fix: preserve changes when diff fails

.project-docs/30-worklog/tasks/20260823-pi-product-tools-a9c4e7d2.md

@@ -98,6 +98,10 @@
   `changes.touched` ACK bridge; full diff/preview data stays Main-only; and
   untracked reads plus previews are both limited to 8 KiB while size/mtime
   detect equal-length changes beyond that window.
+- Closed the follow-up review finding by making per-candidate Git diff failure,
+  non-zero exit, or output-limit rejection non-fatal: the Main snapshot keeps
+  the changed relative path and status while omitting only the unavailable
+  diff. The regression uses the same `Git output is too large` failure shape.
 - The packaged smoke now has two halves: a staged production-closure Pi
   process check and a controlled Electron-Node authenticated bridge check that
   actually executes browser status/screenshot attachment and game asset
@@ -114,7 +118,7 @@
   `Makelore/index.tsx`; none are in this task's changed scope).
 - Final focused PI-090/Pi projection/bridge/game/resource suite: 12 files,
   71 tests passed. The planner's five minimal failure shapes are also covered
-  by the 4-file 19-test tracker/bridge/runtime subset.
+  by the final 4-file 20-test tracker/bridge/runtime subset.
 - Final serial full suite
   (`corepack pnpm vitest run --maxWorkers=1 --no-file-parallelism`): 203 files,
   2226 tests passed, 2 skipped. Two preceding parallel full-suite runs each

electron/coding-projects/conversation-change-tracker.ts

@@ -325,10 +325,17 @@ export class ConversationChangeTracker {
     diff?: string;
     truncated?: boolean;
   }> {
-    const [working, staged] = await Promise.all([
-      this.git.run(projectPath, ['diff', '--no-ext-diff', '--no-color', '--relative', '--', relativePath]),
-      this.git.run(projectPath, ['diff', '--cached', '--no-ext-diff', '--no-color', '--relative', '--', relativePath]),
-    ]);
+    let working: GitCommandResult;
+    let staged: GitCommandResult;
+    try {
+      [working, staged] = await Promise.all([
+        this.git.run(projectPath, ['diff', '--no-ext-diff', '--no-color', '--relative', '--', relativePath]),
+        this.git.run(projectPath, ['diff', '--cached', '--no-ext-diff', '--no-color', '--relative', '--', relativePath]),
+      ]);
+    } catch {
+      return {};
+    }
+    if (working.code !== 0 || staged.code !== 0) return {};
     const bounded = boundedText(`${staged.stdout}${working.stdout}`, MAX_DIFF_BYTES);
     return {
       ...(bounded.text ? { diff: bounded.text } : {}),

tests/unit/pi-product-tools.test.ts

@@ -143,6 +143,40 @@ describe('PI-090 product tools', () => {
     )).files).toEqual([expect.objectContaining({ path: 'notes.txt', preview: 'local notes\n' })]);
   });
 
+  it('keeps the changed path when a candidate diff is unavailable or oversized', async () => {
+    const root = await temporaryRoot('makelore-pi-diff-unavailable-');
+    await writeFile(path.join(root, 'tracked.txt'), 'changed\n', 'utf8');
+    let statusReads = 0;
+    const tracker = new ConversationChangeTracker({
+      async run(_projectPath, args) {
+        if (args[0] === 'rev-parse' && args[1] === '--is-inside-work-tree') {
+          return { code: 0, stdout: 'true\n' };
+        }
+        if (args[0] === 'rev-parse') return { code: 0, stdout: `${'a'.repeat(40)}\n` };
+        if (args[0] === 'status') {
+          statusReads += 1;
+          return {
+            code: 0,
+            stdout: statusReads === 1
+              ? ''
+              : '1 .M N... 100644 100644 100644 abc abc tracked.txt\0',
+          };
+        }
+        if (args[0] === 'diff') throw new Error('Git output is too large');
+        throw new Error(`Unexpected Git call: ${args.join(' ')}`);
+      },
+    });
+    await tracker.beginRun({
+      conversationId: 'conversation-a', runId: 'run-a', projectPath: root,
+    });
+    const snapshot = await tracker.recordTouchedPaths(
+      'conversation-a', 'run-a', ['tracked.txt'],
+    );
+    expect(snapshot.files).toEqual([{
+      path: 'tracked.txt', status: 'modified',
+    }]);
+  });
+
   it('supports no-git projects and rejects paths outside the project', async () => {
     const root = await temporaryRoot('makelore-pi-no-git-');
     await writeFile(path.join(root, 'notes.txt'), 'local notes\n', 'utf8');