set a trap for the editor buffer corruption

Not a fix — I could not find the cause by reading, and shipping a guess dressed as
one is worse than saying so.

What reading DID settle, and it removes two of the three candidates:

- The end-of-turn refresh cannot be it. `reloadFile` sets `originalContent` and
  clears `isDirty`, so no refresh can produce the dirty dot in the screenshot.
- Nothing in the app types into the page: no `execCommand('insertText')`, no
  synthetic keyboard events, no clipboard writes anywhere near the editor.

That leaves Monaco's own change event, which means the model was edited the way a
paste or a programmatic `executeEdits` edits it. Neither is identifiable from a
screenshot taken afterwards, which is why this needs to be caught in the act.

`reportSuspiciousEdit` logs any insertion over 200 characters arriving while the
editor does NOT have focus, with an Error constructed at that moment so the stack
names the caller. A person cannot type 200 characters into an editor they are not
focused on; whatever does will be in that trace.

It prevents nothing and changes no behaviour. Delete it once the cause is known.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

TODO.md

@@ -422,6 +422,17 @@ outside the example's new README:
       only thing that writes a buffer without a keystroke, it runs exactly when a background job is
       producing output, and it lands its result by path.
 
+      **Narrowed 2026-08-16, and a trap is now set.** `reloadFile` sets `originalContent` and clears
+      `isDirty`, so the end-of-turn refresh CANNOT produce the dirty dot in the screenshot — the refresh
+      path is out. Nothing in the app injects text into the page either: no `execCommand('insertText')`,
+      no synthetic keyboard events, no clipboard writes near the editor. That leaves Monaco's own change
+      event, which means it looks like a paste or a programmatic `executeEdits`.
+
+      `reportSuspiciousEdit` in CodeEditor.tsx logs any insertion over 200 characters that arrives while
+      the editor is NOT focused, with a stack trace taken at that moment. That is the missing evidence:
+      whoever calls it will be named in the trace. Delete it once the cause is known — it is a trap, not a
+      feature.
+
       One thing to rule out first, because it is mine and it is recent: `2b70a570` gave `<Editor>` a real
       `path`, so models are now keyed by file URI globally rather than being per-mount `inmemory://`. Two
       panels open on the same file now share one model. That should be an improvement, but it is a change

src/workspaces/officerdev/src/apps/CodeEditor/CodeEditor.tsx

@@ -28,6 +28,41 @@ type CodeEditorViewProps = {
   panelId?: string;
 };
 
+/**
+ * Shout when the buffer changes in a way a person could not have typed.
+ *
+ * Background-job output has twice appeared spliced into an open file — the model mutated, the tab marked
+ * dirty, the file on disk untouched. Two explanations are already ruled out: the end-of-turn refresh
+ * cannot do it (`reloadFile` clears `isDirty`), and nothing in the app types into the page. That leaves
+ * Monaco's own change event, which means it looks like a paste or a programmatic edit — and neither can
+ * be identified from a screenshot after the fact.
+ *
+ * So this does not prevent anything. It records the one thing missing: what arrived, how big it was, and
+ * whether the editor even had focus at the time. A large insertion into an UNFOCUSED editor is not a
+ * user, and the stack trace attached to it names whatever called it.
+ *
+ * Delete this once the cause is known. It is a trap, not a feature.
+ */
+const SUSPICIOUS_INSERT = 200;
+
+function reportSuspiciousEdit(
+  editor: MonacoEditor.IStandaloneCodeEditor | null,
+  file: { path: string; content: string },
+  next: string,
+): void {
+  const grew = next.length - file.content.length;
+  if (grew < SUSPICIOUS_INSERT) return;
+  if (editor?.hasTextFocus()) return;
+
+  // eslint-disable-next-line no-console
+  console.warn(
+    `[editor] ${grew} characters appeared in ${file.path} while the editor was NOT focused. ` +
+      `This is the background-job-output bug (TODO.md → Known bugs). First 120 chars:\n` +
+      next.slice(0, 120),
+    new Error('stack at the moment of the edit'),
+  );
+}
+
 export const CodeEditorView = ({
   className,
   theme = 'vs-dark',
@@ -294,7 +329,10 @@ export const CodeEditorView = ({
                 theme={theme}
                 language={getLanguage(activeFile.name)}
                 value={activeFile.content}
-                onChange={(value) => setContent(activeFile.path, value ?? '')}
+                onChange={(value) => {
+                  reportSuspiciousEdit(editorRef.current, activeFile, value ?? '');
+                  setContent(activeFile.path, value ?? '');
+                }}
                 beforeMount={configureMonacoTypescript}
                 onMount={handleEditorMount}
                 options={{