diff --git a/.github/scripts/shellcheck-all.sh b/.github/scripts/shellcheck-all.sh
new file mode 100755
index 0000000..29c5409
--- /dev/null
+++ b/.github/scripts/shellcheck-all.sh
@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Lint every tracked shell script in the repo, and prove the set is complete
+# (#118). Note for editors: a comment line here must not BEGIN with the word
+# "shellcheck" — that is directive syntax, and prose in that position is a
+# parse error. This file's own sweep catches it, which is how this note exists.
+#
+# WHY THE LIST COMES FROM GIT, NOT FROM A GLOB
+#
+# The obvious sweep is a globstar one:
+#
+#     shopt -s globstar; files=(bin/* **/*.sh)
+#
+# and it is quietly wrong. Globs do not match dot-prefixed names without
+# `dotglob`, so `**/` never descends into `.github/` — which is where
+# release-notes.sh lives, the script that produces the published release body.
+#
+# `shopt -s globstar dotglob` does fix that, and measured in this repo it
+# pulls in nothing unwanted: the sweep runs after `npm ci`, but cast's current
+# dependency tree happens to ship zero `.sh` files, so `**/*.sh` stays clean.
+# "Happens to" is the problem — that is a property of somebody else's package
+# tree, re-decided by every `npm install`, and the day a transitive dep vendors
+# a shell script the lint silently becomes partly about their code. `git
+# ls-files` does not depend on that: it sees the tracked tree exactly, with no
+# dotfile blind spot and no untracked noise, and it stays right when files move.
+#
+# Extensionless scripts (bin/cast) are found by shebang rather than named, so
+# adding one does not require editing this file.
+
+cd "$(git rev-parse --show-toplevel)"
+
+# --- the set to lint -------------------------------------------------------
+
+mapfile -t files < <(
+  {
+    git ls-files '*.sh'
+    git ls-files | while IFS= read -r f; do
+      case "$f" in *.sh) continue ;; esac
+      [ -f "$f" ] || continue
+      IFS= read -r line <"$f" || continue
+      case "$line" in '#!'*) ;; *) continue ;; esac
+      # reduce the shebang to a bare interpreter name: drop the '#!', drop any
+      # flags, then keep the last path/word component — so both '#!/bin/sh -e'
+      # and '#!/usr/bin/env bash' come out as 'sh' and 'bash'.
+      interp="${line#\#!}"
+      interp="${interp%% -*}"
+      interp="${interp##*[ /]}"
+      case "$interp" in sh | bash | dash | ksh | zsh) printf '%s\n' "$f" ;; esac
+    done
+  } | sort -u
+)
+
+[ "${#files[@]}" -gt 0 ] || { echo "shellcheck-all: found no shell scripts — the sweep is broken" >&2; exit 1; }
+
+# --- the class check -------------------------------------------------------
+#
+# Assert the set we are about to lint COVERS every tracked *.sh. Today this
+# can't fail, because the list above is derived from the same `git ls-files`
+# — and that is the point. It is a guard on the STATE ("no tracked script
+# goes unlinted"), not on the instance that broke: the day someone rewrites
+# the derivation above into something cheaper that skips a directory, this
+# fails loudly instead of the lint silently passing over nothing. #118 stayed
+# latent precisely because a shrinking sweep looks exactly like a green one.
+
+unlinted="$(comm -23 <(git ls-files '*.sh' | sort -u) <(printf '%s\n' "${files[@]}" | sort -u))"
+if [ -n "$unlinted" ]; then
+  echo "shellcheck-all: tracked shell scripts that this sweep does not lint:" >&2
+  printf '%s\n' "$unlinted" | sed 's/^/  /' >&2
+  echo "the sweep must cover every tracked *.sh — see #118" >&2
+  exit 1
+fi
+
+# --- lint ------------------------------------------------------------------
+
+printf 'shellcheck: linting %d tracked scripts\n' "${#files[@]}"
+printf '  %s\n' "${files[@]}"
+shellcheck -x "${files[@]}"
+echo "shellcheck: clean"
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dac6604..a44759e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -34,6 +34,12 @@ jobs:
       - run: npm test
       - name: installer is valid bash
         run: bash -n install.sh bin/cast scripts/*.sh .github/scripts/*.sh
+      # `bash -n` above is a syntax check on a hand-maintained list; it is not
+      # a linter and it does not notice a script it was never told about.
+      # This sweep derives its list from git and asserts the list covers every
+      # tracked *.sh, so a new script cannot go unlinted quietly (#118).
+      - name: shellcheck — every tracked shell script
+        run: bash .github/scripts/shellcheck-all.sh
       - name: labels state-machine tests
         run: bash test/labels-reconcile.sh
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8929dce..8ecf24b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -266,6 +266,33 @@ actually cutting it, and this file starts there.
   wind-down window where the two overlap — and the whole check-outcome enum are
   pinned in `test/labels-reconcile.sh` (fixtures 19 → 51).
 
+- **CI now lints every tracked shell script, and proves the set is
+  complete** (#118) — filed as cast's record of heavy-duty/box#116, whose
+  defect is a `shopt -s globstar; files=(bin/* **/*.sh)` sweep that skips
+  `.github/` because globs do not match dot-prefixed names without
+  `dotglob`. cast's CI turned out never to have had a shellcheck step at
+  all: the only shell gate was `bash -n install.sh bin/cast scripts/*.sh
+  .github/scripts/*.sh`, a syntax check over a hand-maintained list. So the
+  reported symptom was right — `release-notes.sh` and
+  `labels-reconcile.sh` shipped unlinted — but so did every other script in
+  the repo, including `install.sh` and `bin/cast`, and `bash -n` would not
+  have caught a quoting or unset-variable bug in any of them.
+  [.github/scripts/shellcheck-all.sh](.github/scripts/shellcheck-all.sh)
+  now runs `shellcheck -x` over the tracked tree, from CI and from
+  `npm run check:shell`. It takes its file list from `git ls-files` rather
+  than from a glob. `shopt -s globstar dotglob` was measured and does work
+  here — cast's dependency tree ships no `.sh` files, so sweeping after
+  `npm ci` pulls in nothing — but that is a property of somebody else's
+  package tree, re-decided by every install; `git ls-files` does not depend
+  on it. Extensionless scripts are found by shebang, which is how
+  `bin/cast` is covered without being named. All seven scripts passed as
+  they stood — the three findings were intentional (`$PATH` written
+  literally into a profile, advice text in backticks) or a false positive,
+  and are annotated as such, so this lands as a no-op on behavior. It ships
+  with a class check in box#112's shape: the sweep asserts its own list
+  covers `git ls-files '*.sh'` and fails naming the strays otherwise, so a
+  future sweep that quietly narrows is red rather than green over nothing.
+
 ## 0.1.1 — 2026-07-19
 
 ### Fixed
diff --git a/bin/cast b/bin/cast
index bb69c71..ebf9fed 100755
--- a/bin/cast
+++ b/bin/cast
@@ -263,6 +263,7 @@ command -v node >/dev/null 2>&1 || {
 }
 
 if [ ! -f "$ROOT/dist/cli.js" ]; then
+  # shellcheck disable=SC2016 # intentional: the backticked text is advice for a human to type, not something to expand here
   printf 'cast: %s/dist/cli.js is missing — run the installer, or `npm ci && npm run build` in %s\n' "$ROOT" "$ROOT" >&2
   exit 1
 fi
diff --git a/install.sh b/install.sh
index 98ce3e1..5d58295 100644
--- a/install.sh
+++ b/install.sh
@@ -410,6 +410,10 @@ profile_for_shell() {
 }
 
 path_line_for() {
+  # $PATH below must land in the profile LITERALLY — it is expanded by the
+  # user's future shells, not by this one. The directive sits on the whole
+  # case because a directive on an individual branch is rejected (SC1124).
+  # shellcheck disable=SC2016
   case "$1" in
     */config.fish) printf 'fish_add_path %s\n' "$BINDIR" ;;
     *) printf 'export PATH="%s:$PATH"\n' "$BINDIR" ;;
@@ -427,6 +431,7 @@ else
     log "$PROFILE already puts $BINDIR on PATH — this shell just predates it."
   else
     mkdir -p "$(dirname "$PROFILE")"
+    # shellcheck disable=SC2094 # false positive: path_line_for only cases on its argument's NAME, it never reads the file
     { printf '\n%s\n' "$MARKER"; path_line_for "$PROFILE"; } >>"$PROFILE" \
       || die "could not write $PROFILE — add this line yourself: $(path_line_for "$PROFILE")"
     log "wired $BINDIR onto PATH in $PROFILE"
diff --git a/package.json b/package.json
index d697f75..64da5ea 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,8 @@
     "build": "tsc",
     "test": "vitest run",
     "format": "biome format --write .",
-    "check": "biome check --error-on-warnings ."
+    "check": "biome check --error-on-warnings .",
+    "check:shell": "bash .github/scripts/shellcheck-all.sh"
   },
   "dependencies": {
     "yaml": "^2.5.0",