Feature: Auto-switch model between Plan Mode and execution

Request

Automatically switch to a different model when entering/exiting Plan Mode:

• When EnterPlanMode is called → switch to Opus
• When ExitPlanMode is called → switch back to default model (Haiku in my case)

Motivation

Plan Mode benefits from a more powerful model for architecture design, while execution should use a faster/cheaper model. Currently requires manual toggling via /fast and /model.

Current Workaround

• /fast before planning (enables Opus)
• /model haiku after planning
• Not ideal for frequent iterations

Implementation Notes

This would require:

• Hooks on EnterPlanMode and ExitPlanMode events that can trigger model configuration changes
• Or: Built-in plan-mode model configuration in settings.json (e.g. planModeModel: "opus")

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_Reported from Claude Code session on 2026-04-17_