Desktop: user reports missing Implement plan action after completed plan

Summary

In Codex desktop on macOS, the user reported that the “Implement plan” action was not visible after a completed and refined plan. Explicit requests to implement did not change the active Plan mode, so the assistant could not start implementation and referred the user to an action they could not find.

Observed sequence

1. The assistant produced completed plans using proposed_plan blocks.
2. The user refined scope and model-quality requirements, then explicitly requested implementation.
3. The assistant still received Plan-mode instructions and explained that implementation required leaving Plan mode.
4. The user reported that no “Implement plan” option appeared.
5. In a later turn, the session did receive a Default-mode update and execution became available. The UI action responsible for that transition was not observed.

Expected behavior

A completed plan should have a discoverable route to execution, and the UI should make the current mode and the required transition clear. The assistant should avoid assuming a specific UI action is visible without verification.

Impact and evidence limits

The implementation start was interrupted by repeated mode-transition guidance. The missing UI action is user-reported; no screenshot or independent UI reproduction is attached. Native computer-use inspection of the Codex app was denied by the tool, so the report does not claim a verified rendering root cause. The issue is currently recoverable because this session subsequently entered Default mode.

Environment: desktop app, macOS; exact app build not established.
Date: 2026-09-05.
Task/session identifier (owner authorized sharing relevant task context): 01a06e2d-282b-7093-8b33-2a1f3b4414b8.

Related: #23341 concerns clicking an existing action without leaving Plan mode; this observation concerns the action not being visible. No account-switch trigger was established here.

No repository contents, local paths, credentials, raw logs, or full transcript are included.

Start by reproducing the reported sequence in the Codex desktop app on macOS: complete and refine a plan, request implementation, and inspect the visible mode and actions. Establish whether the transition to Default mode and the “Implement plan” action are reliably discoverable; done means the execution route and current mode are clear after a completed plan.