[Bug]: preview_evaluate fails with returnByValue: false

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/desktop

Steps to reproduce

1. Start T3 Code Desktop.

2. Open a Codex-backed thread with the T3 preview MCP tools available.

3. Open any page in the browser preview.

4. Call preview_evaluate with returnByValue: false for a simple object expression:

   {
     "expression": "({ alpha: 1, href: location.href })",
     "returnByValue": false
   }
   

5. Call the same expression again with default by-value behavior:

   {
     "expression": "({ alpha: 1, ok: true })"
   }
   

Expected behavior

Either:

• returnByValue: false should return a documented remote-object representation, or
• the tool schema should reject or omit returnByValue: false if non-by-value evaluation is not supported.

It should not accept the parameter and then fail with a generic execution error.

Actual behavior

preview_evaluate with returnByValue: false failed with a generic execution error:

PreviewAutomationExecutionError: Preview automation evaluate failed on client preview-...

Immediately afterward, normal by-value evaluation worked:

{
  "alpha": 1,
  "ok": true
}

Impact

Minor bug or occasional failure

Version or commit

T3 Code desktop 0.0.28-1 via t3code-bin AUR package.

Environment

Arch Linux x86_64, kernel 7.0.13-arch1-1, T3 Code desktop AppImage package via t3code-bin, Codex provider.

Logs or stack traces

PreviewAutomationExecutionError: Preview automation evaluate failed on client preview-...

Screenshots, recordings, or supporting files

No screenshot included. This is an API contract/implementation mismatch.

Workaround

Use default by-value evaluation for ordinary inspection.

Start in apps/desktop by locating the preview_evaluate implementation and its returnByValue schema or handling. Reproduce the object expression with returnByValue set to false, then compare it with the default by-value call. Done when the parameter either produces a documented remote-object result or is rejected or omitted instead of causing a generic execution error.