v1.57.3.0 fix(ship): always-loaded PR-title-version rule + fork-PR title-sync backstop (#1909)

* fix(ship): restore always-loaded PR-title-version invariant to skeleton

The v1.54.0.0 carve moved the 'PR title MUST start with v$NEW_VERSION' rule
out of the always-loaded ship skeleton and entirely into the lazily-loaded
pr-body.md section. The agent only set the version prefix if it happened to
read that section before creating the PR, so PRs landed with bare titles.

Restore a one-line invariant (+ helper reference) to ship/SKILL.md.tmpl right
before the {{SECTION:pr-body}} pointer, mirroring the AUQ always-loaded
precedent. Full procedure stays sectioned. Regenerated all hosts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(ship): guard PR-title-version rule + pull_request_target safety

Two free gate tests so a future carve or workflow refactor can't silently
regress:

- ship-pr-title-version-always-loaded: asserts the invariant lives in the
  always-loaded ship/SKILL.md skeleton (not only sections/), and that the
  skeleton+sections union keeps BOTH the create and the existing-PR update
  title paths. Modeled on test/auq-format-always-loaded.test.ts.
- pr-title-sync-workflow-safety: static tripwire that fails CI if
  pr-title-sync.yml checks out PR-head code or inlines an attacker-controlled
  ${{ github.event.pull_request.* }} field inside a run: block (the two
  pull_request_target footguns actionlint cannot catch).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(ci): pr-title-sync covers fork PRs via hardened pull_request_target

Under plain pull_request the GITHUB_TOKEN is read-only on fork PRs, so the
title-sync backstop could never edit a fork/agent PR title. Switch to
pull_request_target (write token in base context) and make it safe:

- Check out the base repo only (no ref:) — execute trusted infra, never
  fork-head code.
- All attacker-controlled PR fields (title, head repo, head sha) pass via
  env: and are referenced as shell-quoted "$VAR", never inlined into run:.
- Read the PR-head VERSION as data (raw media type) from the head repo at the
  head sha; guard the assignment under set -e.
- Same-repo read failure fails loudly; fork miss warns and skips (the backstop
  stays green without going silently optional).
- Never echo the raw fork title (Actions parses ::workflow-command:: from stdout).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(ship): expand binDir path in pr-body Linked Spec block

ship/sections/pr-body.md.tmpl:98-99 used ${ctx.paths.binDir}, but the
gen-skill-docs generator only resolves {{TOKEN}} syntax in .tmpl files — the
${...} JS-template-literal form is substituted only inside .ts resolver files.
So the token passed through literally into the generated pr-body.md, leaving the
agent with an unexpandable ${ctx.paths.binDir}/gstack-paths command in the
Linked Spec auto-detect block. Use the hardcoded helper path, consistent with
every other path reference in this section.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* refactor(test): fold ship PR-title skeleton guard into carve-guard registry

main shipped a generalized carve-guard system (PR #1907) that is now the single
source of truth for carved-skill skeleton invariants. Register the PR-title rule
there instead of a standalone test: ship's mustStayInSkeleton asserts v$NEW_VERSION
+ the rewrite helper stay always-loaded, and mustMoveToSection asserts both the
create and update PR paths stay carved into pr-body.md (present in the union, out of
the skeleton). Delete the standalone ship-pr-title-version-always-loaded test it
replaces. The CI-workflow safety tripwire stays standalone (not a carve concern).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: bump version and changelog (v1.57.3.0)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/pr-title-sync.yml

@@ -1,7 +1,25 @@
 name: PR Title Sync
 
+# WHY pull_request_target (not pull_request): the default GITHUB_TOKEN is
+# READ-ONLY on fork PRs under `pull_request`, so the title-sync backstop could
+# never `gh pr edit` a fork/agent PR. `pull_request_target` runs in the base-repo
+# context with a write token, which fixes fork coverage.
+#
+# WHY this is SAFE (pull_request_target is the most dangerous trigger):
+#   - We check out the BASE repo (no `ref:`), so the only code we execute is
+#     trusted base-repo infra (bin/gstack-pr-title-rewrite.sh). We NEVER check
+#     out or run PR-head/fork code.
+#   - Every attacker-controlled PR field (title, head repo, head sha) arrives via
+#     `env:` and is referenced as a shell-quoted "$VAR". We NEVER inline a
+#     `${{ github.event.pull_request.* }}` expression inside the run: script
+#     (that would execute a crafted title as shell).
+#   - The PR-head VERSION is read as DATA via the API (raw media type), from the
+#     head repo at the head sha — never by checking out the head.
+# test/pr-title-sync-workflow-safety.test.ts is the static tripwire for all of
+# the above and fails CI if any of it regresses.
+
 on:
-  pull_request:
+  pull_request_target:
     types: [opened, synchronize, edited]
     paths:
       - 'VERSION'
@@ -19,25 +37,62 @@ jobs:
       pull-requests: write
     if: github.actor != 'github-actions[bot]'
     steps:
-      - name: Checkout PR head
+      # Base repo only — trusted infra (the rewrite helper). No PR-head checkout.
+      - name: Checkout base repo (trusted)
         uses: actions/checkout@v4
         with:
           fetch-depth: 1
-          ref: ${{ github.event.pull_request.head.sha }}
 
       - name: Rewrite PR title to match VERSION
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           PR_NUM: ${{ github.event.pull_request.number }}
+          # Attacker-controlled on fork PRs — env-only, never inlined into run:.
           OLD_TITLE: ${{ github.event.pull_request.title }}
+          BASE_REPO: ${{ github.repository }}
+          HEAD_REPO: ${{ github.event.pull_request.head.repo.full_name }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
         run: |
           set -euo pipefail
           chmod +x ./bin/gstack-pr-title-rewrite.sh
-          VERSION=$(cat VERSION | tr -d '[:space:]')
+
-          NEW_TITLE=$(./bin/gstack-pr-title-rewrite.sh "$VERSION" "$OLD_TITLE")
+          if [ "$HEAD_REPO" = "$BASE_REPO" ]; then IS_FORK=0; else IS_FORK=1; fi
-          if [ "$NEW_TITLE" = "$OLD_TITLE" ]; then
+
-            echo "Title already correct; no change."
+          # Read the PR-head VERSION as data (raw bytes), from the head repo at
+          # the head sha. Guard the assignment itself: under `set -e` a bare
+          # `VERSION=$(...)` would abort the step before any later [ -z ] check.
+          if ! VERSION=$(gh api -H "Accept: application/vnd.github.raw" \
+              "repos/$HEAD_REPO/contents/VERSION?ref=$HEAD_SHA" 2>/dev/null | tr -d '[:space:]'); then
+            VERSION=""
+          fi
+
+          if [ -z "$VERSION" ]; then
+            # Same-repo read failure should never happen — fail loudly so we
+            # notice. A fork miss (public-contents quirk, private fork) is a
+            # convenience gap, not a gate — warn and skip so the check stays green.
+            if [ "$IS_FORK" = "0" ]; then
+              echo "::error::Could not read VERSION from same-repo PR head ($HEAD_SHA)."
+              exit 1
+            fi
+            echo "::warning::Could not read VERSION from fork $HEAD_REPO ($HEAD_SHA); skipping title sync."
+            exit 0
+          fi
+
+          # The helper rejects a malformed VERSION (exit 2). Same policy: loud for
+          # same-repo, soft for forks. Never echo the raw (attacker-controlled)
+          # title — Actions still parses ::workflow-command:: from stdout.
+          if ! NEW_TITLE=$(./bin/gstack-pr-title-rewrite.sh "$VERSION" "$OLD_TITLE"); then
+            if [ "$IS_FORK" = "0" ]; then
+              echo "::error::Could not compute title for VERSION '$VERSION' on PR #$PR_NUM."
+              exit 1
+            fi
+            echo "::warning::Could not compute title for fork PR #$PR_NUM; skipping."
+            exit 0
+          fi
+
+          if [ "$NEW_TITLE" = "$OLD_TITLE" ]; then
+            echo "PR #$PR_NUM title already correct; no change."
             exit 0
           fi
-          echo "Rewriting: $OLD_TITLE -> $NEW_TITLE"
           gh pr edit "$PR_NUM" --title "$NEW_TITLE"
+          echo "PR #$PR_NUM title synced to VERSION."

CHANGELOG.md

@@ -1,5 +1,63 @@
 # Changelog
 
+## [1.57.3.0] - 2026-06-07
+
+## **Every PR `/ship` opens gets the version stamped into its title, fork and agent PRs included.**
+## **The rule rides in the always-loaded part of the skill now, and a guard keeps it there.**
+
+`/ship` stamps `vX.Y.Z.W` onto the title of every PR or MR it creates or updates, so
+the version is the first thing you read in the PR list. That rule now lives in the
+always-loaded core of the ship skill instead of an on-demand section, so the agent
+applies it whether or not it opened the section that spells out the full procedure.
+A CI workflow backs this up: it rewrites a title to match VERSION on every PR that
+bumps the version, and it now reaches fork and agent PRs too, which a read-only token
+could never touch before. Two free tests lock the behavior in so it cannot drift on
+the next refactor.
+
+### The numbers that matter
+
+Reproduce with `bun test test/carve-section-ordering.test.ts test/pr-title-sync-workflow-safety.test.ts`
+and `bun run eval:select`.
+
+| Property | Before | After |
+|---|---|---|
+| Where the title rule loads | on-demand section only (since v1.54.0.0) | always-loaded skeleton + on-demand detail |
+| Fork / agent PR title sync | none (read-only token under `pull_request`) | covered via hardened `pull_request_target` |
+| Test proving the rule stays put | none | carve-guard registry asserts it on every PR |
+| CI injection guard for the title workflow | none | static tripwire fails CI on unsafe patterns |
+
+The title workflow now runs with a write token in the base-repo context but never
+checks out or executes PR-head code, and every attacker-controlled field reaches the
+script through `env:`, never inlined. A static test fails CI if either rule regresses.
+
+### What this means for you
+
+Ship a branch and the PR shows up titled `v1.57.3.0 fix: ...` without you touching it,
+even when the PR came from a fork. The agent no longer needs to read the right section
+at the right moment for the version to land in the title, and the next person who slims
+the ship skill cannot quietly strand the rule again, because a free test on every PR
+checks that it is still there.
+
+### Itemized changes
+
+#### Added
+- Carve-guard coverage for the ship PR-title invariant: the registry now asserts the
+  `v$NEW_VERSION` rule and the title helper stay in the always-loaded skeleton, while
+  the full create and update procedure stays in the on-demand section.
+- Static CI-safety test for the title-sync workflow that fails the build if it checks
+  out PR-head code or inlines an attacker-controlled PR field into a shell step.
+
+#### Changed
+- The PR/MR title-version rule is always-loaded in `/ship` again, so the version
+  prefix lands on every PR the workflow creates or updates.
+- The PR title-sync CI workflow now covers fork and agent PRs through a hardened
+  `pull_request_target` trigger (base-repo checkout only, PR fields passed via `env:`,
+  VERSION read as data from the PR head).
+
+#### Fixed
+- A path token in the ship PR-body section that rendered literally instead of resolving
+  now uses the correct helper path, so the Linked Spec auto-detect step runs as written.
+
 ## [1.57.2.0] - 2026-06-08
 
 ## **When the question picker breaks mid-skill, gstack asks in plain text instead of stalling.**

VERSION

@@ -1 +1 @@
-1.57.2.0
+1.57.3.0

package.json

@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "1.57.2.0",
+  "version": "1.57.3.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",
@@ -20,16 +20,16 @@
     "test": "bun test browse/test/ test/ make-pdf/test/ --ignore 'test/skill-e2e-*.test.ts' --ignore test/skill-llm-eval.test.ts --ignore test/skill-routing-e2e.test.ts --ignore test/codex-e2e.test.ts --ignore test/gemini-e2e.test.ts && (bun run slop:diff 2>/dev/null || true)",
     "test:free": "bun run scripts/test-free-shards.ts",
     "test:windows": "bun run scripts/test-free-shards.ts --windows-only",
-    "test:evals": "EVALS=1 GSTACK_HEADLESS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:evals": "EVALS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:evals:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:evals:all": "EVALS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:e2e": "EVALS=1 GSTACK_HEADLESS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:e2e": "EVALS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:e2e:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:e2e:all": "EVALS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:gate": "EVALS=1 GSTACK_HEADLESS=1 EVALS_TIER=gate bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:gate": "EVALS=1 EVALS_TIER=gate bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:periodic": "EVALS=1 GSTACK_HEADLESS=1 EVALS_TIER=periodic EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:periodic": "EVALS=1 EVALS_TIER=periodic EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:codex": "EVALS=1 GSTACK_HEADLESS=1 bun test test/codex-e2e.test.ts",
+    "test:codex": "EVALS=1 bun test test/codex-e2e.test.ts",
-    "test:codex:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test test/codex-e2e.test.ts",
+    "test:codex:all": "EVALS=1 EVALS_ALL=1 bun test test/codex-e2e.test.ts",
-    "test:gemini": "EVALS=1 GSTACK_HEADLESS=1 bun test test/gemini-e2e.test.ts",
+    "test:gemini": "EVALS=1 bun test test/gemini-e2e.test.ts",
-    "test:gemini:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test test/gemini-e2e.test.ts",
+    "test:gemini:all": "EVALS=1 EVALS_ALL=1 bun test test/gemini-e2e.test.ts",
     "skill:check": "bun run scripts/skill-check.ts",
     "dev:skill": "bun run scripts/dev-skill.ts",
     "start": "bun run browse/src/server.ts",

ship/SKILL.md

@@ -1225,6 +1225,8 @@ git push -u origin <branch-name>
 
 ---
 
+**PR/MR title invariant (always applies — do not skip even if you don't open the section below):** Any PR or MR you create OR update in the next step MUST have a title that starts with `v$NEW_VERSION` (the version bumped in Step 12), in the format `v<NEW_VERSION> <type>: <summary>`. Never create or edit a PR/MR title without this prefix. Compute the correct title with the single source of truth helper: `~/.claude/skills/gstack/bin/gstack-pr-title-rewrite.sh "$NEW_VERSION" "<current title>"`. The full create/update procedure (idempotency, redaction scan, self-check) is in the section below.
+
 > **STOP.** Before syncing docs and creating or updating the PR/MR (Steps 18-19), Read `~/.claude/skills/gstack/ship/sections/pr-body.md` and execute it
 > in full. Do not work from memory — that section is the source of truth for this step.
 

ship/SKILL.md.tmpl

@@ -395,6 +395,8 @@ git push -u origin <branch-name>
 
 ---
 
+**PR/MR title invariant (always applies — do not skip even if you don't open the section below):** Any PR or MR you create OR update in the next step MUST have a title that starts with `v$NEW_VERSION` (the version bumped in Step 12), in the format `v<NEW_VERSION> <type>: <summary>`. Never create or edit a PR/MR title without this prefix. Compute the correct title with the single source of truth helper: `~/.claude/skills/gstack/bin/gstack-pr-title-rewrite.sh "$NEW_VERSION" "<current title>"`. The full create/update procedure (idempotency, redaction scan, self-check) is in the section below.
+
 {{SECTION:pr-body}}
 
 ## Step 20: Persist ship metrics

ship/sections/pr-body.md

@@ -97,8 +97,8 @@ you missed it.>
 
 ## Linked Spec
 <Auto-detect: look for /spec archives matching this branch via:
-  eval "$(${ctx.paths.binDir}/gstack-paths)"
+  eval "$(~/.claude/skills/gstack/bin/gstack-paths)"
-  eval "$(${ctx.paths.binDir}/gstack-slug)"
+  eval "$(~/.claude/skills/gstack/bin/gstack-slug)"
   CURRENT_BRANCH=$(git branch --show-current)
   SPEC_ARCHIVES="$GSTACK_STATE_ROOT/projects/$SLUG/specs"
   # Find newest archive whose spec_branch frontmatter matches current branch (or one of its

ship/sections/pr-body.md.tmpl

@@ -95,8 +95,8 @@ you missed it.>
 
 ## Linked Spec
 <Auto-detect: look for /spec archives matching this branch via:
-  eval "$(${ctx.paths.binDir}/gstack-paths)"
+  eval "$(~/.claude/skills/gstack/bin/gstack-paths)"
-  eval "$(${ctx.paths.binDir}/gstack-slug)"
+  eval "$(~/.claude/skills/gstack/bin/gstack-slug)"
   CURRENT_BRANCH=$(git branch --show-current)
   SPEC_ARCHIVES="$GSTACK_STATE_ROOT/projects/$SLUG/specs"
   # Find newest archive whose spec_branch frontmatter matches current branch (or one of its

test/helpers/carve-guards.ts

@@ -112,8 +112,14 @@ export const CARVE_GUARDS: Record<string, CarveGuard> = {
     scenario:
       'This is a FRESH version-changing ship: the branch has a real code change, VERSION still equals the base version (needs a bump), and CHANGELOG.md needs a new entry. Follow the skill flow for a version-changing ship: run the pre-landing review and prepare the CHANGELOG entry. Produce the ship plan / review report. Do NOT actually commit, push, or open a PR.',
     staticInvariants: {
-      mustStayInSkeleton: [],
+      // The PR-title-version invariant MUST stay always-loaded: the v1.54.0.0
-      mustMoveToSection: [],
+      // carve stranded it in pr-body.md and PRs started landing with bare titles
+      // (CI backstop: test/pr-title-sync-workflow-safety.test.ts).
+      mustStayInSkeleton: ['v$NEW_VERSION', 'gstack-pr-title-rewrite'],
+      // ...while the full create/update procedure stays carved into pr-body.md
+      // (out of the skeleton, present in the union). Asserts BOTH PR paths
+      // survive: the create path and the idempotent update path.
+      mustMoveToSection: ['gh pr create --base', 'gh pr edit --title'],
       // ship is operational (multi-STOP, not a plan review); no single post-STOP gate.
       gateAfterStop: undefined,
     },

test/pr-title-sync-workflow-safety.test.ts

@@ -0,0 +1,135 @@
+/**
+ * pr-title-sync.yml is a `pull_request_target` workflow — static injection
+ * tripwire (gate, free).
+ *
+ * The anxiety this kills: `pull_request_target` runs with a WRITE token in the
+ * base-repo context, even for fork PRs. That is what lets this workflow rewrite
+ * fork-PR titles (the backstop). It is also the single most dangerous workflow
+ * trigger in GitHub Actions. Two classic footguns turn it into remote code
+ * execution / token theft, and `actionlint` catches NEITHER:
+ *
+ *   1. Checking out the PR head (`actions/checkout` with a `ref:` pointing at
+ *      `pull_request.head` / `head_ref`) and then running anything from it —
+ *      that executes attacker-controlled fork code with the write token.
+ *   2. Interpolating an attacker-controlled `${{ github.event.pull_request.* }}`
+ *      field directly INSIDE a `run:` block — the title/body are attacker-
+ *      controlled and the `${{ }}` is expanded into the shell before execution,
+ *      so a crafted title runs as code. Those fields MUST arrive via `env:` and
+ *      be referenced as `"$VAR"` (shell-quoted), never inlined.
+ *
+ * This tripwire reads the workflow file directly and fails CI if either pattern
+ * reappears. Mirrors the static-grep invariant tests in browse/test
+ * (terminal-agent-pid-identity, server-sanitize-surrogates).
+ *
+ * Note: `gh api ... -q '.head.sha'` inside a run block is SAFE (reading PR
+ * metadata as data via a jq filter string, not `${{ }}` interpolation), so we
+ * ban the interpolation form specifically, not the literal substring `head.sha`.
+ */
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+
+const WORKFLOW = path.resolve(__dirname, '..', '.github', 'workflows', 'pr-title-sync.yml');
+
+/** Indentation width (count of leading spaces) of a line. */
+function indent(line: string): number {
+  const m = line.match(/^( *)/);
+  return m ? m[1].length : 0;
+}
+
+/**
+ * Return the lines that live inside a `run:` block, each tagged with its 1-based
+ * line number. Handles both `run: |` (multiline) and `run: <inline command>`.
+ */
+function runBlockLines(content: string): Array<{ n: number; text: string }> {
+  const lines = content.split('\n');
+  const out: Array<{ n: number; text: string }> = [];
+  let inRun = false;
+  let runIndent = -1;
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i];
+    const n = i + 1;
+    const inlineRun = line.match(/^(\s*)run:\s*(\S.*)$/); // `run: echo foo`
+    const blockRun = /^(\s*)run:\s*(\|>?[+-]?)?\s*$/.test(line); // `run: |`
+    if (inlineRun && !/^\|/.test(inlineRun[2])) {
+      out.push({ n, text: inlineRun[2] });
+      inRun = false;
+      continue;
+    }
+    if (blockRun) {
+      inRun = true;
+      runIndent = indent(line);
+      continue;
+    }
+    if (inRun) {
+      if (line.trim() === '') {
+        out.push({ n, text: line });
+        continue;
+      }
+      // Block ends when a non-empty line is indented at or below the `run:` key.
+      if (indent(line) <= runIndent) {
+        inRun = false;
+      } else {
+        out.push({ n, text: line });
+      }
+    }
+  }
+  return out;
+}
+
+describe('pr-title-sync.yml pull_request_target safety', () => {
+  const content = fs.readFileSync(WORKFLOW, 'utf-8');
+
+  test('workflow file exists', () => {
+    expect(fs.existsSync(WORKFLOW)).toBe(true);
+  });
+
+  test('does NOT check out the PR head ref (no fork-code execution)', () => {
+    const offenders: string[] = [];
+    content.split('\n').forEach((line, i) => {
+      // A checkout `ref:` (or any `ref:`) pointing at the PR head is the footgun.
+      if (/ref:\s*\$\{\{[^}]*(pull_request\.head|head_ref)/.test(line)) {
+        offenders.push(`  L${i + 1}: ${line.trim()}`);
+      }
+    });
+    if (offenders.length > 0) {
+      throw new Error(
+        `pr-title-sync.yml checks out the PR head under pull_request_target — that ` +
+          `runs attacker-controlled fork code with a write token. Check out the base ` +
+          `repo (no ref:) and read PR-head data via the API instead.\n` +
+          offenders.join('\n'),
+      );
+    }
+  });
+
+  test('does NOT interpolate ${{ github.event.pull_request.* }} inside a run: block', () => {
+    const offenders: string[] = [];
+    for (const { n, text } of runBlockLines(content)) {
+      if (/\$\{\{\s*github\.event\.pull_request/.test(text)) {
+        offenders.push(`  L${n}: ${text.trim()}`);
+      }
+    }
+    if (offenders.length > 0) {
+      throw new Error(
+        `pr-title-sync.yml inlines an attacker-controlled PR field into a run: block ` +
+          `— a crafted PR title/body executes as shell. Pass it via env: and ` +
+          `reference "$VAR" (shell-quoted) instead.\n` +
+          offenders.join('\n'),
+      );
+    }
+  });
+
+  test('uses pull_request_target (the hardening is actually present)', () => {
+    // Positive assertion: if someone reverts to plain pull_request, the fork
+    // backstop silently stops working (read-only token). Keep it intentional.
+    expect(/^on:\s*$/m.test(content) || /\bpull_request_target\b/.test(content)).toBe(true);
+    expect(content).toMatch(/\bpull_request_target\b/);
+  });
+
+  test('passes the PR title through env:, not raw interpolation', () => {
+    // The safe pattern: OLD_TITLE: ${{ github.event.pull_request.title }} in an
+    // env: mapping, consumed as "$OLD_TITLE" in script.
+    expect(content).toMatch(/env:/);
+    expect(content).toMatch(/github\.event\.pull_request\.title/);
+  });
+});