fix(version-gate): regenerate at the merge base VERSION, read tool output from a file, never follow a VERSION symlink

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -5,10 +5,10 @@
 **An unstamped PR can change a release output again (GSTA-96 on #3434).** Regenerating `agents-digest/gstack-AGENTS.md` after a generator change made the Version Gate classify the head as stamped (the digest is in `release_outputs`) and demand base + bump, while changing only `scripts/gen-agents-digest.ts` failed `test/agents-digest.test.ts`'s freshness check, so a digest rewording could not land before its slot.
 
 ### Fixed
-- **Version Gate under a train policy** (`lib/version-gate-train.ts`, `scripts/compare-pr-version.ts`): a changed `release_outputs` file no longer counts as a stamp when it is byte for byte what the policy's `release_tool` generates at the base's `VERSION`; the gate runs the head's tool in a throwaway worktree with the base's `VERSION` (the changed outputs removed first, a bare environment with `GSTACK_RESTAMP_VERSION` and `GSTACK_RESTAMP_STAGING=1` and none of the gate's tokens, no `node_modules` link, a 120 s limit) and compares byte for byte. `VERSION` and `package.json` version changes still classify the head as stamped, as does an output that differs (hand-edited, generated at a bumped version, or never written by the tool) or a policy with no `release_tool`; a tool that exits non-zero, is killed or cannot be staged is an error with the reason, never a pass; the staging worktree is removed and pruned on every path. `version-gate.yml` checks the head out with `persist-credentials: false`, since the head's tool now runs inside the gate. The freshness test stays strict and a stamp commit still changes only the stamp files, since the slot's restamp regenerates the output. `docs/ship-policy.md` states the rule under "Lane: report ready".
+- **Version Gate under a train policy** (`lib/version-gate-train.ts`, `scripts/compare-pr-version.ts`): a changed `release_outputs` file no longer counts as a stamp when it is byte for byte what the policy's `release_tool` generates at the head's merge base's `VERSION` (the head's own, since `VERSION` is unchanged on this path; the base tip may have stamped since, and CREW rule 14 says not to merge it); the gate runs the head's tool in a throwaway worktree with that `VERSION` (the changed outputs removed first, a bare environment with `GSTACK_RESTAMP_VERSION` and `GSTACK_RESTAMP_STAGING=1` and none of the gate's tokens, no `node_modules` link, a 120 s limit, output read from a file so a lingering child cannot hold the gate open) and compares byte for byte. `VERSION` and `package.json` version changes still classify the head as stamped, as does an output that differs (hand-edited, generated at a bumped version, or never written by the tool) or a policy with no `release_tool`; a tool that exits non-zero, is killed or cannot be staged is an error with the reason, never a pass; the staging worktree is removed and pruned on every path. `version-gate.yml` checks the head out with `persist-credentials: false`, since the head's tool now runs inside the gate. The freshness test stays strict and a stamp commit still changes only the stamp files, since the slot's restamp regenerates the output. `docs/ship-policy.md` states the rule under "Lane: report ready".
 
 ### Tests
-- `test/compare-pr-version.test.ts`: a generator change with its regenerated output at the base VERSION passes as unstamped (red without the fix); a hand-edited output, an output generated at the bumped version, an output the tool never writes, a VERSION bump without the output, a failing release tool and a policy without `release_tool` all still refuse; the tool sees no `GH_TOKEN`; no worktree is left behind.
+- `test/compare-pr-version.test.ts`: a generator change with its regenerated output at the merge base VERSION passes as unstamped (red without the fix), and stays unstamped after main stamps again; a tool whose background child outlives it does not hold the gate open; a hand-edited output, an output generated at the bumped version, an output the tool never writes, a VERSION bump without the output, a failing release tool and a policy without `release_tool` all still refuse; the tool sees no `GH_TOKEN`; no worktree is left behind.
 
 ## [1.91.226.0] - 2026-10-26
 

docs/ship-policy.md

@@ -171,7 +171,8 @@ SHIP_RECEIPT: pr=42 head=<head12> …
 CI's Version Gate (`scripts/compare-pr-version.ts`) accepts that head as
 unstamped when `VERSION` and `package.json`'s version match its merge base, the
 CHANGELOG change is confined to `[Unreleased]`, and any changed release output
-is byte for byte what `release_tool` generates at the base's `VERSION`, so a
+is byte for byte what `release_tool` generates at the head's merge base
+`VERSION` (the head's own, so a later stamp on main changes nothing), so a
 generator change ships with its regenerated output and the slot's restamp
 regenerates it again. A release output that differs from that (a hand edit, one generated at a
 bumped version, or one the tool never writes), a `VERSION` bump or a

lib/version-gate-train.ts

@@ -36,9 +36,12 @@ export function bumpVersion(version: string, level: string): string | null {
 /**
  * An unstamped head may regenerate a release output (a generator change, for
  * example) as long as what it committed is exactly what the policy's
- * release_tool produces at the base's VERSION: the slot's restamp regenerates
- * it anyway. Runs the head's tool in a throwaway worktree with VERSION set to
- * the base's and compares each changed output byte for byte. A stamp (new
+ * release_tool produces at its merge base's VERSION (the head's own, since
+ * VERSION is unchanged on this path; the base tip may have stamped since):
+ * the slot's restamp regenerates it anyway. Runs the head's tool in a
+ * throwaway worktree with that VERSION and compares each changed output byte
+ * for byte, reading the tool's output from a file so a lingering child cannot
+ * hold the gate open. A stamp (new
  * VERSION inside the output) differs, so it still classifies as stamped, and
  * so does an output the tool never writes (it is removed before the run).
  * The tool is head code: it runs with a bare environment (no tokens), no
@@ -47,20 +50,25 @@ export function bumpVersion(version: string, level: string): string | null {
  */
 const TOOL_ENV_KEYS = ['PATH', 'HOME', 'TMPDIR', 'LANG', 'LC_ALL', 'BUN_INSTALL', 'SystemRoot', 'TEMP', 'TMP'];
 function regeneratedAtBase(o: { repoRoot: string; head: string; baseVersion: string; tool: string; outputs: string[] }): { kind: 'same' } | { kind: 'differs'; files: string[] } | { kind: 'error'; reason: string } {
-  if (!o.baseVersion.trim()) return { kind: 'error', reason: 'the base has no VERSION to regenerate the release outputs at' };
+  if (!o.baseVersion.trim()) return { kind: 'error', reason: 'the merge base has no VERSION to regenerate the release outputs at' };
   let staging: string;
   try { staging = fs.mkdtempSync(path.join(os.tmpdir(), 'version-gate-regen-')); } catch (e) { return { kind: 'error', reason: `cannot create a staging directory to regenerate the release outputs: ${e instanceof Error ? e.message : String(e)}` }; }
   try {
-    const add = spawnSync('git', ['worktree', 'add', '--detach', '-q', staging, o.head], { cwd: o.repoRoot, encoding: 'utf8', timeout: 60_000 });
+    const add = spawnSync('git', ['worktree', 'add', '--detach', '-q', staging, o.head], { cwd: o.repoRoot, encoding: 'utf8', timeout: 30_000 });
     if (add.status !== 0) return { kind: 'error', reason: `cannot stage ${o.head.slice(0, 12)} to regenerate its release outputs: ${(add.stderr || '').trim().slice(0, 200)}` };
+    fs.rmSync(path.join(staging, 'VERSION'), { force: true });
     fs.writeFileSync(path.join(staging, 'VERSION'), o.baseVersion);
     for (const f of o.outputs) fs.rmSync(path.join(staging, f), { force: true });
     const env: NodeJS.ProcessEnv = { GSTACK_RESTAMP_VERSION: o.baseVersion.trim(), GSTACK_RESTAMP_STAGING: '1' };
     for (const key of TOOL_ENV_KEYS) if (process.env[key] !== undefined) env[key] = process.env[key];
-    const run = spawnSync('sh', ['-c', o.tool], { cwd: staging, encoding: 'utf8', timeout: 120_000, env });
+    const logPath = path.join(os.tmpdir(), path.basename(staging) + '.log');
+    const log = fs.openSync(logPath, 'w');
+    let run: ReturnType<typeof spawnSync>;
+    try { run = spawnSync('sh', ['-c', o.tool], { cwd: staging, stdio: ['ignore', log, log], timeout: 120_000, env }); } finally { fs.closeSync(log); }
+    const output = (() => { try { return fs.readFileSync(logPath, 'utf8'); } catch { return ''; } finally { fs.rmSync(logPath, { force: true }); } })();
     if (run.status !== 0) {
       const how = run.status === null ? (run.error ? run.error.message : `was killed by ${run.signal ?? 'a signal'} (120s limit)`) : `exited ${run.status}`;
-      return { kind: 'error', reason: `release_tool \`${o.tool}\` ${how} at ${o.head.slice(0, 12)} with the base's VERSION, so its release outputs cannot be told from a stamp: ${(run.stderr || run.stdout || '').trim().slice(0, 200)}` };
+      return { kind: 'error', reason: `release_tool \`${o.tool}\` ${how} at ${o.head.slice(0, 12)} with its merge base's VERSION, so its release outputs cannot be told from a stamp: ${output.trim().slice(0, 200)}` };
     }
     const files = o.outputs.filter(f => {
       const committed = spawnSync('git', ['show', `${o.head}:${f}`], { cwd: o.repoRoot, timeout: 30_000, maxBuffer: 64 * 1024 * 1024 });
@@ -70,9 +78,9 @@ function regeneratedAtBase(o: { repoRoot: string; head: string; baseVersion: str
     });
     return files.length ? { kind: 'differs', files } : { kind: 'same' };
   } finally {
-    spawnSync('git', ['worktree', 'remove', '--force', staging], { cwd: o.repoRoot, timeout: 60_000 });
+    spawnSync('git', ['worktree', 'remove', '--force', staging], { cwd: o.repoRoot, timeout: 30_000 });
     fs.rmSync(staging, { recursive: true, force: true });
-    spawnSync('git', ['worktree', 'prune'], { cwd: o.repoRoot, timeout: 60_000 });
+    spawnSync('git', ['worktree', 'prune'], { cwd: o.repoRoot, timeout: 30_000 });
   }
 }
 
@@ -92,13 +100,15 @@ export function classifyTrainHead(o: { repoRoot: string; baseRef: string; head:
   const touched: string[] = changed.filter(f => f === 'VERSION');
   if (npmVersion(mergeBase) !== npmVersion(o.head)) touched.push('package.json version');
   const outputs = changed.filter(f => matchesAny(releaseOutputs, f));
+  const baseVersion = show(base, 'VERSION') ?? '';
   if (!touched.length && outputs.length && typeof policy.release_tool === 'string') {
-    const regen = regeneratedAtBase({ repoRoot: o.repoRoot, head: o.head, baseVersion: show(base, 'VERSION') ?? '', tool: policy.release_tool, outputs });
+    // the head's VERSION is its merge base's (unchanged on this path); the base tip may have stamped since
+    const regen = regeneratedAtBase({ repoRoot: o.repoRoot, head: o.head, baseVersion: show(mergeBase, 'VERSION') ?? '', tool: policy.release_tool, outputs });
     if (regen.kind === 'error') return { kind: 'invalid', reason: regen.reason };
     if (regen.kind === 'differs') touched.push(...regen.files);
   } else touched.push(...outputs);
   if (touched.length) {
-    const expected = bumpVersion(show(base, 'VERSION') ?? '', policy.bump ?? 'patch');
+    const expected = bumpVersion(baseVersion, policy.bump ?? 'patch');
     return expected ? { kind: 'stamped', expected } : { kind: 'invalid', reason: `${base}:VERSION is not a 4-part version` };
   }
 

scripts/compare-pr-version.ts

@@ -41,7 +41,7 @@ const prVersionEnv = (process.env.PR_VERSION ?? "").trim();
 if (process.env.BASE_REF && process.env.HEAD_SHA) {
   const train = classifyTrainHead({ repoRoot: process.cwd(), baseRef: process.env.BASE_REF, head: process.env.HEAD_SHA });
   if (train.kind === "unstamped") {
-    console.log(`✓ ${tag} is unstamped under the base's train policy: VERSION and package.json match its merge base, any changed release output is what the release tool generates at the base's VERSION, and the CHANGELOG change is confined to [Unreleased]. The lane stamps at its slot.`);
+    console.log(`✓ ${tag} is unstamped under the base's train policy: VERSION and package.json match its merge base, any changed release output is what the release tool generates at the merge base's VERSION, and the CHANGELOG change is confined to [Unreleased]. The lane stamps at its slot.`);
     process.exit(0);
   }
   if (train.kind === "invalid") {

test/compare-pr-version.test.ts

@@ -183,6 +183,39 @@ describe('version gate: unstamped heads under a train policy', () => {
       expect(r.git('worktree', 'list').trim().split('\n')).toHaveLength(1);
     });
 
+    test('a regenerated output stays unstamped after main stamps again (the regeneration is at the merge base VERSION, not the base tip)', () => {
+      const r = fixture();
+      branch(r);
+      gen(r, 'reworded body');
+      write(r, 'generated/digest.md', '# digest v1.2.3.0\nreworded body\n');
+      write(r, 'CHANGELOG.md', withUnreleased(r));
+      const head = commit(r, 'reword the digest');
+      r.git('checkout', '-q', 'main');
+      write(r, 'VERSION', '1.2.4.0\n');
+      write(r, 'generated/digest.md', '# digest v1.2.4.0\nbody\n');
+      write(r, 'CHANGELOG.md', read(r, 'CHANGELOG.md').replace('# Changelog\n\n', '# Changelog\n\n## [1.2.4.0] - 2026-10-02\n\n- another release\n\n'));
+      commit(r, 'release 1.2.4.0');
+      r.git('push', '-q', 'origin', 'main');
+      r.git('fetch', '-q', 'origin');
+      const res = run(r, head, '1.2.3.0');
+      expect(res.code).toBe(0);
+      expect(res.out).toContain('is unstamped under the base');
+    });
+
+    test('a tool whose background child outlives it does not hold the gate open', () => {
+      const r = fixture();
+      branch(r);
+      write(r, 'gen.js', "const fs=require('fs');const v=fs.readFileSync('VERSION','utf8').trim();fs.writeFileSync('generated/digest.md','# digest v'+v+'\\nreworded body\\n');require('child_process').spawn('sleep',['20'],{stdio:'inherit'}).unref();\n");
+      write(r, 'generated/digest.md', '# digest v1.2.3.0\nreworded body\n');
+      write(r, 'CHANGELOG.md', withUnreleased(r));
+      const head = commit(r, 'tool with a lingering child');
+      const started = Date.now();
+      const res = run(r, head);
+      expect(Date.now() - started).toBeLessThan(15_000);
+      expect(res.code).toBe(0);
+      expect(res.out).toContain('is unstamped under the base');
+    });
+
     test('the tool runs without the gate\'s tokens, and an output the tool never writes still counts as a stamp', () => {
       const r = fixture();
       branch(r);