From ecd3caa2d62fe395d9897de1e69bdb781e16e60b Mon Sep 17 00:00:00 2001
From: garrytan <garrytan@gmail.com>
Date: Tue, 3 Nov 2026 09:59:11 +0000
Subject: [PATCH] fix(harness-version): a pin ahead of the manifest version
 counts as drift (GST-1084)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>
---
 scripts/bump-harness-version.ts |  4 ++--
 test/harness-version.test.ts    | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/scripts/bump-harness-version.ts b/scripts/bump-harness-version.ts
index d047fabbc..7f7d7d36a 100644
--- a/scripts/bump-harness-version.ts
+++ b/scripts/bump-harness-version.ts
@@ -66,11 +66,11 @@ export function workingHarnessFiles(root: string, patterns: readonly string[]):
   return tracked.map((entry, index) => ({ file: entry.file, blob: blobs[index]! }));
 }
 
-/** Harness files whose blob differs from, is missing from, or no longer matches an entry in the manifest. */
+/** Harness files whose blob differs from, is missing from, or no longer matches an entry in the manifest; a pin ahead of the manifest version (a bump that failed partway) counts as changed. */
 export function harnessDrift(manifest: HarnessManifest, files: TreeEntry[]): Drift {
   const current = new Map(files.map(entry => [entry.file, entry.blob]));
   return {
-    changed: files.filter(entry => manifest.files[entry.file] && manifest.files[entry.file]!.blob !== entry.blob).map(entry => entry.file).sort(),
+    changed: files.filter(entry => manifest.files[entry.file] && (manifest.files[entry.file]!.blob !== entry.blob || manifest.files[entry.file]!.since > manifest.version)).map(entry => entry.file).sort(),
     added: files.filter(entry => !manifest.files[entry.file]).map(entry => entry.file).sort(),
     removed: Object.keys(manifest.files).filter(file => !current.has(file)).sort(),
   };
diff --git a/test/harness-version.test.ts b/test/harness-version.test.ts
index 5ccd013cd..5cb23c9c4 100644
--- a/test/harness-version.test.ts
+++ b/test/harness-version.test.ts
@@ -105,6 +105,31 @@ describe('HARNESS_VERSION guard', () => {
     }
   });
 
+  // Value: protects=a --bump that fails partway (pins written, manifest version not) cannot pass the guard with behavior pooled into the
+  //   old series; fails_when=a pin ahead of the manifest version reads as no drift; seam=writeManifest failing on a real write, then harnessDrift
+  test('a bump that fails partway leaves a pin ahead of the manifest version, and the guard reports it (GST-1084)', () => {
+    const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'harness-partial-'));
+    try {
+      copyManifest(dir);
+      const live = readManifest(dir);
+      const current = workingHarnessFiles(ROOT, live.patterns);
+      const [first, second] = current.map(entry => entry.file);
+      const blocked = path.join(dir, PINS_DIR, `${second}.json`);
+      const original = fs.readFileSync(blocked, 'utf8');
+      fs.rmSync(blocked);
+      fs.mkdirSync(blocked);
+      expect(() => writeManifest(dir, decide(live, current, 'bump', 'behavior changed in the runner'))).toThrow();
+      fs.rmdirSync(blocked);
+      fs.writeFileSync(blocked, original);
+      const after = readManifest(dir);
+      expect(after.version).toBe(live.version);
+      expect(after.files[first!]!.since).toBe(live.version + 1);
+      expect(harnessDrift(after, current).changed).toEqual([first]);
+    } finally {
+      fs.rmSync(dir, { recursive: true, force: true });
+    }
+  });
+
   // Value: protects=PRs that record decisions for different harness files merge without a conflict (the one-line-per-file manifest
   //   conflicted on adjacent lines and on the trailing comma); fails_when=two non-behavioral decisions on adjacent pins conflict in a
   //   real merge, or two decisions on one pin merge silently; seam=writeManifest and git merge-tree --write-tree on two branches