build: unify the gate so root make check covers the backend (closes #16)

Root `make check` only ever ran the frontend, so the "main is always
green" policy was satisfied vacuously: the Go backend could be entirely
broken and the root gate stayed green.

- The backend moves onto scripts-to-rule-them-all. Its test, lint, fmt,
  fmt-check, build, run and clean implementations now live in
  `backend/script/`, and `backend/Makefile` is thin shims. The backend
  is its own project (own module, README, LICENSE, linter config,
  Dockerfile stage), and `Dockerfile.backend` only copies `backend/`
  into its builder, so its scripts have to live under `backend/`.
- The root `script/test`, `script/lint`, `script/fmt` and
  `script/fmt-check` now run the frontend step and then the matching
  `backend/script/*` step, so `script/check` — and therefore the
  pre-commit hook — gates both halves. The frontend-only steps moved
  into `script/frontend-*` so nothing is duplicated.
- `script/bootstrap` now provisions the backend's toolchain as well,
  because widening the gate without widening bootstrap left the
  documented fresh-clone path (`make setup`) installing a pre-commit
  hook that rejected every commit with `golangci-lint: not found`.
  golangci-lint is installed at exactly `2.7.2`, the version
  `Dockerfile.backend` pins, so local findings match CI. Go is reused
  only when the installed version falls inside a window — at least
  `backend/go.mod`'s floor, and no newer in major.minor than the Go the
  pinned linter was built with — otherwise `go1.25.7` is installed. The
  upper bound is load-bearing: golangci-lint links `go/types` from its
  own build toolchain, so the pinned `2.7.2` (built with `go1.25.4`)
  panics with "file requires newer Go version go1.26" against a host Go
  1.26, which would leave `make setup` exiting 0 and every commit
  rejected. Both tools come from a specific release archive whose sha256
  is hardcoded here and verified before anything is unpacked — never an
  install script piped to a shell — and both are symlinked onto `PATH`,
  since nvm-style activation does not reach `make` or the git hook.
- `script/bootstrap` links only into `~/.local/bin` and never into a
  system-wide prefix. `/usr/local/bin` is shared with other users and
  with a package manager — on an Intel Mac it is the Homebrew prefix —
  and pointing an entry there at one user's `$HOME` breaks it for
  everyone else. It also refuses, non-zero, to replace anything it did
  not create: only a symlink already pointing into its own toolchain
  directory is overwritten, so a pre-existing binary is reported rather
  than deleted. `corepack enable` is given `--install-directory` so its
  four shims (`yarn`, `yarnpkg`, `pnpm`, `pnpx`) land inside that same
  toolchain directory instead of beside the corepack binary, and only
  `yarn` is linked onto `PATH`.
- `script/bootstrap` exits non-zero when it cannot guarantee the pinned
  toolchain is the one the gate will run. Reporting success while
  knowing a different linter or a newer Go precedes `~/.local/bin` is
  the same defect this commit exists to remove, so the final step
  re-resolves `go`, `gofmt`, `golangci-lint`, `node` and `yarn` against
  the caller's own `PATH` and fails with what it found and how to fix
  it. The three tools that carry a version constraint are re-checked
  with the same predicates their installs use, not for bare presence:
  `gofmt` is a gate tool — `backend/script/fmt-check` runs it — and its
  output is not guaranteed identical across Go releases, so a `gofmt`
  built by a different Go than the one that compiles the code counts as
  missing. `go` and `gofmt` are relinked on every run in which the
  pinned toolchain is the one in use, rather than only on the run that
  unpacked the archive, so a deleted link is repaired instead of
  falling through to whatever `gofmt` the host happens to have. The
  failure text separates a tool that resolves to the wrong build
  (something shadows `~/.local/bin`) from one that does not resolve at
  all (nothing is shadowing it, it was never installed), and always
  names a real directory rather than interpolating an unset one.
- `script/frontend-check` is the frontend half of the gate, exposed as
  the `frontend-check` target, for the frontend Dockerfile: its build
  stage is a node image with no Go toolchain. The backend half is gated
  by `Dockerfile.backend`, and `script/cibuild` builds both images, so
  the two Dockerfiles together still gate the whole repo. The
  `backend-check` target is the mirror of it. Both targets are named
  after the script they shim, like every other target.
- `script/cibuild` builds both images through one `build_image` helper,
  and the Gitea workflow's only build step is `script/cibuild`; the raw
  `docker build -f Dockerfile.backend .` is gone from the workflow.
  `script/docker` likewise builds and tags both images.
- `backend/Makefile`'s `hooks` target is removed. It wrote the same
  `.git/hooks/pre-commit` as `script/install-precommit`, so the two
  clobbered each other and the developer silently ended up gating on
  only one half of the repo. `script/install-precommit` is now the only
  installer, and the hook it writes runs the repo-wide `script/check`.
- `backend/Makefile`'s `docker` target is removed too: the backend image
  builds from the repo root with a root-level Dockerfile, so it belongs
  to the root `script/docker` and `script/cibuild` rather than to a
  backend script that would have to reach outside `backend/`.
- `backend/script/lint` verifies that `.golangci.yml` still matches its
  pinned sha256 before running the linter. Offline hash comparison, no
  network. The pin is marked provisional in the file: it is the config
  currently on `main`, and the comment names PR #31 and the canonical
  hash that must replace it when #31 lands.
- Every script locates the repo root with the mandated
  `$(cd "$(dirname "$0")/.." && pwd -P)` idiom, `cd`s there, and calls
  siblings as `"$ROOT/script/<name>"`; the `SCRIPT_DIR` variant is gone.

READMEs at the root and in `backend/` document every script, the
backend's Getting Started separates commands run from `backend/` from
those run at the repo root, and `TODO.md` records the change.

Dockerfile

@@ -5,14 +5,14 @@ COPY package.json yarn.lock ./
 RUN yarn install --frozen-lockfile
 RUN apk add --no-cache git make
 COPY . .
-# make check-frontend runs script/frontend-check (test + lint +
+# make frontend-check runs script/frontend-check (test + lint +
 # fmt-check for the frontend); its test step is the production yarn
 # build, so this both produces dist/ and gates the image on
 # lint/fmt-check/test regressions, not merely a broken build. It is the
 # frontend half of `make check` rather than all of it because this stage
 # is a node image with no Go toolchain; the backend half is gated by
 # Dockerfile.backend, and script/cibuild builds both images.
-RUN make check-frontend
+RUN make frontend-check
 
 # nginx:stable-alpine as of 2026-02-22
 FROM nginx@sha256:15e96e59aa3b0aada3a121296e3bce117721f42d88f5f64217ef4b18f458c6ab

Makefile

@@ -1,5 +1,5 @@
-.PHONY: bootstrap setup dev test lint fmt fmt-check check check-frontend \
+.PHONY: bootstrap setup dev test lint fmt fmt-check check frontend-check \
-	check-backend docker hooks
+	backend-check docker hooks
 
 # Standard targets are thin shims; the implementations live in script/
 # per the scripts-to-rule-them-all pattern (see the Entrypoints section
@@ -32,10 +32,11 @@ check:
 
 # Half-repo gates. Used by the two Dockerfiles, whose build stages only
 # have the toolchain for their own half; prefer `make check` otherwise.
-check-frontend:
+# Each is named after the script it shims, like every other target here.
+frontend-check:
 	@script/frontend-check
 
-check-backend:
+backend-check:
 	@backend/script/check
 
 docker:

README.md

@@ -35,8 +35,15 @@ The repo holds two projects: the frontend at the repo root and the Go backend in
 root scripts cover both, so `make check` at the root fails if either half is
 broken. We provide:
 
-- `script/bootstrap` — install all dependencies (pinned node via nvm if needed,
+- `script/bootstrap` — install all dependencies, assuming nothing is present:
-  yarn via corepack, `yarn install --frozen-lockfile`)
+  pinned node via nvm if needed, yarn via corepack,
+  `yarn install --frozen-lockfile`, and the backend's toolchain — Go (an
+  already-installed Go is reused only when its version falls inside the window
+  the pinned golangci-lint can analyse; a newer Go is ignored, not preferred)
+  and golangci-lint at the version `Dockerfile.backend` pins. Everything not
+  installed by the system package manager comes from a hash-verified release
+  archive and is symlinked into `~/.local/bin`, so `make check` works in a plain
+  shell afterwards
 - `script/setup` — make a fresh clone ready for development: bootstrap plus the
   git pre-commit hook
 - `script/projectname` — print the project name (used for the Docker image tags)
@@ -53,8 +60,10 @@ broken. We provide:
 - `script/frontend-lint` — run prettier in check mode
 - `script/frontend-fmt` — format everything prettier understands (writes)
 - `script/frontend-fmt-check` — check prettier formatting (read-only)
-- `script/frontend-check` — the frontend half of `script/check`, used by
+- `script/frontend-check` — the frontend half of `script/check`, shimmed by
-  `Dockerfile`, whose build stage is a node image with no Go toolchain
+  `make frontend-check` and used by `Dockerfile`, whose build stage is a node
+  image with no Go toolchain. Its mirror `make backend-check` shims to
+  `backend/script/check`
 - `script/docker` — build both images, tagged via `script/projectname`:
   `netwatch` from `Dockerfile` and `netwatch-server` from `Dockerfile.backend`
 - `script/cibuild` — CI entrypoint: builds both images; the only build step in

TODO.md

@@ -25,8 +25,17 @@ files, so merging it also closes most compliance gaps.
 - 2026-08-09: unified the gate: the root `make check` now covers the Go backend
   as well as the frontend, the backend moved onto scripts-to-rule-them-all
   (`backend/script/*` with `backend/Makefile` as thin shims), the duplicate
-  pre-commit hook installer in `backend/Makefile` was removed, and
+  pre-commit hook installer in `backend/Makefile` was removed, `script/cibuild`
-  `script/cibuild` now builds both images as the workflow's only build step
+  now builds both images as the workflow's only build step, and
+  `script/bootstrap` provisions the backend toolchain (pinned, hash-verified Go
+  and golangci-lint) so a fresh clone can pass the widened gate. Bootstrap
+  matches the Go pin rather than treating it as a floor, because the pinned
+  golangci-lint cannot analyse packages built by a newer Go; it links only into
+  `~/.local/bin`, never a system-wide prefix, and refuses to replace anything it
+  did not create; and it exits non-zero rather than reporting success when the
+  tools on the caller's `PATH` are not the pinned ones — `gofmt` included, held
+  to the same version agreement as `go` and relinked on every run so a deleted
+  link cannot leave another Go's `gofmt` gating the repo
 - 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints, Makefile
   shims, README Entrypoints section
 - 2026-02-27: backend with buffered zstd-compressed report storage; CI workflow

backend/README.md

@@ -4,15 +4,24 @@ SPA and persists them as zstd-compressed JSONL files on disk.
 
 ## Getting Started
 
+From this directory (`backend/`):
+
 ```bash
 # Build and run locally
 make run
 
-# Run tests, lint, and format check
+# Run the backend's tests, lint, and format check
 make check
+```
 
-# Docker (from the repo root; the image's build context is the repo root)
+From the repo root, one directory up — `Dockerfile.backend` lives there and its
+build context is the repo root, so there is no `docker` target here:
+
+```bash
+# Build both images, including netwatch-server
 make docker
+
+# Run the backend image
 docker run -p 8080:8080 netwatch-server
 ```
 

backend/script/check

@@ -4,12 +4,13 @@
 # gate covers the backend.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
-    "$SCRIPT_DIR/test"
+    cd "$ROOT"
-    "$SCRIPT_DIR/lint"
+    "$ROOT/script/test"
-    "$SCRIPT_DIR/fmt-check"
+    "$ROOT/script/lint"
+    "$ROOT/script/fmt-check"
 }
 
 main "$@"

backend/script/lint

@@ -13,6 +13,16 @@ set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 # sha256 of the pinned backend/.golangci.yml.
+#
+# PROVISIONAL. The hash below is the file currently on main, which is
+# the schema-invalid v1-keyed config described above: it is pinned only
+# so this branch and main stay green, NOT because it is canonical.
+#
+# The canonical org-wide .golangci.yml is
+# 021cc83f4e6fc7c31b95b34b846723dfcf20b66b7baeea1dc40406e643346bcb,
+# and PR #31 replaces backend/.golangci.yml with it. When #31 lands,
+# GOLANGCI_CONFIG_SHA256 must be updated to that hash in the same
+# commit. Until then, do not treat the pinned file as the standard.
 GOLANGCI_CONFIG_SHA256="33ba2bf7fe4a44779d09b0fb31d6daf03685f8dc9d2bc417f963d7aabb0d17dc"
 
 # sha256 <file>: print the file's sha256, coreutils or Darwin/busybox.

backend/script/run

@@ -2,12 +2,11 @@
 # script/run: build and run netwatch-server locally.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
-    "$SCRIPT_DIR/build"
     cd "$ROOT"
+    "$ROOT/script/build"
     exec ./netwatch-server "$@"
 }
 

script/bootstrap

@@ -5,11 +5,50 @@
 # or apk (detected in that order); assumes nothing is present. Node is
 # used directly if installed; otherwise it is installed at a pinned
 # version via nvm (installing nvm itself first, from a hash-verified
-# release archive, never curl | sh).
+# release archive, never curl | sh). Go is used directly only if its
+# version falls inside the pinned window described at GO_MAX_MINOR below
+# -- a newer Go is ignored, not preferred -- and golangci-lint is
+# installed at the exact pinned version; both come from hash-verified
+# official release archives, never an install script.
+#
+# The backend's toolchain is bootstrapped here because script/check runs
+# backend/script/test and backend/script/lint, so a machine that cannot
+# run go and golangci-lint cannot pass the repo-wide gate or the
+# pre-commit hook that script/setup installs.
+#
+# Anything installed outside the system package manager is symlinked
+# into ~/.local/bin, so a later `make check` in a plain shell finds it.
+# nvm only puts node on PATH for shells that source nvm.sh, which
+# neither make nor the git hook does.
+#
+# Three rules govern what this script is allowed to touch:
+#
+#   1. Everything it installs itself lands under $HOME, using $TMPDIR
+#      only for scratch downloads it then deletes. The one exception is
+#      the system package manager, which it shells out to for base
+#      tooling (see pkg_install) and which owns those paths already. A
+#      per-repo bootstrap has no business writing to /usr/local/bin, a
+#      Homebrew prefix, or any other system-wide location behind that
+#      package manager's back.
+#   2. It never replaces something it did not create. Only a symlink
+#      that already points into one of its own managed directories is
+#      overwritten; anything else is left alone and bootstrap exits
+#      non-zero telling you what to remove.
+#   3. It never reports success while the tools a later `make check`
+#      would pick up are not the ones it provisioned. If it cannot
+#      guarantee the pinned toolchain wins on your PATH, it exits
+#      non-zero rather than leaving you a green bootstrap and a broken
+#      gate.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
+# The PATH as the caller had it, captured before ensure_bin_dir amends
+# it. verify_toolchain checks against this rather than against the PATH
+# this script builds for itself, so what it reports is what a later
+# `make check` in the user's own shell will actually resolve.
+ORIG_PATH="$PATH"
+
 # Pinned versions, 2026-07-07
 NODE_VERSION="22.17.0"
 NVM_VERSION="0.40.3"
@@ -17,9 +56,58 @@ NVM_VERSION="0.40.3"
 NVM_SHA256="5f4d6aaa04a177dc93c985e31dbc411ab6b8c6e1e21d8015dbc1372625fcd1d0"
 YARN_VERSION="1.22.22"
 
+# Go 1.25.7 (2026-08-09). This is the toolchain inside the pinned
+# golang:1.25-alpine builder of Dockerfile.backend, so a local build
+# uses the same compiler CI does.
+#
+# The Go pin is a compatibility constraint to match, not a floor to
+# clear. golangci-lint links go/types from the Go release it was built
+# with, and go/types refuses to load packages compiled by a newer Go:
+# with the pinned linter (built with go1.25.4) and a host Go 1.26,
+# `make check` dies with
+#
+#     panic: file requires newer Go version go1.26
+#            (application built with go1.25)
+#
+# So an already-installed go is reused only inside a window:
+# GO_MIN_VERSION is the floor from backend/go.mod, and GO_MAX_MINOR is
+# the major.minor of the Go the pinned golangci-lint was built with.
+# Anything outside that window is ignored and GO_VERSION is installed
+# instead. GO_MAX_MINOR is therefore coupled to GOLANGCI_LINT_VERSION
+# below and must be revisited whenever that pin moves; `golangci-lint
+# version` prints the "built with goX.Y.Z" it needs.
+GO_VERSION="1.25.7"
+GO_MIN_VERSION="1.25.5"
+GO_MAX_MINOR="1.25"
+
+# golangci-lint 2.7.2 (2026-08-09). MUST stay equal to the golangci-lint
+# pinned in Dockerfile.backend (currently commit
+# 9f61b0f53f80672872fced07b6874397c3ed197b, which is tag v2.7.2), so a
+# local `make lint` and CI's in-image `make check` report the same
+# findings.
+#
+# Reconciliation note: PR #31 moves Dockerfile.backend to golangci-lint
+# v2.12.2, commit c0d3ddc9cf3faa61a4e378e879ece580256d76e5. When that
+# lands, GOLANGCI_LINT_VERSION and every hash in golangci_lint_sha256()
+# below must be updated to the v2.12.2 release archives in the same
+# commit, or local and CI will disagree. GO_MAX_MINOR must move with
+# it, to the major.minor that release reports as "built with".
+GOLANGCI_LINT_VERSION="2.7.2"
+
+# Where hash-verified archives are unpacked. Version-scoped, so bumping
+# a pin installs alongside the old copy instead of half-overwriting it.
+# Filled in by main() from script/projectname. TOOLCHAIN is also the
+# ownership boundary used by link_bin: a symlink pointing inside it is
+# one this script created and may replace.
+TOOLCHAIN=""
+GO_DIR=""
+GOLANGCI_LINT_DIR=""
+
 PKGMGR=""
 SUDO=""
 APT_UPDATED=""
+BIN_DIR=""
+NODE_BIN=""
 
 detect_pkgmgr() {
     [ -n "$PKGMGR" ] && return 0
@@ -79,6 +167,119 @@ verify_sha256() {
     fi
 }
 
+# fetch_verified <url> <expected-hash> <dest>: download a release
+# archive and check it against a hash hardcoded in this script before
+# anything is unpacked or run. Never pipe a remote script to a shell.
+fetch_verified() {
+    if missing curl; then pkg_install curl curl curl curl; fi
+    curl -fsSL -o "$3" "$1"
+    verify_sha256 "$3" "$2"
+}
+
+# platform: <os>-<arch> as used in the Go and golangci-lint release
+# archive filenames.
+platform() {
+    plat_os="$(uname -s)"
+    plat_arch="$(uname -m)"
+    case "$plat_os" in
+        Linux) plat_os="linux" ;;
+        Darwin) plat_os="darwin" ;;
+        *)
+            echo "bootstrap: unsupported OS $plat_os" >&2
+            exit 1
+            ;;
+    esac
+    case "$plat_arch" in
+        x86_64 | amd64) plat_arch="amd64" ;;
+        aarch64 | arm64) plat_arch="arm64" ;;
+        *)
+            echo "bootstrap: unsupported architecture $plat_arch" >&2
+            exit 1
+            ;;
+    esac
+    echo "$plat_os-$plat_arch"
+}
+
+# ver_ge <have> <want>: succeed if dotted version <have> is at least
+# <want>, comparing up to three numeric components.
+ver_ge() {
+    awk -v have="$1" -v want="$2" '
+        BEGIN {
+            n = split(have, h, ".")
+            m = split(want, w, ".")
+            for (i = 1; i <= 3; i++) {
+                hv = (i <= n) ? h[i] + 0 : 0
+                wv = (i <= m) ? w[i] + 0 : 0
+                if (hv > wv) exit 0
+                if (hv < wv) exit 1
+            }
+            exit 0
+        }'
+}
+
+# ensure_bin_dir: the directory provisioned tools are linked into. It is
+# always ~/.local/bin: per-user, never a system-wide or package-manager
+# prefix. It is put at the front of PATH for the rest of this run, and
+# reported if the caller's own PATH did not already contain it.
+ensure_bin_dir() {
+    [ -n "$BIN_DIR" ] && return 0
+    BIN_DIR="$HOME/.local/bin"
+    mkdir -p "$BIN_DIR"
+    case "$PATH" in
+        "$BIN_DIR":*) ;;
+        *)
+            PATH="$BIN_DIR:$PATH"
+            export PATH
+            ;;
+    esac
+    case ":$ORIG_PATH:" in
+        *":$BIN_DIR:"*) ;;
+        *)
+            echo "bootstrap: add $BIN_DIR to the front of your PATH, e.g." >&2
+            echo "  export PATH=\"\$HOME/.local/bin:\$PATH\"" >&2
+            ;;
+    esac
+}
+
+# owned_path <path>: true when <path> lies inside a directory this
+# script provisions, i.e. a link to it is one this script created and
+# may replace. Everything else belongs to the user or to a package
+# manager and is never touched.
+owned_path() {
+    case "$1" in
+        "$TOOLCHAIN"/*) return 0 ;;
+        "$HOME"/.nvm/*) return 0 ;;
+        *) return 1 ;;
+    esac
+}
+
+# refuse_clobber <path> <what>: report that <path> is not ours and stop.
+refuse_clobber() {
+    echo "bootstrap: $1 already exists and $2." >&2
+    echo "  Refusing to replace something this script did not create." >&2
+    echo "  Remove or rename it and re-run bootstrap." >&2
+    exit 1
+}
+
+# link_bin <target> <name>: idempotently expose one provisioned binary
+# on PATH. Only an existing symlink into one of our own directories is
+# replaced; a regular file, a directory, or a symlink pointing anywhere
+# else is left intact and bootstrap fails.
+link_bin() {
+    ensure_bin_dir
+    link="$BIN_DIR/$2"
+    if [ -L "$link" ]; then
+        existing="$(readlink "$link")"
+        if ! owned_path "$existing"; then
+            refuse_clobber "$link" \
+                "is a symlink to $existing, outside this repo's toolchain"
+        fi
+    elif [ -e "$link" ]; then
+        refuse_clobber "$link" "is not a symlink"
+    fi
+    ln -sfn "$1" "$link"
+}
+
 # nvm is a bash script; run a command in a bash with nvm loaded
 nvm_sh() {
     bash -c ". \"\$HOME/.nvm/nvm.sh\" && $*"
@@ -91,9 +292,9 @@ ensure_nvm() {
     if missing curl; then pkg_install curl curl curl curl; fi
     if missing git; then pkg_install git git git git; fi
     tmp="$(mktemp -d)"
-    curl -fsSL -o "$tmp/nvm.tar.gz" \
+    fetch_verified \
-        "https://github.com/nvm-sh/nvm/archive/refs/tags/v${NVM_VERSION}.tar.gz"
+        "https://github.com/nvm-sh/nvm/archive/refs/tags/v${NVM_VERSION}.tar.gz" \
-    verify_sha256 "$tmp/nvm.tar.gz" "$NVM_SHA256"
+        "$NVM_SHA256" "$tmp/nvm.tar.gz"
     mkdir -p "$HOME/.nvm"
     tar -xzf "$tmp/nvm.tar.gz" -C "$HOME/.nvm" --strip-components=1
     rm -rf "$tmp"
@@ -103,18 +304,37 @@ ensure_node() {
     if ! missing node; then return 0; fi
     ensure_nvm
     nvm_sh "nvm install $NODE_VERSION"
+    NODE_BIN="$HOME/.nvm/versions/node/v$NODE_VERSION/bin"
+    for nb in node npm npx corepack; do
+        if [ -e "$NODE_BIN/$nb" ]; then link_bin "$NODE_BIN/$nb" "$nb"; fi
+    done
 }
 
+# ensure_yarn: yarn comes from corepack. Left to itself, `corepack
+# enable` writes its shims next to the corepack binary it resolved, and
+# it writes four of them (yarn, yarnpkg, pnpm, pnpx), not the one asked
+# for. --install-directory keeps all four inside this repo's own
+# toolchain directory, and only yarn is then linked onto PATH. The
+# no-corepack fallback likewise installs into a per-user npm prefix
+# under the toolchain directory instead of npm's global one. Nothing
+# here writes outside $HOME.
 ensure_yarn() {
     if ! missing yarn; then return 0; fi
+    yarn_bin="$TOOLCHAIN/corepack-shims"
+    mkdir -p "$yarn_bin"
     if ! missing corepack; then
-        corepack enable
+        corepack enable --install-directory "$yarn_bin"
         corepack prepare "yarn@$YARN_VERSION" --activate
     elif [ -s "$HOME/.nvm/nvm.sh" ]; then
-        nvm_sh "nvm use $NODE_VERSION >/dev/null && corepack enable && \
+        nvm_sh "nvm use $NODE_VERSION >/dev/null && \
+            corepack enable --install-directory \"$yarn_bin\" && \
             corepack prepare yarn@$YARN_VERSION --activate"
     else
-        npm install -g "yarn@$YARN_VERSION"
+        yarn_bin="$TOOLCHAIN/npm-global/bin"
+        npm install -g --prefix "$TOOLCHAIN/npm-global" "yarn@$YARN_VERSION"
+    fi
+    if [ -e "$yarn_bin/yarn" ]; then
+        link_bin "$yarn_bin/yarn" yarn
     fi
 }
 
@@ -127,9 +347,247 @@ install_js_deps() {
     fi
 }
 
+# go_sha256 <platform>: sha256 of
+# https://go.dev/dl/go1.25.7.<platform>.tar.gz, from the signed release
+# index at https://go.dev/dl/?mode=json (2026-08-09).
+go_sha256() {
+    case "$1" in
+        linux-amd64)
+            echo "12e6d6a191091ae27dc31f6efc630e3a3b8ba409baf3573d955b196fdf086005"
+            ;;
+        linux-arm64)
+            echo "ba611a53534135a81067240eff9508cd7e256c560edd5d8c2fef54f083c07129"
+            ;;
+        darwin-amd64)
+            echo "bf5050a2152f4053837b886e8d9640c829dbacbc3370f913351eb0904cb706f5"
+            ;;
+        darwin-arm64)
+            echo "ff18369ffad05c57d5bed888b660b31385f3c913670a83ef557cdfd98ea9ae1b"
+            ;;
+        *)
+            echo "bootstrap: no pinned Go archive hash for $1" >&2
+            exit 1
+            ;;
+    esac
+}
+
+# go_ok: an already-installed go is acceptable only inside the window
+# described at GO_MAX_MINOR: at least GO_MIN_VERSION, and no newer in
+# major.minor than the Go the pinned golangci-lint was built with. A
+# newer host Go is not "good enough", it makes `make check` panic, so it
+# is treated exactly like a missing one.
+go_ok() {
+    if missing go; then return 1; fi
+    have="$(go version 2>/dev/null | awk '{print $3}')"
+    have="${have#go}"
+    [ -n "$have" ] || return 1
+    ver_ge "$have" "$GO_MIN_VERSION" || return 1
+    ver_ge "$GO_MAX_MINOR" "$(echo "$have" | cut -d. -f1,2)"
+}
+
+# gofmt_ok: gofmt is a gate tool -- backend/script/fmt-check runs it --
+# and its output is not guaranteed byte-identical across Go releases, so
+# a gofmt from a different release than the go that compiles the code is
+# treated exactly like a missing one, the same way a mismatched
+# golangci-lint is. `go version <file>` prints the toolchain a Go binary
+# was built with, so this compares the gofmt that resolves on PATH
+# against the go that resolves on PATH, without depending on where
+# either one lives. Anything it cannot read -- no go to ask, gofmt
+# absent, not a Go binary -- fails closed.
+gofmt_ok() {
+    if missing go; then return 1; fi
+    if missing gofmt; then return 1; fi
+    go_have="$(go version 2>/dev/null | awk '{print $3}')"
+    [ -n "$go_have" ] || return 1
+    fmt_have="$(go version "$(command -v gofmt)" 2>/dev/null | awk '{print $NF}')"
+    [ "$fmt_have" = "$go_have" ]
+}
+
+# ensure_go: reuse the host toolchain only when the go on PATH is inside
+# the window AND a gofmt from that same release is on PATH with it. Both
+# link_bin calls sit outside that early return, so whenever the pinned
+# toolchain is the one in use they run on every bootstrap, not only on
+# the run that unpacked the archive: a deleted or never-created gofmt
+# link is restored rather than silently left to some other Go's gofmt.
+ensure_go() {
+    if go_ok && gofmt_ok; then return 0; fi
+    if [ ! -x "$GO_DIR/bin/go" ]; then
+        plat="$(platform)"
+        tmp="$(mktemp -d)"
+        fetch_verified \
+            "https://go.dev/dl/go${GO_VERSION}.${plat}.tar.gz" \
+            "$(go_sha256 "$plat")" "$tmp/go.tar.gz"
+        rm -rf "$GO_DIR.partial"
+        mkdir -p "$GO_DIR.partial"
+        tar -xzf "$tmp/go.tar.gz" -C "$GO_DIR.partial" --strip-components=1
+        rm -rf "$GO_DIR"
+        mv "$GO_DIR.partial" "$GO_DIR"
+        rm -rf "$tmp"
+    fi
+    link_bin "$GO_DIR/bin/go" go
+    link_bin "$GO_DIR/bin/gofmt" gofmt
+}
+
+# golangci_lint_sha256 <platform>: sha256 of the golangci-lint 2.7.2
+# release archive for that platform, from
+# https://github.com/golangci/golangci-lint/releases/download/v2.7.2/golangci-lint-2.7.2-checksums.txt
+# (2026-08-09).
+golangci_lint_sha256() {
+    case "$1" in
+        linux-amd64)
+            echo "ce46a1f1d890e7b667259f70bb236297f5cf8791a9b6b98b41b283d93b5b6e88"
+            ;;
+        linux-arm64)
+            echo "7028e810837722683dab679fb121336cfa303fecff39dfe248e3e36bc18d941b"
+            ;;
+        darwin-amd64)
+            echo "6966554840a02229a14c52641bc38c2c7a14d396f4c59ba0c7c8bb0675ca25c9"
+            ;;
+        darwin-arm64)
+            echo "6ce86a00e22b3709f7b994838659c322fdc9eae09e263db50439ad4f6ec5785c"
+            ;;
+        *)
+            echo "bootstrap: no pinned golangci-lint archive hash for $1" >&2
+            exit 1
+            ;;
+    esac
+}
+
+# golangci_lint_ok: unlike go, this must be the exact pinned version.
+# A different version reports a different set of findings, so local
+# results would stop matching what Dockerfile.backend gates on.
+golangci_lint_ok() {
+    if missing golangci-lint; then return 1; fi
+    have="$(golangci-lint version 2>&1 | awk '
+        {
+            for (i = 1; i < NF; i++) {
+                if ($i == "version") {
+                    v = $(i + 1)
+                    sub(/^v/, "", v)
+                    print v
+                    exit
+                }
+            }
+        }')"
+    [ "$have" = "$GOLANGCI_LINT_VERSION" ]
+}
+
+ensure_golangci_lint() {
+    if golangci_lint_ok; then return 0; fi
+    if [ ! -x "$GOLANGCI_LINT_DIR/golangci-lint" ]; then
+        plat="$(platform)"
+        base="golangci-lint-${GOLANGCI_LINT_VERSION}-${plat}"
+        tmp="$(mktemp -d)"
+        fetch_verified \
+            "https://github.com/golangci/golangci-lint/releases/download/v${GOLANGCI_LINT_VERSION}/${base}.tar.gz" \
+            "$(golangci_lint_sha256 "$plat")" "$tmp/golangci-lint.tar.gz"
+        mkdir -p "$tmp/x"
+        tar -xzf "$tmp/golangci-lint.tar.gz" -C "$tmp/x" --strip-components=1
+        rm -rf "$GOLANGCI_LINT_DIR.partial"
+        mkdir -p "$GOLANGCI_LINT_DIR.partial"
+        cp "$tmp/x/golangci-lint" "$GOLANGCI_LINT_DIR.partial/golangci-lint"
+        chmod +x "$GOLANGCI_LINT_DIR.partial/golangci-lint"
+        rm -rf "$GOLANGCI_LINT_DIR"
+        mv "$GOLANGCI_LINT_DIR.partial" "$GOLANGCI_LINT_DIR"
+        rm -rf "$tmp"
+    fi
+    link_bin "$GOLANGCI_LINT_DIR/golangci-lint" golangci-lint
+}
+
+# verify_toolchain: bootstrap must not exit 0 while the tools the gate
+# will actually run are not the provisioned ones. Everything above only
+# guarantees the right tools exist and are linked into $BIN_DIR; if
+# something earlier on the caller's PATH shadows them, `make check` --
+# and the pre-commit hook script/setup installs -- still break, and a
+# warning buried in a long bootstrap log is not enough. So the checks
+# re-run against the PATH the caller will have (theirs, plus $BIN_DIR at
+# the front if bootstrap had to ask for it), and a failure is fatal.
+#
+# Every gate tool that has a version constraint is checked with the same
+# predicate its install used -- go_ok, gofmt_ok, golangci_lint_ok -- not
+# with a bare presence test, because a wrong-version gate tool produces
+# different results from the one CI runs, which is the failure this
+# function exists to prevent. node and yarn have no pinned version to
+# disagree about, so presence is the whole constraint for them.
+verify_toolchain() {
+    # BIN_DIR is only set once something needed linking, but the remedy
+    # text must name a real directory in every reachable state, so fall
+    # back to the one ensure_bin_dir would have chosen.
+    bin_dir="${BIN_DIR:-$HOME/.local/bin}"
+
+    # Model the PATH the caller will actually have: their own, plus
+    # $BIN_DIR at the front only if bootstrap linked something there and
+    # therefore told them to add it.
+    verify_path="$ORIG_PATH"
+    if [ -n "$BIN_DIR" ]; then
+        case ":$ORIG_PATH:" in
+            *":$BIN_DIR:"*) ;;
+            *) verify_path="$BIN_DIR:$ORIG_PATH" ;;
+        esac
+    fi
+
+    saved_path="$PATH"
+    PATH="$verify_path"
+    export PATH
+    bad=""
+    go_ok || bad="$bad go"
+    gofmt_ok || bad="$bad gofmt"
+    golangci_lint_ok || bad="$bad golangci-lint"
+    for t in node yarn; do
+        if missing "$t"; then bad="$bad $t"; fi
+    done
+    PATH="$saved_path"
+    export PATH
+
+    [ -z "$bad" ] && return 0
+
+    # Two different faults land here and they need different remedies: a
+    # tool that resolves but is the wrong build is being shadowed, and
+    # telling the user to fix PATH is right; a tool that does not resolve
+    # at all is not being shadowed by anything, and saying so would send
+    # them hunting for a conflict that does not exist.
+    echo "bootstrap: the toolchain on your PATH cannot run the gate." >&2
+    wrong=""
+    absent=""
+    for t in $bad; do
+        where="$(
+            export PATH="$verify_path"
+            command -v "$t" 2>/dev/null || true
+        )"
+        if [ -n "$where" ]; then
+            echo "  $t: $where (wrong version)" >&2
+            wrong="$wrong $t"
+        else
+            echo "  $t: not found" >&2
+            absent="$absent $t"
+        fi
+    done
+    echo "  The pinned toolchain is linked into $bin_dir." >&2
+    if [ -n "$wrong" ]; then
+        echo "  The tools shown with a path resolve to a build this" >&2
+        echo "  script did not provision: something earlier on your PATH" >&2
+        echo "  shadows $bin_dir. Put $bin_dir first in" >&2
+        echo "  PATH, or remove the conflicting tool, then re-run." >&2
+    fi
+    if [ -n "$absent" ]; then
+        echo "  The tools shown as not found are on no directory of your" >&2
+        echo "  PATH at all, so nothing is shadowing them. Add $bin_dir" >&2
+        echo "  to PATH and re-run; if they are still not found after" >&2
+        echo "  that, bootstrap failed to install them and that is a bug" >&2
+        echo "  in this script, not in your environment." >&2
+    fi
+    echo "  Failing rather than leaving you a bootstrap that reports" >&2
+    echo "  success and a \`make check\` that does not run." >&2
+    exit 1
+}
+
 main() {
     cd "$ROOT"
 
+    TOOLCHAIN="$HOME/.local/share/$("$ROOT/script/projectname")/toolchain"
+    GO_DIR="$TOOLCHAIN/go-$GO_VERSION"
+    GOLANGCI_LINT_DIR="$TOOLCHAIN/golangci-lint-$GOLANGCI_LINT_VERSION"
+
     if missing make; then pkg_install gnumake make make make; fi
     if missing git; then pkg_install git git git git; fi
 
@@ -137,6 +595,11 @@ main() {
     ensure_yarn
     install_js_deps
 
+    ensure_go
+    ensure_golangci_lint
+
+    verify_toolchain
+
     echo "bootstrap complete"
 }
 

script/check

@@ -4,12 +4,13 @@
 # scripts-to-rule-them-all. Must not modify any files.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
-    "$SCRIPT_DIR/test"
+    cd "$ROOT"
-    "$SCRIPT_DIR/lint"
+    "$ROOT/script/test"
-    "$SCRIPT_DIR/fmt-check"
+    "$ROOT/script/lint"
+    "$ROOT/script/fmt-check"
 }
 
 main "$@"

script/docker

@@ -4,12 +4,11 @@
 # as <name>-server. Both build from the repo root as their context.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
 
 main() {
     cd "$ROOT"
-    name="$("$SCRIPT_DIR/projectname")"
+    name="$("$ROOT/script/projectname")"
     timeout 300 docker build -t "$name" -f Dockerfile .
     timeout 300 docker build -t "$name-server" -f Dockerfile.backend .
 }

script/frontend-check

@@ -6,12 +6,13 @@
 # the whole repo. Must not modify any files.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
-    "$SCRIPT_DIR/frontend-test"
+    cd "$ROOT"
-    "$SCRIPT_DIR/frontend-lint"
+    "$ROOT/script/frontend-test"
-    "$SCRIPT_DIR/frontend-fmt-check"
+    "$ROOT/script/frontend-lint"
+    "$ROOT/script/frontend-fmt-check"
 }
 
 main "$@"

script/precommit

@@ -3,10 +3,11 @@
 # checks fail. Our own extension to scripts-to-rule-them-all.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
-    "$SCRIPT_DIR/check"
+    cd "$ROOT"
+    "$ROOT/script/check"
 }
 
 main "$@"

script/setup

@@ -3,11 +3,12 @@
 # installs dependencies and the git pre-commit hook.
 set -eu
 
-SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
 main() {
-    "$SCRIPT_DIR/bootstrap"
+    cd "$ROOT"
-    "$SCRIPT_DIR/install-precommit"
+    "$ROOT/script/bootstrap"
+    "$ROOT/script/install-precommit"
 }
 
 main "$@"