Plan mode fails to block Edit tool calls

During a VSCode extension session, plan mode was active (green indicator visible in UX) but the Edit tool was not blocked — file modifications went through successfully. The system-reminder about plan mode restrictions appeared in subsequent messages but did not prevent the edits that had already been applied.

When confronted, the assistant acknowledged that the edits went through during plan mode and confirmed the file had been modified. Note: I cannot verify as a user whether the assistant actually executed edits during plan mode or is hallucinating that it did — either way, something is wrong.

Expected behavior: Edit tool calls should be rejected while plan mode is active.

Environment: Linux, Claude Code VSCode extension, Claude Opus 4.6