Harden against mixed collaboration mode instructions from Codex CLI #330
Description
Summary
When resuming threads that have switched between collaboration modes (plan ↔ code), Codex CLI sends mixed/conflicting mode instructions to the model. This causes the model to see both plan and code mode templates simultaneously, leading to confusion visible in reasoning traces, and (possibly) issues in plans displaying (hidden entirely or displayed in visible quote blocks).
This is a known Codex CLI bug - we're tracking whether to harden CodexMonitor against it regardless of upstream fix.
Decision (I can work it if you want tackle)
- Tackle now - Implement lightweight hardening that's defensive regardless of upstream
- Wait - Monitor upstream PRs (#10254) and revisit if fix doesn't land soon
Upstream Status
| Reference | Status | Description |
|---|---|---|
| #10185 | OPEN | Root bug - mode switch Plan→Code still behaves like Plan |
| #10254 | OPEN PR | Fix for backtrack + developer instructions sync |
| #10545 | MERGED | Improved mode prompts to reduce confusion |
| #10570 | OPEN | Our report - linked to #10185 |
Should CodexMonitor Harden Against This?
| Consideration | Assessment |
|---|---|
| If they fix it | Our hardening becomes a no-op (defensive code that doesn't hurt) |
| If they don't fix it | CodexMonitor provides better UX than raw Codex |
| If fix is partial | CodexMonitor catches edge cases they miss |
| User perception | CodexMonitor "just works" regardless of upstream bugs |
| Maintenance cost | Low - simple filtering/UI logic |
Potential Approaches
- Mode state tracking - Track mode locally, inject clarifying instruction on resume if history shows mixed modes
- UI indicator - Warn user when thread has mode switch history
- Fresh mode injection - On thread resume, send developer instruction reinforcing current mode
- Display filtering - Don't surface stale mode instructions in UI