ExitPlanMode permission prompt returns 'permission denied' with isAbort=undefined when approving default selection

Environment

• Claude Code v2.1.73
• macOS (Darwin 25.3.0)
• Terminal: tmux over mosh/ssh remote connection
• Permission mode: bypassPermissions

Description

When ExitPlanMode displays its approval prompt, selecting the default option (approve) and pressing Enter results in the plan being rejected instead of approved. The debug log shows isAbort=undefined — which should be a boolean (true for reject, false for approve) — suggesting the user's input is not being properly interpreted.

Steps to Reproduce

1. Enter plan mode (via EnterPlanMode tool or /plan)
2. Claude generates a plan and calls ExitPlanMode
3. The approval prompt appears with options
4. Press Enter on the default selection (approve/accept)
5. Plan is rejected with "User rejected Claude's plan"

Observed Behavior

The plan is rejected despite selecting "approve." Debug log shows:

Aborting: tool=ExitPlanMode isAbort=undefined hasFeedback=false isSubagent=false
ExitPlanMode tool permission denied

isAbort=undefined indicates the user's input was not properly resolved to approve or reject.

Reproducibility

Reproduced twice in the same session within ~40 minutes:

| Occurrence | Prompt shown | Abort logged | Delta |
|---|---|---|---|
| 1st | 00:44:51.899Z | 00:45:04.404Z | 12.5s |
| 2nd | 01:26:35.274Z | 01:26:38.289Z | 3.0s |

Both times: isAbort=undefined, hasFeedback=false, no hooks matched (0 PreToolUse, 0 PermissionRequest hooks).

Investigation Notes

• No custom hooks are configured for ExitPlanMode (PreToolUse: 0 matches, PermissionRequest: 0 matches)
• No external automation sent keystrokes during the permission prompt
• Other permission prompts (Bash, Edit, etc.) work correctly in the same session and environment
• The issue appears specific to ExitPlanMode's approval UI
• The undefined value for isAbort suggests a code path where the user's selection is not being mapped to a boolean result

Possibly Related Issues

• #15755 (Allow does not exit plan mode — CLOSED)
• #29548 (ExitPlanMode skips approval prompt — CLOSED)
• #23754 (ExitPlanMode rejection causes session restart — CLOSED)