[FEATURE] Allow users to default different models for planning and building. I'd like to use Opus for planning and Sonnet for building

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

When using plan mode, I want to use a more capable (and expensive) model like Opus for architectural planning, then switch to a faster/cheaper model like Sonnet for implementation. This balances cost and quality - complex reasoning during planning, efficient execution during building.

Current behavior

The model setting is a single value. To switch models mid-session, I have to manually run /model after plan approval. This adds friction and is easy to forget.

Proposed Solution

Proposed solution

Add optional settings for mode-specific models:

{
"permissions": {
"defaultMode": "plan"
},
"model": "sonnet",
"planModeModel": "opus"
}
When entering plan mode, use planModeModel (if set). When exiting plan mode to implement, switch to model. If planModeModel isn't set, use model for everything (current behavior).

Alternative Solutions

Using /model manually after each plan approval (current workaround, but adds friction)

Priority

Medium - Would be very helpful

Feature Category

Performance and speed

Use Case Example

_No response_

Additional Context

_No response_