Plan Mode still halts YOLO / non-interactive runs while waiting for user agreement #28913

What happened?

This is to be a re-report of the bug from #26004, which was closed as stale without a resolution.

In non-interactive execution (for example gemini -p "..." -y), the agent can enter Plan Mode, but the Plan Mode prompt instructs it to stop and wait for informal user agreement before drafting/exiting the plan.

"You MUST NOT proceed to Step 3 (Draft) or Step 4 (Review & Approval) in the same turn as your initial strategy proposal. You MUST wait for user feedback..."

Because there is no user turn in non-interactive mode, the model can emit a text-only response asking for confirmation and terminate the run instead of calling exit_plan_mode and proceeding with implementation.

Relevant history

There are a few related changes that might explain how we got here:

• fix(plan): exclude EnterPlanMode tool from YOLO mode #19570 made enter_plan_mode unavailable in YOLO mode.
• feat(plan): support plan mode in non-interactive mode #22670 intentionally enabled Plan Mode transitions in non-interactive sessions. In this mode, enter_plan_mode / exit_plan_mode are automatically allowed so headless workflows can plan and then implement autonomously.
• feat(core): prioritize discussion before formal plan approval #24423 later added an informal-agreement step to the Plan Mode prompt, including instructions to "STOP and wait" and "MUST wait for user feedback" before drafting/exiting.

There was actually discussion on #24423 about non-interactive mode. It was suggested that this would not block because ask_user is denied in non-interactive sessions, but the issue is that the blocking behavior does not require ask_user - a normal text response with no tool call is sufficient to terminate a non-interactive run.

What did you expect to happen?

In non-interactive mode, Plan Mode should remain autonomous:

1. Enter Plan Mode
2. Research / determine a strategy
3. Draft the plan without waiting for user feedback
4. Call exit_plan_mode
5. Continue with implementation

Client information

CLI Version    0.55.1
Model          gemini-3.5-flash (thinkingLevel: HIGH)
OS             linux
Auth Method    gemini-api-key

Login information

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Anything else we need to know?

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