Run the linter at the pinned version locally too (closes #78)

`script/lint` ran whatever `golangci-lint` was on `PATH` while CI ran
the digest-pinned image from the `Dockerfile` lint stage. The two
versions disagree about real findings, so `make check` could be green
on a tree CI fails - and, on this host's 2.10.1, red on a tree CI
passes. A gate that can differ from CI is not a gate.

`script/lint` now runs the pinned image itself. The single source of
truth for the linter version is the `Dockerfile` lint stage `FROM`
line: `script/lint` parses the image reference (tag AND digest) out of
it with awk and runs exactly that image, so bumping the linter is a
one-line edit there and nowhere else. The duplicate pin in the
`Makefile` `deps` target (`go install ...@v2.12.2`) and the unpinned
`golangci-lint` install in `script/bootstrap` are removed rather than
kept in sync: with linting containerized, a second copy on `PATH` is
only a way to drift.

A `golangci-lint` on `PATH` is used only when its version is exactly
equal to the pin - the same binary by definition, and the case that
matters is the lint stage itself, which runs `make lint` inside the
pinned container where no Docker daemon exists. Every other version
goes through Docker, and a missing or unreachable daemon is a hard
error naming the required image, never a silent fallback.

The container run mounts persistent `GOCACHE`, `GOMODCACHE` and
`GOLANGCI_LINT_CACHE` directories under `${XDG_CACHE_HOME:-~/.cache}`
and runs as the invoking uid/gid, so repeat runs stay fast (2.7s warm
vs 1.8s for the ambient binary) and nothing lands root-owned.
`script/lint-fix` delegates to `script/lint --fix` so autofixes come
from the same pinned linter.

README documents that `make check` is authoritative because of this,
and points at `script/cibuild` as the full CI-equivalent gate.

Dockerfile

@@ -1,4 +1,10 @@
 # Lint stage
+#
+# This FROM line is the single source of truth for the linter version:
+# script/lint parses the image reference out of it and runs that exact
+# image, so a local `make lint` and CI use the same linter. Bump the
+# linter here (tag AND digest) and nowhere else.
+#
 # golangci/golangci-lint:v2.12.2-alpine, 2026-08-07
 FROM golangci/golangci-lint:v2.12.2-alpine@sha256:91b27804074a0bacea298707f016911e60cf0cdbc6c7bf5ccacb5f0606d18d60 AS lint
 

Makefile

@@ -56,10 +56,13 @@ clean:
 	rm -f vaultik
 	go clean
 
-# Install dependencies.
+# Install dependencies. The linter is deliberately not installed here:
+# script/lint runs the digest-pinned golangci-lint image declared by the
+# Dockerfile's lint stage, which is the single source of truth for the
+# linter version. A second, separately pinned copy on PATH could drift
+# from it and make a local `make lint` disagree with CI.
 deps:
 	go mod download
-	go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.12.2
 
 # Run tests with coverage.
 test-coverage:

README.md

@@ -564,23 +564,34 @@ standard: normalized scripts in `script/` are the entrypoints for the
 development workflow, and the Makefile targets are thin shims that call
 them. We provide:
 
-* `script/bootstrap` — install all development dependencies (go,
-  golangci-lint, Go module download)
+* `script/bootstrap` — install all development dependencies (go, sqlite3,
+  Go module download). It deliberately does not install `golangci-lint`;
+  see `script/lint` below.
 * `script/setup` — make a fresh clone ready for development: runs
   `script/bootstrap`, then `script/install-precommit`
 * `script/projectname` — print the project name (used for the Docker
   image tag)
 * `script/test` — run the test suite (verbose rerun on failure)
-* `script/lint` — run `golangci-lint run ./...`
-* `script/lint-fix` — apply the linter's autofixes (rewrites files)
+* `script/lint` — run `golangci-lint run ./...` at the exact version CI
+  uses, by running the digest-pinned `golangci-lint` image declared by
+  the `Dockerfile` lint stage (requires Docker; it fails loudly rather
+  than falling back to a differently versioned `golangci-lint` on
+  `PATH`). That `FROM` line is the single source of truth for the linter
+  version — bump it there and nowhere else.
+* `script/lint-fix` — apply the linter's autofixes (rewrites files),
+  using the same pinned linter
 * `script/fmt` — format all code (writes)
 * `script/fmt-check` — check formatting (read-only)
 * `script/check` — run `script/test`, `script/lint`, and
-  `script/fmt-check`
+  `script/fmt-check`. This is authoritative *because* `script/lint` uses
+  the pinned linter: a local `make check` and CI cannot disagree about
+  lint findings.
 * `script/docker` — build the Docker image tagged via
   `script/projectname`
 * `script/cibuild` — CI entrypoint: `docker build .` (the Dockerfile
-  runs the checks)
+  runs the checks). This is the full CI-equivalent gate — it runs the
+  checks in the same containers CI does, from a clean copy of the tree,
+  so it also catches anything that depends on host state.
 * `script/precommit` — pre-commit gate: `go mod tidy` + `go fmt` (must
   not change files), then `script/check`
 * `script/install-precommit` — install the git pre-commit hook that

TODO.md

@@ -19,6 +19,17 @@ or delete the branch.
 
 # Completed Steps
 
+- 2026-08-09: Closed the gap between `make lint` and CI (issue #78).
+  `script/lint` now runs the digest-pinned `golangci-lint` image taken
+  from the `Dockerfile` lint stage, which is the single source of truth
+  for the linter version; the duplicate pin in the `Makefile` `deps`
+  target and the unpinned `golangci-lint` install in `script/bootstrap`
+  are gone. A `golangci-lint` on `PATH` is used only when its version is
+  exactly the pinned one (which is how the lint stage runs it inside the
+  container); anything else goes through Docker, and a missing or
+  unreachable Docker daemon is a hard error rather than a silent
+  fallback. `make check` is therefore now as trustworthy as
+  `script/cibuild`.
 - 2026-08-09: Finished the lint remediation under the canonical
   `.golangci.yml` (issue #61, which also unblocks issue #59). The
   remaining findings were fixed behavior-preservingly: `wsl_v5`

script/bootstrap

@@ -58,11 +58,13 @@ main() {
     # Go toolchain
     if missing go; then pkg_install go golang go go; fi
 
-    # golangci-lint: packaged in nix, brew, and apk. There is no apt
-    # package; on apt systems install it manually from a hash-verified
-    # GitHub release archive (never curl | sh).
-    if missing golangci-lint; then
-        pkg_install golangci-lint golangci-lint golangci-lint golangci-lint
+    # golangci-lint is deliberately NOT installed: script/lint runs the
+    # digest-pinned golangci-lint image from the Dockerfile's lint stage,
+    # so whatever a package manager happens to ship would only be a
+    # shadow of the pinned version that could drift from CI.
+    if missing docker; then
+        echo "bootstrap: docker not found; script/lint needs it to run" >&2
+        echo "bootstrap: the pinned linter (see the Dockerfile lint stage)" >&2
     fi
 
     # sqlite3 CLI: the test suite shells out to it (VACUUM).

script/lint

@@ -1,12 +1,126 @@
 #!/bin/sh
 # script/lint: run the linter.
+#
+# The linter always runs at the version pinned by the Dockerfile's lint
+# stage, so a local run and a CI run of the same tree cannot disagree.
+# That FROM line (image tag plus digest) is the single source of truth
+# for the linter version in this repo: bump it there and nothing else
+# needs editing.
+#
+# Normally that means running the pinned image with docker. The one
+# exception is a golangci-lint on PATH whose version is exactly equal to
+# the pin: that is the same linter, so it is run directly. This is what
+# happens inside the lint container itself (Dockerfile runs `make lint`,
+# and there is no docker daemon in there). A PATH binary at any other
+# version is never used - that silent substitution is the bug this
+# script exists to prevent.
+#
+# Extra arguments are passed through to `golangci-lint run`, before
+# `./...` (see script/lint-fix).
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+DOCKERFILE="$ROOT/Dockerfile"
+
+# The image reference of the Dockerfile's lint stage, tag and digest
+# included, e.g.
+# golangci/golangci-lint:v2.12.2-alpine@sha256:91b2...
+lint_image() {
+    awk '$1 == "FROM" && $3 == "AS" && $4 == "lint" { print $2; exit }' \
+        "$DOCKERFILE"
+}
+
+# The bare version that image reference pins, e.g. 2.12.2
+pinned_version() {
+    lint_image | sed -e 's/@.*//' -e 's/.*://' -e 's/^v//' -e 's/-.*//'
+}
+
+# The version of the golangci-lint on PATH, if any, e.g. 2.12.2
+installed_version() {
+    command -v golangci-lint >/dev/null 2>&1 || return 0
+    golangci-lint version 2>/dev/null | awk '
+        {
+            for (i = 1; i <= NF; i++) {
+                if ($i ~ /^[0-9]+\.[0-9]+\.[0-9]+$/) {
+                    print $i
+                    exit
+                }
+            }
+        }'
+}
+
+require_docker() {
+    image="$1"
+    if ! command -v docker >/dev/null 2>&1; then
+        cat >&2 <<EOF
+lint: docker is required to run the pinned linter.
+
+  pinned image: $image
+
+Install docker, or install golangci-lint $(pinned_version) on PATH.
+Linting with any other version is not supported: it is what lets a
+local run pass while CI fails.
+EOF
+        exit 1
+    fi
+    if ! docker info >/dev/null 2>&1; then
+        cat >&2 <<EOF
+lint: the docker daemon is not reachable, so the pinned linter cannot
+run.
+
+  pinned image: $image
+
+Start the daemon (and check DOCKER_HOST / your group membership), or
+install golangci-lint $(pinned_version) on PATH. This script will not
+fall back to a different linter version.
+EOF
+        exit 1
+    fi
+}
+
+# Caches for the containerized linter. Keeping them out of the repo and
+# persisting them between runs is what keeps the inner loop fast: a warm
+# run costs about the same as a native one plus container startup.
+cache_root() {
+    echo "${XDG_CACHE_HOME:-${HOME:-/tmp}/.cache}/vaultik-lint"
+}
+
+run_in_docker() {
+    image="$1"
+    shift
+    require_docker "$image"
+
+    cache="$(cache_root)"
+    mkdir -p "$cache/go-build" "$cache/go-mod" "$cache/golangci-lint"
+
+    exec docker run --rm \
+        --user "$(id -u):$(id -g)" \
+        --env HOME=/tmp \
+        --env GOFLAGS=-buildvcs=false \
+        --env GOCACHE=/cache/go-build \
+        --env GOMODCACHE=/cache/go-mod \
+        --env GOLANGCI_LINT_CACHE=/cache/golangci-lint \
+        --volume "$ROOT:/src" \
+        --volume "$cache:/cache" \
+        --workdir /src \
+        "$image" \
+        golangci-lint run "$@" ./...
+}
 
 main() {
     cd "$ROOT"
-    golangci-lint run ./...
+
+    image="$(lint_image)"
+    if [ -z "$image" ]; then
+        echo "lint: no lint stage found in $DOCKERFILE" >&2
+        exit 1
+    fi
+
+    if [ "$(installed_version)" = "$(pinned_version)" ]; then
+        exec golangci-lint run "$@" ./...
+    fi
+
+    run_in_docker "$image" "$@"
 }
 
 main "$@"

script/lint-fix

@@ -3,13 +3,16 @@
 # for every finding the enabled linters know how to fix; findings
 # without an autofix are reported but left alone (exit status is
 # nonzero while any remain).
+#
+# Delegates to script/lint so the autofixer is the same pinned linter
+# version that script/lint and CI use - fixes written by a different
+# version are not necessarily fixes for the version that gates.
 set -eu
 
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
 
 main() {
-    cd "$ROOT"
-    golangci-lint run --fix ./...
+    exec "$SCRIPT_DIR/lint" --fix "$@"
 }
 
 main "$@"