Plan mode does not block Edit/Write tool calls

Bug Description

When plan mode is active, Claude can still execute Edit and Write tool calls. The system reminder says plan mode is read-only, but the tools are not actually blocked at the tool-execution level — they go through successfully.

Expected Behavior

Edit and Write tool calls should be rejected/blocked when plan mode is active, similar to how other restricted tools are blocked.

Actual Behavior

Edit and Write tools execute normally despite plan mode being active. The only enforcement is via system reminder instructions, which the model can (and does) ignore.

Steps to Reproduce

1. Enter plan mode (e.g., via /plan or automatic plan mode trigger)
2. Ask Claude to investigate and fix a bug
3. Claude proceeds to use Edit tool to modify files despite plan mode being active
4. Edits succeed without any blocking

Environment

• Claude Code on Windows 11
• Model: claude-opus-4-6