[UX] Plan mode should offer model and effort switching before execution

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Problem:
When using Plan Mode with Opus 4.6, effort High, after the plan is ready Claude presents options to proceed with execution (clear context + auto-accept, auto-accept edits, manually approve, or type a response). There is no option to switch the model and effort before execution begins.

This is a critical workflow gap. The recommended practice is to plan with Opus and execute with Sonnet for cost/speed efficiency. The opusplan alias exists for this purpose but:

1. It's not discoverable - not listed in the /model picker menu
2. It's not documented in the model selection UI
3. When it doesn't auto-switch correctly, the user has no clean way to switch models at the plan-ready prompt
4. It doesn't switch the effort.

Expected behavior:
The plan-ready prompt should include an explicit option like:
"5. Switch model and/or effort before executing"

Or better - the opusplan alias should be a first-class option in the /model picker with a clear description: "Opus High effort for planning, Sonnet Medium effort for execution (auto-switch)".

Additional context:

• New users have no way to discover opusplan without searching the web
• OS: Pop!_OS (Linux), Claude Code 2.1.78

This is the single most common workflow (plan with best model, execute with fast model) and it should be seamless, not require hidden aliases and workarounds.

Proposed Solution

The plan-ready prompt should include an explicit option like:
"5. Switch model and/or effort before executing"

Or better - the opusplan alias should be a first-class option in the /model picker with a clear description: "Opus High effort for planning, Sonnet Medium effort for execution (auto-switch)".

Alternative Solutions

_No response_

Priority

High - Significant impact on productivity and budget!

Feature Category

CLI commands and flags

Use Case Example

1. I'm working on a Python project
2. I enter Plan Mode with Opus 4.6 effort High to design a complex changes across 15+ files
3. After 15 minutes of planning, Claude presents the "ready to execute" prompt
4. I want to switch to Sonnet 4.6 Medium effort for the implementation (faster, cheaper, plan is already written)
5. There's no option to switch models and effort

Additional Context

_No response_