context root. A `.dockerignore` listing `.env`, `*.pem` and `*.key`
  therefore excludes only the copies at the repository root, while `config/.env`
  and `certs/server.key` still reach the context and can land in an image layer
  — which is more dangerous than a short file with no secret patterns at all,
  because it reads as solved and stops anyone looking. Give every
  depth-independent pattern the `**/` prefix and leave only genuinely
  root-anchored entries unprefixed: `.claude`, and the repo's own host-built
  binary, written `/myapp` and never `**/myapp`, which would also match
  `cmd/myapp/` and delete the package directory from the context. Matching is
  case-sensitive, and an ALL-CAPS twin per pattern still misses `Server.Key`, so
  secret names use character ranges — `**/*.[kK][eE][yY]`, `**/*.[pP][eE][mM]`,
  and likewise for `.envrc` and the extensionless SSH keys. Where such a pattern
  also catches something the build needs, re-include it with a negation
  (`!docs/example.env`); deleting the pattern reopens the exposure for every
  other file it covers. Fetch the standard `.dockerignore` from
  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.dockerignore` and extend
  it with the repo's own artifacts.
 - **In-repo agent scratch belongs in both files, written to each file's own
  semantics.** `.claude/` holds one worktree per in-flight agent — an entire
  additional checkout of the repo — so under `COPY . .` the build context
  inflates by a multiple of the repo and another session's unreviewed work can
  be copied into an image layer. In `.gitignore` the entry is `.claude/`,
  unanchored. In `.dockerignore` it is `.claude`, anchored and with **no** `**/`
  prefix, because the prefixed form would also delete any nested directory of
  that name from the build. Anchoring carries a known gap that the canonical
  `.dockerignore` states in its own comment, since consuming repos receive the
  file and not the tracker: the directory is created in the agent's working
  directory, so a repo running agents in subdirectories still ships
  `services/api/.claude/` and must add its own anchored entry there.
 - **A plain `docker build .` of a clone stamps the version that
  `git describe --tags --always` gives**, derived from the `.git` in the build
  context as the canonical `Dockerfile` above shows. Without its failure check,
  a missing `git` or an unreadable checkout would leave `-X main.Version=` empty
  and the build would still exit 0. `script/docker` and `script/cibuild` pass
  the version they compute on the host; it takes precedence. They do this
  byte-identically across repos:
    ```sh
    # The version and the tag each get their own line: a failing command
    # substitution inside an argument does not trip `set -e`, so the inline
    # form degrades to an empty constant.
    version="$(git describe --tags --always --dirty 2>/dev/null || true)"
    [ -n "$version" ] || version="unknown"
    tag="$(script/projectname)"
    docker build --no-cache \
        --build-arg VERSION="$version" \
        -t "$tag" .
    ```
    `--always` makes an untagged repo yield an abbreviated commit hash rather
    than failing, and the `[ -n "$version" ]` line is the single place the
    fallback is applied — a live check that fires on a build from an export with
    no `.git` and on a repository with no commits yet. Do not fold it into the
    substitution as `|| echo unknown`, which makes the guard unreachable. The
    Dockerfile's side is `ARG VERSION` in the stage that compiles, declared
    there because `ARG` is stage-scoped; passing `VERSION` to a repo whose
    Dockerfile declares no such `ARG` is ignored and costs nothing, which is why
    the scripts stay byte-identical. One consequence for CI: the standard
    checkout action clones shallow and fetches no tags, so the canonical
    `.gitea/workflows/check.yml` sets `fetch-depth: 0` on its checkout step.
 - **Verify `.dockerignore` by enumerating the image, not by reading the
  patterns.** Plant files at the root _and_ at least two directories deep, build
  a probe image that does `COPY . .`, and list what actually landed
  (`docker run --rm --entrypoint find IMAGE /app`). The `transferring context`
  size is not a substitute: a nested secret is a few bytes, and BuildKit
  transfers only the delta from the previous build.
 - **No build artifacts in version control.** Code-derived data (compiled
  bundles, minified output, generated assets) must never be committed to the
@@ -505,56 +258,9 @@ style conventions are in separate documents:
 - Make all changes on a feature branch. You can do whatever you want on a
  feature branch.
- `.golangci.yml` is standardized. The vendored copy in a consuming repo must
+- `.golangci.yml` is standardized and must _NEVER_ be modified by an agent, only
-  _NEVER_ be modified by an agent: fetch it from
+  manually by the user. Fetch from
-  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml` and keep it
+  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.golangci.yml`.
  byte-identical, so that no repo can quietly loosen its own linting. Linter
  configuration changes are made to the canonical copy in the `prompts` repo and
  reach consuming repos by re-vendoring; an agent may open a PR against
  canonical, which only the user merges. One list is exempt from byte-identity,
  because it cannot be written once for every repo: the `deny` list of the
  `test-support` depguard rule, where a repo names its own test-support packages
  by full import path. A repo adds entries there and changes nothing else, and a
  re-vendor carries its entries forward. The canonical golangci-lint version is
  v2.14.0 (released 2026-09-24), pinned as the digest of the lint phase's base
  image
  (`golangci/golangci-lint@sha256:ad862ba6b3798cbe0fd9fd7408d498fd74fbd2623a92406b2fd3898faf0bf98f`,
  which reports `2.14.0 built with go1.27.0 from 114493f9`). A module's `go`
  directive must not name a newer Go minor version than the one golangci-lint
  was built with, or golangci-lint refuses to lint it: this release lints
  `go 1.27.1` but not `go 1.28`. That digest is the only pin, since no repo
  installs golangci-lint on the host. A repo sets the lint phase digest to the
  one named here and re-vendors `.golangci.yml` in the same commit, whichever of
  the two prompted the change: the canonical copy can name linters that an older
  golangci-lint rejects, and a newer golangci-lint can add linters that
  `default: all` switches on until the canonical copy disables them.
 - **`script/bootstrap` installs a pinned tool by comparing versions, never by
  testing presence.** An `if ! command -v <tool>; then install; fi` guard tests
  `PATH` only, so on an already-provisioned machine the pin is inert and a
  version bump is a silent no-op — while the Dockerfile, installing into a clean
  image, gets the pinned version, so a local `make check` and `make docker` can
  disagree about what the tool even is. The canonical form:
    - compares the installed version against the pin over the **whole** version
      token; a parser that stops at the first `-` reports `2.12.2` for a host
      running `2.12.2-rc1` and skips the install;
    - treats absent, non-zero, empty or unrecognised `--version` output as a
      mismatch, so the failure direction is a redundant install and never a
      skipped one;
    - after installing, re-resolves the binary the way callers do — `hash -r`,
      then through `PATH`, not through the directory the installer wrote to —
      and fails naming the resolved path, since an install that a shadowing
      binary hides succeeds while changing nothing any caller sees;
    - is actually called, and prints the version on both success paths: a
      function defined and never invoked has the same exit status and the same
      empty output as one that worked.
    Keep it POSIX sh: no arrays, no `[[`, no `grep -P`.
    A Go tool a repo needs on the host is installed with `go install` pinned to
    a commit hash (`go install <package>@<commit hash>`). It is never tracked as
    a `go.mod` tool dependency or through a `tools.go` file, either of which
    pulls the tool's own dependencies into the repo's `go.mod` and `go.sum`.
 - When pinning images or packages by hash, add a comment above the reference
  with the version and date (YYYY-MM-DD).
@@ -665,21 +371,15 @@ style conventions are in separate documents:
      Never edit existing migrations after release.
 - All repos should have an `.editorconfig` enforcing the project's indentation
-  settings: the standard file from
+  settings.
  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.editorconfig`, which sets
  tabs for `Makefile` and Go files, followed by the repo's own sections, such as
  one for another language it uses. A re-vendor replaces the standard part and
  keeps those sections.
 - Avoid putting files in the repo root unless necessary. Root should contain
-  only project-level config files (`README.md`, `AGENTS.md`, `Makefile`,
+  only project-level config files (`README.md`, `Makefile`, `Dockerfile`,
-  `Dockerfile`, `LICENSE`, `.gitignore`, `.editorconfig`, `REPO_POLICIES.md`,
+  `LICENSE`, `.gitignore`, `.editorconfig`, `REPO_POLICIES.md`, and
-  and language-specific config). Everything else goes in a subdirectory.
+  language-specific config). Everything else goes in a subdirectory. Canonical
-  Canonical subdirectory names:
+  subdirectory names:
    - `bin/` — executable scripts and tools
-    - `cmd/` — Go command entrypoints; thin only: one `main.go` per binary whose
+    - `cmd/` — Go command entrypoints
      body is a single call into `internal/` or `pkg/`, no project logic in
      `cmd/`
    - `configs/` — configuration templates and examples
    - `deploy/` — deployment manifests (k8s, compose, terraform)
    - `docs/` — documentation and markdown (README.md stays in root)
@@ -706,7 +406,3 @@ style conventions are in separate documents:
    - Go: `go.mod`, `go.sum`, `.golangci.yml`
    - JS: `package.json`, `yarn.lock`, `.prettierrc`, `.prettierignore`
    - Python: `pyproject.toml`
 - Guidance for coding agents lives in one `AGENTS.md` at the repository root. It
  is never committed under a file or directory named after one agent tool, such
  as `CLAUDE.md` or `.claude/`, and never split into separate memory files.
@@ -1,373 +1,453 @@
 # Workflow
- take an issue from the `1.0.0` milestone on the tracker; work not yet on the
+- take an issue from the `1.0.0` milestone on the tracker; work not
-  tracker gets filed as an issue first
+  yet on the tracker gets filed as an issue first
- branch from `next`
+- branch (from `main`)
 - do the work, with tests, in small focused commits
- record it at the top of Completed Steps (`TODO.md` changes in the same commit
+- record it at the top of Completed Steps (`TODO.md` changes in the
-  as the work)
+  same commit as the work)
- push the branch and open a PR against `next` whose title ends with
+- push the branch and open a PR whose title ends with
  ` (closes #N)`
- an independent review gates each merge to `next`; every finding is addressed
+- an independent review gates the merge; every finding is addressed
  or explicitly rebutted on the PR
- only the owner merges `next` to `main`
+- merge to `main` once the review passes
 # Status
 - pre-1.0
- the Gitea tracker is authoritative for the pre-1.0 backlog: the open issues
+- the Gitea tracker is authoritative for the pre-1.0 backlog: the
-  under the `1.0.0` milestone are what remains before the tag, and this file
+  open issues under the `1.0.0` milestone are what remains before
-  records history and process, not the queue
+  the tag, and this file records history and process, not the queue
 # Next Step
 - take the next issue from the `1.0.0` milestone on the tracker:
-  https://git.eeqj.de/sneak/sfdupes/milestone/17 — the milestone is the source
+  https://git.eeqj.de/sneak/sfdupes/milestone/17 — the milestone is
-  of truth for what is left before 1.0.0. Individual issues are deliberately not
+  the source of truth for what is left before 1.0.0. Individual
-  restated here; a copy in this file drifts out of date the moment the tracker
+  issues are deliberately not restated here; a copy in this file
-  moves
+  drifts out of date the moment the tracker moves
 # Completed Steps
- re-vendor the canonical files and model scripts from `sneak/prompts` `next` at
+- replace the 1 KiB end-window sampling with the head/tail plus
-  `c55a0cb`: golangci-lint v2.14.0; lint and test are phases of the `Dockerfile`
+  content-hash ladder (2026-09-22, branch `next`, closes
-  that write no image, and `make test` runs the suite under the race detector,
+  https://git.eeqj.de/sneak/sfdupes/issues/61): a file under 10 MiB is
-  so `Dockerfile.lint`, `script/verify-lint-image-pin` and `make test-race` are
+  hashed in full and compared directly, with no end-window step — its
-  gone; every `docker build` in `script/` passes `--no-cache`; prettier runs on
+  `head`, `tail`, and `content` all hold the whole-file hash. A file at
-  the host, from the node and yarn `script/bootstrap` installs, so the
+  10 MiB or above gets only the 64 KiB `head` and `tail` in the hash
-  `prettier` and `markdown` stages are gone and the build stage installs `git`
+  phase; a new content phase, after the update phase, reads it for its
-  and `make` itself; a new push cancels the workflow's older run on the same
+  `content` hash — the whole file below 50 MiB, gigabyte-spaced 1 MiB
-  branch, and a run stops after 20 minutes; `.claude/settings.json` is deleted
+  samples at or above — only when its size, `head`, and `tail` match
-  (2026-10-08, https://git.eeqj.de/sneak/sfdupes/issues/95)
+  another record's, from the same scan or stored by an earlier one, so
  a stored file gains its content hash when it gains a match. A file
  that is gone or has changed since its record was written is not
  read. The `content` column is part of the version 1 schema. `report`
  and `trees` group by the extended signature and leave out any record
  without a `content` hash, so the ladder is applied across the whole
  database. README "Duplicate detection" documents every rung including
  the probabilistic large-file path.
- `scan` records mtime to the nanosecond, as whole seconds in `mtime` plus
+- remove the dead `files.dat` references from `Makefile`, `.gitignore`
-  `mtime_nsec`, and compares it at that resolution, so a same-size rewrite
+  and `.dockerignore` (2026-09-21, branch `next`, closes
  within the same second is re-hashed (2026-10-07,
  https://git.eeqj.de/sneak/sfdupes/issues/12)
 - cut the narration from `TODO.md` Completed Steps and from the comments in
  `script/`, `Dockerfile` and `Dockerfile.lint` (gone since
  https://git.eeqj.de/sneak/sfdupes/issues/95); §Workflow now branches from and
  merges to `next` (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/49)
 - `make test-race` ran the test suite under the race detector in a cgo-enabled
  container, outside `make check` (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/18). Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 `make test` itself runs the suite
  under the race detector, in the `Dockerfile`'s Debian-based `test` phase, and
  `make test-race` is gone
 - a bare `docker build .` failed, naming `script/cibuild` and `script/docker`,
  rather than serve the gates from cache (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/39). Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 a bare build succeeds, as
  `REPO_POLICIES.md` requires, and may serve the gates from cache; the builds in
  `script/` pass `--no-cache`, so theirs always run
 - `make fmt` and `make fmt-check` run prettier over all Markdown, and CI checks
  it; all Markdown reformatted (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/19)
 - `script/lint` writes no image, so a run no longer leaves an untagged one
  behind (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/48)
 - tests cover a missing database, `scan` keeping stdout empty, its skip warning,
  the `report` and `trees` summary lines, and every subcommand going through
  `runE` (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/16)
 - `.golangci.yml` replaced with the current canonical copy, which uses
  `gomodguard_v2`, so lint no longer prints a deprecation warning (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/26)
 - a test fails when either `hashWorker` cancellation check in `scan.go` is
  removed (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/83)
 - a database path holding `?`, `#` or `%` opens exactly the file it names
  (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/55)
 - `scan` rejects `--workers` below 1 as a usage error instead of running
  single-threaded (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/10)
 - a test fails when either walk cancellation check in `scan.go` is removed
  (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/81)
 - test that `scan` refuses a database with another schema version (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/64)
 - correct four inaccurate comments in `cancel_test.go` and rename
  `walkCancelInFlightDirs` to `walkCancelInFlightFiles` (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/33)
 - test the `-x` filesystem-boundary rules in `subdirJob` (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/17)
 - `scan` creates the schema in one transaction; a version-0 database with a
  `files` table is refused with a clear schema-version error (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/11)
 - README documents install, Docker, a daily cron scan and how to read and check
  the reports (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/54)
 - the `Dockerfile` build stage kept the Go module cache out of `builder`'s home
  and copied the sources with `--chown`, so no `chown -R` walked them
  (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/43). Since
  https://git.eeqj.de/sneak/sfdupes/issues/95 there is no `builder` user and
  nothing changes owner: the build stage only compiles, as root, and the tests
  run as `nobody` in the `test` phase
 - `--version` prints `sfdupes VERSION` to stdout; README documents it and
  `--help` (2026-10-04, https://git.eeqj.de/sneak/sfdupes/issues/15)
 - `scan` stops cleanly on `SIGINT` or `SIGTERM`: commits what it has hashed,
  deletes nothing more, exits 1 (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/5)
 - `report` and `trees` stream the records instead of holding them all in memory;
  the schema gains the `files_signature` index (2026-10-04,
  https://git.eeqj.de/sneak/sfdupes/issues/14)
 - progress prints at once on a non-terminal, uses a real terminal test, and
  prints warnings through a spinner instead of racing its redraw (2026-10-03,
  https://git.eeqj.de/sneak/sfdupes/issues/13)
 - warn about and skip symlink, socket, FIFO, device and `.zfs` operands, keeping
  the records beneath them (2026-10-03,
  https://git.eeqj.de/sneak/sfdupes/issues/9)
 - `scan` holds a lock on a lock file beside the database for its whole run, so a
  second `scan` fails at once with exit 1 (2026-10-03,
  https://git.eeqj.de/sneak/sfdupes/issues/53)
 - test stdout write failures in `report` and `trees`; README states that
  `| head` ends sfdupes by `SIGPIPE` and `>&-` writes to `/dev/null`
  (2026-10-03, https://git.eeqj.de/sneak/sfdupes/issues/30)
 - `report` and `trees` open the database read-only, and `scan` leaves it out of
  WAL mode, so reading needs only read access (2026-10-03, closes
  https://git.eeqj.de/sneak/sfdupes/issues/8)
 - escape tabs, newlines, carriage returns and backslashes in report, trees and
  warning paths; the root directory's path is `/` (2026-10-03,
  https://git.eeqj.de/sneak/sfdupes/issues/7)
 - stamp the git tag or short commit in a plain `docker build .` instead of `dev`
  (2026-10-02, branch `next`, closes
  https://git.eeqj.de/sneak/sfdupes/issues/67): `.dockerignore` sends `.git`
  without `.git/config`; the build stage stamps the `VERSION` build argument,
  else `git describe --tags --always`, and fails if the context carries `.git`
  and the version is still empty, `dev` or `unknown`. CI checks out the full
  history (`fetch-depth: 0`) so it stamps the same value as `make build`.
 - replace the 1 KiB end-window sampling with the head/tail plus content-hash
  ladder (2026-09-22, branch `next`, closes
  https://git.eeqj.de/sneak/sfdupes/issues/61); README "Duplicate detection"
  documents every rung. A file under 10 MiB is hashed in full, and its `head`,
  `tail` and `content` all hold that hash. A larger file gets only its 64 KiB
  `head` and `tail` in the hash phase; the content phase, after the update
  phase, reads it for `content` (the whole file below 50 MiB, gigabyte-spaced 1
  MiB samples at or above) only when its size, `head` and `tail` match another
  record's from this scan or an earlier one, and never reads a file gone or
  changed since its record was written. `report` and `trees` leave out any
  record without a `content` hash. The `content` column is part of the version 1
  schema.
 - remove the dead `files.dat` references from `Makefile`, `.gitignore` and
  `.dockerignore` (2026-09-21, branch `next`, closes
  https://git.eeqj.de/sneak/sfdupes/issues/22)
 - fix the lint-image pin comments and `FROM` form in `Dockerfile` and
  `Dockerfile.lint` (2026-08-10, branch `next`, closes
-  https://git.eeqj.de/sneak/sfdupes/issues/25): both pins became the policy
+  https://git.eeqj.de/sneak/sfdupes/issues/25): dropped the false
-  `# image:vX.Y.Z, YYYY-MM-DD` comment over a bare `FROM image@sha256:...`,
+  `(Debian-based)` parenthetical (v2.12.1 was Debian too) and the
-  without the false `(Debian-based)` note or the tag. Since
+  redundant tag, so both pins are the policy `# image:vX.Y.Z,
-  https://git.eeqj.de/sneak/sfdupes/issues/95 the `Dockerfile`'s `lint` phase
+  YYYY-MM-DD` comment over a bare `FROM image@sha256:...`. Digest
-  holds the only golangci-lint pin, in that form, so `Dockerfile.lint` and
+  unchanged. `script/verify-lint-image-pin` parses those `FROM` lines
-  `script/verify-lint-image-pin`, which compared the two pins, are gone.
+  and still matches the tagless form; its advice line lost the now
  meaningless "tag and digest". With no tag in either reference, a
  tag-only disagreement no longer exists — a one-sided tag is caught as
  a plain mismatch.
- run all linting in Docker via `Dockerfile.lint` and `script/lint` (2026-08-10,
+- run all linting in Docker via `Dockerfile.lint` and `script/lint`
-  branch `next`, closes https://git.eeqj.de/sneak/sfdupes/issues/46): per the
+  (2026-08-10, branch `next`, closes
-  owner ruling the linter is never installed on a host, and
+  https://git.eeqj.de/sneak/sfdupes/issues/46): per the owner ruling, the
-  `golangci-lint config verify` runs before `golangci-lint run`.
+  linter runs inside a container invoked through the `script/`
-  `script/bootstrap` stopped installing or pinning the linter, and
+  entrypoint and is never installed on a host. New root
-  `script/verify-linter-pin` was retired. Since
+  `Dockerfile.lint` COPYs the repo into the digest-pinned
-  https://git.eeqj.de/sneak/sfdupes/issues/95 both commands run in the
+  `golangci/golangci-lint:v2.12.2` image and runs
-  `Dockerfile`'s `lint` phase, which `script/lint` builds alone and the build
+  `golangci-lint config verify` and `golangci-lint run` as build
-  stage depends on through `COPY --from=lint /src/go.sum /dev/null`;
+  steps, so a successful build IS a clean lint; `script/lint` is
-  `Dockerfile.lint` and `script/verify-lint-image-pin` are gone. Nothing inside
+  reduced to building it. `script/bootstrap` loses the `go install`,
-  an image build may run docker, so the phase calls `golangci-lint` directly.
+  the pin constants, the version parser and `verify_golangci_lint`
  outright rather than hardening them — with nothing linting on the
  host, the `$GOPATH/bin` versus `PATH` problem that motivated them has
  no subject — and now warns rather than fails when `docker` is absent.
  Two traps handled. A lint build on an unchanged tree returns success
  in well under a second having run no linter, which is
  https://git.eeqj.de/sneak/sfdupes/issues/32 and
  https://git.eeqj.de/sneak/sfdupes/issues/39 again, so
  `Dockerfile.lint` carries `ARG CHECK_EPOCH` referenced
  inside every gate `RUN` (BuildKit hashes the expanded command, not
  the declaration) and `script/lint` passes `"$(date +%s)-$$"` — the
  PID matters because two lint runs land inside the same second easily.
  And nothing inside an image build may shell out to docker, so the
  main `Dockerfile`'s lint stage now invokes `golangci-lint` directly
  instead of `make lint`, and its build stage runs `make test` and
  `make fmt-check` instead of the `make check` aggregate (`make`, not
  the scripts bare, because the Makefile's `export CGO_ENABLED = 0`
  only reaches what it invokes). `COPY --from=lint`
  `/usr/bin/golangci-lint` is replaced by
  `COPY --from=lint /src/go.sum /dev/null`: the copied binary was the
  only edge forcing BuildKit to finish linting before the build stage
  starts, and dropping it without replacing the edge would have ended
  fail-fast linting silently under a still-green build. That is
  canonical `REPO_POLICIES.md:107`'s ordering edge, restored.
  `ENV PATH=/home/builder/go/bin:$PATH` is gone with the `go install`
  that justified it. `script/verify-linter-pin` is retired, deleted
  along with its README entry, because both of its subjects ceased to
  exist in the same change: it compared a linter binary against
  `GOLANGCI_LINT_VERSION` in `script/bootstrap`, and there is now
  neither a binary crossing between stages nor a version pin in
  bootstrap. The drift it guarded has not gone away, it has moved — the
  linter is still pinned twice, now as the `FROM` line of
  `Dockerfile.lint` and the `FROM` line of the `Dockerfile` lint stage,
  with nothing syncing them, which is exactly what
  https://git.eeqj.de/sneak/sfdupes/issues/42 made a build failure. Its
  replacement is one new `script/verify-lint-image-pin`,
  run as a gate in both files, which compares the two references to
  each other and deliberately restates neither: a hardcoded expected
  digest would be a third copy and the same drift one file further out.
  `golangci-lint config verify` is included per the ruling, and the
  concern about its unpinned live HTTPS schema fetch was measured
  rather than assumed — under `--network none` the pinned binary both
  passes a valid config and rejects an invalid one with the jsonschema
  error, so it validates from an embedded schema and makes no network
  call of its own. The README scopes that to the gate steps rather
  than to linting as a whole: `Dockerfile.lint` runs `go mod download`
  above them, so a cold cache still needs the network and only a warm
  one lints offline. Verified: `make lint` green with every `PATH`
  directory containing a `golangci-lint` removed
  (`/home/user/go/bin`, `/home/user/.local/bin`, `/usr/local/bin`;
  `command -v golangci-lint` empty); two consecutive `script/lint` runs
  on an untouched tree both executed the linter, 27.7s and 28.7s in the
  lint step under distinct epochs with the `COPY . .` layer `CACHED`
  above them, at 42.2s and 41.8s wall clock — the no-cache rule was not
  weakened to shorten that. Negative control: a planted
  `var unusedIssue46Sentinel = 1` failed `script/lint` with
  `report.go:173:5: var unusedIssue46Sentinel is unused (unused)`, and
  failed `make docker` at `[lint 9/9]` with the build stage stopped at
  `[builder 3/12]` — `COPY --from=lint`, `script/bootstrap`, the test
  gate and `make build` all zero occurrences — then reverted clean. The
  drift guard fails on a tag-only disagreement, on a digest-only
  disagreement, and on an unreadable reference, naming both sides.
  `make docker` green in 5m35s with all six gates executing under one
  epoch (lint 37.6s, test 25.2s reporting
  `ok sneak.berlin/go/sfdupes 1.938s coverage: 88.5%`, not `(cached)`).
  The non-root quirk still holds: in the builder image with the Go test
  cache off, `--user 0:0` fails `TestScanHardlinkRunFailsTogether`
  (exit 1) where the unprivileged user passes (exit 0). Noted for
  follow-up, not fixed here: `golangci-lint` warns that the
  `gomodguard` linter is deprecated since v2.12.0 in favour of
  `gomodguard_v2`.
- install the Docker build stage's prerequisites by running `script/bootstrap`
+- install the Docker build stage's prerequisites by running
-  instead of `apk add --no-cache make` inline (2026-08-09, branch
+  `script/bootstrap` instead of `apk add --no-cache make` inline
-  `dockerfile-bootstrap`, closes https://git.eeqj.de/sneak/sfdupes/issues/42),
+  (2026-08-09, branch `dockerfile-bootstrap`, closes #42): canonical
-  with `script/verify-linter-pin` failing the build unless the linter copied
+  `REPO_POLICIES.md:97` requires it, and the inline install left the
-  from the lint stage was the version `script/bootstrap` pinned. Builds then
+  build stage maintaining its own notion of the toolchain — exactly
-  took up to 5m14s cold, mostly in a `chown -R` of the module cache, filed as
+  the divergence #24 exists to close, one layer down. The stage now
-  https://git.eeqj.de/sneak/sfdupes/issues/43. Since
+  copies `script/` plus `go.mod`/`go.sum` and runs `script/bootstrap`,
-  https://git.eeqj.de/sneak/sfdupes/issues/95 the build stage installs `git` and
+  which ends in `go mod download`, so the separate invocation of that
-  `make` with `apk add --no-cache` and only compiles; the `lint` and `test`
+  is gone. `COPY --from=lint /usr/bin/golangci-lint` stays, and moves
-  phases are the gates
+  above the bootstrap layer. It is the only edge making this stage
- bust the Docker layer cache for the gate steps, so `script/cibuild` and
+  depend on the lint stage, so deleting it as redundant would end
-  `script/docker` cannot report a green they did not earn (2026-08-09, branch
+  fail-fast linting silently. Letting bootstrap install its own linter
-  `cibuild-cache-bust`, closes https://git.eeqj.de/sneak/sfdupes/issues/32): the
+  here would have reintroduced the second toolchain and paid for a
-  `Dockerfile` copies the tree before its gates, so on an unchanged tree Docker
+  from-source build of it. What makes the two stages provably one
-  served them from cache and the build exited 0 having run nothing. The fix was
+  toolchain rather than two that happen to agree is a new
-  a `CHECK_EPOCH` build argument; since
+  `script/verify-linter-pin`, run in the build stage on the binary
-  https://git.eeqj.de/sneak/sfdupes/issues/95 every `docker build` in `script/`
+  that arrives from the lint stage, before bootstrap: it fails the
-  passes `--no-cache` instead. Run as root, the tests fail
+  build naming both versions unless that binary is the version
-  `TestScanHardlinkRunFailsTogether`, because root reads through the `chmod(0)`
+  `script/bootstrap` pins. Bootstrap's own check could not serve that
-  the test relies on, so the `test` phase runs them as `nobody`
+  purpose — it reinstalls its pin from source and then verifies
- check the installed golangci-lint version in `script/bootstrap` instead of
+  whatever `PATH` resolves, so drift self-heals silently and a lint
-  only its presence (2026-08-09, branch `bootstrap-version-check`, closes
+  stage image bumped on its own would lint at the new version while
-  https://git.eeqj.de/sneak/sfdupes/issues/24): the version lives only in
+  `make check` ran at the old one, green. The linter version is pinned
-  `GOLANGCI_LINT_VERSION`, with the `go install` module ref derived from it, and
+  in two independent places (the lint stage image digest and
-  any installed version that is not the pin — older, newer, absent or
+  `GOLANGCI_LINT_VERSION`) and nothing else keeps them in sync, so a
-  unparseable — is reinstalled. `go install` writes into `GOBIN` (or
+  half-applied bump is now a build failure. The pin is read out of
-  `GOPATH/bin`) while `make lint` runs the first `golangci-lint` on `PATH`, so
+  `script/bootstrap`, which stays the single source of truth; a pin
-  bootstrap re-reads the effective version after installing and, on a mismatch,
+  that cannot be read is a hard failure, not a skip. The check needs
-  prints both paths and both versions and exits non-zero; it does not reorder
+  no `CHECK_EPOCH`: its only inputs are the copied binary and
-  `PATH` or delete anyone's binary. The `--version` call keeps its stderr and is
+  `script/`, so Docker invalidates the layer exactly when a cached
-  bounded by `timeout(1)` where that exists. `git`, `make` and `go` keep
+  result would stop being true, and it is documented with the other
-  presence-only checks. Verified by bootstrapping this host from v2.10.1 to
+  entrypoints in the README. `$GOPATH/bin` joins `PATH` because
-  v2.12.2 and again to a no-op, and by stub runs of the script under `dash`
+  that is where bootstrap's `go install` lands and bootstrap verifies
-  covering a thirteen-input version-parse matrix, a shadowed install that must
+  its installs against what `PATH` resolves — nothing in the image is
-  exit non-zero, an install destination not on `PATH`, `GOBIN` set, and a wedged
+  shadowed by it, the directory does not exist until bootstrap runs.
-  binary that must hit the timeout; `make check` and `make lint` are clean at
+  Everything added sits above `ARG CHECK_EPOCH`, and the `chown` and
-  v2.12.2, so v2.10.1 was not hiding any findings on `main`
+  `USER builder` still precede `make check`. Verified: the guard fails
  the build with both versions named when the lint stage's linter is
  faked to a different version, and an unmodified build still passes
  it; bootstrap runs clean under Alpine's `sh` and its `apk` branch,
  installing `git` and `make` and finding the copied
  linter already at the pin; a second build served the bootstrap and
  dependency layers `CACHED` while both gates ran with a fresh epoch;
  a planted `unused` finding failed the build at the lint gate in
  48.9s with the build stage's `make check` never starting; and the
  suite run in the image as `--user 0:0` fails
  `TestScanHardlinkRunFailsTogether`, so the drop to the unprivileged
  user is still load-bearing. That last check needs the Go test cache
  disabled — the first attempt reported `ok ... (cached)` as root,
  reusing the result the build-time run had left in the shared cache,
  which would have read as a pass. Build wall time, on a shared host
  running many concurrent builds and so noisy: 2m13s on an unchanged
  tree, 2m17s and 4m29s for two builds after a source change, 5m14s
  cold. Only the cold one breaches the policy ceiling, and not because
  of this change — `chown -R builder:builder /src /home/builder` walks
  the module cache and re-runs on every source change, and it alone
  varied between 77s and 210s across those four builds, which is also
  the whole spread in the totals. The same cold measurement against
  `main` is 5m03s with a 209s `chown`. Filed as #43
 - bust the Docker layer cache for the gate steps, so `script/cibuild`
  and `script/docker` cannot report a green they did not earn
  (2026-08-09, branch `cibuild-cache-bust`, closes #32): both scripts
  were bare `docker build` invocations with no cache control, and the
  `Dockerfile` copies the tree before running its gates, so on an
  unchanged tree Docker served those layers from cache and the build
  exited 0 having executed nothing. That is not hypothetical here —
  every merge this repo has done is a non-fast-forward merge of an
  undiverged branch, so each merge commit's tree is byte-identical to
  the branch head's and each merge CI run was almost certainly a full
  cache hit; and PR #31's reviewer found `make docker` returning
  success as a 17-layer cache hit, catching it only by being
  suspicious. The fix is `ARG CHECK_EPOCH` with the scripts passing
  `--build-arg CHECK_EPOCH="$(date +%s)"`. Two details make or break
  it. `ARG` is scoped per stage and this `Dockerfile` has three gates
  across two — `make fmt-check` and `make lint` in the lint stage,
  `make check` in the build stage — so a single declaration would have
  left one stage silently cacheable; it is declared in both. And
  BuildKit hashes the expanded command, not the declaration, so a
  declared-but-unreferenced `ARG` invalidates nothing: each gate `RUN`
  echoes the epoch, which also puts the value in the build log as
  evidence the layer really ran. Placement is below the dependency
  layers on purpose — a build that goes cold every time would be a
  different bug, not a fix. Verified by running each script twice back
  to back on an unchanged tree under `BUILDKIT_PROGRESS=plain`: all
  three gates executed on all four runs, each with a fresh epoch in
  the log (`script/cibuild` 78.8s then 61.1s; `script/docker` 61.1s
  then 53.4s), and twelve steps were still served `CACHED` in the
  steady state — both `go mod download`s, `apk add`, `adduser`, the
  `chown`, every `go.mod`/`go.sum` and source copy, the linter copy
  out of the lint stage, and the binary copy into the runtime stage.
  The lint stage still gates the build stage: with a deliberate
  `unused` finding planted in the tree, the build failed at
  `make lint` in 36.1s and the build-stage `make check` never started.
  The build stage also still drops to the unprivileged `builder` user
  before `make check`, which the suite depends on rather than merely
  prefers: forcing the same image to run the tests as root fails
  `TestScanHardlinkRunFailsTogether`, because root reads straight
  through the `chmod(0)` the test uses to prove hard links are read
  once. This is the local fix only; propagating it to the canonical
  templates is `prompts` #26
 - check the installed golangci-lint version in `script/bootstrap`
  instead of only its presence (2026-08-09, branch
  `bootstrap-version-check`, closes #24): `missing golangci-lint` meant
  any linter already on `PATH` satisfied the check, so the pin was never
  consulted and the v2.12.2 bump from #3 was inert on every host that
  already had one — this host ran v2.10.1 against a v2.12.2 pin,
  `make check` went green, and `make docker` then rejected the same
  commit with findings the local gate never saw. The version now lives
  in one place, `GOLANGCI_LINT_VERSION`, with the `go install` module
  ref derived from it so a bump cannot half-apply; a
  `golangci_lint_version` helper parses `golangci-lint --version`
  (taking the field after the word `version` and tolerating an optional
  leading `v`, which the module ref carries and the binary's output does
  not), and any version that is not the pin — older, newer, absent or
  unparseable — is reinstalled. The install is then verified against the
  binary `PATH` actually resolves: `go install` writes into `GOBIN` (or
  `GOPATH/bin`) while `make lint` runs whichever `golangci-lint` comes
  first on `PATH`, so a wrong-version one sitting ahead of it — nix,
  apt, brew, apk, or the `/usr/local/bin` copy the `Dockerfile` builder
  stage makes — would swallow the install and leave the local gate
  disagreeing with CI under an affirmative `bootstrap complete`.
  Bootstrap now re-reads the effective version after installing and, on
  a mismatch, prints both paths and both versions to stderr and exits
  non-zero instead of claiming success; it does not reorder anyone's
  `PATH` or delete their binary. The `--version` call keeps its stderr
  connected, so a present-but-broken binary says why rather than
  reinstalling forever in silence, and is bounded by `timeout(1)` where
  that exists, so a wedged binary cannot hang bootstrap. `git`, `make`
  and `go` keep their presence-only checks and now say why in a
  comment: they are host package-manager tools the repo deliberately
  does not pin, with `go.mod` governing the language version and the
  digest-pinned images covering reproducible builds. Verified on this
  host by bootstrapping from v2.10.1 to v2.12.2 and running it again to
  a no-op, plus stub runs of the real script under `dash` covering a
  thirteen-input parse matrix (absent, older, newer, host-style,
  image-style, leading-`v`, stderr-only, empty, non-zero exit, impostor
  binary, `(devel)`, trailing `version`), a shadowed install that must
  exit non-zero, an install destination not on `PATH` at all, `GOBIN`
  set, and a wedged binary that must hit the timeout; `make check` and
  `make lint` are clean at v2.12.2, so v2.10.1 was not hiding any
  findings on `main`
 - unwind the hash worker pool on the error path (2026-08-09, branch
-  `hash-pool-cleanup`, closes https://git.eeqj.de/sneak/sfdupes/issues/6): the
+  `hash-pool-cleanup`, closes #6): `hashPhase` used to return the
-  pool is now an owned, context-aware `hashPool`: every blocking send in the
+  moment `recordRun` failed and abandon the pool — the feeder parked
-  feeder and the workers selects on `ctx.Done()`, `jobs` is closed on every path
+  forever on a full `jobs` channel and every worker on a full
-  out, and `hashPhase` defers `pool.stop()`, which cancels and then drains
+  `results` channel. That only stopped being invisible when #4 landed
-  `results` until the last goroutine has exited — draining is what frees a
+  and `runScan` began unwinding instead of calling `os.Exit`. The
-  worker already parked on a send. `ctx` is threaded from `cmd.Context()`
+  pool is now an owned, context-aware `hashPool`: every blocking send
-  through `runScan`, `syncScan`, both worker pools and the whole database layer,
+  in the feeder and the workers selects on `ctx.Done()`, `jobs` is
-  as the first parameter everywhere. The walk pool gets the same treatment plus
+  closed on every path out, and `hashPhase` defers `pool.stop()`,
-  a `ctx.Err()` guard after the walk: a cancelled walk yields a partial size
+  which cancels and then drains `results` until the last goroutine
-  census, and every file it never reached looks vanished to the update phase.
+  has exited — draining is what frees a worker already parked on a
-  That phase's own `BeginTx` also fails on the cancelled context before deleting
+  send. `ctx` is threaded from `cmd.Context()` through `runScan`,
-  anything, but the guard is the barrier that still holds once an interrupted
+  `syncScan`, both worker pools and the whole database layer (it is
-  scan may commit what it has. Tests drive `run(scan)` against a database whose
+  the first parameter everywhere), so #5 can hand this path a signal
-  insert trigger aborts and assert that the scan fails instead of hanging and
+  and needs to add nothing else. The walk pool never leaked, because
-  that `runtime.NumGoroutine()` polls back to its pre-scan baseline; others
+  `walkPhase` always drains its events to close, but it has the same
-  cancel a scan part-way through the walk, deterministically, by counting its
+  unbounded-send shape and #5 will give it an early return, so it
-  own consultations of `ctx.Done()`, and assert that it stops at the guard
+  gets the same treatment plus a `ctx.Err()` guard after the walk: a
-  holding a partial census and a still-populated record index, with every record
+  cancelled walk yields a partial size census, and every file it never
-  intact. Direct tests of `sendEvent`, the walk workers, `dispatchDirs`,
+  reached looks vanished to the update phase. That phase's own
-  `feedHashJobs`, `hashWorker` and `hashPhase` cover the remaining cancellation
+  `BeginTx` fails on the same cancelled context before deleting
-  branches of both pools
+  anything, so the guard is defence in depth rather than the only
- guarantee the database is closed on every fatal exit path (2026-08-09, branch
+  barrier — but it is the one that survives #5 deciding an interrupted
-  `db-close-on-fatal`, closes https://git.eeqj.de/sneak/sfdupes/issues/4):
+  scan may commit what it has. Tests drive `run(scan)` against a
-  `fatalf` and its `os.Exit(1)` are gone, so the deferred `db.Close()` — and
+  database whose insert trigger aborts, and assert both that the scan
-  with it the SQLite WAL checkpoint — now actually runs when a subcommand fails;
+  fails instead of hanging and that `runtime.NumGoroutine()` polls
-  `runScan`, `runReport`, `runTrees`, `loadRecords` and `resolveRoots` return
+  back to its pre-scan baseline; a second set cancels a scan part-way
-  errors instead. The single exit point is `run` in `main.go`: it maps a
+  through the walk — deterministically, by counting the scan's own
-  `fatalError` (anything a subcommand returned) to exit 1 and cobra's own
+  consultations of `ctx.Done()` rather than racing a timer — and
-  argument and flag errors to exit 2, which keeps a runtime failure from being
+  asserts that it stops at the guard holding a partial census and a
-  reported as a usage error or printing the usage text. New `main_test.go`
+  still-populated record index, with every record intact. The
-  drives the CLI in-process and asserts the exit codes from README §Error
+  remaining cancellation branches of both pools are covered by direct
-  handling plus the stdout/stderr split, including that a fatal error raised
+  tests of `sendEvent`, the walk workers, `dispatchDirs`,
-  after the database is open leaves no `-wal`/`-shm` sidecar behind for `scan`,
+  `feedHashJobs`, `hashWorker` and `hashPhase`
-  `report` or `trees`
+- guarantee the database is closed on every fatal exit path
- update golangci-lint to v2.12.2 with the canonical config (2026-08-09, branch
+  (2026-08-09, branch `db-close-on-fatal`, closes #4): `fatalf` and
-  `golangci-v2.12.2`, merged as `38a01bd`, closes
+  its `os.Exit(1)` are gone, so the deferred `db.Close()` — and with
-  https://git.eeqj.de/sneak/sfdupes/issues/3): bumped the pinned linter in the
+  it the SQLite WAL checkpoint — now actually runs when a subcommand
-  `Dockerfile` lint stage and `script/bootstrap` from v2.12.1 to v2.12.2, and
+  fails; `runScan`, `runReport`, `runTrees`, `loadRecords` and
-  replaced `.golangci.yml` with the canonical file — the linter settings (`lll`,
+  `resolveRoots` return errors instead. The single exit point is `run`
-  `funlen`, `cyclop`, `dupl` thresholds) now live under `linters.settings` per
+  in `main.go`: it maps a `fatalError` (anything a subcommand
-  the v2 schema, so they are actually applied; no new lint findings surfaced
+  returned) to exit 1 and cobra's own argument and flag errors to exit
- convert Makefile targets to scripts-to-rule-them-all `script/` entrypoints
+  2, which keeps a runtime failure from being reported as a usage
-  like the other managed repos (2026-07-26, commit `3abeacf`, closes
+  error or printing the usage text. New `main_test.go` drives the CLI
-  https://git.eeqj.de/sneak/sfdupes/issues/1): all 12 `script/` entrypoints
+  in-process and asserts the exit codes from README §Error handling
-  exist (`bootstrap`, `setup`, `projectname`, `test`, `lint`, `fmt`,
+  plus the stdout/stderr split, including that a fatal error raised
-  `fmt-check`, `check`, `docker`, `cibuild`, `precommit`, `install-precommit`)
+  after the database is open leaves no `-wal`/`-shm` sidecar behind
-  and every Makefile target is now a thin shim over them
+  for `scan`, `report` or `trees`
 - update golangci-lint to v2.12.2 with the canonical config
  (2026-08-09, branch `golangci-v2.12.2`, merged as `38a01bd`,
  closes #3): bumped the pinned linter in the `Dockerfile` lint
  stage and `script/bootstrap` from v2.12.1 to v2.12.2, and replaced
  `.golangci.yml` with the canonical file — the linter settings
  (`lll`, `funlen`, `cyclop`, `dupl` thresholds) now live under
  `linters.settings` per the v2 schema, so they are actually
  applied; no new lint findings surfaced
 - convert Makefile targets to scripts-to-rule-them-all `script/`
  entrypoints like the other managed repos (2026-07-26, commit
  `3abeacf`, closes #1): all 12 `script/` entrypoints exist
  (`bootstrap`, `setup`, `projectname`, `test`, `lint`, `fmt`,
  `fmt-check`, `check`, `docker`, `cibuild`, `precommit`,
  `install-precommit`) and every Makefile target is now a thin shim
  over them, matching the other managed repos
 - make the binary the default Make target (2026-07-24, branch
-  `make-default-target`): plain `make` now builds `sfdupes` (previously it ran
+  `make-default-target`): plain `make` now builds `sfdupes`
-  `check` plus `build`); `make build` remains as an alias
+  (previously it ran `check` plus `build`); `make build` remains as
- scan-wide phases, concurrent operands, batched updates (2026-07-24, branch
+  an alias
-  `scan-wide-phases`): all operands seed the shared walk pool and every pass
+- scan-wide phases, concurrent operands, batched updates (2026-07-24,
-  runs once over the whole scan, so totals and ETAs are scan-global; the
+  branch `scan-wide-phases`): all operands seed the shared walk pool
-  per-operand walk/hash/update cycles and their stderr announcements are gone;
+  and every pass runs once over the whole scan, so totals and ETAs
-  the update pass commits in batched transactions — the filesystem is
+  are scan-global; the per-operand walk/hash/update cycles and their
-  authoritative and the database an eventually-consistent reflection, so
+  stderr announcements are gone; the update pass commits in batched
-  scan-level atomicity is not required
+  transactions — the filesystem is authoritative and the database an
  eventually-consistent reflection, so scan-level atomicity is not
  required
 - split the stat pass back out of the walk (2026-07-24, branch
-  `parallel-phases`): phases are strictly sequential again — walk, stat, hash,
+  `parallel-phases`): phases are strictly sequential again — walk,
-  update per operand — with parallelism only inside each phase; the walk
+  stat, hash, update per operand — with parallelism only inside each
-  enumerates paths with per-directory workers and the stat pass lstats them with
+  phase; the walk enumerates paths with per-directory workers and the
-  per-file workers, restoring the exact total/ETA stat bar
+  stat pass lstats them with per-file workers, restoring the exact
- announce each operand on stderr before its passes (2026-07-24, branch
+  total/ETA stat bar
-  `scan-operand-progress`): with per-operand walk/hash/update cycles, a
+- announce each operand on stderr before its passes (2026-07-24,
-  multi-operand run (e.g. `scan /srv/*`) showed pass totals that looked like the
+  branch `scan-operand-progress`): with per-operand walk/hash/update
-  whole run's
+  cycles, a multi-operand run (e.g. `scan /srv/*`) showed pass totals
- parallel walk (2026-07-24, branch `parallel-walk`): the walk pass was a single
+  that looked like the whole run's — an operator watching operand 3 of
-  goroutine and took hours at ~20M files on a busy pool (observed: 22M files in
+  14 hash 300k files concluded 20M files were being skipped
-  4h on a ZFS server); it is now a per-directory worker-pool traversal that
+- parallel walk (2026-07-24, branch `parallel-walk`): the walk pass
-  records size/mtime during the walk (folding away the separate stat pass,
+  was a single goroutine and took hours at ~20M files on a busy pool
-  halving metadata I/O), and each `PATH` operand commits in its own transaction
+  (observed: 22M files in 4h on a ZFS server); it is now a
-  so an interrupted scan keeps completed operands
+  per-directory worker-pool traversal that records size/mtime during
  the walk (folding away the separate stat pass, halving metadata
  I/O), and each `PATH` operand commits in its own transaction so an
  interrupted scan keeps completed operands
- persistent scan database (2026-07-24, branch `persistent-database`): `scan`
+- persistent scan database (2026-07-24, branch `persistent-database`):
-  now maintains a SQLite database (`modernc.org/sqlite`, pure Go, cgo stays
+  `scan` now maintains a SQLite database (`modernc.org/sqlite`, pure
-  disabled) keyed by absolute path that survives between runs — a rescan hashes
+  Go, cgo stays disabled) keyed by absolute path that survives between
-  only new or changed files (by mtime/size), deletes records for files vanished
+  runs — a rescan hashes only new or changed files (by mtime/size),
-  from under the scanned operands, and leaves records outside them untouched, so
+  deletes records for files vanished from under the scanned operands,
-  `scan` can be cronned daily; `report` and `trees` read the database (no
+  and leaves records outside them untouched, so `scan` can be cronned
-  positional arguments) instead of a scan stream. Database at
+  daily; `report` and `trees` read the database (no positional
-  `/var/lib/sfdupes/db.sqlite`, overridable via `SFDUPES_DATABASE`; WAL
+  arguments) instead of a scan stream. Database at
-  journaling plus a single-transaction update keep a report run during a scan
+  `/var/lib/sfdupes/db.sqlite`, overridable via `SFDUPES_DATABASE`;
-  safe
+  WAL journaling plus a single-transaction update keep a report run
- add the `origin` remote (`git@git.eeqj.de:sneak/sfdupes.git`), tag `v0.0.1`,
+  during a scan safe
-  and push `main` plus tags (2026-07-23)
+- add the `origin` remote (`git@git.eeqj.de:sneak/sfdupes.git`), tag
  `v0.0.1`, and push `main` plus tags (2026-07-23)
 - `scan` CLI rework (2026-07-23, branch `scan-required-paths`): required
-  `PATH...` operands via cobra flags replacing the `/srv` `-root` default; new
+  `PATH...` operands via cobra flags replacing the `/srv` `-root`
-  `-x`/`--one-file-system` flag (GNU convention) to stop at filesystem
+  default; new `-x`/`--one-file-system` flag (GNU convention) to stop
-  boundaries, which are crossed by default
+  at filesystem boundaries, which are crossed by default
 - bring the repo into full policy compliance (2026-07-23, branch
  `repo-policy-compliance`; checklist below)
- `git init` with README-only first commit; code baseline committed on `main`
+- `git init` with README-only first commit; code baseline committed on
-  (2026-07-22)
+  `main` (2026-07-22)
 - implement `scan`, `report`, and `trees` subcommands (pre-git history)
 # Future Steps
- possible later features (explicitly out of scope per README): full-content
+- possible later features (explicitly out of scope per README):
-  verification of candidates, removal-script helpers
+  full-content verification of candidates, removal-script helpers
 # Repo Policy Compliance
-Audited 2026-07-22 against `REPO_POLICIES.md` (2026-07-06), the existing repo
+Audited 2026-07-22 against `REPO_POLICIES.md` (2026-07-06), the existing
-checklist, and the Go styleguide. Code is already gofmt-clean, so no standalone
+repo checklist, and the Go styleguide. Code is already gofmt-clean, so no
-formatting commit is needed.
+standalone formatting commit is needed.
- [x] `.gitignore` missing — the compiled `sfdupes` binary and `files.dat` sit
+- [x] `.gitignore` missing — the compiled `sfdupes` binary and
-      untracked in the tree; needs OS/editor/Go artifacts plus secrets patterns
+      `files.dat` sit untracked in the tree; needs OS/editor/Go
      artifacts plus secrets patterns
 - [x] `.editorconfig` missing
- [x] `LICENSE` missing and README has no License section (MIT assumed from
+- [x] `LICENSE` missing and README has no License section (MIT assumed
-      house convention — user to confirm)
+      from house convention — user to confirm)
 - [x] `REPO_POLICIES.md` missing from repo root
- [x] `.golangci.yml` missing (install canonical copy); code must then pass
+- [x] `.golangci.yml` missing (install canonical copy); code must then
-      `make lint` (150 findings fixed; `make lint` is clean)
+      pass `make lint` (150 findings fixed; `make lint` is clean)
- [x] `Makefile` lacks required targets `test`, `lint`, `fmt`, `fmt-check`,
+- [x] `Makefile` lacks required targets `test`, `lint`, `fmt`,
-      `docker`, `hooks`; `check` currently depends on `build`, which writes the
+      `fmt-check`, `docker`, `hooks`; `check` currently depends on
-      binary (`make check` must not modify files)
+      `build`, which writes the binary (`make check` must not modify
- [x] no tests — `go test ./...` has nothing to run; policy requires real tests
+      files)
-      with a 30-second timeout and the conditional `-v` rerun pattern (suite
+- [x] no tests — `go test ./...` has nothing to run; policy requires
-      covers parsing, grouping, digests, suppression, hashing, and the scan
+      real tests with a 30-second timeout and the conditional `-v`
-      pipeline; 64% coverage)
+      rerun pattern (suite covers parsing, grouping, digests,
- [x] `Dockerfile` missing — Go multistage with hash-pinned images: fail-fast
+      suppression, hashing, and the scan pipeline; 64% coverage)
-      lint stage, build stage running `make check`
+- [x] `Dockerfile` missing — Go multistage with hash-pinned images:
      fail-fast lint stage, build stage running `make check`
 - [x] `.dockerignore` missing
- [x] `.gitea/workflows/check.yml` missing (`docker build .` on push, checkout
+- [x] `.gitea/workflows/check.yml` missing (`docker build .` on push,
-      action pinned by commit SHA)
+      checkout action pinned by commit SHA)
 - [x] README lacks required sections: Description first line
-      (name/purpose/category/license/author), Getting Started, Rationale, TODO,
+      (name/purpose/category/license/author), Getting Started,
-      License, Author
+      Rationale, TODO, License, Author
- [x] README non-goal "no git repository setup and no CI" is stale now that the
+- [x] README non-goal "no git repository setup and no CI" is stale now
-      repo is under git with CI
+      that the repo is under git with CI
- [x] pre-commit hook not installed (`make hooks` once the target exists)
+- [x] pre-commit hook not installed (`make hooks` once the target
      exists)
 Accepted divergences (no action):
- flat single-package layout with `.go` files in the repo root — fine for a
+- flat single-package layout with `.go` files in the repo root — fine
-  small single-binary tool per the Go styleguide; the tracker audit agrees
+  for a small single-binary tool per the Go styleguide; the tracker
  audit agrees
 - `go test` runs without `-race` — the repo mandates `CGO_ENABLED=0`
  (pure-Go builds) and the race detector requires cgo
@@ -4,35 +4,20 @@ import (
 	"context"
 	"database/sql"
 	"errors"
 	"fmt"
 	"os"
 	"os/signal"
 	"path/filepath"
 	"slices"
 	"strconv"
 	"strings"
 	"sync"
 	"sync/atomic"
 	"syscall"
 	"testing"
 	"time"
 )
-// This file gathers the tests for scan cancellation and worker-pool
+// poolUnwind bounds how long a goroutine is given to leave a pool
-// unwinding. Everything it exercises lives in scan.go, so by the repo's
+// after its context is cancelled. Only a failing run ever waits this
-// convention of one test file per source file it would belong in
+// long: a pool that ignored its cancellation parks forever, and this
-// scan_test.go. It is kept separate on purpose: cancellation behaviour
+// is what turns that into a failed assertion instead of a suite that
-// cuts across both the walk pool and the hash pool as a single concern,
+// hangs until the test binary's own timeout.
 // and scan_test.go is already over 1,600 lines. That is the deliberate
 // exception the convention otherwise expects to be stated.
 // poolUnwind bounds how long a test waits for a cancellation to take
 // effect: for a goroutine to return or a channel to close once its
 // context is cancelled, or for a signal to cancel the scan's context.
 // Only a failing run waits this long, and the bound is what makes that
 // failure an assertion instead of a hang. A call made without it, as
 // most of this file's scans are, has no bound: a regression that parks
 // it is caught only as the test binary's own timeout.
 const poolUnwind = 2 * time.Second
 // walkClock is a context whose cancellation is driven by the scan's
@@ -43,14 +28,9 @@ const poolUnwind = 2 * time.Second
 //
 // The accounting behind the n chosen by each test: every blocking
 // channel operation in the walk selects on Done, so the walk spends
-// one consultation per file event plus a couple per directory. The
+// one consultation per file event plus a couple per directory, while
-// index load that runs ahead of it also consults Done, but a bounded
+// the index load that runs ahead of it spends a small fixed number
-// number of times that does not grow with the record count. The tests
+// (three) whatever the record count.
 // depend on that property, not on the bound's exact value: each test
 // sets n from the consultations of the walk, plus those of the hash
 // phase when it cancels mid-hash, far from both ends of the phase it
 // interrupts, so the cancellation lands inside that phase whatever the
 // record count.
 type walkClock struct {
 	n    int64
 	seen atomic.Int64
@@ -110,10 +90,7 @@ const (
 	walkCancelFilesPerDir  = 20
 	walkCancelFiles        = walkCancelDirs * walkCancelFilesPerDir
 	walkCancelWorkers      = 4
-	// The most files the walkCancelWorkers directories already in
+	walkCancelInFlightDirs = walkCancelWorkers * walkCancelFilesPerDir
 	// flight when the scan is cancelled can still emit, at
 	// walkCancelFilesPerDir each. A file count, not a directory count.
 	walkCancelInFlightFiles = walkCancelWorkers * walkCancelFilesPerDir
 )
 // walkCancelAtDone is the consultation on which the fixture's context
@@ -173,13 +150,9 @@ func assertRecordsIntact(t *testing.T, db *sql.DB, before []string) {
 // Every one of those records would look vanished to the update phase.
 // The guard is what stops the scan there, and this test is what
 // notices if it stops doing so: deleting the guard, or making it
-// unreachable, makes the scan carry its truncated view into the update
+// unreachable, makes the scan carry its truncated view into a later
-// phase, which counts every record the walk never reached for removal.
+// phase and fail there instead, with a wrapped error rather than the
-//
+// bare cancellation.
 // The syncScan call here is not bounded by poolUnwind: a regression
 // that left a worker pool parked would hang it, and that regression is
 // caught only by the test binary's own timeout, not by a quick
 // assertion.
 //
 //nolint:paralleltest // counts goroutines: must not run beside others
 func TestSyncScanCancelledMidWalkKeepsRecords(t *testing.T) {
@@ -209,10 +182,10 @@ func TestSyncScanCancelledMidWalkKeepsRecords(t *testing.T) {
 // assertWalkGuardAborted checks that the scan stopped at the post-walk
 // guard: with a census that is neither empty (the walk really ran)
-// nor complete (it really was cut short), and with no record counted
+// nor complete (it really was cut short), and with the guard's own
-// for removal. A removal count means the partial census was carried
+// bare cancellation as the error. A wrapped error means the partial
-// past the guard into the update phase, which is the failure this test
+// census was carried past the guard into the hash or update phase,
-// exists to catch.
+// which is the failure this test exists to catch.
 func assertWalkGuardAborted(t *testing.T, st scanStats, err error) {
 	t.Helper()
@@ -221,6 +194,12 @@ func assertWalkGuardAborted(t *testing.T, st scanStats, err error) {
 			err, context.Canceled)
 	}
 	if errors.Unwrap(err) != nil {
 		t.Errorf("syncScan reported %q, want the guard's bare "+
 			"cancellation: a wrapped error means the truncated census "+
 			"reached a later phase", err)
 	}
 	if st.unchanged == 0 {
 		t.Fatalf("stats = %+v: the census is empty, so the walk never "+
 			"ran and the guard was reached for the wrong reason", st)
@@ -232,11 +211,10 @@ func assertWalkGuardAborted(t *testing.T, st scanStats, err error) {
 	}
 	// The workers drop every directory still queued once the scan is
-	// cancelled, so only the files in the directories already in flight
+	// cancelled, so only the directories already in flight can add to
-	// can add to the census after the fact. A census beyond that bound
+	// the census after the fact. A census beyond that bound would mean
-	// would mean the cancellation was not observed where it should have
+	// the cancellation was not observed where it should have been.
-	// been.
+	limit := walkCancelAtDone + walkCancelInFlightDirs
 	limit := walkCancelAtDone + walkCancelInFlightFiles
 	if st.unchanged > limit {
 		t.Errorf("census covers %d files, want at most %d: the walk kept "+
 			"taking directories off the queue after cancellation",
@@ -282,252 +260,6 @@ func TestSyncScanCancelledBeforeLoadIndex(t *testing.T) {
 	assertRecordsIntact(t, db, before)
 }
 // hashCancelAtDone is the consultation on which the mid-hash test's
 // context cancels itself. The walk of buildWalkCancelTree spends about
 // one per file and three per directory, and the hash phase then one per
 // file hashed, so this lands about half way through the hash phase.
 const hashCancelAtDone = walkCancelFiles + 3*walkCancelDirs +
 	walkCancelFiles/2
 // TestSyncScanCancelledMidHashKeepsHashedRecords cancels a first scan
 // part-way through its hash phase. The fixture holds fewer files than a
 // batch, so every file hashed is still waiting to be committed: the scan
 // must commit them all before it returns, and the next scan must hash
 // only the rest.
 func TestSyncScanCancelledMidHashKeepsHashedRecords(t *testing.T) {
 	t.Parallel()
 	dir := buildWalkCancelTree(t)
 	db := openTestDB(t)
 	st, err := syncScan(newWalkClock(hashCancelAtDone), db,
 		[]string{dir}, walkCancelWorkers, false)
 	if !errors.Is(err, context.Canceled) {
 		t.Fatalf("syncScan cancelled mid-hash = %v, want %v",
 			err, context.Canceled)
 	}
 	if st.walked != walkCancelFiles || st.added == 0 ||
 		st.added >= walkCancelFiles {
 		t.Fatalf("stats = %+v: want the walk complete and the hash phase "+
 			"cut short", st)
 	}
 	if got := len(dbRecords(t, db)); got != st.added {
 		t.Errorf("%d records after the cancelled scan, want the %d it hashed",
 			got, st.added)
 	}
 	hashed := st.added
 	st = syncTree(t, db, dir)
 	if st.added != walkCancelFiles-hashed || st.unchanged != hashed {
 		t.Errorf("next scan stats = %+v, want %d added %d unchanged",
 			st, walkCancelFiles-hashed, hashed)
 	}
 }
 // storedPaths opens the database at path as report does, which fails
 // unless it is a valid database, and returns its records' paths.
 func storedPaths(t *testing.T, path string) []string {
 	t.Helper()
 	db, err := openReportDatabase(t.Context(), path)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer func() { _ = db.Close() }()
 	return recordPaths(dbRecords(t, db))
 }
 // TestRunScanInterrupted calls the scan entrypoint with a context that
 // is already cancelled, as when a signal arrives at once. It must return
 // errInterrupted promptly with its one line on stderr and nothing on
 // stdout, leave the database valid and as it was, and leave nothing in
 // the way of the next scan, which must bring the database up to date.
 func TestRunScanInterrupted(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	stdout := captureStdout(t)
 	stderr := captureStderr(t)
 	dir := buildSmokeTree(t)
 	err := runScan(t.Context(), []string{dir}, walkCancelWorkers, false)
 	if err != nil {
 		t.Fatal(err)
 	}
 	before := storedPaths(t, path)
 	// A vanished file and a new one: the interrupted scan records
 	// neither.
 	gone := filepath.Join(dir, "a", "unique.bin")
 	err = os.Remove(gone)
 	if err != nil {
 		t.Fatal(err)
 	}
 	added := writeFile(t, dir, "a/new.bin", pattern(50, 10))
 	shown := len(stderr())
 	done := make(chan struct{})
 	go func() {
 		defer close(done)
 		err = runScan(cancelledContext(t), []string{dir}, walkCancelWorkers,
 			false)
 	}()
 	awaitReturn(t, done, "runScan")
 	if !errors.Is(err, errInterrupted) {
 		t.Fatalf("runScan on a cancelled context = %v, want %v",
 			err, errInterrupted)
 	}
 	want := "scan: interrupted after 0 files\n"
 	if got := stderr()[shown:]; got != want {
 		t.Errorf("stderr = %q, want %q", got, want)
 	}
 	if got := stdout(); got != "" {
 		t.Errorf("stdout = %q, want nothing (data only)", got)
 	}
 	assertNoSidecars(t, path)
 	if got := storedPaths(t, path); !slices.Equal(got, before) {
 		t.Errorf("records = %q after the interrupted scan, want %q",
 			got, before)
 	}
 	err = runScan(t.Context(), []string{dir}, walkCancelWorkers, false)
 	if err != nil {
 		t.Fatal(err)
 	}
 	got := storedPaths(t, path)
 	if slices.Contains(got, gone) || !slices.Contains(got, added) {
 		t.Errorf("records = %q after the next scan, want %q gone and %q "+
 			"added", got, gone, added)
 	}
 }
 // TestRunScanInterruptedMidHash interrupts the scan entrypoint part-way
 // through its hash phase, after the database is open. It must return
 // errInterrupted, release the lock, end stderr with its line counting
 // every file the walk reached, write nothing to stdout, close the
 // database out of WAL mode, and keep the records it hashed.
 func TestRunScanInterruptedMidHash(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	stdout := captureStdout(t)
 	stderr := captureStderr(t)
 	dir := buildWalkCancelTree(t)
 	err := runScan(newWalkClock(hashCancelAtDone), []string{dir},
 		walkCancelWorkers, false)
 	if !errors.Is(err, errInterrupted) {
 		t.Fatalf("runScan interrupted mid-hash = %v, want %v",
 			err, errInterrupted)
 	}
 	holdScanLock(t, path)
 	want := fmt.Sprintf("scan: interrupted after %d files\n", walkCancelFiles)
 	if got := stderr(); !strings.HasSuffix(got, want) {
 		t.Errorf("stderr = %q, want it to end with %q", got, want)
 	}
 	if got := stdout(); got != "" {
 		t.Errorf("stdout = %q, want nothing (data only)", got)
 	}
 	assertNoSidecars(t, path)
 	db, err := openReportDatabase(t.Context(), path)
 	if err != nil {
 		t.Fatal(err)
 	}
 	defer func() { _ = db.Close() }()
 	// A plain close also removes the sidecars, but leaves WAL mode on.
 	var mode string
 	err = db.QueryRowContext(t.Context(), "PRAGMA journal_mode").Scan(&mode)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if mode != "delete" {
 		t.Errorf("journal mode = %q after the interrupted scan, want %q",
 			mode, "delete")
 	}
 	kept := len(dbRecords(t, db))
 	if kept == 0 || kept >= walkCancelFiles {
 		t.Errorf("%d records after the interrupted scan, want those it "+
 			"hashed: some but not all of the %d files", kept, walkCancelFiles)
 	}
 }
 // TestInterruptContextCatchesSIGTERM sends SIGTERM to the test process
 // while the scan's handler is installed, and checks that it cancels the
 // scan's context.
 //
 //nolint:paralleltest // signals the whole process: must not run beside a scan
 func TestInterruptContextCatchesSIGTERM(t *testing.T) {
 	// Caught here as well, so that a handler that misses SIGTERM fails
 	// this test instead of ending the test process.
 	caught := make(chan os.Signal, 1)
 	signal.Notify(caught, syscall.SIGTERM)
 	defer signal.Stop(caught)
 	ctx, stop := interruptContext(t.Context())
 	defer stop()
 	err := syscall.Kill(os.Getpid(), syscall.SIGTERM)
 	if err != nil {
 		t.Fatal(err)
 	}
 	select {
 	case <-ctx.Done():
 	case <-time.After(poolUnwind):
 		t.Fatal("SIGTERM did not cancel the scan's context")
 	}
 }
 // TestCommitFullBatchKeepsFailedBatch checks that a full batch whose
 // commit fails, as it does once the scan is interrupted, stays in the
 // batch, so that syncScan's final commit saves it.
 func TestCommitFullBatchKeepsFailedBatch(t *testing.T) {
 	t.Parallel()
 	s := &scanState{db: openTestDB(t)}
 	for i := range updateBatchSize {
 		s.batch = append(s.batch, scanRec{path: "/f" + strconv.Itoa(i)})
 	}
 	err := s.commitFullBatch(cancelledContext(t))
 	if !errors.Is(err, context.Canceled) {
 		t.Fatalf("commitFullBatch on a cancelled context = %v, want %v",
 			err, context.Canceled)
 	}
 	if len(s.batch) != updateBatchSize {
 		t.Errorf("batch holds %d records after the failed commit, want %d",
 			len(s.batch), updateBatchSize)
 	}
 }
 // drainClosed counts the values received from ch until it closes,
 // failing the test if it does not close within poolUnwind. A pool that
 // ignored its cancellation leaves its channel open with its goroutines
@@ -596,49 +328,20 @@ func TestSendEventAbandonsBlockedSend(t *testing.T) {
 	awaitReturn(t, done, "sendEvent")
 }
 // TestWalkOneDirStopsWhenCancelled checks that a cancelled scan stops
 // reading a directory instead of going through the rest of its
 // entries. A walk that kept going would return the subdirectory below
 // to descend into. Unlike a file event, that return is not a send the
 // cancellation can abandon, so the test catches the regression every
 // time.
 func TestWalkOneDirStopsWhenCancelled(t *testing.T) {
 	t.Parallel()
 	dir := t.TempDir()
 	err := os.Mkdir(filepath.Join(dir, "sub"), 0o750)
 	if err != nil {
 		t.Fatal(err)
 	}
 	// Unbuffered and unread: on a cancelled scan every send gives up.
 	events := make(chan walkEvent)
 	subs := walkOneDir(cancelledContext(t), dirJob{path: dir}, false, events)
 	if len(subs) != 0 {
 		t.Errorf("cancelled walkOneDir returned %+v to descend into, "+
 			"want none", subs)
 	}
 }
 // TestWalkWorkersDropQueuedDirs checks that cancelled walk workers keep
 // reading jobs and drop the directories rather than stopping their
 // read: the range over jobs has to run out for the pool to tear down
-// and close its event stream. The queued directory does not exist, so
+// and close its event stream.
 // a worker that walked it anyway would send a warning before
 // walkOneDir's own cancellation check could stop it. On a cancelled
 // scan that send delivers or gives up at random, so with 64 jobs
 // queued the regression has a one in 2^64 chance of passing.
 func TestWalkWorkersDropQueuedDirs(t *testing.T) {
 	t.Parallel()
-	missing := filepath.Join(t.TempDir(), "missing")
+	dir := t.TempDir()
 	writeEmptyFiles(t, dir, walkCancelFilesPerDir)
 	jobs, _, events := startWalkWorkers(cancelledContext(t), 2, false)
-	for range 64 {
+	for range 4 {
-		jobs <- dirJob{path: missing}
+		jobs <- dirJob{path: dir}
 	}
 	close(jobs)
@@ -709,11 +412,7 @@ func TestDispatchDirsClosesJobsWhenCancelled(t *testing.T) {
 // TestFeedHashJobsClosesJobsWhenCancelled checks that the hash feeder
 // abandons the runs it has not queued yet and still closes the job
-// channel, which is what lets the workers' range terminate. The
+// channel, which is what lets the workers' range terminate.
 // receive on jobs below is not bounded: a feeder that returned without
 // closing jobs would leave that receive with no sender and no close, so
 // this regression is caught by the test binary's timeout rather than by
 // a bounded assertion.
 func TestFeedHashJobsClosesJobsWhenCancelled(t *testing.T) {
 	t.Parallel()
@@ -739,84 +438,41 @@ func TestFeedHashJobsClosesJobsWhenCancelled(t *testing.T) {
 // TestHashWorkerDropsQueuedRuns checks that a cancelled hash worker
 // keeps reading jobs and drops the runs rather than reading files
 // nobody wants the hashes of — while still letting the range run out
-// so the pool tears down. The hash function records that it was
+// so the pool tears down. The queued run names a file that does not
-// called, so a worker that hashed the queued run anyway is caught
+// exist, so a worker that hashed it anyway would produce a result.
 // every time.
 func TestHashWorkerDropsQueuedRuns(t *testing.T) {
 	t.Parallel()
 	done := make(chan struct{})
 	jobs := make(chan []fileRec, 1)
-	results := make(chan hashResult)
+	results := make(chan hashResult, 1)
-	jobs <- []fileRec{{path: filepath.Join(t.TempDir(), "missing"), size: 1}}
+	run := []fileRec{{path: filepath.Join(t.TempDir(), "missing"), size: 1}}
 	jobs <- run
 	close(jobs)
 	var hashed atomic.Bool
 	hash := func(path string, size int64) (string, string, string, error) {
 		hashed.Store(true)
 		return hashSignature(path, size)
 	}
 	go func() {
 		defer close(done)
-		hashWorker(cancelledContext(t), jobs, results, hash)
+		hashWorker(cancelledContext(t), jobs, results, hashSignature)
 	}()
 	awaitReturn(t, done, "hashWorker")
-	if hashed.Load() {
+	select {
-		t.Error("cancelled hash worker hashed the queued run, want it dropped")
+	case r := <-results:
 		t.Errorf("cancelled hash worker produced %+v, want the run dropped",
 			r)
 	default:
 	}
 }
 // TestHashWorkerAbandonsBlockedSend checks that a hash worker with a
 // result to deliver and nobody to deliver it to leaves once the scan
 // is cancelled, instead of holding the pool open. The scan tests do
 // not catch this: stop drains results, which frees a parked worker
 // anyway.
 func TestHashWorkerAbandonsBlockedSend(t *testing.T) {
 	t.Parallel()
 	ctx, cancel := context.WithCancel(t.Context())
 	defer cancel()
 	done := make(chan struct{})
 	jobs := make(chan []fileRec, 1)
 	// Unbuffered and unread, with jobs left open: the worker's only way
 	// out is the cancellation case beside its send.
 	results := make(chan hashResult)
 	jobs <- []fileRec{{path: filepath.Join(t.TempDir(), "missing"), size: 1}}
 	// The scan is cancelled while the worker hashes, so the worker has
 	// already passed the check that drops queued runs.
 	hash := func(path string, size int64) (string, string, string, error) {
 		cancel()
 		return hashSignature(path, size)
 	}
 	go func() {
 		defer close(done)
 		hashWorker(ctx, jobs, results, hash)
 	}()
 	awaitReturn(t, done, "hashWorker")
 }
 // TestHashPhaseCancelledReturnsContextError checks the result loop's
 // own exit: with the pool cancelled, no result will ever arrive, and
 // the loop must leave through the cancellation rather than wait for a
-// receive that cannot happen. This call is not bounded by poolUnwind: a
+// receive that cannot happen.
 // loop that dropped its cancellation case would block on that receive,
 // so the regression surfaces as the test binary's timeout rather than
 // as a bounded assertion.
 func TestHashPhaseCancelledReturnsContextError(t *testing.T) {
 	t.Parallel()
@@ -6,14 +6,11 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
 	"net/url"
 	"os"
 	"path/filepath"
 	"slices"
 	"strconv"
 	"time"
 	"golang.org/x/sys/unix"
 	// The pure-Go SQLite driver, registered as "sqlite"; keeps cgo
 	// disabled.
 	_ "modernc.org/sqlite"
@@ -35,41 +32,26 @@ const schemaVersion = 1
 // scan.
 const dbDirPerm = 0o755
 // lockFilePerm is the mode for the scan lock file. Anyone who can open
 // the file can hold the lock and keep every scan from running, so it
 // is open to its owner only.
 const lockFilePerm = 0o600
 // createTableSQL is the schema applied to a fresh database. Paths are
-// BLOBs because Unix paths are raw bytes, not guaranteed UTF-8. mtime
+// BLOBs because Unix paths are raw bytes, not guaranteed UTF-8.
 // holds whole Unix seconds and mtime_nsec the nanoseconds within that
 // second.
 const createTableSQL = `
 CREATE TABLE files (
    path    BLOB PRIMARY KEY,
    size    INTEGER NOT NULL,
    mtime   INTEGER NOT NULL,
    mtime_nsec INTEGER NOT NULL,
    head    TEXT NOT NULL,
    tail    TEXT NOT NULL,
    content TEXT NOT NULL
 ) WITHOUT ROWID
 `
 // createIndexSQL indexes the records by signature, so report can have
 // SQLite group them without sorting the whole table.
 const createIndexSQL = `
 CREATE INDEX files_signature ON files (size, head, tail, content)
 `
 // upsertSQL inserts one file record, replacing any existing record for
 // the same path.
 const upsertSQL = `
-INSERT INTO files (path, size, mtime, mtime_nsec, head, tail, content)
+INSERT INTO files (path, size, mtime, head, tail, content)
-VALUES (?, ?, ?, ?, ?, ?, ?)
+VALUES (?, ?, ?, ?, ?, ?)
 ON CONFLICT (path) DO UPDATE SET
    size = excluded.size, mtime = excluded.mtime,
    mtime_nsec = excluded.mtime_nsec,
    head = excluded.head, tail = excluded.tail,
    content = excluded.content
 `
@@ -82,10 +64,6 @@ var errNoDatabase = errors.New(
 // does not understand.
 var errSchemaVersion = errors.New("unsupported database schema version")
 // errScanRunning reports that another scan holds the lock on the
 // database.
 var errScanRunning = errors.New("another scan is running")
 // databasePath resolves the database location: SFDUPES_DATABASE when
 // set and non-empty, the compiled-in default otherwise.
 func databasePath() string {
@@ -96,36 +74,16 @@ func databasePath() string {
 	return defaultDatabasePath
 }
-// scanParams are the connection parameters for scan: read-write, with
+// openDB opens the SQLite database at path with WAL journaling and a
-// WAL journaling and a busy timeout, so a report can run while a cron
+// busy timeout, so a report can run while a cron scan is in progress.
-// scan is in progress. closeScanDatabase leaves WAL mode again.
+// It does not create or verify the schema.
-const scanParams = "_pragma=busy_timeout(10000)" +
+func openDB(path string) (*sql.DB, error) {
 	dsn := "file:" + path +
 		"?_pragma=busy_timeout(10000)" +
 		"&_pragma=journal_mode(WAL)" +
 		"&_pragma=synchronous(NORMAL)"
-// reportParams are the connection parameters for report and trees:
+	db, err := sql.Open("sqlite", dsn)
 // read-only, with the same busy timeout. They set no journal mode,
 // because setting one is a write.
 const reportParams = "mode=ro" +
 	"&_pragma=busy_timeout(10000)" +
 	"&_pragma=query_only(1)"
 // openDB opens the SQLite database at path with the connection
 // parameters params. It does not create or verify the schema.
 func openDB(path, params string) (*sql.DB, error) {
 	// The path is escaped into a file: URI, so ?, # and % in it stay
 	// part of the file name. SQLite reads what follows file:// up to
 	// the next / as a host name, so an absolute path goes after an
 	// empty host (file:///abs) and a relative path goes without one
 	// (file:rel).
 	uri := url.URL{
 		Scheme:   "file",
 		OmitHost: !filepath.IsAbs(path),
 		Path:     path,
 		RawQuery: params,
 	}
 	db, err := sql.Open("sqlite", uri.String())
 	if err != nil {
 		return nil, fmt.Errorf("open database %s: %w", path, err)
 	}
@@ -138,43 +96,6 @@ func openDB(path, params string) (*sql.DB, error) {
 	return db, nil
 }
 // lockScanDatabase takes the lock that keeps a second scan off the
 // database at path: an exclusive flock(2) on the file beside it named
 // path with ".lock" appended, created along with the database's parent
 // directory if missing. A lock held by another scan fails at once
 // instead of waiting. The lock lasts until the returned file is closed
 // or the process ends. The file is never deleted: a scan that deleted
 // it would let the next scan lock a new file while another still holds
 // the old one.
 func lockScanDatabase(path string) (*os.File, error) {
 	err := os.MkdirAll(filepath.Dir(path), dbDirPerm)
 	if err != nil {
 		return nil, fmt.Errorf("create database directory: %w", err)
 	}
 	lockPath := path + ".lock"
 	//nolint:gosec // the operator chooses the database path
 	f, err := os.OpenFile(lockPath, os.O_RDWR|os.O_CREATE, lockFilePerm)
 	if err != nil {
 		return nil, err
 	}
 	err = unix.Flock(int(f.Fd()), unix.LOCK_EX|unix.LOCK_NB)
 	if err != nil {
 		_ = f.Close()
 		if errors.Is(err, unix.EWOULDBLOCK) {
 			return nil, fmt.Errorf("%w (lock held on %s)",
 				errScanRunning, lockPath)
 		}
 		return nil, fmt.Errorf("lock %s: %w", lockPath, err)
 	}
 	return f, nil
 }
 // openScanDatabase opens the database for the scan subcommand, creating
 // the file, its parent directory, and the schema as needed.
 func openScanDatabase(ctx context.Context, path string) (*sql.DB, error) {
@@ -183,7 +104,7 @@ func openScanDatabase(ctx context.Context, path string) (*sql.DB, error) {
 		return nil, fmt.Errorf("create database directory: %w", err)
 	}
-	db, err := openDB(path, scanParams)
+	db, err := openDB(path)
 	if err != nil {
 		return nil, err
 	}
@@ -198,24 +119,6 @@ func openScanDatabase(ctx context.Context, path string) (*sql.DB, error) {
 	return db, nil
 }
 // closeScanDatabase switches the database at path from WAL back to
 // rollback-journal mode and closes it. Out of WAL mode the database
 // file alone holds the whole database, so a reader needs no -wal or
 // -shm file beside it, nor write access to create them. The switch
 // fails while a report has the database open; the database then stays
 // in WAL mode, still readable, until a later scan closes it.
 func closeScanDatabase(ctx context.Context, db *sql.DB, path string) {
 	// Runs on the way out of a cancelled scan too.
 	_, err := db.ExecContext(context.WithoutCancel(ctx),
 		"PRAGMA journal_mode = DELETE")
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "scan: database %s left in WAL mode: %v\n",
 			path, err)
 	}
 	_ = db.Close()
 }
 // openReportDatabase opens an existing database for the report and
 // trees subcommands. A missing database file is an error directing the
 // user to run scan first; the schema version must match exactly.
@@ -231,18 +134,12 @@ func openReportDatabase(ctx context.Context,
 		return nil, fmt.Errorf("database: %w", err)
 	}
-	db, err := openDB(path, reportParams)
+	db, err := openDB(path)
 	if err != nil {
 		return nil, err
 	}
 	v, err := userVersion(ctx, db)
 	if err == nil && v == 0 {
 		// An empty database passes this check and fails the version
 		// check below.
 		err = checkUnversioned(ctx, db)
 	}
 	if err != nil {
 		_ = db.Close()
@@ -269,11 +166,6 @@ func initSchema(ctx context.Context, db *sql.DB) error {
 	switch v {
 	case 0:
 		err = checkUnversioned(ctx, db)
 		if err != nil {
 			return err
 		}
 		return createSchema(ctx, db)
 	case schemaVersion:
 		return nil
@@ -283,65 +175,20 @@ func initSchema(ctx context.Context, db *sql.DB) error {
 	}
 }
 // checkUnversioned checks a database at user_version 0 before it is
 // taken for an empty one. createSchema creates the files table and
 // sets the version together, so a files table at version 0 was made by
 // something else. Adopting it could corrupt unrelated data, so that is
 // a schema-version error telling the operator to remove the file and
 // rescan.
 func checkUnversioned(ctx context.Context, db *sql.DB) error {
 	var name string
 	err := db.QueryRowContext(ctx,
 		"SELECT name FROM sqlite_master "+
 			"WHERE type = 'table' AND name = 'files'").Scan(&name)
 	switch {
 	case err == nil:
 		return fmt.Errorf(
 			"has a files table but no schema version; "+
 				"remove the file and rescan: %w", errSchemaVersion)
 	case errors.Is(err, sql.ErrNoRows):
 		return nil
 	default:
 		return fmt.Errorf("check for files table: %w", err)
 	}
 }
 // createSchema applies the schema to a fresh database and stamps the
-// schema version in one transaction, so a creation stopped partway, by
+// schema version.
 // an interrupt or an error, leaves an empty database the next scan
 // sets up, never a files table at version 0, which checkUnversioned
 // refuses.
 func createSchema(ctx context.Context, db *sql.DB) error {
-	tx, err := db.BeginTx(ctx, nil)
+	_, err := db.ExecContext(ctx, createTableSQL)
 	if err != nil {
 		return fmt.Errorf("create schema: %w", err)
 	}
-	defer func() { _ = tx.Rollback() }()
+	_, err = db.ExecContext(ctx,
 	_, err = tx.ExecContext(ctx, createTableSQL)
 	if err != nil {
 		return fmt.Errorf("create schema: %w", err)
 	}
 	_, err = tx.ExecContext(ctx, createIndexSQL)
 	if err != nil {
 		return fmt.Errorf("create schema: %w", err)
 	}
 	_, err = tx.ExecContext(ctx,
 		"PRAGMA user_version = "+strconv.Itoa(schemaVersion))
 	if err != nil {
 		return fmt.Errorf("set schema version: %w", err)
 	}
 	err = tx.Commit()
 	if err != nil {
 		return fmt.Errorf("create schema: %w", err)
 	}
 	return nil
 }
@@ -357,115 +204,40 @@ func userVersion(ctx context.Context, db *sql.DB) (int, error) {
 	return v, nil
 }
-// loadFileRows streams every record to fn in path order: byte order,
+// loadFileRows reads every record from the files table.
-// which is the order of the primary key, so SQLite does not sort.
+func loadFileRows(ctx context.Context, db *sql.DB) ([]scanRec, error) {
 func loadFileRows(ctx context.Context, db *sql.DB, fn func(r scanRec)) error {
 	rows, err := db.QueryContext(ctx,
-		"SELECT path, size, mtime, mtime_nsec, head, tail, content "+
+		"SELECT path, size, mtime, head, tail, content FROM files")
 			"FROM files ORDER BY path")
 	if err != nil {
-		return fmt.Errorf("read records: %w", err)
+		return nil, fmt.Errorf("read records: %w", err)
 	}
 	defer func() { _ = rows.Close() }()
 	var recs []scanRec
 	for rows.Next() {
 		var (
 			path []byte
 			sec, nsec int64
 			r    scanRec
 		)
-		err = rows.Scan(&path, &r.size, &sec, &nsec, &r.head, &r.tail,
+		err = rows.Scan(&path, &r.size, &r.mtime, &r.head, &r.tail,
 			&r.content)
 		if err != nil {
-			return fmt.Errorf("read record: %w", err)
+			return nil, fmt.Errorf("read record: %w", err)
 		}
 		r.path = string(path)
-		r.mtime = time.Unix(sec, nsec)
+		recs = append(recs, r)
 		fn(r)
 	}
 	err = rows.Err()
 	if err != nil {
-		return fmt.Errorf("read records: %w", err)
+		return nil, fmt.Errorf("read records: %w", err)
 	}
-	return nil
+	return recs, nil
 }
 // dupeRowsSQL selects every record in a duplicate group, with the
 // group's first path. A group is the records with a content hash that
 // share a size, head, tail, and content, when there are two or more of
 // them. The rows come in report order: groups by size descending, then
 // by first path, and each group's paths ascending.
 const dupeRowsSQL = `
 SELECT g.first, f.path, f.size
 FROM files AS f
 JOIN (
    SELECT size, head, tail, content, MIN(path) AS first
    FROM files
    WHERE content <> ''
    GROUP BY size, head, tail, content
    HAVING COUNT(*) > 1
 ) AS g USING (size, head, tail, content)
 ORDER BY f.size DESC, g.first, f.path
 `
 // loadDupeRows streams the rows of dupeRowsSQL to fn and returns the
 // number of records in the database. The count and the rows are read
 // in one transaction, so they agree while a scan is committing. An
 // error from fn stops the reading and is returned as it is.
 func loadDupeRows(ctx context.Context, db *sql.DB,
 	fn func(first, path string, size int64) error,
 ) (int, error) {
 	// Everything goes through tx: the report connection is the only
 	// one, so a query on db would wait for tx forever.
 	tx, err := db.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
 	if err != nil {
 		return 0, fmt.Errorf("read records: %w", err)
 	}
 	defer func() { _ = tx.Rollback() }()
 	var records int
 	err = tx.QueryRowContext(ctx, "SELECT COUNT(*) FROM files").Scan(&records)
 	if err != nil {
 		return 0, fmt.Errorf("read records: %w", err)
 	}
 	rows, err := tx.QueryContext(ctx, dupeRowsSQL)
 	if err != nil {
 		return 0, fmt.Errorf("read records: %w", err)
 	}
 	defer func() { _ = rows.Close() }()
 	for rows.Next() {
 		var (
 			first, path []byte
 			size        int64
 		)
 		err = rows.Scan(&first, &path, &size)
 		if err != nil {
 			return 0, fmt.Errorf("read record: %w", err)
 		}
 		err = fn(string(first), string(path), size)
 		if err != nil {
 			return 0, err
 		}
 	}
 	err = rows.Err()
 	if err != nil {
 		return 0, fmt.Errorf("read records: %w", err)
 	}
 	return records, nil
 }
 // loadFileMeta streams every record's path, size, mtime, and whether
@@ -473,10 +245,10 @@ func loadDupeRows(ctx context.Context, db *sql.DB,
 // values, and skipping the hash columns keeps the scan's in-memory
 // index small on multi-million-file databases.
 func loadFileMeta(ctx context.Context, db *sql.DB,
-	fn func(path string, size int64, mtime time.Time, hashed bool),
+	fn func(path string, size, mtime int64, hashed bool),
 ) error {
 	rows, err := db.QueryContext(ctx,
-		"SELECT path, size, mtime, mtime_nsec, head <> '' FROM files")
+		"SELECT path, size, mtime, head <> '' FROM files")
 	if err != nil {
 		return fmt.Errorf("read records: %w", err)
 	}
@@ -486,16 +258,16 @@ func loadFileMeta(ctx context.Context, db *sql.DB,
 	for rows.Next() {
 		var (
 			path        []byte
-			size, sec, nsec int64
+			size, mtime int64
 			hashed      int64
 		)
-		err = rows.Scan(&path, &size, &sec, &nsec, &hashed)
+		err = rows.Scan(&path, &size, &mtime, &hashed)
 		if err != nil {
 			return fmt.Errorf("read record: %w", err)
 		}
-		fn(string(path), size, time.Unix(sec, nsec), hashed != 0)
+		fn(string(path), size, mtime, hashed != 0)
 	}
 	err = rows.Err()
@@ -514,7 +286,7 @@ func loadFileMeta(ctx context.Context, db *sql.DB,
 // memory; the rows come ordered by size, head, and tail, so each
 // group's rows arrive together.
 const contentCandidatesSQL = `
-SELECT f.path, f.size, f.mtime, f.mtime_nsec, f.head, f.tail, f.content <> ''
+SELECT f.path, f.size, f.mtime, f.head, f.tail, f.content <> ''
 FROM files AS f
 JOIN (
    SELECT size, head, tail
@@ -541,19 +313,16 @@ func loadContentCandidates(ctx context.Context, db *sql.DB,
 	for rows.Next() {
 		var (
 			path   []byte
 			sec, nsec int64
 			r      scanRec
 			hashed int64
 		)
-		err = rows.Scan(&path, &r.size, &sec, &nsec, &r.head, &r.tail,
+		err = rows.Scan(&path, &r.size, &r.mtime, &r.head, &r.tail, &hashed)
 			&hashed)
 		if err != nil {
 			return fmt.Errorf("read record: %w", err)
 		}
 		r.path = string(path)
 		r.mtime = time.Unix(sec, nsec)
 		fn(r, hashed != 0)
 	}
@@ -637,8 +406,8 @@ func execUpserts(ctx context.Context, tx *sql.Tx, upserts []scanRec,
 	defer func() { _ = st.Close() }()
 	for _, r := range upserts {
-		_, err = st.ExecContext(ctx, []byte(r.path), r.size,
+		_, err = st.ExecContext(ctx,
-			r.mtime.Unix(), r.mtime.Nanosecond(), r.head, r.tail, r.content)
+			[]byte(r.path), r.size, r.mtime, r.head, r.tail, r.content)
 		if err != nil {
 			return fmt.Errorf("upsert %s: %w", r.path, err)
 		}
@@ -5,12 +5,10 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
 	"slices"
 	"strings"
 	"testing"
 	"time"
 )
 // testDBPath returns a database path inside a fresh temp dir.
@@ -74,78 +72,9 @@ func TestOpenScanDatabaseCreates(t *testing.T) {
 	defer func() { _ = db.Close() }()
-	if recs := dbRecords(t, db); len(recs) != 0 {
+	recs, err := loadFileRows(t.Context(), db)
-		t.Fatalf("records = %v, want none", recs)
+	if err != nil || len(recs) != 0 {
-	}
+		t.Fatalf("loadFileRows = %v, %v; want empty, nil", recs, err)
 }
 func TestOpenDatabaseUnversionedForeign(t *testing.T) {
 	t.Parallel()
 	// A database that has a files table but user_version 0, written by
 	// some other tool. report, trees and scan must refuse it with the
 	// schema-version error, not adopt it and not emit a raw SQLite
 	// "table files already exists".
 	path := testDBPath(t)
 	db, err := sql.Open("sqlite", path)
 	if err != nil {
 		t.Fatal(err)
 	}
 	_, err = db.ExecContext(t.Context(), "CREATE TABLE files (x INTEGER)")
 	if err != nil {
 		t.Fatal(err)
 	}
 	_ = db.Close()
 	_, err = openReportDatabase(t.Context(), path)
 	if !errors.Is(err, errSchemaVersion) ||
 		!strings.Contains(err.Error(), "remove the file and rescan") {
 		t.Fatalf("report: err = %v, want errSchemaVersion telling the "+
 			"operator to remove the file and rescan", err)
 	}
 	_, err = openScanDatabase(t.Context(), path)
 	if !errors.Is(err, errSchemaVersion) ||
 		!strings.Contains(err.Error(), "remove the file and rescan") {
 		t.Fatalf("scan: err = %v, want errSchemaVersion telling the "+
 			"operator to remove the file and rescan", err)
 	}
 }
 func TestSchemaCreationStoppedPartway(t *testing.T) {
 	t.Parallel()
 	// A first scan stopped while creating the schema must leave a
 	// database the next scan accepts. max_page_count(2) leaves room for
 	// the files table but not its index, so schema creation fails right
 	// after CREATE TABLE, a point an interrupt could also stop it at.
 	path := testDBPath(t)
 	db, err := openDB(path, scanParams+"&_pragma=max_page_count(2)")
 	if err != nil {
 		t.Fatal(err)
 	}
 	err = initSchema(t.Context(), db)
 	_ = db.Close()
 	if err == nil {
 		t.Fatal("initSchema with no room for the index succeeded")
 	}
 	db, err = openScanDatabase(t.Context(), path)
 	if err != nil {
 		t.Fatalf("next scan: %v", err)
 	}
 	defer func() { _ = db.Close() }()
 	v, err := userVersion(t.Context(), db)
 	if err != nil || v != schemaVersion {
 		t.Fatalf("userVersion = %d, %v; want %d, nil", v, err, schemaVersion)
 	}
 }
@@ -158,11 +87,9 @@ func TestOpenReportDatabaseMissing(t *testing.T) {
 	}
 }
-func TestOpenDatabaseVersionMismatch(t *testing.T) {
+func TestOpenReportDatabaseVersionMismatch(t *testing.T) {
 	t.Parallel()
 	// A database stamped with a schema version other than 0 and
 	// schemaVersion. report, trees and scan must all refuse it.
 	path := testDBPath(t)
 	db, err := openScanDatabase(t.Context(), path)
@@ -179,12 +106,7 @@ func TestOpenDatabaseVersionMismatch(t *testing.T) {
 	_, err = openReportDatabase(t.Context(), path)
 	if !errors.Is(err, errSchemaVersion) {
-		t.Fatalf("report: err = %v, want errSchemaVersion", err)
+		t.Fatalf("err = %v, want errSchemaVersion", err)
 	}
 	_, err = openScanDatabase(t.Context(), path)
 	if !errors.Is(err, errSchemaVersion) {
 		t.Fatalf("scan: err = %v, want errSchemaVersion", err)
 	}
 }
@@ -208,49 +130,6 @@ func TestOpenReportDatabaseOK(t *testing.T) {
 	_ = db.Close()
 }
 func TestCloseScanDatabaseWhileReportOpen(t *testing.T) {
 	t.Parallel()
 	// A report holding the database open stops scan from taking it out
 	// of WAL mode. The -wal and -shm files must then stay beside it, so
 	// that a later report still needs only read access.
 	path := testDBPath(t)
 	scanDB, err := openScanDatabase(t.Context(), path)
 	if err != nil {
 		t.Fatal(err)
 	}
 	reportDB, err := openReportDatabase(t.Context(), path)
 	if err != nil {
 		t.Fatal(err)
 	}
 	closeScanDatabase(t.Context(), scanDB, path)
 	_ = reportDB.Close()
 	_, err = os.Stat(path + "-wal")
 	if err != nil {
 		t.Fatalf("no -wal left: the switch out of WAL mode was not "+
 			"stopped: %v", err)
 	}
 	makeReadOnly(t, path)
 	reportDB, err = openReportDatabase(t.Context(), path)
 	if err != nil {
 		t.Fatalf("openReportDatabase: %v", err)
 	}
 	defer func() { _ = reportDB.Close() }()
 	err = loadFileRows(t.Context(), reportDB, func(scanRec) {})
 	if err != nil {
 		t.Fatalf("loadFileRows: %v", err)
 	}
 }
 func TestApplyChangesRoundTrip(t *testing.T) {
 	t.Parallel()
@@ -261,13 +140,10 @@ func TestApplyChangesRoundTrip(t *testing.T) {
 	// written.
 	recs := []scanRec{
 		{
-			size: 2, mtime: time.Unix(20, 999_999_999), head: "h2", tail: "t2",
+			size: 2, mtime: 20, head: "h2", tail: "t2", content: "c2",
-			content: "c2", path: "/a/tab\tnew\nline",
+			path: "/a/tab\tnew\nline",
 		},
 		{
 			size: 1, mtime: time.Unix(10, 0), head: "h1", tail: "t1",
 			content: "c1", path: "/a/x",
 		},
 		{size: 1, mtime: 10, head: "h1", tail: "t1", content: "c1", path: "/a/x"},
 	}
 	err := applyChanges(t.Context(), db, recs, nil,
@@ -276,8 +152,15 @@ func TestApplyChangesRoundTrip(t *testing.T) {
 		t.Fatalf("applyChanges: %v", err)
 	}
-	// The records come back in path order, which is the order of recs.
+	got, err := loadFileRows(t.Context(), db)
-	got := dbRecords(t, db)
+	if err != nil {
 		t.Fatal(err)
 	}
 	slices.SortFunc(got, func(a, b scanRec) int {
 		return strings.Compare(a.path, b.path)
 	})
 	if !slices.Equal(got, recs) {
 		t.Fatalf("rows = %+v, want %+v", got, recs)
 	}
@@ -285,8 +168,7 @@ func TestApplyChangesRoundTrip(t *testing.T) {
 	// An upsert for an existing path updates in place; a delete
 	// removes exactly its path.
 	upd := scanRec{
-		size: 3, mtime: time.Unix(30, 0), head: "h3", tail: "t3", content: "c3",
+		size: 3, mtime: 30, head: "h3", tail: "t3", content: "c3", path: "/a/x",
 		path: "/a/x",
 	}
 	err = applyChanges(t.Context(), db, []scanRec{upd},
@@ -295,7 +177,11 @@ func TestApplyChangesRoundTrip(t *testing.T) {
 		t.Fatalf("applyChanges: %v", err)
 	}
-	got = dbRecords(t, db)
+	got, err = loadFileRows(t.Context(), db)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if len(got) != 1 || got[0] != upd {
 		t.Fatalf("rows = %+v, want just %+v", got, upd)
 	}
@@ -313,7 +199,7 @@ func TestApplyChangesBatching(t *testing.T) {
 	recs := make([]scanRec, 0, n)
 	for i := range n {
 		recs = append(recs, scanRec{
-			size: int64(i), mtime: time.Unix(1, 0), head: "h", tail: "t",
+			size: int64(i), mtime: 1, head: "h", tail: "t",
 			path: fmt.Sprintf("/batch/%07d", i),
 		})
 	}
@@ -324,8 +210,9 @@ func TestApplyChangesBatching(t *testing.T) {
 		t.Fatalf("applyChanges: %v", err)
 	}
-	if got := dbRecords(t, db); len(got) != n {
+	got, err := loadFileRows(t.Context(), db)
-		t.Fatalf("records = %d, want %d", len(got), n)
+	if err != nil || len(got) != n {
 		t.Fatalf("loadFileRows = %d rows, %v; want %d", len(got), err, n)
 	}
 	deletes := make([]string, 0, n)
@@ -339,7 +226,8 @@ func TestApplyChangesBatching(t *testing.T) {
 		t.Fatalf("applyChanges deletes: %v", err)
 	}
-	if got := dbRecords(t, db); len(got) != 0 {
+	got, err = loadFileRows(t.Context(), db)
-		t.Fatalf("records = %d, want 0", len(got))
+	if err != nil || len(got) != 0 {
 		t.Fatalf("loadFileRows = %d rows, %v; want 0", len(got), err)
 	}
 }
@@ -5,8 +5,6 @@ go 1.25.7
 require (
 	github.com/schollz/progressbar/v3 v3.19.1
 	github.com/spf13/cobra v1.10.2
 	golang.org/x/sys v0.46.0
 	golang.org/x/term v0.44.0
 	modernc.org/sqlite v1.54.0
 )
@@ -20,6 +18,8 @@ require (
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	golang.org/x/sys v0.46.0 // indirect
 	golang.org/x/term v0.44.0 // indirect
 	modernc.org/libc v1.74.1 // indirect
 	modernc.org/mathutil v1.7.1 // indirect
 	modernc.org/memory v1.11.0 // indirect
@@ -15,7 +15,6 @@
 //	sfdupes scan [--workers N] [-x] PATH...
 //	sfdupes report > dupes.tsv
 //	sfdupes trees > dupetrees.tsv
 //	sfdupes --version
 //
 // See README.md for the complete specification.
 package main
@@ -51,10 +50,6 @@ const (
 // cobra prints for it is the whole message.
 var errNoSubcommand = errors.New("no subcommand")
 // errWorkersBelowOne is the usage error for a scan --workers value
 // below 1.
 var errWorkersBelowOne = errors.New("--workers must be at least 1")
 // Version is the build version, injected at link time via -ldflags
 // (see the Makefile); "dev" for a plain go build.
 //
@@ -62,27 +57,22 @@ var errWorkersBelowOne = errors.New("--workers must be at least 1")
 var Version = "dev"
 func main() {
-	// Once the reader of a stdout pipe has gone, as in "sfdupes report |
+	os.Exit(run(os.Args[1:], os.Stderr))
 	// head", the Go runtime ends the process with SIGPIPE on the next
 	// write instead of returning an error (README "Error handling").
 	// Registering for SIGPIPE with os/signal would change that.
 	os.Exit(run(os.Args[1:], os.Stdout, os.Stderr))
 }
 // run executes args against the command tree and returns the process
 // exit code. It is the program's single exit point: the subcommands
 // return their errors instead of exiting, so every deferred cleanup —
 // above all closing the database, which checkpoints the SQLite WAL —
-// runs before the process ends. The report and trees subcommands write
+// runs before the process ends.
-// their data to stdout.
+func run(args []string, stderr io.Writer) int {
 func run(args []string, stdout, stderr io.Writer) int {
 	// A nil slice makes cobra fall back to os.Args, which would let a
 	// test binary's own flags reach the command tree.
 	if args == nil {
 		args = []string{}
 	}
-	root := newRootCommand(stdout, stderr)
+	root := newRootCommand(stderr)
 	root.SetArgs(args)
 	err := root.Execute()
@@ -92,9 +82,6 @@ func run(args []string, stdout, stderr io.Writer) int {
 	switch {
 	case err == nil:
 		return exitOK
 	case errors.Is(err, errInterrupted):
 		// The interrupted scan has printed its own line.
 		return exitFatal
 	case errors.As(err, &fatal):
 		// The command ran and failed: a runtime error, reported
 		// without the usage text that a usage error gets.
@@ -102,35 +89,22 @@ func run(args []string, stdout, stderr io.Writer) int {
 		return exitFatal
 	default:
-		// A usage error, which cobra has already reported on stderr.
+		// A usage error: cobra has already printed the message and
 		// the usage text.
 		return exitUsage
 	}
 }
 // newRootCommand builds the command tree. Everything on stdout is
-// machine-readable data, the version line included; all human-facing
+// machine-readable data; all human-facing output (help, usage, errors)
-// output (help, usage, errors) goes to stderr.
+// goes to stderr.
-func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
+func newRootCommand(stderr io.Writer) *cobra.Command {
 	var showVersion bool
 	printVersion := runE(func(context.Context, []string) error {
 		_, err := fmt.Fprintf(stdout, "sfdupes %s\n", Version)
 		if err != nil {
 			return fmt.Errorf("write stdout: %w", err)
 		}
 		return nil
 	})
 	root := &cobra.Command{
 		Use:     "sfdupes",
 		Short:   "Find candidate duplicate files by size and head/tail/content SHA-256",
 		Version: Version,
 		Args:    cobra.NoArgs,
-		RunE: func(cmd *cobra.Command, args []string) error {
+		RunE: func(cmd *cobra.Command, _ []string) error {
 			if showVersion {
 				return printVersion(cmd, args)
 			}
 			// A missing subcommand prints usage and exits 2: cobra
 			// prints the usage text for the returned error, and run
 			// maps everything that is not a fatal error to exit 2.
@@ -143,11 +117,6 @@ func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 	root.SetErr(stderr)
 	root.CompletionOptions.DisableDefaultCmd = true
 	// Cobra's built-in version flag prints through the help writer,
 	// stderr; this one prints to stdout.
 	root.Flags().BoolVarP(&showVersion, "version", "v", false,
 		"print the version to stdout")
 	var (
 		scanWorkers int
 		scanOneFS   bool
@@ -157,13 +126,7 @@ func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 		Use:   cmdScan + " [--workers N] [-x] PATH...",
 		Short: "Walk trees and synchronize the scan database",
 		Args:  cobra.MinimumNArgs(1),
 		PreRunE: func(cmd *cobra.Command, _ []string) error {
 			return checkScanWorkers(cmd, scanWorkers)
 		},
 		RunE: runE(func(ctx context.Context, args []string) error {
 			ctx, stop := interruptContext(ctx)
 			defer stop()
 			return runScan(ctx, args, scanWorkers, scanOneFS)
 		}),
 	}
@@ -177,7 +140,7 @@ func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 		Short: "Read the scan database and print the file-level duplicates report",
 		Args:  cobra.NoArgs,
 		RunE: runE(func(ctx context.Context, _ []string) error {
-			return runReport(ctx, stdout)
+			return runReport(ctx)
 		}),
 	}
@@ -186,7 +149,7 @@ func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 		Short: "Read the scan database and print the duplicate-tree report",
 		Args:  cobra.NoArgs,
 		RunE: runE(func(ctx context.Context, _ []string) error {
-			return runTrees(ctx, stdout)
+			return runTrees(ctx)
 		}),
 	}
@@ -195,26 +158,13 @@ func newRootCommand(stdout, stderr io.Writer) *cobra.Command {
 	return root
 }
-// checkScanWorkers rejects a scan --workers value below 1. That is a
+// runE adapts a subcommand implementation to cobra's RunE. Cobra
-// usage error reported in one line: cobra prints the returned message
+// prints the error and the command's usage text for every error RunE
-// without the usage text, and run exits 2.
+// returns, but a subcommand that ran and failed has no usage problem
-func checkScanWorkers(cmd *cobra.Command, workers int) error {
+// to report: both are silenced here, and the error is marked fatal so
-	if workers >= 1 {
+// that run reports it on stderr and exits 1 rather than 2. The command's
-		return nil
+// context is handed to the implementation: cancelling it unwinds the
-	}
+// scan's worker pools.
 	cmd.SilenceUsage = true
 	return fmt.Errorf("%w, got %d", errWorkersBelowOne, workers)
 }
 // runE adapts a subcommand implementation, or the version print, to
 // cobra's RunE. Cobra prints the error and the command's usage text for
 // every error RunE returns, but a subcommand that ran and failed has no
 // usage problem to report: both are silenced here, and the error is
 // marked fatal so that run reports it on stderr and exits 1 rather than
 // 2. The command's context is handed to the implementation: cancelling
 // it unwinds the scan's worker pools.
 func runE(
 	fn func(ctx context.Context, args []string) error,
 ) func(*cobra.Command, []string) error {
@@ -8,7 +8,6 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
 	"slices"
 	"strconv"
 	"strings"
 	"testing"
@@ -45,81 +44,23 @@ func assertNoSidecars(t *testing.T, path string) {
 	}
 }
-// makeReadOnly takes write permission away from the database at path,
+// captureStdout redirects os.Stdout to a file for the rest of the test
-// from any WAL sidecar beside it, and from their directory, as for a
+// and returns a function reading back everything written to it. Only
-// user reading a database that a root cron scan keeps. Root ignores
+// machine-readable data belongs on stdout (README design goal 4), so
-// file permissions, so it skips the test when run as root.
+// the tests assert on it directly.
 func makeReadOnly(t *testing.T, path string) {
 	t.Helper()
 	if os.Geteuid() == 0 {
 		t.Skip("root ignores file permissions")
 	}
 	err := os.Chmod(path, 0o400)
 	if err != nil {
 		t.Fatal(err)
 	}
 	for _, suffix := range walSuffixes {
 		err = os.Chmod(path+suffix, 0o400)
 		if err != nil && !errors.Is(err, fs.ErrNotExist) {
 			t.Fatal(err)
 		}
 	}
 	dir := filepath.Dir(path)
 	//nolint:gosec // reaching the database needs the search bit
 	err = os.Chmod(dir, 0o500)
 	if err != nil {
 		t.Fatal(err)
 	}
 	// Runs before t.TempDir's own cleanup, which must delete the files.
 	t.Cleanup(func() {
 		//nolint:gosec // removing the directory needs its search bit back
 		_ = os.Chmod(dir, 0o700)
 	})
 }
 // captureStderr redirects os.Stderr to a file for the rest of the test
 // and returns a function reading back everything written to it. scan
 // writes its warnings and summary, and report and trees their
 // summaries, straight to os.Stderr, not to the stderr writer run is
 // given.
 func captureStderr(t *testing.T) func() string {
 	t.Helper()
 	return capture(t, &os.Stderr)
 }
 // captureStdout does for os.Stdout what captureStderr does for
 // os.Stderr. scan is never given run's stdout writer, so anything it
 // printed would go straight to os.Stdout. The scan tests pass os.Stdout
 // as run's stdout too, so the one capture sees both.
 func captureStdout(t *testing.T) func() string {
 	t.Helper()
-	return capture(t, &os.Stdout)
+	f, err := os.Create(filepath.Join(t.TempDir(), "stdout"))
 }
 // capture redirects *std, which is os.Stdout or os.Stderr, to a file
 // for the rest of the test and returns a function reading back
 // everything written to it.
 func capture(t *testing.T, std **os.File) func() string {
 	t.Helper()
 	f, err := os.Create(filepath.Join(t.TempDir(), "output"))
 	if err != nil {
 		t.Fatal(err)
 	}
-	saved := *std
+	saved := os.Stdout
-	*std = f
+	os.Stdout = f
 	t.Cleanup(func() {
-		*std = saved
+		os.Stdout = saved
 		_ = f.Close()
 	})
@@ -150,13 +91,13 @@ func capture(t *testing.T, std **os.File) func() string {
 // brokenDatabase writes a database that opens cleanly and passes the
 // schema-version check but has no files table, so the first query
 // fails with the database already open: a fatal error on a path that
-// owns an open database. It closes the database the way scan does.
+// owns an open database.
 func brokenDatabase(t *testing.T) string {
 	t.Helper()
 	path := testDBPath(t)
-	db, err := openDB(path, scanParams)
+	db, err := openDB(path)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -167,7 +108,10 @@ func brokenDatabase(t *testing.T) string {
 		t.Fatal(err)
 	}
-	closeScanDatabase(t.Context(), db, path)
+	err = db.Close()
 	if err != nil {
 		t.Fatal(err)
 	}
 	return path
 }
@@ -200,31 +144,27 @@ func TestOpenDatabaseKeepsWALWhileOpen(t *testing.T) {
 func TestRunFatalAfterOpenClosesDatabase(t *testing.T) {
 	// Every subcommand that owns an open database must close it when
-	// it fails: no os.Exit between the open and the return. The
+	// it fails: no os.Exit between the open and the return.
-	// sidecar check is evidence of the close only for scan: report and
+	cases := map[string][]string{
-	// trees only read a database that is out of WAL mode, which leaves
+		cmdScan:   {cmdScan},
-	// nothing on disk whether they close it or not.
+		cmdReport: {cmdReport},
-	//
+		cmdTrees:  {cmdTrees},
-	// The subcommands come from the command tree, so a new one is
+	}
 	// checked too: one wired with a bare RunE instead of runE reports
 	// its failure as a usage error, exit 2 with the usage text.
 	for _, cmd := range newRootCommand(io.Discard, io.Discard).Commands() {
 		name := cmd.Name()
 	for name, args := range cases {
 		t.Run(name, func(t *testing.T) {
 			path := brokenDatabase(t)
 			t.Setenv(databaseEnv, path)
 			args := []string{name}
 			if name == cmdScan {
 				args = append(args, t.TempDir())
 			}
 			stdout := captureStdout(t)
 			var stderr bytes.Buffer
-			code := run(args, os.Stdout, &stderr)
+			stdout := captureStdout(t)
 			code := run(args, &stderr)
 			if code != exitFatal {
 				t.Errorf("run(%v) = %d, want %d", args, code, exitFatal)
 			}
@@ -242,19 +182,19 @@ func TestRunFatalAfterOpenClosesDatabase(t *testing.T) {
 	}
 }
-func TestRunNonexistentPathIsFatalNotUsage(t *testing.T) {
+func TestRunMissingOperandIsFatalNotUsage(t *testing.T) {
 	// README §Error handling: a PATH operand that does not exist is a
 	// fatal error (1), not a usage error (2) — and a runtime failure
 	// must not dump the usage text.
 	t.Setenv(databaseEnv, testDBPath(t))
 	stdout := captureStdout(t)
 	var stderr bytes.Buffer
 	stdout := captureStdout(t)
 	missing := filepath.Join(t.TempDir(), "nope")
-	code := run([]string{cmdScan, missing}, os.Stdout, &stderr)
+	code := run([]string{cmdScan, missing}, &stderr)
 	if code != exitFatal {
 		t.Errorf("run(scan %s) = %d, want %d", missing, code, exitFatal)
 	}
@@ -283,34 +223,6 @@ func assertFatalOutput(t *testing.T, stderr, stdout string) {
 	}
 }
 func TestRunMissingDatabaseIsFatal(t *testing.T) {
 	// README §Database: report and trees need an existing database; a
 	// missing one exits 1 with a message telling the user to run scan.
 	for _, name := range []string{cmdReport, cmdTrees} {
 		t.Run(name, func(t *testing.T) {
 			path := testDBPath(t)
 			t.Setenv(databaseEnv, path)
 			var stdout, stderr bytes.Buffer
 			code := run([]string{name}, &stdout, &stderr)
 			if code != exitFatal {
 				t.Errorf("run(%s) = %d, want %d", name, code, exitFatal)
 			}
 			want := "sfdupes: " + path + ": no database (run \"sfdupes " +
 				"scan\" first, or set " + databaseEnv + ")\n"
 			if got := stderr.String(); got != want {
 				t.Errorf("stderr = %q, want %q", got, want)
 			}
 			if got := stdout.String(); got != "" {
 				t.Errorf("stdout = %q, want nothing (data only)", got)
 			}
 		})
 	}
 }
 func TestRunUsageErrors(t *testing.T) {
 	// Usage errors keep exiting 2 with cobra's own report on stderr.
 	cases := map[string]struct {
@@ -331,9 +243,11 @@ func TestRunUsageErrors(t *testing.T) {
 			// path that does not exist.
 			t.Setenv(databaseEnv, testDBPath(t))
-			var stdout, stderr bytes.Buffer
+			var stderr bytes.Buffer
-			code := run(tc.args, &stdout, &stderr)
+			stdout := captureStdout(t)
 			code := run(tc.args, &stderr)
 			if code != exitUsage {
 				t.Errorf("run(%v) = %d, want %d", tc.args, code, exitUsage)
 			}
@@ -342,115 +256,43 @@ func TestRunUsageErrors(t *testing.T) {
 				t.Errorf("stderr = %q, want %q", stderr.String(), tc.want)
 			}
-			if got := stdout.String(); got != "" {
+			if got := stdout(); got != "" {
 				t.Errorf("stdout = %q, want nothing (data only)", got)
 			}
 		})
 	}
 }
-func TestRunScanRejectsWorkersBelowOne(t *testing.T) {
+// TestRunHelpAndVersionSucceed checks that the two informational flags
-	// README §scan mode: --workers below 1 is a usage error reported in
+// exit 0 and keep their human-facing output on stderr.
-	// one line on stderr, before the scan opens the database.
+//
-	for _, workers := range []string{"0", "-1"} {
+//nolint:paralleltest // captureStdout replaces the process-wide os.Stdout
-		t.Run(workers, func(t *testing.T) {
+func TestRunHelpAndVersionSucceed(t *testing.T) {
-			dbPath := testDBPath(t)
+	assertHumanOutput(t, "--help")
-			t.Setenv(databaseEnv, dbPath)
+	assertHumanOutput(t, "--version")
 			var stdout, stderr bytes.Buffer
 			args := []string{cmdScan, "--workers", workers, t.TempDir()}
 			code := run(args, &stdout, &stderr)
 			if code != exitUsage {
 				t.Errorf("run(%v) = %d, want %d", args, code, exitUsage)
 			}
 			want := "Error: --workers must be at least 1, got " + workers +
 				"\n"
 			if got := stderr.String(); got != want {
 				t.Errorf("stderr = %q, want %q", got, want)
 			}
 			if got := stdout.String(); got != "" {
 				t.Errorf("stdout = %q, want nothing (data only)", got)
 			}
 			_, err := os.Stat(dbPath)
 			if !errors.Is(err, fs.ErrNotExist) {
 				t.Errorf("stat %s: %v, want the database never created",
 					dbPath, err)
 			}
 		})
 	}
 }
-func TestRunHelp(t *testing.T) {
+// assertHumanOutput runs sfdupes with one informational flag and checks
-	t.Parallel()
+// that it succeeds with its output on stderr and stdout untouched
 // (README design goal 4).
 func assertHumanOutput(t *testing.T, arg string) {
 	t.Helper()
-	// README §Subcommands: help goes to stderr, exits 0, and leaves
+	var stderr bytes.Buffer
 	// stdout empty.
 	cases := [][]string{{"--help"}, {"-h"}, {cmdScan, "--help"}}
-	for _, args := range cases {
+	stdout := captureStdout(t)
 		var stdout, stderr bytes.Buffer
-		code := run(args, &stdout, &stderr)
+	code := run([]string{arg}, &stderr)
 		if code != exitOK {
 			t.Errorf("run(%v) = %d, want %d", args, code, exitOK)
 		}
 		if !strings.Contains(stderr.String(), usageMarker) {
 			t.Errorf("run(%v) stderr = %q, want the help text",
 				args, stderr.String())
 		}
 		if got := stdout.String(); got != "" {
 			t.Errorf("run(%v) stdout = %q, want nothing (data only)",
 				args, got)
 		}
 	}
 }
 func TestRunVersion(t *testing.T) {
 	t.Parallel()
 	// README §Subcommands: the version is one line on stdout, with
 	// nothing on stderr, and exits 0.
 	for _, arg := range []string{"--version", "-v"} {
 		var stdout, stderr bytes.Buffer
 		code := run([]string{arg}, &stdout, &stderr)
 	if code != exitOK {
 		t.Errorf("run(%s) = %d, want %d", arg, code, exitOK)
 	}
-		want := "sfdupes " + Version + "\n"
+	if stderr.Len() == 0 {
-		if got := stdout.String(); got != want {
+		t.Errorf("run(%s) wrote nothing to stderr", arg)
 			t.Errorf("run(%s) stdout = %q, want %q", arg, got, want)
 	}
-		if got := stderr.String(); got != "" {
+	if got := stdout(); got != "" {
-			t.Errorf("run(%s) stderr = %q, want nothing", arg, got)
+		t.Errorf("stdout = %q, want nothing (data only)", got)
 		}
 	}
 }
 func TestRunVersionWriteFailureIsFatal(t *testing.T) {
 	t.Parallel()
 	// README §Error handling: a stdout write failure exits 1, reported
 	// in one line on stderr.
 	var stderr bytes.Buffer
 	code := run([]string{"--version"}, failingWriter{}, &stderr)
 	if code != exitFatal {
 		t.Errorf("run(--version) = %d, want %d", code, exitFatal)
 	}
 	want := "sfdupes: write stdout: " + errWriteFailed.Error() + "\n"
 	if got := stderr.String(); got != want {
 		t.Errorf("stderr = %q, want %q", got, want)
 	}
 }
@@ -478,195 +320,52 @@ func scanFixture(t *testing.T) []string {
 		t.Fatal(err)
 	}
-	scanOK(t, dir)
+	var stderr bytes.Buffer
 	return dupes
 }
 // scanOK runs scan over operands, fails the test unless it exits 0 with
 // nothing on stdout, and returns everything it printed to stderr.
 func scanOK(t *testing.T, operands ...string) string {
 	t.Helper()
 	stdout := captureStdout(t)
 	stderr := captureStderr(t)
-	code := run(append([]string{cmdScan}, operands...), os.Stdout, os.Stderr)
+	code := run([]string{cmdScan, dir}, &stderr)
 	if code != exitOK {
-		t.Fatalf("run(scan %q) = %d, want %d; stderr: %s",
+		t.Fatalf("run(scan) = %d, want %d; stderr: %s",
-			operands, code, exitOK, stderr())
+			code, exitOK, stderr.String())
 	}
 	if got := stdout(); got != "" {
 		t.Errorf("scan stdout = %q, want nothing (data only)", got)
 	}
-	return stderr()
+	return dupes
 }
 func TestRunScanSucceedsDespiteWarnings(t *testing.T) {
 	// README §Error handling: a scan that skips a file it cannot read
 	// warns, counts the skip in its summary, and still exits 0, which
 	// scanOK checks along with the empty stdout.
 	if os.Geteuid() == 0 {
 		t.Skip("root ignores file permissions")
 	}
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
-	dir := t.TempDir()
+	scanFixture(t)
 	writeFile(t, dir, "a.bin", pattern(1, 300))
 	// Same size as a.bin, so the scan reads it, and the read fails.
 	unreadable := writeFile(t, dir, "unreadable.bin", pattern(2, 300))
 	err := os.Chmod(unreadable, 0)
 	if err != nil {
 		t.Fatal(err)
 	}
 	stderr := scanOK(t, dir)
 	warning := "hash " + unreadable + ": open " + unreadable +
 		": permission denied\n"
 	if !strings.Contains(stderr, warning) {
 		t.Errorf("stderr = %q, want %q", stderr, warning)
 	}
 	summary := "scan: 1 files seen (1 added, 0 updated, 0 removed, " +
 		"0 unchanged), 1 skipped\n"
 	if !strings.Contains(stderr, summary) {
 		t.Errorf("stderr = %q, want %q", stderr, summary)
 	}
 	assertNoSidecars(t, path)
 }
 func TestRunScanSkipsSymlinkOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := t.TempDir()
 	writeFile(t, dir, "target/sub/f", pattern(1, 10))
 	link := filepath.Join(dir, "link")
 	err := os.Symlink(filepath.Join(dir, "target"), link)
 	if err != nil {
 		t.Fatal(err)
 	}
 	// Scanning a directory through the symlink stores a record beneath
 	// the symlink's own path for a file beneath its target.
 	scanOK(t, filepath.Join(link, "sub"))
 	assertOperandSkipped(t, path, link, "symlink",
 		filepath.Join(link, "sub", "f"))
 }
 func TestRunScanWalksOperandUnderSymlinkOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dir := t.TempDir()
 	writeFile(t, dir, "target/sub/f", pattern(1, 10))
 	link := filepath.Join(dir, "link")
 	err := os.Symlink(filepath.Join(dir, "target"), link)
 	if err != nil {
 		t.Fatal(err)
 	}
 	// link is dropped as a symlink, but link/sub must still be scanned,
 	// not dropped as lying under link.
 	scanOK(t, link, filepath.Join(link, "sub"))
 	db, err := openDB(path, reportParams)
 	if err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { _ = db.Close() })
 	recordByPath(t, dbRecords(t, db), filepath.Join(link, "sub", "f"))
 }
 func TestRunScanSkipsZFSOperand(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	zfs := filepath.Join(t.TempDir(), ".zfs")
 	snapshot := filepath.Join(zfs, "snapshot", "hourly")
 	f := writeFile(t, snapshot, "f", pattern(1, 10))
 	// An operand beneath a .zfs directory is walked, because it is not
 	// itself named .zfs.
 	scanOK(t, snapshot)
 	assertOperandSkipped(t, path, zfs, ".zfs directory", f)
 }
 // assertOperandSkipped scans operand alone and checks that it is skipped
 // as kind: a warning naming it, one skip in the summary, exit 0, and the
 // record for kept, which an earlier scan stored beneath operand, still
 // in the database at dbPath.
 func assertOperandSkipped(t *testing.T, dbPath, operand, kind,
 	kept string,
 ) {
 	t.Helper()
 	stderr := scanOK(t, operand)
 	warning := "walk " + operand + ": skipping " + kind + " operand\n"
 	if !strings.Contains(stderr, warning) {
 		t.Errorf("stderr = %q, want %q", stderr, warning)
 	}
 	summary := "scan: 0 files seen (0 added, 0 updated, 0 removed, " +
 		"0 unchanged), 1 skipped\n"
 	if !strings.Contains(stderr, summary) {
 		t.Errorf("stderr = %q, want %q", stderr, summary)
 	}
 	db, err := openDB(dbPath, reportParams)
 	if err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(func() { _ = db.Close() })
 	recordByPath(t, dbRecords(t, db), kept)
 }
 func TestRunReportSucceeds(t *testing.T) {
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dupes := scanFixture(t)
-	var stdout bytes.Buffer
+	var stderr bytes.Buffer
-	stderr := captureStderr(t)
+	stdout := captureStdout(t)
-	code := run([]string{cmdReport}, &stdout, os.Stderr)
+	code := run([]string{cmdReport}, &stderr)
 	if code != exitOK {
 		t.Fatalf("run(report) = %d, want %d; stderr: %s",
-			code, exitOK, stderr())
+			code, exitOK, stderr.String())
 	}
 	want := "first\tdupe\tsize\n" + dupes[0] + "\t" + dupes[1] + "\t300\n"
-	if got := stdout.String(); got != want {
+	if got := stdout(); got != want {
 		t.Errorf("stdout = %q, want %q", got, want)
 	}
 	want = "report: 2 records read, 1 duplicate groups, 1 dupe files, " +
 		"300 B reclaimable\n"
 	if got := stderr(); got != want {
 		t.Errorf("stderr = %q, want %q", got, want)
 	}
 	assertNoSidecars(t, path)
 }
@@ -676,286 +375,23 @@ func TestRunTreesSucceeds(t *testing.T) {
 	dupes := scanFixture(t)
-	var stdout bytes.Buffer
+	var stderr bytes.Buffer
-	stderr := captureStderr(t)
+	stdout := captureStdout(t)
-	code := run([]string{cmdTrees}, &stdout, os.Stderr)
+	code := run([]string{cmdTrees}, &stderr)
 	if code != exitOK {
 		t.Fatalf("run(trees) = %d, want %d; stderr: %s",
-			code, exitOK, stderr())
+			code, exitOK, stderr.String())
 	}
 	// The two directories holding the duplicate pair are duplicate
 	// trees of each other.
 	want := "first\tdupe\tfiles\tsize\n" +
 		filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) + "\t1\t300\n"
-	if got := stdout.String(); got != want {
+	if got := stdout(); got != want {
 		t.Errorf("stdout = %q, want %q", got, want)
 	}
 	want = "trees: 2 records read, 1 duplicate tree groups, 1 dupe trees, " +
 		"300 B reclaimable\n"
 	if got := stderr(); got != want {
 		t.Errorf("stderr = %q, want %q", got, want)
 	}
 	assertNoSidecars(t, path)
 }
 func TestRunReportsNeedOnlyReadAccess(t *testing.T) {
 	// README §Database: report and trees need only read access to the
 	// database file. With its directory read-only as well, SQLite
 	// cannot create any file beside it.
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	dupes := scanFixture(t)
 	assertNoSidecars(t, path)
 	makeReadOnly(t, path)
 	cases := map[string]string{
 		cmdReport: "first\tdupe\tsize\n" +
 			dupes[0] + "\t" + dupes[1] + "\t300\n",
 		cmdTrees: "first\tdupe\tfiles\tsize\n" +
 			filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) +
 			"\t1\t300\n",
 	}
 	for name, want := range cases {
 		var stdout, stderr bytes.Buffer
 		code := run([]string{name}, &stdout, &stderr)
 		if code != exitOK {
 			t.Errorf("run(%s) = %d, want %d; stderr: %s",
 				name, code, exitOK, stderr.String())
 			continue
 		}
 		if got := stdout.String(); got != want {
 			t.Errorf("%s stdout = %q, want %q", name, got, want)
 		}
 	}
 }
 // assertRunsUseDatabase runs scan, then report and trees, against the
 // database that SFDUPES_DATABASE names, the file name in dir. It fails
 // unless the reports find the duplicate pair the scan recorded and dir
 // then holds only that file and its lock file: nothing was created
 // under a shortened name.
 func assertRunsUseDatabase(t *testing.T, dir, name string) {
 	t.Helper()
 	dupes := scanFixture(t)
 	want := "first\tdupe\tsize\n" + dupes[0] + "\t" + dupes[1] + "\t300\n"
 	if got := runStdout(t, cmdReport); got != want {
 		t.Errorf("report stdout = %q, want %q", got, want)
 	}
 	want = "first\tdupe\tfiles\tsize\n" +
 		filepath.Dir(dupes[0]) + "\t" + filepath.Dir(dupes[1]) + "\t1\t300\n"
 	if got := runStdout(t, cmdTrees); got != want {
 		t.Errorf("trees stdout = %q, want %q", got, want)
 	}
 	entries, err := os.ReadDir(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
 	got := make([]string, 0, len(entries))
 	for _, e := range entries {
 		got = append(got, e.Name())
 	}
 	if wantFiles := []string{name, name + ".lock"}; !slices.Equal(got, wantFiles) {
 		t.Errorf("%s holds %q, want %q", dir, got, wantFiles)
 	}
 }
 func TestRunDatabasePathUsedAsGiven(t *testing.T) {
 	// README §Database: the path names the database file exactly. In
 	// SQLite's connection string an unescaped ? or # would end the file
 	// name and % would start an escape, and a path starting with //
 	// could be read as a host name. %25 is a valid escape, so unescaped
 	// this name opens a file named a without any error.
 	const name = "a?b#c%25d e.sqlite"
 	t.Run("absolute", func(t *testing.T) {
 		dir := t.TempDir()
 		t.Setenv(databaseEnv, filepath.Join(dir, name))
 		assertRunsUseDatabase(t, dir, name)
 	})
 	t.Run("leading double slash", func(t *testing.T) {
 		dir := t.TempDir()
 		t.Setenv(databaseEnv, "/"+filepath.Join(dir, name))
 		assertRunsUseDatabase(t, dir, name)
 	})
 	t.Run("relative", func(t *testing.T) {
 		dir := t.TempDir()
 		t.Chdir(dir)
 		t.Setenv(databaseEnv, name)
 		assertRunsUseDatabase(t, dir, name)
 	})
 }
 // holdScanLock takes the lock on the database at path, as a running
 // scan does, and holds it until the test ends. It fails the test when
 // the lock is already held.
 func holdScanLock(t *testing.T, path string) {
 	t.Helper()
 	lock, err := lockScanDatabase(path)
 	if err != nil {
 		t.Fatalf("lock %s: %v", path, err)
 	}
 	t.Cleanup(func() { _ = lock.Close() })
 }
 func TestRunSecondScanFails(t *testing.T) {
 	// README §Database: while one scan holds the lock, a second scan
 	// fails at once, naming the lock file, without creating the
 	// database.
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	holdScanLock(t, path)
 	stdout := captureStdout(t)
 	var stderr bytes.Buffer
 	code := run([]string{cmdScan, t.TempDir()}, os.Stdout, &stderr)
 	if code != exitFatal {
 		t.Errorf("run(scan) = %d, want %d", code, exitFatal)
 	}
 	want := "sfdupes: another scan is running (lock held on " +
 		path + ".lock)\n"
 	if got := stderr.String(); got != want {
 		t.Errorf("stderr = %q, want %q", got, want)
 	}
 	if got := stdout(); got != "" {
 		t.Errorf("stdout = %q, want nothing (data only)", got)
 	}
 	_, err := os.Stat(path)
 	if !errors.Is(err, fs.ErrNotExist) {
 		t.Errorf("stat %s = %v, want the database not created", path, err)
 	}
 }
 func TestRunScanReleasesLock(t *testing.T) {
 	// README §Database: a scan releases the lock however it ends.
 	t.Run("success", func(t *testing.T) {
 		path := testDBPath(t)
 		t.Setenv(databaseEnv, path)
 		scanFixture(t)
 		holdScanLock(t, path)
 	})
 	t.Run("fatal error", func(t *testing.T) {
 		path := brokenDatabase(t)
 		t.Setenv(databaseEnv, path)
 		code := run([]string{cmdScan, t.TempDir()}, io.Discard, io.Discard)
 		if code != exitFatal {
 			t.Fatalf("run(scan) = %d, want %d", code, exitFatal)
 		}
 		holdScanLock(t, path)
 	})
 }
 func TestRunReportsDuringScan(t *testing.T) {
 	// README §Database: report and trees never take the lock, so they
 	// run while a scan holds it.
 	path := testDBPath(t)
 	t.Setenv(databaseEnv, path)
 	scanFixture(t)
 	holdScanLock(t, path)
 	for _, name := range []string{cmdReport, cmdTrees} {
 		var stderr bytes.Buffer
 		code := run([]string{name}, io.Discard, &stderr)
 		if code != exitOK {
 			t.Errorf("run(%s) = %d, want %d; stderr: %s",
 				name, code, exitOK, stderr.String())
 		}
 	}
 }
 func TestRunStdoutClosedIsFatal(t *testing.T) {
 	// README §Error handling: a stdout write failure exits 1, reported
 	// in one line on stderr.
 	for _, name := range []string{cmdReport, cmdTrees} {
 		t.Run(name, func(t *testing.T) {
 			t.Setenv(databaseEnv, testDBPath(t))
 			scanFixture(t)
 			stdout, err := os.Create(filepath.Join(t.TempDir(), "stdout"))
 			if err != nil {
 				t.Fatal(err)
 			}
 			err = stdout.Close()
 			if err != nil {
 				t.Fatal(err)
 			}
 			var stderr bytes.Buffer
 			code := run([]string{name}, stdout, &stderr)
 			if code != exitFatal {
 				t.Errorf("run(%s) = %d, want %d", name, code, exitFatal)
 			}
 			got := stderr.String()
 			if !strings.HasPrefix(got, "sfdupes: write stdout: ") ||
 				!strings.Contains(got, os.ErrClosed.Error()) ||
 				strings.Count(got, "\n") != 1 {
 				t.Errorf("stderr = %q, want one line reporting the "+
 					"failed stdout write", got)
 			}
 		})
 	}
 }
 // errWriteFailed is the error failingWriter returns.
 var errWriteFailed = errors.New("write failed")
 // failingWriter is a stdout that fails every write.
 type failingWriter struct{}
 func (failingWriter) Write([]byte) (int, error) { return 0, errWriteFailed }
 func TestStdoutWriteErrorPropagates(t *testing.T) {
 	t.Setenv(databaseEnv, testDBPath(t))
 	scanFixture(t)
 	cases := map[string]func(context.Context, io.Writer) error{
 		cmdReport: runReport,
 		cmdTrees:  runTrees,
 	}
 	for name, fn := range cases {
 		err := fn(t.Context(), failingWriter{})
 		if !errors.Is(err, errWriteFailed) {
 			t.Errorf("%s: error = %v, want %v", name, err, errWriteFailed)
 		}
 	}
 }
@@ -1,5 +0,0 @@
 {
  "devDependencies": {
    "prettier": "3.8.1"
  }
 }
@@ -6,7 +6,6 @@ import (
 	"time"
 	"github.com/schollz/progressbar/v3"
 	"golang.org/x/term"
 )
 // plainInterval is the minimum time between progress lines when stderr
@@ -25,23 +24,24 @@ const percentScale = 100
 // stderrIsTTY reports whether stderr is attached to a terminal.
 func stderrIsTTY() bool {
-	return term.IsTerminal(int(os.Stderr.Fd()))
+	fi, err := os.Stderr.Stat()
 	if err != nil {
 		return false
 	}
 	return fi.Mode()&os.ModeCharDevice != 0
 }
 // progress renders one scan pass's progress on stderr. On a TTY it
 // delegates to the progressbar library (spinner style when the total is
 // unknown, full bar with count/percent/rate/elapsed/ETA otherwise). When
 // stderr is not a TTY it emits no ANSI redraws: it prints a plain
-// one-line update as the pass starts, then no more often than every
+// one-line update no more often than every plainInterval.
 // plainInterval.
 //
-// All methods must be called from the main goroutine only. On a TTY
+// All methods must be called from the main goroutine only. A nil
-// the library also redraws a spinner from its own goroutine, several
+// *progress is a valid no-display receiver: every method is a no-op,
-// times a second, so its count and elapsed time stay current while a
+// so batched database flushes during the streaming pass can reuse the
-// pass waits for its next item. A nil *progress is a valid
+// update-pass helpers without rendering anything.
 // no-display receiver: every method is a no-op, so batched database
 // flushes during the streaming pass can reuse the update-pass helpers
 // without rendering anything.
 type progress struct {
 	label string
 	total int64 // -1 when unknown (walk pass)
@@ -53,22 +53,10 @@ type progress struct {
 func newProgress(label string, total int64) *progress {
 	p := &progress{label: label, total: total, start: time.Now()}
-	if stderrIsTTY() {
+	if !stderrIsTTY() {
 		p.bar = newBar(label, total)
 		return p
 	}
 	// Print the zero state at once: the first item may take minutes,
 	// and a pass must never look hung.
 	p.last = p.start
 	fmt.Fprintln(os.Stderr, p.plainLine())
 	return p
 }
 // newBar builds the TTY display for newProgress.
 func newBar(label string, total int64) *progressbar.ProgressBar {
 	opts := []progressbar.Option{
 		progressbar.OptionSetWriter(os.Stderr),
 		progressbar.OptionSetDescription(label),
@@ -93,7 +81,9 @@ func newBar(label string, total int64) *progressbar.ProgressBar {
 		)
 	}
-	return progressbar.NewOptions64(total, opts...)
+	p.bar = progressbar.NewOptions64(total, opts...)
 	return p
 }
 // increment records one completed item and refreshes the display.
@@ -116,45 +106,26 @@ func (p *progress) increment() {
 }
 // warnf prints a one-line warning to stderr without corrupting the bar.
 // The whole message is escaped like a report's path columns, so a path
 // holding a newline cannot split the warning.
 func (p *progress) warnf(format string, args ...any) {
 	if p == nil {
 		return
 	}
 	msg := escapePath(fmt.Sprintf(format, args...))
 	if p.bar != nil && p.total < 0 {
 		// The library also redraws a spinner from its own goroutine, so
 		// a direct write could land inside a redraw. The bar prints the
 		// warning itself, just before its next redraw.
 		_, _ = progressbar.Bprintln(p.bar, msg)
 		return
 	}
 	if p.bar != nil {
 		_ = p.bar.Clear()
 	}
-	fmt.Fprintln(os.Stderr, msg)
+	fmt.Fprintf(os.Stderr, format+"\n", args...)
 }
-// finish terminates the pass's display. A bar whose pass stopped short
+// finish terminates the pass's display.
 // of its total, as an interrupted one does, is left as last drawn; the
 // library's Finish would fill it up.
 func (p *progress) finish() {
 	if p == nil {
 		return
 	}
 	if p.bar != nil {
 		if p.total >= 0 && p.count < p.total {
 			_ = p.bar.Exit()
 		} else {
 		_ = p.bar.Finish()
 		}
 		fmt.Fprintln(os.Stderr)
@@ -1,189 +0,0 @@
 package main
 import (
 	"os"
 	"path/filepath"
 	"strings"
 	"testing"
 	"time"
 )
 // spinnerIdle comfortably outlasts the 100ms interval at which the
 // progressbar library redraws a spinner from its own goroutine.
 const spinnerIdle = 500 * time.Millisecond
 //nolint:paralleltest // replaces the process-wide os.Stderr
 func TestStderrIsTTYFalseForNonTerminals(t *testing.T) {
 	r, pipe, err := os.Pipe()
 	if err != nil {
 		t.Fatal(err)
 	}
 	regular, err := os.Create(filepath.Join(t.TempDir(), "stderr"))
 	if err != nil {
 		t.Fatal(err)
 	}
 	devNull, err := os.OpenFile(os.DevNull, os.O_WRONLY, 0)
 	if err != nil {
 		t.Fatal(err)
 	}
 	saved := os.Stderr
 	t.Cleanup(func() {
 		os.Stderr = saved
 		for _, f := range []*os.File{r, pipe, regular, devNull} {
 			_ = f.Close()
 		}
 	})
 	cases := map[string]*os.File{
 		"a pipe":         pipe,
 		"a regular file": regular,
 		os.DevNull:       devNull,
 	}
 	for name, f := range cases {
 		os.Stderr = f
 		if stderrIsTTY() {
 			t.Errorf("stderrIsTTY() = true with stderr on %s", name)
 		}
 	}
 }
 // TestNewProgressPrintsBeforeFirstItem checks that each pass shows its
 // zero state the moment it starts when stderr is not a terminal, and
 // that the next line still waits for plainInterval.
 //
 //nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
 func TestNewProgressPrintsBeforeFirstItem(t *testing.T) {
 	stderr := captureStderr(t)
 	newProgress("walk", -1).increment()
 	newProgress("hash", 10).increment()
 	want := "walk: 0 files, elapsed 0s\n" +
 		"hash: [0/10] 0% 0 files/s elapsed 0s eta ?\n"
 	if got := stderr(); got != want {
 		t.Errorf("stderr = %q, want %q", got, want)
 	}
 }
 // newWalkSpinner returns the walk pass's terminal display, writing to
 // os.Stderr whether or not it is a terminal, and stops the library's
 // redraws when the test ends.
 func newWalkSpinner(t *testing.T) *progress {
 	t.Helper()
 	p := &progress{
 		label: "walk", total: -1, start: time.Now(),
 		bar: newBar("walk", -1),
 	}
 	t.Cleanup(p.finish)
 	return p
 }
 // TestProgressWarningsOnOwnLines drives the terminal display of the walk
 // pass through a run of warnings with no items between them, as when the
 // walk meets many unreadable paths, for several of the spinner's
 // redraws: every warning must land on a line of its own, never inside a
 // redraw.
 //
 //nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
 func TestProgressWarningsOnOwnLines(t *testing.T) {
 	stderr := captureStderr(t)
 	p := newWalkSpinner(t)
 	// No pause between warnings: one written straight to stderr is
 	// garbled only if a redraw lands while it is being written.
 	issued := 0
 	for start := time.Now(); time.Since(start) < spinnerIdle; issued++ {
 		p.warnf("warning")
 	}
 	// The spinner prints the warnings at its next redraw.
 	time.Sleep(spinnerIdle)
 	// A terminal shows each line as the text after its last carriage
 	// return.
 	shown := 0
 	for line := range strings.SplitSeq(stderr(), "\n") {
 		if !strings.Contains(line, "warning") {
 			continue
 		}
 		shown++
 		if text := line[strings.LastIndex(line, "\r")+1:]; text != "warning" {
 			t.Errorf("terminal shows %q, want %q", text, "warning")
 		}
 	}
 	if shown != issued {
 		t.Errorf("%d warning lines, want %d", shown, issued)
 	}
 }
 // TestSpinnerShowsCountAfterBurst checks that once a burst of items
 // faster than the redraw limit is over, the walk display shows every
 // item completed while it waits for the next one.
 //
 //nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
 func TestSpinnerShowsCountAfterBurst(t *testing.T) {
 	stderr := captureStderr(t)
 	p := newWalkSpinner(t)
 	for range 50 {
 		p.increment()
 	}
 	time.Sleep(spinnerIdle)
 	if shown := lastFrame(stderr()); !strings.Contains(shown, "(50/-,") {
 		t.Errorf("terminal shows %q, want a count of 50", shown)
 	}
 }
 // lastFrame returns what a terminal shows of the frames a bar drew: the
 // last one. The library starts each frame with a carriage return and
 // erases the previous one with spaces first.
 func lastFrame(out string) string {
 	var shown string
 	for frame := range strings.SplitSeq(out, "\r") {
 		if strings.TrimSpace(frame) != "" {
 			shown = frame
 		}
 	}
 	return shown
 }
 // TestBarStoppedShortKeepsCount checks that the terminal display of a
 // pass that stops before its total, as an interrupted one does, is left
 // as last drawn instead of being filled up.
 //
 //nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
 func TestBarStoppedShortKeepsCount(t *testing.T) {
 	stderr := captureStderr(t)
 	p := &progress{
 		label: "hash", total: 10, start: time.Now(),
 		bar: newBar("hash", 10),
 	}
 	p.increment()
 	// Past the redraw limit, so the bar draws the next count.
 	time.Sleep(2 * barThrottle)
 	p.increment()
 	p.finish()
 	if shown := lastFrame(stderr()); !strings.Contains(shown, "(2/10,") {
 		t.Errorf("terminal shows %q, want a count of 2 of 10", shown)
 	}
 }
@@ -4,10 +4,9 @@ import (
 	"bufio"
 	"context"
 	"fmt"
 	"io"
 	"os"
 	"slices"
 	"strings"
 	"time"
 )
 // ioBufSize is the buffer size for the buffered stdout writers.
@@ -22,66 +21,80 @@ const minGroupSize = 2
 // only and used by scan for change detection.
 type scanRec struct {
 	size    int64
-	mtime   time.Time
+	mtime   int64
 	head    string
 	tail    string
 	content string
 	path    string
 }
-// runReport implements the report subcommand: it prints the file-level
+// loadRecords opens the database and reads every file record for the
-// duplicates report as TSV on stdout. SQLite groups and orders the
+// report and trees subcommands. Any database problem — including a
-// records, and each row is written as it is read, so no group is held
+// missing database — is fatal. The error is returned rather than
-// in memory. It never touches the scanned filesystem; its only I/O is
+// exiting, so that the deferred close — which checkpoints the SQLite
-// the database (with SQLite's temporary sort file), stdout, and stderr.
+// WAL — always runs; the database is closed before the caller formats
-// Any database problem, including a missing database, is fatal.
+// its output, so it stays closed even if that output fails.
-func runReport(ctx context.Context, stdout io.Writer) error {
+func loadRecords(ctx context.Context) ([]scanRec, error) {
 	dbPath := databasePath()
 	db, err := openReportDatabase(ctx, dbPath)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	defer func() { _ = db.Close() }()
-	out := bufio.NewWriterSize(stdout, ioBufSize)
+	recs, err := loadFileRows(ctx, db)
 	if err != nil {
 		return nil, fmt.Errorf("database %s: %w", dbPath, err)
 	}
 	return recs, nil
 }
 // dupeGroup is one set of candidate-duplicate files: identical size,
 // head hash, tail hash, and content hash. paths is sorted
 // lexicographically; the first entry is the group's "first", the rest
 // are dupes.
 type dupeGroup struct {
 	size  int64
 	paths []string
 }
 // runReport implements the report subcommand: it reads every record
 // from the database and prints the file-level duplicates report as TSV
 // on stdout. It never touches the scanned filesystem; its only I/O is
 // the database, stdout, and stderr.
 func runReport(ctx context.Context) error {
 	recs, err := loadRecords(ctx)
 	if err != nil {
 		return err
 	}
 	dupes := collectDupeGroups(recs)
 	out := bufio.NewWriterSize(os.Stdout, ioBufSize)
 	_, err = fmt.Fprintln(out, "first\tdupe\tsize")
 	if err != nil {
 		return fmt.Errorf("write stdout: %w", err)
 	}
-	var (
+	dupeFiles := 0
 		groups, dupeFiles int
 		reclaimable       int64
 		writeErr          error
 	)
-	records, err := loadDupeRows(ctx, db,
+	var reclaimable int64
 		func(first, path string, size int64) error {
 			// A group's first path is its first row; every other
 			// path is a dupe.
 			if path == first {
 				groups++
 				return nil
 			}
 			_, writeErr = fmt.Fprintf(out, "%s\t%s\t%d\n",
 				escapePath(first), escapePath(path), size)
 			dupeFiles++
 			reclaimable += size
 			return writeErr
 		})
 	if writeErr != nil {
 		return fmt.Errorf("write stdout: %w", writeErr)
 	}
 	for _, g := range dupes {
 		for _, p := range g.paths[1:] {
 			_, err = fmt.Fprintf(out, "%s\t%s\t%d\n",
 				g.paths[0], p, g.size)
 			if err != nil {
-		return fmt.Errorf("database %s: %w", dbPath, err)
+				return fmt.Errorf("write stdout: %w", err)
 			}
 			dupeFiles++
 			reclaimable += g.size
 		}
 	}
 	err = out.Flush()
@@ -92,24 +105,55 @@ func runReport(ctx context.Context, stdout io.Writer) error {
 	fmt.Fprintf(os.Stderr,
 		"report: %d records read, %d duplicate groups, %d dupe files, "+
 			"%s reclaimable\n",
-		records, groups, dupeFiles, humanBytes(reclaimable))
+		len(recs), len(dupes), dupeFiles, humanBytes(reclaimable))
 	return nil
 }
-// escapePath returns a path as it is written in a report column (README
+// collectDupeGroups groups records by signature and returns every group
-// "Report output format"): a backslash, tab, newline or carriage return
+// with two or more paths, each group's paths sorted lexicographically,
-// becomes \\, \t, \n or \r, and every other byte is kept as it is.
+// groups ordered by size descending then by first path ascending.
-// Grouping and sorting use the raw path, never this form.
+func collectDupeGroups(recs []scanRec) []dupeGroup {
-func escapePath(p string) string {
+	groups := make(map[fileSig][]string)
-	// Most paths need no escaping; skip building a replacer for them.
+
-	if !strings.ContainsAny(p, "\\\t\n\r") {
+	for _, r := range recs {
-		return p
+		// A record without a content hash has unknown content and is
 		// never reported as a duplicate (README "Database").
 		if r.content == "" {
 			continue
 		}
-	return strings.NewReplacer(
+		k := fileSig{
-		`\`, `\\`, "\t", `\t`, "\n", `\n`, "\r", `\r`,
+			size: r.size, head: r.head, tail: r.tail, content: r.content,
-	).Replace(p)
+		}
 		groups[k] = append(groups[k], r.path)
 	}
 	var dupes []dupeGroup
 	for k, paths := range groups {
 		if len(paths) < minGroupSize {
 			continue
 		}
 		slices.Sort(paths)
 		dupes = append(dupes, dupeGroup{size: k.size, paths: paths})
 	}
 	// Biggest reclaimable space first; ties broken by first path.
 	slices.SortFunc(dupes, func(a, b dupeGroup) int {
 		if a.size != b.size {
 			if a.size > b.size {
 				return -1
 			}
 			return 1
 		}
 		return strings.Compare(a.paths[0], b.paths[0])
 	})
 	return dupes
 }
 // humanBytes formats a byte count in human units (binary prefixes).
@@ -1,255 +1,11 @@
 package main
 import (
 	"bytes"
 	"database/sql"
 	"errors"
 	"fmt"
 	"io"
 	"os"
 	"path/filepath"
 	"slices"
 	"strings"
 	"testing"
 	"time"
 )
-// awkwardDir is a directory name holding every byte the reports escape.
+func TestCollectDupeGroups(t *testing.T) {
 const awkwardDir = "/d/\tone\ntwo\rthree\\four"
 // awkwardPairRecs is a duplicate pair in sibling directories /d/A and
 // awkwardDir. A raw tab sorts before "A" but its escaped form `\t`
 // sorts after it, so awkwardDir coming first shows that sorting uses
 // the raw path.
 func awkwardPairRecs() []scanRec {
 	return []scanRec{
 		{size: 5, head: "h", tail: "t", content: "c", path: "/d/A/f"},
 		{size: 5, head: "h", tail: "t", content: "c", path: awkwardDir + "/f"},
 	}
 }
 // seedDatabase writes recs into a fresh database and returns its path.
 func seedDatabase(t *testing.T, recs []scanRec) string {
 	t.Helper()
 	path := testDBPath(t)
 	db, err := openScanDatabase(t.Context(), path)
 	if err != nil {
 		t.Fatal(err)
 	}
 	err = applyChanges(t.Context(), db, recs, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
 	err = db.Close()
 	if err != nil {
 		t.Fatal(err)
 	}
 	return path
 }
 // dupeGroup is one duplicate group as report reads it: the size, and
 // the paths in report order, first path first.
 type dupeGroup struct {
 	size  int64
 	paths []string
 }
 // dupeGroups returns the duplicate groups report reads from db, in
 // report order.
 func dupeGroups(t *testing.T, db *sql.DB) []dupeGroup {
 	t.Helper()
 	var groups []dupeGroup
 	_, err := loadDupeRows(t.Context(), db,
 		func(first, path string, size int64) error {
 			if path == first {
 				groups = append(groups, dupeGroup{size: size})
 			}
 			g := &groups[len(groups)-1]
 			g.paths = append(g.paths, path)
 			return nil
 		})
 	if err != nil {
 		t.Fatal(err)
 	}
 	return groups
 }
 // dupeGroupsOf writes recs into a fresh database and returns the
 // duplicate groups report reads from it.
 func dupeGroupsOf(t *testing.T, recs []scanRec) []dupeGroup {
 	t.Helper()
 	db := openTestDB(t)
 	err := applyChanges(t.Context(), db, recs, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
 	return dupeGroups(t, db)
 }
 func TestRunReportEscapesPaths(t *testing.T) {
 	t.Setenv(databaseEnv, seedDatabase(t, awkwardPairRecs()))
 	var stdout, stderr bytes.Buffer
 	code := run([]string{cmdReport}, &stdout, &stderr)
 	if code != exitOK {
 		t.Fatalf("run(report) = %d, want %d; stderr: %s",
 			code, exitOK, stderr.String())
 	}
 	want := "first\tdupe\tsize\n" +
 		`/d/\tone\ntwo\rthree\\four/f` + "\t/d/A/f\t5\n"
 	if got := stdout.String(); got != want {
 		t.Errorf("stdout = %q, want %q", got, want)
 	}
 }
 func TestReportStdoutFailsWhileReading(t *testing.T) {
 	// Each row holds two paths longer than dir, so the report is more
 	// than twice the stdout buffer and stdout fails while rows are
 	// still being read, not at the final flush.
 	dir := "/" + strings.Repeat("d", 4096)
 	recs := make([]scanRec, ioBufSize/len(dir))
 	for i := range recs {
 		recs[i] = scanRec{
 			size: 1, head: "h", tail: "t", content: "c",
 			path: fmt.Sprintf("%s/%d", dir, i),
 		}
 	}
 	t.Setenv(databaseEnv, seedDatabase(t, recs))
 	err := runReport(t.Context(), failingWriter{})
 	if !errors.Is(err, errWriteFailed) ||
 		!strings.HasPrefix(err.Error(), "write stdout: ") {
 		t.Errorf("error = %v, want write stdout: %v", err, errWriteFailed)
 	}
 }
 func TestRunReportsIgnoreInsertionOrder(t *testing.T) {
 	// README §Constraints: identical database contents give identical
 	// output, whatever order the records were inserted in.
 	recs := append(smokeTreeRecs(), awkwardPairRecs()...)
 	recs = append(recs,
 		scanRec{size: 50, head: "b", tail: "b", content: "b", path: "/y/2"},
 		scanRec{size: 50, head: "b", tail: "b", content: "b", path: "/y/1"},
 		scanRec{size: 50, head: "a", tail: "a", content: "a", path: "/x/2"},
 		scanRec{size: 50, head: "a", tail: "a", content: "a", path: "/x/1"},
 		scanRec{size: 50, path: "/x/unhashed"},
 	)
 	reversed := slices.Clone(recs)
 	slices.Reverse(reversed)
 	for _, name := range []string{cmdReport, cmdTrees} {
 		t.Run(name, func(t *testing.T) {
 			t.Setenv(databaseEnv, seedDatabase(t, recs))
 			forward := runStdout(t, name)
 			t.Setenv(databaseEnv, seedDatabase(t, reversed))
 			backward := runStdout(t, name)
 			if strings.Count(forward, "\n") < 3 {
 				t.Errorf("stdout = %q, want at least two rows", forward)
 			}
 			if forward != backward {
 				t.Errorf("stdout depends on insertion order: %q vs %q",
 					forward, backward)
 			}
 		})
 	}
 }
 // runStdout runs the subcommand name and returns its stdout, failing
 // the test unless it succeeds.
 func runStdout(t *testing.T, name string) string {
 	t.Helper()
 	var stdout, stderr bytes.Buffer
 	code := run([]string{name}, &stdout, &stderr)
 	if code != exitOK {
 		t.Fatalf("run(%s) = %d, want %d; stderr: %s",
 			name, code, exitOK, stderr.String())
 	}
 	return stdout.String()
 }
 func TestEscapePath(t *testing.T) {
 	t.Parallel()
 	cases := map[string]string{
 		"/srv/plain":    "/srv/plain",
 		"/a\tb":         `/a\tb`,
 		"/a\nb":         `/a\nb`,
 		"/a\rb":         `/a\rb`,
 		`/a\b`:          `/a\\b`,
 		`/a\tb`:         `/a\\tb`,
 		"/not-utf8\xff": "/not-utf8\xff",
 	}
 	for in, want := range cases {
 		if got := escapePath(in); got != want {
 			t.Errorf("escapePath(%q) = %q, want %q", in, got, want)
 		}
 	}
 }
 // TestWarnfEscapes checks that a warning naming a path that holds a
 // newline is still one line.
 //
 //nolint:paralleltest // replaces the process-wide os.Stderr
 func TestWarnfEscapes(t *testing.T) {
 	f, err := os.Create(filepath.Join(t.TempDir(), "stderr"))
 	if err != nil {
 		t.Fatal(err)
 	}
 	saved := os.Stderr
 	os.Stderr = f
 	t.Cleanup(func() {
 		os.Stderr = saved
 		_ = f.Close()
 	})
 	(&progress{}).warnf("stat %s: %s", "/d/a\nb", "gone")
 	_, err = f.Seek(0, io.SeekStart)
 	if err != nil {
 		t.Fatal(err)
 	}
 	got, err := io.ReadAll(f)
 	if err != nil {
 		t.Fatal(err)
 	}
 	want := `stat /d/a\nb: gone` + "\n"
 	if string(got) != want {
 		t.Errorf("warning = %q, want %q", got, want)
 	}
 }
 func TestDupeGroups(t *testing.T) {
 	t.Parallel()
 	recs := []scanRec{
@@ -264,7 +20,7 @@ func TestDupeGroups(t *testing.T) {
 		{size: 7, head: "u", tail: "u", content: "u", path: "/lonely"},
 	}
-	groups := dupeGroupsOf(t, recs)
+	groups := collectDupeGroups(recs)
 	if len(groups) != 2 {
 		t.Fatalf("len(groups) = %d, want 2", len(groups))
 	}
@@ -282,7 +38,7 @@ func TestDupeGroups(t *testing.T) {
 	}
 }
-func TestDupeGroupsContentSeparates(t *testing.T) {
+func TestCollectDupeGroupsContentSeparates(t *testing.T) {
 	t.Parallel()
 	// Same size, head, and tail, but different content hashes: the final
@@ -297,7 +53,7 @@ func TestDupeGroupsContentSeparates(t *testing.T) {
 		{size: 100, head: "h", tail: "t", path: "/e"},
 	}
-	groups := dupeGroupsOf(t, recs)
+	groups := collectDupeGroups(recs)
 	if len(groups) != 1 {
 		t.Fatalf("len(groups) = %d, want 1 (only the matching content)",
 			len(groups))
@@ -308,41 +64,33 @@ func TestDupeGroupsContentSeparates(t *testing.T) {
 	}
 }
-func TestDupeGroupsMtimeExcluded(t *testing.T) {
+func TestCollectDupeGroupsMtimeExcluded(t *testing.T) {
 	t.Parallel()
 	// mtime is informational only; records differing only in mtime
 	// still group together.
 	recs := []scanRec{
-		{
+		{size: 9, mtime: 100, head: "h", tail: "t", content: "c", path: "/m/1"},
-			size: 9, mtime: time.Unix(100, 0), head: "h", tail: "t",
+		{size: 9, mtime: 200, head: "h", tail: "t", content: "c", path: "/m/2"},
 			content: "c", path: "/m/1",
 		},
 		{
 			size: 9, mtime: time.Unix(200, 0), head: "h", tail: "t",
 			content: "c", path: "/m/2",
 		},
 	}
-	groups := dupeGroupsOf(t, recs)
+	groups := collectDupeGroups(recs)
 	if len(groups) != 1 {
 		t.Fatalf("len(groups) = %d, want 1", len(groups))
 	}
 }
-func TestDupeGroupsTieBreak(t *testing.T) {
+func TestCollectDupeGroupsTieBreak(t *testing.T) {
 	t.Parallel()
 	// The hashes sort opposite to the first paths, so ordering the
 	// groups by hash instead of by first path fails this test.
 	recs := []scanRec{
-		{size: 50, head: "a", tail: "a", content: "a", path: "/beta/2"},
+		{size: 50, head: "b", tail: "b", content: "b", path: "/beta/2"},
-		{size: 50, head: "a", tail: "a", content: "a", path: "/beta/1"},
+		{size: 50, head: "b", tail: "b", content: "b", path: "/beta/1"},
-		{size: 50, head: "b", tail: "b", content: "b", path: "/alpha/2"},
+		{size: 50, head: "a", tail: "a", content: "a", path: "/alpha/2"},
-		{size: 50, head: "b", tail: "b", content: "b", path: "/alpha/1"},
+		{size: 50, head: "a", tail: "a", content: "a", path: "/alpha/1"},
 	}
-	groups := dupeGroupsOf(t, recs)
+	groups := collectDupeGroups(recs)
 	if len(groups) != 2 {
 		t.Fatalf("len(groups) = %d, want 2", len(groups))
 	}
@@ -354,7 +102,7 @@ func TestDupeGroupsTieBreak(t *testing.T) {
 	}
 }
-func TestDupeGroupsDeterministic(t *testing.T) {
+func TestCollectDupeGroupsDeterministic(t *testing.T) {
 	t.Parallel()
 	recs := []scanRec{
@@ -364,12 +112,12 @@ func TestDupeGroupsDeterministic(t *testing.T) {
 		{size: 2, head: "b", tail: "b", content: "b", path: "/q/2"},
 	}
-	forward := dupeGroupsOf(t, recs)
+	forward := collectDupeGroups(recs)
 	reversed := slices.Clone(recs)
 	slices.Reverse(reversed)
-	backward := dupeGroupsOf(t, reversed)
+	backward := collectDupeGroups(reversed)
 	if !slices.EqualFunc(forward, backward, func(a, b dupeGroup) bool {
 		return a.size == b.size && slices.Equal(a.paths, b.paths)
 	}) {
@@ -11,13 +11,11 @@ import (
 	"io"
 	"io/fs"
 	"os"
 	"os/signal"
 	"path/filepath"
 	"slices"
 	"strings"
 	"sync"
 	"syscall"
 	"time"
 )
 // The duplicate ladder (see hashSignature and README "Duplicate
@@ -59,17 +57,13 @@ const sampleWindow = 1024 * 1024
 // and hash worker pools.
 const workQueueDepth = 1024
 // errInterrupted reports a scan stopped by SIGINT or SIGTERM. runScan
 // has already printed its line, so run prints nothing more.
 var errInterrupted = errors.New("scan interrupted")
 // fileRec carries one statted file between the scan phases. dev and
 // ino identify the underlying inode so hard-linked paths can share
 // one read; both are zero when the platform exposes no inode.
 type fileRec struct {
 	path  string
 	size  int64
-	mtime time.Time
+	mtime int64
 	dev   uint64
 	ino   uint64
 }
@@ -80,7 +74,7 @@ type fileRec struct {
 // they would dominate the scan's memory.
 type fileMeta struct {
 	size   int64
-	mtime  time.Time
+	mtime  int64
 	hashed bool
 }
@@ -91,19 +85,17 @@ type fileMeta struct {
 // least one other file shares are ever hashed: a size-unique file
 // cannot be a duplicate. A file of headTailMin or more gets its content
 // hash only when its size, head, and tail match another file's. Flag
-// parsing and the at-least-one-operand check are done by cobra. The
+// parsing and the at-least-one-operand check are done by cobra. Errors
-// scan holds the lock on the database for its whole run, so a second
+// are returned rather than exiting, so that the deferred close — which
-// scan fails before it walks the filesystem or opens the database.
+// checkpoints the SQLite WAL — always runs. Cancelling ctx unwinds the
-// Errors are returned rather than exiting, so that the deferred close —
+// worker pools and aborts the scan with the context's error.
 // which takes the database out of WAL mode — always runs, and the lock
 // is released after it. When ctx is cancelled, as by the SIGINT or
 // SIGTERM that interruptContext catches, the scan keeps what it has
 // hashed (see syncScan), prints how many files its walk reached, and
 // returns errInterrupted. workers must be at least 1; the scan command
 // rejects anything less.
 func runScan(ctx context.Context, roots []string, workers int,
 	oneFS bool,
 ) error {
 	if workers < 1 {
 		workers = 1
 	}
 	roots, err := resolveRoots(roots)
 	if err != nil {
 		return err
@@ -111,31 +103,14 @@ func runScan(ctx context.Context, roots []string, workers int,
 	dbPath := databasePath()
 	lock, err := lockScanDatabase(dbPath)
 	if err != nil {
 		return err
 	}
 	defer func() { _ = lock.Close() }()
 	db, err := openScanDatabase(ctx, dbPath)
 	if err != nil && ctx.Err() != nil {
 		// Interrupted while opening; SQLite may report that with an
 		// error of its own rather than the context's.
 		return interrupted(0)
 	}
 	if err != nil {
 		return err
 	}
-	defer closeScanDatabase(ctx, db, dbPath)
+	defer func() { _ = db.Close() }()
 	st, err := syncScan(ctx, db, roots, workers, oneFS)
 	if errors.Is(err, context.Canceled) {
 		return interrupted(st.walked)
 	}
 	if err != nil {
 		return fmt.Errorf("update database %s: %w", dbPath, err)
 	}
@@ -149,34 +124,6 @@ func runScan(ctx context.Context, roots []string, workers int,
 	return nil
 }
 // interruptContext returns a copy of ctx that the first SIGINT or
 // SIGTERM cancels; the scan command runs the scan under it. stop
 // releases the signals.
 func interruptContext(ctx context.Context) (context.Context, func()) {
 	// A SIGINT ignored from the start, as by a script's background job,
 	// stays ignored.
 	signals := []os.Signal{syscall.SIGTERM}
 	if !signal.Ignored(syscall.SIGINT) {
 		signals = append(signals, syscall.SIGINT)
 	}
 	ctx, stop := signal.NotifyContext(ctx, signals...)
 	// Stopping restores the default handling, so a second signal ends
 	// the process at once.
 	context.AfterFunc(ctx, stop)
 	return ctx, stop
 }
 // interrupted prints the line for a scan stopped by a signal after its
 // walk reached walked files, and returns errInterrupted.
 func interrupted(walked int) error {
 	fmt.Fprintf(os.Stderr, "scan: interrupted after %d files\n", walked)
 	return errInterrupted
 }
 // resolveRoots converts each PATH operand to an absolute, lexically
 // cleaned path (symlinks are not resolved) and verifies that it
 // exists. Database records are keyed by absolute path, so scan results
@@ -230,9 +177,8 @@ func pruneRoots(roots []string) []string {
 }
 // scanStats summarizes one scan's database synchronization for the
-// final stderr summary, or for the line an interrupted scan prints.
+// final stderr summary.
 type scanStats struct {
 	walked    int // files the walk reached
 	added     int
 	updated   int
 	removed   int
@@ -254,30 +200,7 @@ type scanState struct {
 	st        scanStats
 }
-// syncScan synchronizes the database with the filesystem under roots;
+// syncScan synchronizes the database with the filesystem under roots
 // see runPhases. When ctx is cancelled, as by an interrupt, it commits
 // the hashed records still waiting in the batch, starts no other write
 // or deletion, and returns the cancellation.
 func syncScan(ctx context.Context, db *sql.DB, roots []string,
 	workers int, oneFS bool,
 ) (scanStats, error) {
 	s := &scanState{db: db}
 	err := s.runPhases(ctx, roots, workers, oneFS)
 	if err == nil || ctx.Err() == nil {
 		return s.st, err
 	}
 	// The one write made after the cancellation, so it cannot use ctx.
 	err = applyChanges(context.WithoutCancel(ctx), db, s.batch, nil, nil)
 	if err != nil {
 		return s.st, err
 	}
 	return s.st, ctx.Err()
 }
 // runPhases synchronizes the database with the filesystem under roots
 // in four sequential phases: walk (enumerate and stat every file,
 // building a complete size census), hash (read only the new or
 // changed — or previously unhashed — files whose size at least one
@@ -287,73 +210,47 @@ func syncScan(ctx context.Context, db *sql.DB, roots []string,
 // in the content hash of every record of headTailMin or more whose
 // size, head, and tail match another record's). Records outside the
 // roots are never touched, except that the content phase fills in
-// their content hash. Operands the walk cannot start from are dropped
+// their content hash.
-// first, so the records beneath them count as outside the roots unless
+func syncScan(ctx context.Context, db *sql.DB, roots []string,
 // they lie under another root.
 func (s *scanState) runPhases(ctx context.Context, roots []string,
 	workers int, oneFS bool,
-) error {
+) (scanStats, error) {
-	// Types are checked before pruning so that an operand under a
+	roots = pruneRoots(roots)
-	// dropped one is still scanned, not dropped as lying under it.
+
-	roots = pruneRoots(s.walkableRoots(roots))
+	s := &scanState{db: db}
 	err := s.loadIndex(ctx, roots)
 	if err != nil {
-		return err
+		return s.st, err
 	}
 	changed, unhashed := s.walkPhase(startWalk(ctx, roots, oneFS, workers))
 	// A cancelled walk stops early, so its size census covers only part
-	// of the roots, and every file it never reached would look vanished
+	// of the roots, and every file it never reached looks vanished to
-	// to the update phase. Stop before anything is written or deleted.
+	// the update phase. Defence in depth rather than the only barrier:
 	// that phase would today fail on its first BeginTx with the same
 	// cancelled context before deleting anything. But it is the barrier
 	// that survives a later decision to let an interrupted scan commit
 	// what it has, and it turns a confusing failure deep in the update
 	// phase into a clean abort at the phase boundary.
 	err = ctx.Err()
 	if err != nil {
-		return err
+		return s.st, err
 	}
 	s.partition(changed, unhashed)
 	err = s.hashPhase(ctx, workers)
 	if err != nil {
-		return err
+		return s.st, err
 	}
 	err = s.updatePhase(ctx)
 	if err != nil {
-		return err
+		return s.st, err
 	}
-	return s.contentPhase(ctx, workers)
+	return s.st, s.contentPhase(ctx, workers)
 }
 // walkableRoots returns the operands the walk can start from: regular
 // files, and directories not named .zfs. Every other operand is warned
 // about, counted as skipped, and dropped. A dropped operand is no
 // longer a root, so the records stored beneath it count as outside the
 // roots and are not deleted as unverified, unless it lies under another
 // root. An operand that fails lstat here is kept, and the walk warns
 // about it.
 func (s *scanState) walkableRoots(roots []string) []string {
 	kept := make([]string, 0, len(roots))
 	for _, root := range roots {
 		fi, err := os.Lstat(root)
 		if err == nil {
 			warn := operandWarning(root, fi)
 			if warn != "" {
 				s.st.skipped++
 				fmt.Fprintln(os.Stderr, escapePath(warn))
 				continue
 			}
 		}
 		kept = append(kept, root)
 	}
 	return kept
 }
 // loadIndex indexes the database records under the scan roots for
@@ -370,7 +267,7 @@ func (s *scanState) loadIndex(ctx context.Context, roots []string) error {
 	s.existing = make(map[string]fileMeta)
 	return loadFileMeta(ctx, s.db,
-		func(path string, size int64, mtime time.Time, hashed bool) {
+		func(path string, size, mtime int64, hashed bool) {
 			prog.increment()
 			if underAnyRoot(path, roots) {
@@ -409,14 +306,13 @@ func (s *scanState) walkPhase(
 		}
 		s.sizes = append(s.sizes, ev.rec.size)
 		s.st.walked++
 		prog.increment()
 		old, ok := s.existing[ev.rec.path]
 		switch {
-		case !ok || old.size != ev.rec.size || mtimeAfter(ev.rec.mtime, old.mtime):
+		case !ok || old.size != ev.rec.size || old.mtime < ev.rec.mtime:
 			changed = append(changed, ev.rec)
 		case old.hashed:
 			delete(s.existing, ev.rec.path)
@@ -613,22 +509,16 @@ func (s *scanState) recordRun(ctx context.Context, r hashResult) error {
 }
 // commitFullBatch commits the running batch once it holds
-// updateBatchSize records. A batch that fails to commit is kept: the
+// updateBatchSize records.
 // commit fails when the scan is interrupted, and syncScan then commits
 // the batch itself.
 func (s *scanState) commitFullBatch(ctx context.Context) error {
 	if len(s.batch) < updateBatchSize {
 		return nil
 	}
 	err := applyBatch(ctx, s.db, s.batch, nil, nil)
 	if err != nil {
 		return err
 	}
 	s.batch = s.batch[:0]
-	return nil
+	return err
 }
 // updatePhase writes the scan's tail under one progress display: the
@@ -808,7 +698,7 @@ func unchangedFile(r scanRec) (fileRec, bool, error) {
 	}
 	if !fi.Mode().IsRegular() || fi.Size() != r.size ||
-		mtimeAfter(fi.ModTime(), r.mtime) {
+		fi.ModTime().Unix() > r.mtime {
 		return fileRec{}, false, nil
 	}
@@ -819,16 +709,6 @@ func unchangedFile(r scanRec) (fileRec, bool, error) {
 	}, true, nil
 }
 // mtimeAfter reports whether mtime a is later than mtime b.
 // Not a.After(b): time.Time wraps an mtime past year 292 billion; Unix() undoes it.
 func mtimeAfter(a, b time.Time) bool {
 	if a.Unix() != b.Unix() {
 		return a.Unix() > b.Unix()
 	}
 	return a.Nanosecond() > b.Nanosecond()
 }
 // underAnyRoot reports whether path is any of the roots or lies under
 // one of them.
 func underAnyRoot(path string, roots []string) bool {
@@ -909,43 +789,11 @@ func sendEvent(ctx context.Context, events chan<- walkEvent,
 	}
 }
 // operandWarning returns the one-line warning for an operand the walk
 // does not start from, naming the path and what it is, or "" for one it
 // does: a regular file, or a directory not named .zfs. Symlinks are
 // never followed, including as operands.
 func operandWarning(root string, fi fs.FileInfo) string {
 	var kind string
 	switch mode := fi.Mode(); {
 	case mode.IsRegular():
 		return ""
 	case mode.IsDir():
 		if filepath.Base(root) != ".zfs" {
 			return ""
 		}
 		kind = ".zfs directory"
 	case mode&fs.ModeSymlink != 0:
 		kind = "symlink"
 	case mode&fs.ModeSocket != 0:
 		kind = "socket"
 	case mode&fs.ModeNamedPipe != 0:
 		kind = "FIFO"
 	case mode&fs.ModeDevice != 0:
 		kind = "device node"
 	default:
 		kind = "non-regular file"
 	}
 	return fmt.Sprintf("walk %s: skipping %s operand", root, kind)
 }
 // seedRoot turns one PATH operand into the walk's starting state: a
-// regular-file operand is statted and emitted directly, and a directory
+// regular-file operand is statted and emitted directly, a directory
-// operand becomes an initial job. walkableRoots has already dropped
+// operand becomes an initial job, and a symlink or other non-regular
-// every other operand. One that has changed into something else since
+// operand yields nothing (symlinks are never followed, including as
-// is warned about and skipped here; it is still a root, so the records
+// operands).
 // stored beneath it are deleted as unverified.
 func seedRoot(ctx context.Context, root string,
 	events chan<- walkEvent,
 ) []dirJob {
@@ -959,30 +807,30 @@ func seedRoot(ctx context.Context, root string,
 		return nil
 	}
-	warn := operandWarning(root, fi)
+	switch {
-	if warn != "" {
+	case fi.IsDir():
-		sendEvent(ctx, events, walkEvent{warn: warn, fail: true})
+		if filepath.Base(root) == ".zfs" {
 			return nil
 		}
 	if fi.IsDir() {
 		dev, ok := deviceOfInfo(fi)
 		return []dirJob{{path: root, rootDev: dev, rootDevOK: ok}}
-	}
+	case fi.Mode().IsRegular():
 		dev, ino := inodeOfInfo(fi)
 		sendEvent(ctx, events, walkEvent{rec: fileRec{
 			path:  root,
 			size:  fi.Size(),
-		mtime: fi.ModTime(),
+			mtime: fi.ModTime().Unix(),
 			dev:   dev,
 			ino:   ino,
 		}})
 		return nil
 	default:
 		return nil
 	}
 }
 // startWalkWorkers starts the walk worker pool. Each worker processes
@@ -1081,12 +929,6 @@ func walkOneDir(ctx context.Context, job dirJob, oneFS bool,
 	var subs []dirJob
 	for _, e := range entries {
 		// A cancelled scan wants nothing more from this directory: stop
 		// rather than lstat the rest of a large one.
 		if ctx.Err() != nil {
 			return nil
 		}
 		p := filepath.Join(job.path, e.Name())
 		if e.IsDir() {
@@ -1135,7 +977,7 @@ func emitFile(ctx context.Context, p string, e fs.DirEntry,
 	sendEvent(ctx, events, walkEvent{rec: fileRec{
 		path:  p,
 		size:  info.Size(),
-		mtime: info.ModTime(),
+		mtime: info.ModTime().Unix(),
 		dev:   dev,
 		ino:   ino,
 	}})
@@ -6,22 +6,15 @@ import (
 	"crypto/sha256"
 	"database/sql"
 	"encoding/hex"
 	"errors"
 	"fmt"
 	"io"
 	"io/fs"
 	"os"
 	"os/signal"
 	"path/filepath"
 	"runtime"
 	"slices"
 	"strconv"
 	"strings"
 	"syscall"
 	"testing"
 	"time"
 	"golang.org/x/sys/unix"
 )
 // writeFile creates a file with the given content and returns its path.
@@ -406,7 +399,7 @@ func TestScanContentGate(t *testing.T) {
 		}
 	}
-	groups := dupeGroups(t, db)
+	groups := collectDupeGroups(recs)
 	if len(groups) != 1 || !slices.Equal(groups[0].paths, same) {
 		t.Fatalf("groups = %+v, want only the identical pair %q",
 			groups, same)
@@ -441,7 +434,7 @@ func TestScanContentAcrossOperands(t *testing.T) {
 	want := []string{a, b}
 	slices.Sort(want)
-	groups := dupeGroups(t, db)
+	groups := collectDupeGroups(recs)
 	if len(groups) != 1 || !slices.Equal(groups[0].paths, want) {
 		t.Fatalf("groups = %+v, want the pair %q", groups, want)
 	}
@@ -462,13 +455,13 @@ func TestScanContentWithinOperand(t *testing.T) {
 	added := sparseFile(t, dir, "d2", headTailMin)
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: 3, added: 1, unchanged: 2}) {
+	if st != (scanStats{added: 1, unchanged: 2}) {
 		t.Fatalf("rescan stats = %+v, want 1 added 2 unchanged", st)
 	}
 	want := []string{stored, added}
-	groups := dupeGroups(t, db)
+	groups := collectDupeGroups(dbRecords(t, db))
 	if len(groups) != 1 || !slices.Equal(groups[0].paths, want) {
 		t.Fatalf("groups = %+v, want the pair %q", groups, want)
 	}
@@ -508,7 +501,7 @@ func TestScanContentStalePartners(t *testing.T) {
 	sparseFile(t, dirB, "changed-copy", headTailMin+1)
 	st := syncTree(t, db, dirB)
-	if st != (scanStats{walked: 2, added: 2}) {
+	if st != (scanStats{added: 2}) {
 		t.Errorf("stats = %+v, want 2 added and nothing skipped", st)
 	}
@@ -526,7 +519,7 @@ func TestScanContentStalePartners(t *testing.T) {
 		}
 	}
-	if groups := dupeGroups(t, db); len(groups) != 0 {
+	if groups := collectDupeGroups(recs); len(groups) != 0 {
 		t.Errorf("groups = %+v, want none", groups)
 	}
 }
@@ -565,7 +558,7 @@ func TestScanContentHashedStalePartners(t *testing.T) {
 	b := sparseFile(t, t.TempDir(), "copy", headTailMin)
 	st := syncTree(t, db, filepath.Dir(b))
-	if st != (scanStats{walked: 1, added: 1}) {
+	if st != (scanStats{added: 1}) {
 		t.Errorf("stats = %+v, want 1 added and nothing skipped", st)
 	}
@@ -577,71 +570,12 @@ func TestScanContentHashedStalePartners(t *testing.T) {
 	// The stored records lie outside the operand and are left as they
 	// are, so they still group with each other, but not with the copy.
-	groups := dupeGroups(t, db)
+	groups := collectDupeGroups(recs)
 	if len(groups) != 1 || !slices.Equal(groups[0].paths, stored) {
 		t.Errorf("groups = %+v, want only the stored pair %q", groups, stored)
 	}
 }
 // TestScanContentSameSecondRewrite is TestScanContentStalePartners for
 // a stored file rewritten in place at the same size with an mtime later
 // in the same second than recorded: the file counts as changed, so
 // neither it nor its match inside the operand is read.
 func TestScanContentSameSecondRewrite(t *testing.T) {
 	t.Parallel()
 	db := openTestDB(t)
 	dirA := t.TempDir()
 	changed := sparseFileWithoutMatch(t, dirA, "changed", headTailMin)
 	first := time.Date(2026, 1, 2, 3, 4, 5, 100_000_000, time.UTC)
 	err := os.Chtimes(changed, first, first)
 	if err != nil {
 		t.Fatal(err)
 	}
 	syncTree(t, db, dirA)
 	before := dbRecords(t, db)
 	// Rewrite one byte in place, keeping the size.
 	pokeAt(t, changed, headTailMin/2, []byte{1})
 	later := first.Add(500 * time.Millisecond)
 	err = os.Chtimes(changed, later, later)
 	if err != nil {
 		t.Fatal(err)
 	}
 	dirB := t.TempDir()
 	sparseFile(t, dirB, "changed-copy", headTailMin)
 	st := syncTree(t, db, dirB)
 	if st != (scanStats{walked: 1, added: 1}) {
 		t.Errorf("stats = %+v, want 1 added and nothing skipped", st)
 	}
 	recs := dbRecords(t, db)
 	for _, r := range recs {
 		if r.content != "" {
 			t.Errorf("%s: content = %q, want none: its only match is stale",
 				r.path, r.content)
 		}
 	}
 	for _, old := range before {
 		if r := recordByPath(t, recs, old.path); r != old {
 			t.Errorf("record = %+v, want it left as %+v", r, old)
 		}
 	}
 	if groups := dupeGroups(t, db); len(groups) != 0 {
 		t.Errorf("groups = %+v, want none", groups)
 	}
 }
 // TestScanContentReadFailure checks that a failed content read is
 // counted as skipped and leaves the record without a content hash, and
 // that a later scan tries the read again.
@@ -664,7 +598,7 @@ func TestScanContentReadFailure(t *testing.T) {
 	b := sparseFile(t, dirB, "b", headTailMin)
 	st := syncTree(t, db, dirB)
-	if st != (scanStats{walked: 1, added: 1, skipped: 1}) {
+	if st != (scanStats{added: 1, skipped: 1}) {
 		t.Fatalf("stats = %+v, want 1 added 1 skipped", st)
 	}
@@ -678,14 +612,14 @@ func TestScanContentReadFailure(t *testing.T) {
 	}
 	st = syncTree(t, db, dirB)
-	if st != (scanStats{walked: 1, unchanged: 1}) {
+	if st != (scanStats{unchanged: 1}) {
 		t.Fatalf("rescan stats = %+v, want 1 unchanged", st)
 	}
 	want := []string{a, b}
 	slices.Sort(want)
-	groups := dupeGroups(t, db)
+	groups := collectDupeGroups(dbRecords(t, db))
 	if len(groups) != 1 || !slices.Equal(groups[0].paths, want) {
 		t.Fatalf("groups = %+v, want the pair %q after the retry",
 			groups, want)
@@ -724,7 +658,7 @@ func TestScanContentCheckError(t *testing.T) {
 	b := sparseFile(t, t.TempDir(), "b", headTailMin)
 	st := syncTree(t, db, filepath.Dir(b))
-	if st != (scanStats{walked: 1, added: 1, skipped: 1}) {
+	if st != (scanStats{added: 1, skipped: 1}) {
 		t.Fatalf("stats = %+v, want 1 added 1 skipped", st)
 	}
@@ -752,7 +686,7 @@ func TestScanContentHardlinks(t *testing.T) {
 	c := sparseFile(t, dir, "copy", headTailMin)
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: 3, added: 3}) {
+	if st != (scanStats{added: 3}) {
 		t.Fatalf("stats = %+v, want 3 added", st)
 	}
@@ -844,8 +778,8 @@ func TestWalk(t *testing.T) {
 			t.Errorf("%s: size = %d, want 1..3", r.path, r.size)
 		}
-		if r.mtime.Unix() <= 0 {
+		if r.mtime <= 0 {
-			t.Errorf("%s: mtime = %v, want after 1970", r.path, r.mtime)
+			t.Errorf("%s: mtime = %d, want positive", r.path, r.mtime)
 		}
 	}
 }
@@ -922,11 +856,9 @@ func TestWalkFileAndSymlinkOperands(t *testing.T) {
 		t.Fatalf("file operand: recs = %+v, errs = %d", recs, errs)
 	}
-	// A symlink operand that reaches the walk (it became one after
+	// A symlink operand is not followed and yields nothing.
 	// walkableRoots checked it) is not followed: it yields a warning and
 	// no records.
 	recs, errs = collectWalk(t, []string{link}, false, 2)
-	if errs != 1 || len(recs) != 0 {
+	if errs != 0 || len(recs) != 0 {
 		t.Fatalf("symlink operand: recs = %+v, errs = %d", recs, errs)
 	}
 }
@@ -975,159 +907,6 @@ func TestDeviceOfInfo(t *testing.T) {
 	}
 }
 // dirEntryFor returns the fs.DirEntry for name within dir, obtained via
 // the same os.ReadDir the walk uses, so it carries a real Info().
 func dirEntryFor(t *testing.T, dir, name string) fs.DirEntry {
 	t.Helper()
 	entries, err := os.ReadDir(dir)
 	if err != nil {
 		t.Fatal(err)
 	}
 	for _, e := range entries {
 		if e.Name() == name {
 			return e
 		}
 	}
 	t.Fatalf("entry %q not found in %q", name, dir)
 	return nil
 }
 // callSubdirJob runs subdirJob against e under parent, collecting any
 // warning events it emits (subdirJob emits at most one).
 func callSubdirJob(t *testing.T, p string, e fs.DirEntry,
 	parent dirJob, oneFS bool,
 ) (dirJob, bool, []walkEvent) {
 	t.Helper()
 	events := make(chan walkEvent, 1)
 	job, ok := subdirJob(t.Context(), p, e, parent, oneFS, events)
 	close(events)
 	var evs []walkEvent
 	for ev := range events {
 		evs = append(evs, ev)
 	}
 	return job, ok, evs
 }
 // TestSubdirJobOneFilesystem exercises the -x boundary check in
 // subdirJob directly, so no second real filesystem is needed. The
 // subdirectory's real device is compared against a fabricated operand
 // device.
 func TestSubdirJobOneFilesystem(t *testing.T) {
 	t.Parallel()
 	dir := t.TempDir()
 	sub := filepath.Join(dir, "sub")
 	err := os.Mkdir(sub, 0o750)
 	if err != nil {
 		t.Fatal(err)
 	}
 	info, err := os.Lstat(sub)
 	if err != nil {
 		t.Fatal(err)
 	}
 	dev, ok := deviceOfInfo(info)
 	if !ok {
 		t.Skip("platform exposes no device id")
 	}
 	// A device the subdirectory is not on, standing in for an operand
 	// rooted on a different filesystem.
 	otherDev := dev + 1
 	e := dirEntryFor(t, dir, "sub")
 	cases := []struct {
 		name   string
 		oneFS  bool
 		parent dirJob
 		wantOK bool
 	}{
 		// -x on, subdirectory on a different device than its operand:
 		// descent is refused.
 		{"reject across boundary", true,
 			dirJob{rootDev: otherDev, rootDevOK: true}, false},
 		// -x on but the operand's own device is unknown: the boundary
 		// check is bypassed and descent proceeds.
 		{"bypass when root device unknown", true,
 			dirJob{rootDev: otherDev, rootDevOK: false}, true},
 		// Default (no -x): boundaries are crossed even onto a different
 		// device.
 		{"cross by default", false,
 			dirJob{rootDev: otherDev, rootDevOK: true}, true},
 	}
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			job, ok, evs := callSubdirJob(t, sub, e, tc.parent, tc.oneFS)
 			if ok != tc.wantOK {
 				t.Fatalf("accepted = %v, want %v", ok, tc.wantOK)
 			}
 			if len(evs) != 0 {
 				t.Fatalf("unexpected events: %+v", evs)
 			}
 			// The accepted job must carry the operand's device down, or -x
 			// stops checking below the first level.
 			want := dirJob{
 				path:      sub,
 				rootDev:   tc.parent.rootDev,
 				rootDevOK: tc.parent.rootDevOK,
 			}
 			if ok && job != want {
 				t.Fatalf("job = %+v, want %+v", job, want)
 			}
 		})
 	}
 }
 // errInfoUnavailable is returned by errDirEntry.Info().
 var errInfoUnavailable = errors.New("info unavailable")
 // errDirEntry is a directory entry whose Info() always fails, driving
 // subdirJob's stat-error branch deterministically.
 type errDirEntry struct{ name string }
 func (e errDirEntry) Name() string { return e.name }
 func (errDirEntry) IsDir() bool    { return true }
 func (errDirEntry) Type() fs.FileMode {
 	return fs.ModeDir
 }
 func (errDirEntry) Info() (fs.FileInfo, error) {
 	return nil, errInfoUnavailable
 }
 // TestSubdirJobStatError asserts that when a subdirectory's Info()
 // fails under -x, subdirJob warns and refuses descent.
 func TestSubdirJobStatError(t *testing.T) {
 	t.Parallel()
 	p := "/does/not/matter/sub"
 	_, ok, evs := callSubdirJob(t, p, errDirEntry{name: "sub"},
 		dirJob{rootDev: 1, rootDevOK: true}, true)
 	if ok {
 		t.Fatal("descent accepted after stat error, want refused")
 	}
 	if len(evs) != 1 || !evs[0].fail || !strings.Contains(evs[0].warn, p) {
 		t.Fatalf("want one warning naming the path, got %+v", evs)
 	}
 }
 // buildSmokeTree recreates the README smoke-test filesystem layout
 // with deterministic content and returns the tree root.
 func buildSmokeTree(t *testing.T) string {
@@ -1174,16 +953,11 @@ func syncTree(t *testing.T, db *sql.DB, roots ...string) scanStats {
 	return st
 }
-// dbRecords returns every record currently in the database, in path
+// dbRecords returns every record currently in the database.
 // order.
 func dbRecords(t *testing.T, db *sql.DB) []scanRec {
 	t.Helper()
-	var recs []scanRec
+	recs, err := loadFileRows(t.Context(), db)
 	err := loadFileRows(t.Context(), db, func(r scanRec) {
 		recs = append(recs, r)
 	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1220,10 +994,10 @@ func recordPaths(recs []scanRec) []string {
 // assertSmokeDupeGroups checks the file-level duplicate groups for the
 // smoke tree rooted at dir.
-func assertSmokeDupeGroups(t *testing.T, dir string, db *sql.DB) {
+func assertSmokeDupeGroups(t *testing.T, dir string, parsed []scanRec) {
 	t.Helper()
-	groups := dupeGroups(t, db)
+	groups := collectDupeGroups(parsed)
 	if len(groups) != 5 {
 		t.Fatalf("len(groups) = %d, want 5", len(groups))
 	}
@@ -1248,10 +1022,11 @@ func assertSmokeDupeGroups(t *testing.T, dir string, db *sql.DB) {
 // assertSmokeTreeGroups checks the duplicate-tree groups for the smoke
 // tree rooted at dir.
-func assertSmokeTreeGroups(t *testing.T, dir string, db *sql.DB) {
+func assertSmokeTreeGroups(t *testing.T, dir string, parsed []scanRec) {
 	t.Helper()
-	super, dirs := dbTree(t, db)
+	super, dirs := buildHierarchy(parsed)
 	super.compute()
 	tg := collectTreeGroups(dirs, super)
 	if len(tg) != 1 {
@@ -1276,7 +1051,7 @@ func TestScanPipeline(t *testing.T) {
 	db := openTestDB(t)
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: smokeTreeFiles, added: smokeTreeFiles}) {
+	if st != (scanStats{added: smokeTreeFiles}) {
 		t.Fatalf("stats = %+v, want %d added only", st, smokeTreeFiles)
 	}
@@ -1285,8 +1060,8 @@ func TestScanPipeline(t *testing.T) {
 		t.Fatalf("len(records) = %d, want %d", len(parsed), smokeTreeFiles)
 	}
-	assertSmokeDupeGroups(t, dir, db)
+	assertSmokeDupeGroups(t, dir, parsed)
-	assertSmokeTreeGroups(t, dir, db)
+	assertSmokeTreeGroups(t, dir, parsed)
 }
 func TestSyncScanUnchangedReuse(t *testing.T) {
@@ -1299,7 +1074,7 @@ func TestSyncScanUnchangedReuse(t *testing.T) {
 	writeFile(t, dir, "b.bin", pattern(2, 600))
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: 2, added: 2}) {
+	if st != (scanStats{added: 2}) {
 		t.Fatalf("first scan stats = %+v, want 2 added", st)
 	}
@@ -1313,7 +1088,7 @@ func TestSyncScanUnchangedReuse(t *testing.T) {
 	}
 	st = syncTree(t, db, dir)
-	if st != (scanStats{walked: 2, unchanged: 2}) {
+	if st != (scanStats{unchanged: 2}) {
 		t.Fatalf("rescan stats = %+v, want 2 unchanged", st)
 	}
@@ -1342,176 +1117,15 @@ func TestSyncScanMtimeBump(t *testing.T) {
 	}
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: 1, updated: 1}) {
+	if st != (scanStats{updated: 1}) {
 		t.Fatalf("mtime-bump stats = %+v, want 1 updated", st)
 	}
-	if r := recordByPath(t, dbRecords(t, db), a); !r.mtime.Equal(future) {
+	if r := recordByPath(t, dbRecords(t, db), a); r.mtime != future.Unix() {
-		t.Fatalf("mtime = %v, want %v", r.mtime, future)
+		t.Fatalf("mtime = %d, want %d", r.mtime, future.Unix())
 	}
 }
 // assertWholeFileHashed fails unless the record for path holds the
 // whole-file hash of data as its head, tail, and content.
 func assertWholeFileHashed(t *testing.T, db *sql.DB, path string,
 	data []byte,
 ) {
 	t.Helper()
 	r := recordByPath(t, dbRecords(t, db), path)
 	if want := hexSum(data); r.head != want || r.tail != want ||
 		r.content != want {
 		t.Fatalf("head, tail, content = %q, %q, %q, want %q for each",
 			r.head, r.tail, r.content, want)
 	}
 }
 // TestSyncScanSameSecondRewrite rewrites a file in place at the same
 // size with an mtime later in the same second as the recorded one: the
 // next scan must notice the change and re-hash the file.
 func TestSyncScanSameSecondRewrite(t *testing.T) {
 	t.Parallel()
 	dir := t.TempDir()
 	db := openTestDB(t)
 	a := writeFile(t, dir, "a.bin", pattern(1, 500))
 	// b.bin shares the size of a.bin, so a.bin is hashed.
 	writeFile(t, dir, "b.bin", pattern(2, 500))
 	first := time.Date(2026, 1, 2, 3, 4, 5, 100_000_000, time.UTC)
 	err := os.Chtimes(a, first, first)
 	if err != nil {
 		t.Fatal(err)
 	}
 	syncTree(t, db, dir)
 	rewritten := pattern(3, 500)
 	writeFile(t, dir, "a.bin", rewritten)
 	later := first.Add(500 * time.Millisecond)
 	err = os.Chtimes(a, later, later)
 	if err != nil {
 		t.Fatal(err)
 	}
 	st := syncTree(t, db, dir)
 	if st != (scanStats{walked: 2, updated: 1, unchanged: 1}) {
 		t.Fatalf("rescan stats = %+v, want 1 updated 1 unchanged", st)
 	}
 	assertWholeFileHashed(t, db, a, rewritten)
 }
 // TestSyncScanOperandSameSecondRewrite is TestSyncScanSameSecondRewrite
 // for files given to scan as operands, which scan stats without reading
 // their directory.
 func TestSyncScanOperandSameSecondRewrite(t *testing.T) {
 	t.Parallel()
 	dir := t.TempDir()
 	db := openTestDB(t)
 	a := writeFile(t, dir, "a.bin", pattern(1, 500))
 	// b.bin shares the size of a.bin, so a.bin is hashed.
 	b := writeFile(t, dir, "b.bin", pattern(2, 500))
 	first := time.Date(2026, 1, 2, 3, 4, 5, 100_000_000, time.UTC)
 	err := os.Chtimes(a, first, first)
 	if err != nil {
 		t.Fatal(err)
 	}
 	syncTree(t, db, a, b)
 	rewritten := pattern(3, 500)
 	writeFile(t, dir, "a.bin", rewritten)
 	later := first.Add(500 * time.Millisecond)
 	err = os.Chtimes(a, later, later)
 	if err != nil {
 		t.Fatal(err)
 	}
 	st := syncTree(t, db, a, b)
 	if st != (scanStats{walked: 2, updated: 1, unchanged: 1}) {
 		t.Fatalf("rescan stats = %+v, want 1 updated 1 unchanged", st)
 	}
 	assertWholeFileHashed(t, db, a, rewritten)
 }
 // TestSyncScanRewriteAfter2262 runs assertLateRewriteRehashed with an
 // mtime after 2262, a time too late to count in nanoseconds in an int64.
 func TestSyncScanRewriteAfter2262(t *testing.T) {
 	t.Parallel()
 	assertLateRewriteRehashed(t, time.Date(2300, 1, 2, 3, 4, 5, 0, time.UTC))
 }
 // TestSyncScanRewritePastTimeLimit runs assertLateRewriteRehashed with an
 // mtime one second past the latest a time.Time holds without wrapping it
 // to a time far in the past.
 func TestSyncScanRewritePastTimeLimit(t *testing.T) {
 	t.Parallel()
 	assertLateRewriteRehashed(t, time.Unix(9223371974719179008, 0))
 }
 // assertLateRewriteRehashed scans a directory, rewrites a file in it in
 // place at the same size, sets its mtime to late, and fails unless the
 // next scan re-hashes the file. It skips where late does not fit the
 // platform's timespec or the filesystem does not store it.
 func assertLateRewriteRehashed(t *testing.T, late time.Time) {
 	t.Helper()
 	dir := t.TempDir()
 	db := openTestDB(t)
 	a := writeFile(t, dir, "a.bin", pattern(1, 500))
 	// b.bin shares the size of a.bin, so a.bin is hashed.
 	writeFile(t, dir, "b.bin", pattern(2, 500))
 	syncTree(t, db, dir)
 	rewritten := pattern(3, 500)
 	writeFile(t, dir, "a.bin", rewritten)
 	// os.Chtimes cannot set such a time: it converts through UnixNano.
 	ts, err := unix.TimeToTimespec(late)
 	if err != nil {
 		t.Skipf("an mtime %d seconds after 1970 does not fit this platform's "+
 			"timespec: %v", late.Unix(), err)
 	}
 	err = unix.UtimesNano(a, []unix.Timespec{ts, ts})
 	if err != nil {
 		t.Fatal(err)
 	}
 	fi, err := os.Lstat(a)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if fi.ModTime().Unix() != late.Unix() {
 		t.Skipf("the filesystem stored the mtime as %d seconds after 1970, "+
 			"not %d", fi.ModTime().Unix(), late.Unix())
 	}
 	st := syncTree(t, db, dir)
 	if st != (scanStats{walked: 2, updated: 1, unchanged: 1}) {
 		t.Fatalf("rescan stats = %+v, want 1 updated 1 unchanged", st)
 	}
 	assertWholeFileHashed(t, db, a, rewritten)
 }
 func TestSyncScanAddRemove(t *testing.T) {
 	t.Parallel()
@@ -1531,7 +1145,7 @@ func TestSyncScanAddRemove(t *testing.T) {
 	}
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: 2, added: 1, removed: 1, unchanged: 1}) {
+	if st != (scanStats{added: 1, removed: 1, unchanged: 1}) {
 		t.Fatalf("add/remove stats = %+v, want 1 added 1 removed 1 unchanged",
 			st)
 	}
@@ -1557,7 +1171,9 @@ func TestSyncScanSizeChange(t *testing.T) {
 	writeFile(t, dir, "f", pattern(1, 200))
-	err := os.Chtimes(p, old.mtime, old.mtime)
+	mt := time.Unix(old.mtime, 0)
 	err := os.Chtimes(p, mt, mt)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1646,7 +1262,7 @@ func TestSyncScanOverlappingRoots(t *testing.T) {
 	// A file reachable via two overlapping operands is deduplicated
 	// by path in the shared walk and processed once.
 	st := syncTree(t, db, dir, filepath.Join(dir, "sub"))
-	if st != (scanStats{walked: 1, added: 1}) {
+	if st != (scanStats{added: 1}) {
 		t.Fatalf("stats = %+v, want 1 added", st)
 	}
@@ -1667,7 +1283,7 @@ func TestScanSkipsUniqueSizes(t *testing.T) {
 	// Neither size is shared, so neither file is read: both records
 	// are written without hashes and no duplicates are reported.
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: 2, added: 2}) {
+	if st != (scanStats{added: 2}) {
 		t.Fatalf("stats = %+v, want 2 added", st)
 	}
@@ -1679,7 +1295,7 @@ func TestScanSkipsUniqueSizes(t *testing.T) {
 		}
 	}
-	if groups := dupeGroups(t, db); len(groups) != 0 {
+	if groups := collectDupeGroups(recs); len(groups) != 0 {
 		t.Fatalf("groups = %+v, want none from unhashed records", groups)
 	}
@@ -1689,12 +1305,12 @@ func TestScanSkipsUniqueSizes(t *testing.T) {
 	c := writeFile(t, dir, "c.bin", pattern(1, 500))
 	st = syncTree(t, db, dir)
-	if st != (scanStats{walked: 3, added: 1, updated: 1, unchanged: 1}) {
+	if st != (scanStats{added: 1, updated: 1, unchanged: 1}) {
 		t.Fatalf("rescan stats = %+v, want 1 added 1 updated 1 unchanged",
 			st)
 	}
-	groups := dupeGroups(t, db)
+	groups := collectDupeGroups(dbRecords(t, db))
 	if len(groups) != 1 {
 		t.Fatalf("groups = %+v, want the a/c pair", groups)
 	}
@@ -1730,7 +1346,8 @@ func TestTreesUnhashedNeverEqual(t *testing.T) {
 	}
 	for name, unknown := range cases {
-		super, dirs := treeOf(t, append(slices.Clone(shared), unknown...))
+		super, dirs := buildHierarchy(append(slices.Clone(shared), unknown...))
 		super.compute()
 		if tg := collectTreeGroups(dirs, super); len(tg) != 0 {
 			t.Errorf("%s: tree groups = %d, want 0 (the files may differ)",
@@ -1753,7 +1370,7 @@ func TestScanHardlinksReadOnce(t *testing.T) {
 	}
 	st := syncTree(t, db, dir)
-	if st != (scanStats{walked: 2, added: 2}) {
+	if st != (scanStats{added: 2}) {
 		t.Fatalf("stats = %+v, want 2 added", st)
 	}
@@ -1767,7 +1384,7 @@ func TestScanHardlinksReadOnce(t *testing.T) {
 		t.Fatalf("hardlink hashes differ: %+v vs %+v", ra, rb)
 	}
-	if groups := dupeGroups(t, db); len(groups) != 1 {
+	if groups := collectDupeGroups(recs); len(groups) != 1 {
 		t.Fatalf("groups = %+v, want the hardlink pair", groups)
 	}
 }
@@ -1875,13 +1492,6 @@ func injectWriteFailure(t *testing.T, path string) {
 func baselineGoroutines(t *testing.T) int {
 	t.Helper()
 	// The first scan command in a process starts os/signal's goroutine,
 	// which never exits. Start it now, so the baseline counts it
 	// instead of the scan seeming to leave it behind.
 	ch := make(chan os.Signal, 1)
 	signal.Notify(ch, syscall.SIGINT)
 	signal.Stop(ch)
 	deadline := time.Now().Add(goroutineSettle)
 	last := runtime.NumGoroutine()
@@ -1938,7 +1548,7 @@ func TestScanHashWriteFailureUnwindsPool(t *testing.T) {
 	code := run([]string{
 		cmdScan, "--workers", strconv.Itoa(hashLeakWorkers), dir,
-	}, io.Discard, &stderr)
+	}, &stderr)
 	if code != exitFatal {
 		t.Fatalf("run(scan) = %d, want %d; stderr: %s",
 			code, exitFatal, stderr.String())
@@ -2015,8 +1625,10 @@ func TestReportsNeverTouchFilesystem(t *testing.T) {
 		t.Fatal(err)
 	}
-	assertSmokeDupeGroups(t, dir, db)
+	recs := dbRecords(t, db)
-	assertSmokeTreeGroups(t, dir, db)
+
 	assertSmokeDupeGroups(t, dir, recs)
 	assertSmokeTreeGroups(t, dir, recs)
 }
 func TestUnderRoot(t *testing.T) {
@@ -2,21 +2,15 @@
 # script/bootstrap: install all dependencies needed to build and develop
 # this repo. Idempotent: every install is guarded by a check so already
 # installed tools are skipped. Base tooling comes from nix, apt, brew,
-# or apk (detected in that order); assumes nothing is present. Node is
+# or apk (detected in that order); assumes nothing is present (not git,
-# used directly if installed; otherwise it is installed at a pinned
+# make, or go). The linter is NOT installed: golangci-lint runs via
-# version via nvm (installing nvm itself first, from a hash-verified
+# docker only (script/lint), pinned by image digest, so the only lint
-# release archive, never curl | sh).
+# prerequisite is a working docker — which is warned about, not
 # installed, because everything except linting works without it.
 set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 # Pinned versions, 2026-07-06
 NODE_VERSION="22.17.0"
 NVM_VERSION="0.40.3"
 # sha256 of https://github.com/nvm-sh/nvm/archive/refs/tags/v0.40.3.tar.gz
 NVM_SHA256="5f4d6aaa04a177dc93c985e31dbc411ab6b8c6e1e21d8015dbc1372625fcd1d0"
 YARN_VERSION="1.22.22"
 PKGMGR=""
 SUDO=""
 APT_UPDATED=""
@@ -49,7 +43,6 @@ pkg_install() {
    case "$PKGMGR" in
        nix) nix-env -iA "nixpkgs.$1" ;;
        apt)
            # Package lists may be empty (fresh images); refresh once per run.
            if [ -z "$APT_UPDATED" ]; then
                $SUDO env DEBIAN_FRONTEND=noninteractive apt-get update
                APT_UPDATED=1
@@ -65,82 +58,30 @@ missing() {
    ! command -v "$1" >/dev/null 2>&1
 }
 # verify_sha256 <file> <expected-hash>
 verify_sha256() {
    if command -v sha256sum >/dev/null 2>&1; then
        actual="$(sha256sum "$1" | cut -d' ' -f1)"
    else
        actual="$(shasum -a 256 "$1" | cut -d' ' -f1)"
    fi
    if [ "$actual" != "$2" ]; then
        echo "bootstrap: sha256 mismatch for $1" >&2
        echo "  expected: $2" >&2
        echo "  actual:   $actual" >&2
        exit 1
    fi
 }
 # nvm is a bash script; run a command in a bash with nvm loaded
 nvm_sh() {
    bash -c ". \"\$HOME/.nvm/nvm.sh\" && $*"
 }
 ensure_nvm() {
    [ -s "$HOME/.nvm/nvm.sh" ] && return 0
    # nvm prerequisites; nvm itself requires bash
    if missing bash; then pkg_install bash bash bash bash; fi
    if missing curl; then pkg_install curl curl curl curl; fi
    if missing git; then pkg_install git git git git; fi
    tmp="$(mktemp -d)"
    curl -fsSL -o "$tmp/nvm.tar.gz" \
        "https://github.com/nvm-sh/nvm/archive/refs/tags/v${NVM_VERSION}.tar.gz"
    verify_sha256 "$tmp/nvm.tar.gz" "$NVM_SHA256"
    mkdir -p "$HOME/.nvm"
    tar -xzf "$tmp/nvm.tar.gz" -C "$HOME/.nvm" --strip-components=1
    rm -rf "$tmp"
 }
 ensure_node() {
    if ! missing node; then return 0; fi
    ensure_nvm
    nvm_sh "nvm install $NODE_VERSION"
 }
 ensure_yarn() {
    if ! missing yarn; then return 0; fi
    if ! missing corepack; then
        corepack enable
        corepack prepare "yarn@$YARN_VERSION" --activate
    elif [ -s "$HOME/.nvm/nvm.sh" ]; then
        nvm_sh "nvm use $NODE_VERSION >/dev/null && corepack enable && \
            corepack prepare yarn@$YARN_VERSION --activate"
    else
        npm install -g "yarn@$YARN_VERSION"
    fi
 }
 install_js_deps() {
    if missing yarn && [ -s "$HOME/.nvm/nvm.sh" ]; then
        nvm_sh "nvm use $NODE_VERSION >/dev/null && cd \"$ROOT\" && \
            yarn install --frozen-lockfile"
    else
        yarn install --frozen-lockfile
    fi
 }
 main() {
    cd "$ROOT"
-    if missing make; then pkg_install gnumake make make make; fi
+    # System tooling, deliberately unpinned: these come from the host
    # package manager and whatever version it ships is what the host
    # gets, so a presence check is the right check. The repo pins no
    # system toolchain versions — the Go language version is governed by
    # go.mod, and builds that must be reproducible run in the Docker
    # image, whose base images are pinned by digest.
    if missing git; then pkg_install git git git git; fi
-    # Go builds the binary and runs gofmt. Presence is the whole check:
+    if missing make; then pkg_install gnumake make make make; fi
    # go.mod names the Go version, and the tests and the linter run in
    # digest-pinned images.
    if missing go; then pkg_install go golang go go; fi
-    ensure_node
+    # Linting runs via docker only (script/lint), so docker is a lint
-    ensure_yarn
+    # prerequisite rather than something bootstrap installs. Warn, do
-    install_js_deps
+    # not fail: everything except `make lint` — and, through it,
    # `make check`, `make docker` and the pre-commit hook — works
    # without it.
    if missing docker; then
        echo "bootstrap: WARNING: docker not found; make lint, make check" >&2
        echo "bootstrap: and make docker require it. Install docker to" >&2
        echo "bootstrap: run the linter." >&2
    fi
    go mod download
    echo "bootstrap complete"
@@ -1,8 +1,6 @@
 #!/bin/sh
 # script/check: run all checks (test, lint, fmt-check). Our own
-# extension to scripts-to-rule-them-all. test and lint are Docker
+# extension to scripts-to-rule-them-all. Must not modify any files.
 # phases; fmt-check is native, because a formatter writes the working
 # tree. Must not modify any files.
 set -eu
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -1,30 +1,34 @@
 #!/bin/sh
-# script/cibuild: run the CI build. It bootstraps first: a CI runner
+# script/cibuild: run the CI build. The Gitea workflow runs this on
-# checks out and runs this and nothing else, and script/fmt-check runs
+# push.
-# the formatter on the host, which a pristine checkout cannot do.
+#
-# --no-cache for the same reason as script/docker: the gate phases the
+# The Dockerfile runs the gates individually as build steps, not the
-# final stage depends on are RUN steps, and a cached one is a check that
+# make check aggregate: the lint stage runs make fmt-check,
-# did not run.
+# script/verify-lint-image-pin, golangci-lint config verify and
 # golangci-lint run; the build stage, dropped to an unprivileged user,
 # runs make test and make fmt-check. Neither make lint nor make check
 # appears, because both reach script/lint, which is itself a docker
 # build, and a docker build cannot run inside one. Lint is not skipped
 # by that — the linter is invoked directly in the lint stage, and the
 # build stage's COPY --from=lint makes that stage a prerequisite, so
 # BuildKit must finish it first. Between the two stages everything
 # make check would run has run, which is why a successful build here
 # implies the repo is green.
 #
 # That implication holds only because of CHECK_EPOCH. A COPY layer is
 # invalidated by changed content, and a merge commit's tree is
 # byte-identical to the branch head it merges, so without a fresh value
 # here Docker serves the gate layers from cache and the build reports a
 # green it never earned. Passing the current epoch invalidates the gate
 # layers on every run while leaving the pinned base images and
 # go mod download cached; see the Dockerfile for the placement.
 set -eu
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 main() {
    cd "$ROOT"
-    "$SCRIPT_DIR/bootstrap"
+    docker build --build-arg CHECK_EPOCH="$(date +%s)" .
    "$SCRIPT_DIR/check"
    # The version and the tag each get their own line: a failing
    # command substitution inside an argument does not trip `set -e`,
    # so the inline form degrades silently to an empty constant. The
    # VERSION build argument takes precedence over the version a build
    # stage derives from the .git in the context.
    version="$(git describe --tags --always --dirty 2>/dev/null || true)"
    [ -n "$version" ] || version="unknown"
    tag="$("$SCRIPT_DIR/projectname")"
    docker build --no-cache \
        --build-arg VERSION="$version" \
        -t "$tag" .
 }
 main "$@"
@@ -1,8 +1,14 @@
 #!/bin/sh
 # script/docker: build the Docker image tagged with the project name.
-# Identical in all repos; the tag comes from script/projectname.
+# The tag comes from script/projectname.
-# --no-cache because the gate phases the final stage depends on are RUN
+#
-# steps, and a cached one is a check that did not run.
+# CHECK_EPOCH is passed for the same reason script/cibuild passes it:
 # without it Docker serves the Dockerfile's gate layers from cache on an
 # unchanged tree and this exits 0 having run neither the lint stage's
 # gates nor the builder stage's test and fmt-check gates. This is the
 # set of gates a developer or reviewer runs by hand, so a cached pass
 # here is the most misleading result the repo can produce. Dependency
 # layers sit above the ARG and stay cached.
 set -eu
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -10,17 +16,10 @@ ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 main() {
    cd "$ROOT"
-    # The version and the tag each get their own line: a failing
+    docker build \
-    # command substitution inside an argument does not trip `set -e`,
+        --build-arg CHECK_EPOCH="$(date +%s)" \
-    # so the inline form degrades silently to an empty constant. The
+        -t "$("$SCRIPT_DIR/projectname")" \
-    # VERSION build argument takes precedence over the version a build
+        .
    # stage derives from the .git in the context.
    version="$(git describe --tags --always --dirty 2>/dev/null || true)"
    [ -n "$version" ] || version="unknown"
    tag="$("$SCRIPT_DIR/projectname")"
    docker build --no-cache \
        --build-arg VERSION="$version" \
        -t "$tag" .
 }
 main "$@"
@@ -4,29 +4,9 @@ set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 # Must match the pin in script/bootstrap.
 NODE_VERSION="22.17.0"
 # script/bootstrap installs node and yarn under nvm and leaves neither
 # on the PATH of the shell that called it, so resolve the pinned
 # toolchain here the way bootstrap's own install step does. nvm is a
 # bash script, hence the subshell.
 run_yarn() {
    if command -v yarn >/dev/null 2>&1; then
        exec yarn "$@"
    fi
    if [ ! -s "$HOME/.nvm/nvm.sh" ]; then
        echo "fmt: no yarn; run script/bootstrap first" >&2
        exit 1
    fi
    exec bash -c '. "$HOME/.nvm/nvm.sh" && nvm use "$1" >/dev/null &&
        shift && exec yarn "$@"' bash "$NODE_VERSION" "$@"
 }
 main() {
    cd "$ROOT"
    gofmt -s -w .
    run_yarn run prettier --write '**/*.md' --tab-width 4 --prose-wrap always
 }
 main "$@"
@@ -1,50 +1,18 @@
 #!/bin/sh
-# script/fmt-check: check formatting (read-only).
+# script/fmt-check: check formatting (read-only). Same scope as
 # script/fmt, but fails instead of writing.
 set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 # Must match the pin in script/bootstrap.
 NODE_VERSION="22.17.0"
 # script/bootstrap installs node and yarn under nvm and leaves neither
 # on the PATH of the shell that called it, so resolve the pinned
 # toolchain here the way bootstrap's own install step does. nvm is a
 # bash script, hence the subshell.
 run_yarn() {
    if command -v yarn >/dev/null 2>&1; then
        exec yarn "$@"
    fi
    if [ ! -s "$HOME/.nvm/nvm.sh" ]; then
        echo "fmt-check: no yarn; run script/bootstrap first" >&2
        exit 1
    fi
    exec bash -c '. "$HOME/.nvm/nvm.sh" && nvm use "$1" >/dev/null &&
        shift && exec yarn "$@"' bash "$NODE_VERSION" "$@"
 }
 main() {
    cd "$ROOT"
-    status=0
+    files="$(gofmt -s -l .)"
    # gofmt and prettier both run every time, so the output names each
    # one that fails. Under set -e a bare assignment would end the
    # script when gofmt fails (a Go file it cannot parse).
    if ! files="$(gofmt -s -l .)"; then
        echo "gofmt: failed; see its errors above" >&2
        status=1
    fi
    if [ -n "$files" ]; then
        echo "gofmt: files not formatted:" >&2
        echo "$files" >&2
-        status=1
+        exit 1
    fi
    # run_yarn ends in exec; the subshell returns here afterwards.
    (run_yarn run prettier --check '**/*.md' --tab-width 4 --prose-wrap always) ||
        status=1
    exit "$status"
 }
 main "$@"
@@ -1,15 +1,19 @@
 #!/bin/sh
 # script/install-precommit: install the git pre-commit hook that runs
 # script/precommit. Our own extension to scripts-to-rule-them-all.
 # Hooks are shared between the main checkout and all worktrees, so
 # resolve the common git dir instead of assuming .git is a directory.
 set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 main() {
    cd "$ROOT"
-    hook=".git/hooks/pre-commit"
+    hooks_dir="$(git rev-parse --git-common-dir)/hooks"
-    printf '#!/bin/sh\nset -e\nscript/precommit\n' > .git/hooks/pre-commit
+    mkdir -p "$hooks_dir"
-    chmod +x .git/hooks/pre-commit
+    hook="$hooks_dir/pre-commit"
    printf '#!/bin/sh\nset -e\nscript/precommit\n' > "$hook"
    chmod +x "$hook"
    echo "pre-commit hook installed: runs script/precommit"
 }
@@ -1,23 +1,29 @@
 #!/bin/sh
-# script/lint: run the linter. Linting is a phase of the Dockerfile and
+# script/lint: run the linter. golangci-lint is never installed on a
-# this builds that phase alone; the linter is never installed or run on
+# host: it runs via docker only, one way, everywhere — this builds
-# a developer host, where a shared result cache and a host-global lock
+# Dockerfile.lint, which COPYs the repo into the digest-pinned
-# make its answer untrustworthy.
+# golangci-lint image and lints as a build step, so a successful build
 # is a clean lint. The only prerequisite is a working docker. The gate
 # steps make no network calls of their own, but Dockerfile.lint runs
 # `go mod download` above them, so a cold cache does reach the network
 # (as does pulling the pinned image); that layer stays cached, and once
 # it is warm this runs offline until go.mod or go.sum changes.
 #
-# The phase is not the last stage in the file, so it is built only when
+# CHECK_EPOCH is what makes the result mean anything. Without it docker
-# --target names it. --no-cache because a cached lint layer is a lint
+# serves the gate layers from cache on an unchanged tree and this exits
-# that did not run. --output type=cacheonly writes no image, since
+# 0 in well under a second having run no linter. The PID is in the value
-# nothing uses one.
+# as well as the epoch because two lint runs land inside the same second
 # easily, and `date +%s` alone would cache the second one.
 set -eu
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 main() {
    cd "$ROOT"
-    docker build --no-cache \
+    docker build \
-        --target lint \
+        --build-arg CHECK_EPOCH="$(date +%s)-$$" \
-        --output type=cacheonly .
+        -f Dockerfile.lint \
        .
 }
 main "$@"
@@ -1,13 +1,13 @@
 #!/bin/sh
 # script/precommit: run by the git pre-commit hook; fails the commit if
-# checks fail. Our own extension to scripts-to-rule-them-all.
+# checks fail. Our own extension to scripts-to-rule-them-all. Go extra:
 # go mod tidy must be a no-op before the checks run.
 set -eu
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
 ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 main() {
    # Go extra: go mod tidy must be a no-op before the checks run.
    cd "$ROOT"
    go mod tidy
    if ! git diff --exit-code -- go.mod go.sum; then
@@ -1,6 +1,6 @@
 #!/bin/sh
 # script/setup: set up the repo for development after a fresh clone:
-# installs dependencies and the git pre-commit hook.
+# installs dependencies (script/bootstrap) and the git pre-commit hook.
 set -eu
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
@@ -1,19 +1,17 @@
 #!/bin/sh
-# script/test: run the test suite. Testing is a phase of the Dockerfile
+# script/test: run the test suite. Reruns verbosely on failure so CI
-# and this builds that phase alone, on the same terms as script/lint:
+# logs show which test failed.
 # --target because a phase that is not the last stage is built only when
 # named, and --no-cache because a cached test layer is a test that did
 # not run. --output type=cacheonly writes no image, since nothing uses one.
 set -eu
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 main() {
    cd "$ROOT"
-    docker build --no-cache \
+    go test -timeout 30s -cover ./... || {
-        --target test \
+        echo "--- Rerunning with -v for details ---"
-        --output type=cacheonly .
+        go test -timeout 30s -v ./...
        exit 1
    }
 }
 main "$@"
@@ -0,0 +1,84 @@
 #!/bin/sh
 # script/verify-lint-image-pin: fail unless the golangci-lint image
 # referenced by Dockerfile.lint and the one referenced by the main
 # Dockerfile's lint stage are the same image at the same digest. Our own
 # extension to scripts-to-rule-them-all, not one of its entrypoints.
 #
 # The linter version is pinned in two independent files. That is the
 # shape #42 turned into a build failure rather than tolerate: nothing
 # else keeps the two in sync, and a bump applied to one file alone would
 # leave `make lint` and the fail-fast lint stage of `make docker`
 # linting the same tree against different rulesets, both green. This is
 # the single guard that stops it, run as a gate in both files.
 #
 # It deliberately restates neither pin. A hardcoded expected digest here
 # would be a third copy — one more thing to bump, and the same drift one
 # file further out. It compares the two files to each other and knows
 # nothing about which version is correct.
 #
 # A reference that cannot be read is a hard failure, not a skip: a
 # comparison of two empty strings succeeds, which would turn this guard
 # into exactly the unearned green it exists to prevent.
 set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 LINT_DOCKERFILE="Dockerfile.lint"
 MAIN_DOCKERFILE="Dockerfile"
 # Echo the single golangci-lint image reference in the named Dockerfile.
 # Scans every argument of every FROM instruction rather than assuming a
 # field position, so `FROM --platform=... img AS stage` reads correctly.
 # Exits non-zero, with a diagnosis, unless there is exactly one.
 lint_image_ref() {
    file="$1"
    if [ ! -f "$file" ]; then
        echo "verify-lint-image-pin: $file: not found" >&2
        return 1
    fi
    refs="$(
        awk '
            toupper($1) == "FROM" {
                for (i = 2; i <= NF; i++) {
                    if ($i ~ /^golangci\/golangci-lint[:@]/) {
                        print $i
                    }
                }
            }
        ' "$file"
    )"
    count="$(printf '%s' "$refs" | grep -c . || true)"
    if [ "$count" -ne 1 ]; then
        echo "verify-lint-image-pin: $file: expected exactly one" \
            "golangci/golangci-lint FROM reference, found $count" >&2
        return 1
    fi
    printf '%s\n' "$refs"
 }
 main() {
    cd "$ROOT"
    lint_ref="$(lint_image_ref "$LINT_DOCKERFILE")"
    main_ref="$(lint_image_ref "$MAIN_DOCKERFILE")"
    if [ "$lint_ref" != "$main_ref" ]; then
        echo "verify-lint-image-pin: the linter image is pinned twice and" \
            "the two pins disagree:" >&2
        echo "verify-lint-image-pin:   $LINT_DOCKERFILE: $lint_ref" >&2
        echo "verify-lint-image-pin:   $MAIN_DOCKERFILE: $main_ref" >&2
        echo "verify-lint-image-pin: bump both FROM lines together so" \
            "script/lint and the Dockerfile lint stage keep running the" \
            "same linter" >&2
        exit 1
    fi
    echo "verify-lint-image-pin: $LINT_DOCKERFILE and $MAIN_DOCKERFILE" \
        "agree on $lint_ref"
 }
 main "$@"
@@ -5,59 +5,49 @@ import (
 	"context"
 	"crypto/sha256"
 	"fmt"
 	"io"
 	"os"
 	"slices"
 	"strconv"
 	"strings"
 )
-// treeNode is one directory reconstructed from the record paths.
+// fileSig is a file's duplicate signature; mtime is excluded.
 type fileSig struct {
 	size    int64
 	head    string
 	tail    string
 	content string
 }
 // treeNode is one directory reconstructed from the scan stream.
 type treeNode struct {
 	path      string
 	parent    *treeNode
-	// entries holds the serialized child entries until the digest is
+	dirs      map[string]*treeNode
-	// computed from them, and is then dropped.
+	files     map[string]fileSig
 	entries   []string
 	digest    [sha256.Size]byte
 	fileCount int64
 	totalSize int64
 }
 // runTrees implements the trees subcommand: it reads every record from
-// the database in path order, reconstructs the directory hierarchy from
+// the database, reconstructs the directory hierarchy from the record
-// the record paths, computes a Merkle-style digest per directory, and
+// paths, computes a Merkle-style digest per directory, and prints
-// prints maximal duplicate-tree groups as TSV on stdout. It never
+// maximal duplicate-tree groups as TSV on stdout. It never touches the
-// touches the scanned filesystem; its only I/O is the database, stdout,
+// scanned filesystem; its only I/O is the database, stdout, and
-// and stderr. Any database problem, including a missing database, is
+// stderr.
-// fatal.
+func runTrees(ctx context.Context) error {
-func runTrees(ctx context.Context, stdout io.Writer) error {
+	recs, err := loadRecords(ctx)
 	dbPath := databasePath()
 	db, err := openReportDatabase(ctx, dbPath)
 	if err != nil {
 		return err
 	}
-	defer func() { _ = db.Close() }()
+	super, allDirs := buildHierarchy(recs)
-
+	super.compute()
 	records := 0
 	tree := newTreeBuilder()
 	err = loadFileRows(ctx, db, func(r scanRec) {
 		records++
 		tree.add(r)
 	})
 	if err != nil {
 		return fmt.Errorf("database %s: %w", dbPath, err)
 	}
 	super, allDirs := tree.finish()
 	dupes := collectTreeGroups(allDirs, super)
-	out := bufio.NewWriterSize(stdout, ioBufSize)
+	out := bufio.NewWriterSize(os.Stdout, ioBufSize)
 	_, err = fmt.Fprintln(out, "first\tdupe\tfiles\tsize")
 	if err != nil {
@@ -72,8 +62,7 @@ func runTrees(ctx context.Context, stdout io.Writer) error {
 		first := g[0]
 		for _, n := range g[1:] {
 			_, err = fmt.Fprintf(out, "%s\t%s\t%d\t%d\n",
-				escapePath(first.path), escapePath(n.path),
+				first.path, n.path, first.fileCount, first.totalSize)
 				first.fileCount, first.totalSize)
 			if err != nil {
 				return fmt.Errorf("write stdout: %w", err)
 			}
@@ -91,128 +80,65 @@ func runTrees(ctx context.Context, stdout io.Writer) error {
 	fmt.Fprintf(os.Stderr,
 		"trees: %d records read, %d duplicate tree groups, %d dupe trees, "+
 			"%s reclaimable\n",
-		records, len(dupes), dupeTrees, humanBytes(reclaimable))
+		len(recs), len(dupes), dupeTrees, humanBytes(reclaimable))
 	return nil
 }
-// treeBuilder reconstructs the directory hierarchy from records added
+// buildHierarchy reconstructs the directory hierarchy from the record
-// in path order, under a synthetic super-root. Paths are split on "/";
+// paths under a synthetic super-root. Paths are split on "/"; for
-// for absolute paths the first component is empty, which becomes the
+// absolute paths the first component is empty, which simply becomes a
-// top-level directory with path "/". In path order all the paths under
+// top-level node representing "/". It returns the super-root and every
-// one directory come together, so a directory is complete once a path
+// directory node created.
-// outside it is added: its digest is computed then and its entries are
+func buildHierarchy(recs []scanRec) (*treeNode, []*treeNode) {
 // dropped. Only the directories holding the latest path keep entries.
 type treeBuilder struct {
 	super *treeNode
 	// open lists the directories holding the latest path, outermost
 	// first, starting with the super-root; names[i] is open[i]'s name.
 	open  []*treeNode
 	names []string
 	// dirs lists every completed directory.
 	dirs []*treeNode
 }
 func newTreeBuilder() *treeBuilder {
 	super := &treeNode{}
-	return &treeBuilder{
+	var allDirs []*treeNode
 		super: super,
 		open:  []*treeNode{super},
 		names: []string{""},
 	}
 }
-// add adds one record. Each record must come after the previous one in
+	for _, r := range recs {
 // path order (byte order); otherwise a completed directory would be
 // started again as a second directory with the same path.
 func (b *treeBuilder) add(r scanRec) {
 		comps := strings.Split(r.path, "/")
 	dirNames, name := comps[:len(comps)-1], comps[len(comps)-1]
-	// Keep the open directories that hold this path; complete the rest.
+		node := super
-	depth := 1
+		for _, c := range comps[:len(comps)-1] {
-	for depth < len(b.open) && depth <= len(dirNames) &&
+			child := node.dirs[c]
-		b.names[depth] == dirNames[depth-1] {
+			if child == nil {
-		depth++
+				childPath := c
 				if node != super {
 					childPath = node.path + "/" + c
 				}
-	b.closeTo(depth)
+				child = &treeNode{path: childPath, parent: node}
-
+				if node.dirs == nil {
-	for _, c := range dirNames[depth-1:] {
+					node.dirs = make(map[string]*treeNode)
 		b.openDir(c)
 				}
-	dir := b.open[len(b.open)-1]
+				node.dirs[c] = child
-	dir.entries = append(dir.entries, fileEntry(name, r))
+				allDirs = append(allDirs, child)
 	dir.fileCount++
 	dir.totalSize += r.size
 }
 // openDir starts the directory called name inside the innermost open
 // one.
 func (b *treeBuilder) openDir(name string) {
 	parent := b.open[len(b.open)-1]
 	path := parent.path + "/" + name
 	// The root directory's path is "/", not empty, and its children's
 	// paths start with one slash, not two.
 	switch {
 	case parent == b.super && name == "":
 		path = "/"
 	case parent == b.super:
 		path = name
 	case parent.path == "/":
 		path = "/" + name
 			}
-	b.open = append(b.open, &treeNode{path: path, parent: parent})
+			node = child
 	b.names = append(b.names, name)
 }
 // closeTo completes the open directories after the first n, innermost
 // first: each one's digest is computed and entered in its parent along
 // with its totals.
 func (b *treeBuilder) closeTo(n int) {
 	for len(b.open) > n {
 		last := len(b.open) - 1
 		dir, name := b.open[last], b.names[last]
 		b.open, b.names = b.open[:last], b.names[:last]
 		dir.computeDigest()
 		dir.parent.entries = append(dir.parent.entries,
 			"d\x00"+name+"\x00"+string(dir.digest[:]))
 		dir.parent.fileCount += dir.fileCount
 		dir.parent.totalSize += dir.totalSize
 		b.dirs = append(b.dirs, dir)
 		}
 }
-// finish completes every open directory and returns the super-root and
+		if node.files == nil {
-// every directory.
+			node.files = make(map[string]fileSig)
-func (b *treeBuilder) finish() (*treeNode, []*treeNode) {
+		}
 	b.closeTo(1)
-	return b.super, b.dirs
+		sig := fileSig{
-}
+			size: r.size, head: r.head, tail: r.tail, content: r.content,
-
+		}
 // fileEntry serializes a file child for its directory's digest: its
 // name and its signature (size, head, tail, content); mtime is
 // excluded.
 func fileEntry(name string, r scanRec) string {
 	content := r.content
 		// A record without a content hash has unknown content (README
 		// "Database"): give it a signature no other file can share, so
-	// trees containing it never compare equal. Real hashes are hex, so
+		// trees containing it never compare equal. Real hashes are
-	// the NUL-prefixed form cannot collide.
+		// hex, so the NUL-prefixed form cannot collide.
-	if content == "" {
+		if sig.content == "" {
-		content = "unhashed\x00" + r.path
+			sig.content = "unhashed\x00" + r.path
 		}
-	return "f\x00" + name + "\x00" + strconv.FormatInt(r.size, 10) +
+		node.files[comps[len(comps)-1]] = sig
-		"\x00" + r.head + "\x00" + r.tail + "\x00" + content
+	}
 	return super, allDirs
 }
 // collectTreeGroups groups directories by digest and returns every
@@ -254,22 +180,38 @@ func collectTreeGroups(allDirs []*treeNode, super *treeNode) [][]*treeNode {
 	return dupes
 }
-// computeDigest sets n's digest and drops its entries. A directory's
+// compute fills in digest, fileCount, and totalSize for n and all of
-// digest is the SHA-256 of its child entries — files serialized with
+// its descendants. A directory's digest is the SHA-256 of its child
-// name and signature, subdirectories with name and recursive digest —
+// entries — files serialized with name and signature, subdirectories
-// sorted byte-lexicographically. Filenames cannot contain NUL or "/",
+// with name and recursive digest — sorted byte-lexicographically.
-// so NUL delimiters are unambiguous.
+// Filenames cannot contain NUL or "/", so NUL delimiters are
-func (n *treeNode) computeDigest() {
+// unambiguous.
-	slices.Sort(n.entries)
+func (n *treeNode) compute() {
 	entries := make([]string, 0, len(n.dirs)+len(n.files))
 	for name, sig := range n.files {
 		entries = append(entries,
 			"f\x00"+name+"\x00"+strconv.FormatInt(sig.size, 10)+
 				"\x00"+sig.head+"\x00"+sig.tail+"\x00"+sig.content)
 		n.fileCount++
 		n.totalSize += sig.size
 	}
 	for name, child := range n.dirs {
 		child.compute()
 		entries = append(entries, "d\x00"+name+"\x00"+string(child.digest[:]))
 		n.fileCount += child.fileCount
 		n.totalSize += child.totalSize
 	}
 	slices.Sort(entries)
 	h := sha256.New()
-	for _, e := range n.entries {
+	for _, e := range entries {
 		h.Write([]byte(e))
 		h.Write([]byte{0})
 	}
 	copy(n.digest[:], h.Sum(nil))
 	n.entries = nil
 }
 // suppressed reports whether a duplicate-tree group is non-maximal: its
@@ -1,8 +1,6 @@
 package main
 import (
 	"bytes"
 	"database/sql"
 	"slices"
 	"testing"
 )
@@ -31,36 +29,6 @@ func smokeTreeRecs() []scanRec {
 	}
 }
 // dbTree builds the directory hierarchy from the records in db the way
 // trees does, and returns the super-root and every directory.
 func dbTree(t *testing.T, db *sql.DB) (*treeNode, []*treeNode) {
 	t.Helper()
 	tree := newTreeBuilder()
 	err := loadFileRows(t.Context(), db, tree.add)
 	if err != nil {
 		t.Fatal(err)
 	}
 	return tree.finish()
 }
 // treeOf writes recs into a fresh database and builds the directory
 // hierarchy from it the way trees does.
 func treeOf(t *testing.T, recs []scanRec) (*treeNode, []*treeNode) {
 	t.Helper()
 	db := openTestDB(t)
 	err := applyChanges(t.Context(), db, recs, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
 	return dbTree(t, db)
 }
 // nodeByPath finds the directory node with the given path.
 func nodeByPath(t *testing.T, dirs []*treeNode, path string) *treeNode {
 	t.Helper()
@@ -91,10 +59,11 @@ func groupPaths(groups [][]*treeNode) [][]string {
 	return out
 }
-func TestTreeCounts(t *testing.T) {
+func TestBuildHierarchyCounts(t *testing.T) {
 	t.Parallel()
-	_, dirs := treeOf(t, smokeTreeRecs())
+	super, dirs := buildHierarchy(smokeTreeRecs())
 	super.compute()
 	d := nodeByPath(t, dirs, "/d")
 	if d.fileCount != 6 || d.totalSize != 9300 {
@@ -115,98 +84,11 @@ func TestTreeCounts(t *testing.T) {
 	}
 }
 func TestTreeRootPath(t *testing.T) {
 	t.Parallel()
 	// The root directory's path is "/", never empty, and its
 	// children's paths start with a single slash.
 	_, dirs := treeOf(t, []scanRec{{path: "/f"}, {path: "/srv/g"}})
 	got := make([]string, 0, len(dirs))
 	for _, d := range dirs {
 		got = append(got, d.path)
 	}
 	slices.Sort(got)
 	want := []string{"/", "/srv"}
 	if !slices.Equal(got, want) {
 		t.Fatalf("directory paths = %q, want %q", got, want)
 	}
 }
 func TestTreeNamesSortingBeforeSlash(t *testing.T) {
 	t.Parallel()
 	// In path order "/a/b-x/f" and "/a/b.txt" come between the file
 	// "/a/b" and "/a/b/f", because "-" and "." sort before "/". Each
 	// directory must still be built once, whole, so /a matches /c.
 	recs := make([]scanRec, 0, 8)
 	for _, top := range []string{"/a", "/c"} {
 		for _, p := range []string{"/b", "/b-x/f", "/b.txt", "/b/f"} {
 			content := "c"
 			if p == "/b-x/f" {
 				content = "other"
 			}
 			recs = append(recs, scanRec{
 				size: 1, head: "h", tail: "t", content: content, path: top + p,
 			})
 		}
 	}
 	super, dirs := treeOf(t, recs)
 	got := make([]string, 0, len(dirs))
 	for _, d := range dirs {
 		got = append(got, d.path)
 	}
 	slices.Sort(got)
 	want := []string{"/", "/a", "/a/b", "/a/b-x", "/c", "/c/b", "/c/b-x"}
 	if !slices.Equal(got, want) {
 		t.Fatalf("directory paths = %q, want %q", got, want)
 	}
 	groups := collectTreeGroups(dirs, super)
 	gotGroups := groupPaths(groups)
 	wantGroups := [][]string{{"/a", "/c"}}
 	if !slices.EqualFunc(gotGroups, wantGroups, slices.Equal) {
 		t.Fatalf("groups = %v, want %v", gotGroups, wantGroups)
 	}
 	if groups[0][0].fileCount != 4 || groups[0][0].totalSize != 4 {
 		t.Errorf("group totals: %d files %d bytes, want 4 4",
 			groups[0][0].fileCount, groups[0][0].totalSize)
 	}
 }
 func TestRunTreesEscapesPaths(t *testing.T) {
 	t.Setenv(databaseEnv, seedDatabase(t, awkwardPairRecs()))
 	var stdout, stderr bytes.Buffer
 	code := run([]string{cmdTrees}, &stdout, &stderr)
 	if code != exitOK {
 		t.Fatalf("run(trees) = %d, want %d; stderr: %s",
 			code, exitOK, stderr.String())
 	}
 	want := "first\tdupe\tfiles\tsize\n" +
 		`/d/\tone\ntwo\rthree\\four` + "\t/d/A\t1\t5\n"
 	if got := stdout.String(); got != want {
 		t.Errorf("stdout = %q, want %q", got, want)
 	}
 }
 func TestTreeDigests(t *testing.T) {
 	t.Parallel()
-	_, dirs := treeOf(t, smokeTreeRecs())
+	super, dirs := buildHierarchy(smokeTreeRecs())
 	super.compute()
 	t1 := nodeByPath(t, dirs, "/d/t1")
 	t2 := nodeByPath(t, dirs, "/d/t2")
@@ -239,7 +121,8 @@ func TestTreeDigestContentSensitivity(t *testing.T) {
 		{size: 10, head: "DIFF", tail: sharedTail, content: "c", path: "/r/b/f"},
 	}
-	_, dirs := treeOf(t, recs)
+	super, dirs := buildHierarchy(recs)
 	super.compute()
 	a := nodeByPath(t, dirs, "/r/a")
 	b := nodeByPath(t, dirs, "/r/b")
@@ -252,7 +135,8 @@ func TestTreeDigestContentSensitivity(t *testing.T) {
 func TestCollectTreeGroupsMaximal(t *testing.T) {
 	t.Parallel()
-	super, dirs := treeOf(t, smokeTreeRecs())
+	super, dirs := buildHierarchy(smokeTreeRecs())
 	super.compute()
 	groups := collectTreeGroups(dirs, super)
@@ -276,14 +160,16 @@ func TestCollectTreeGroupsDeterministic(t *testing.T) {
 	recs := smokeTreeRecs()
-	super, dirs := treeOf(t, recs)
+	super, dirs := buildHierarchy(recs)
 	super.compute()
 	forward := groupPaths(collectTreeGroups(dirs, super))
 	reversed := slices.Clone(recs)
 	slices.Reverse(reversed)
-	superR, dirsR := treeOf(t, reversed)
+	superR, dirsR := buildHierarchy(reversed)
 	superR.compute()
 	backward := groupPaths(collectTreeGroups(dirsR, superR))
 	if !slices.EqualFunc(forward, backward, slices.Equal) {
@@ -302,7 +188,8 @@ func TestCollectTreeGroupsSiblings(t *testing.T) {
 		{size: 10, head: "h", tail: "t", content: "c", path: "/p/x2/f"},
 	}
-	super, dirs := treeOf(t, recs)
+	super, dirs := buildHierarchy(recs)
 	super.compute()
 	got := groupPaths(collectTreeGroups(dirs, super))
@@ -324,7 +211,8 @@ func TestCollectTreeGroupsDifferingParents(t *testing.T) {
 		{size: 10, head: "h", tail: "t", content: "c", path: "/q/b/x/f"},
 	}
-	super, dirs := treeOf(t, recs)
+	super, dirs := buildHierarchy(recs)
 	super.compute()
 	got := groupPaths(collectTreeGroups(dirs, super))
@@ -1,8 +0,0 @@
 # THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
 # yarn lockfile v1
 prettier@3.8.1:
  version "3.8.1"
  resolved "https://registry.yarnpkg.com/prettier/-/prettier-3.8.1.tgz#edf48977cf991558f4fcbd8a3ba6015ba2a3a173"
  integrity sha512-UOnG6LftzbdaHZcKoPFtOcCKztrQ57WkHDeRD9t/PTQtmT0NHSeWWepj6pS0z/N7+08BHFDQVUrfmfMRcZwbMg==