What variant of Codex are you using?

App and IDE Extension

What feature would you like to see?

Feature Request: Add plan_model Configuration for /plan Mode

Summary

Currently, Codex allows configuring a dedicated review_model for
/review mode.
However, /plan mode always uses the active session model and does not
support a separate model override.

This proposal suggests adding a plan_model configuration option,
similar to review_model, so that /plan mode can use a different
model from the main execution model.

Problem

In practical engineering workflows, planning and execution have
different optimization goals:

• Planning benefits from stronger reasoning capability.
• Execution may prioritize speed, cost efficiency, or determinism.

At present, to use a stronger model for planning, users must:

1. Start a separate session with a different model, or
2. Manually switch models before entering /plan, then switch back
   before execution.

This introduces operational friction and increases the chance of
mistakes.

Proposed Solution

Introduce a configuration option:

plan_model = "gpt-5.3-codex"

Expected Behavior

• When entering /plan, Codex uses plan_model if defined.
• If plan_model is not defined, fallback to the current session
  model (existing behavior).
• Normal execution continues to use the main model.
• /review continues to use review_model.

Example Configuration

model = "gpt-5.3-codex-spark"
plan_model = "gpt-5.3-codex"
review_model = "gpt-5.3-codex"

Resulting Behavior

• /plan → uses gpt-5.3-codex
• normal execution → uses gpt-5.3-codex-spark
• /review → uses gpt-5.3-codex

Why This Matters

1. Enables separation of reasoning-heavy planning from cost-efficient
   execution.
2. Reduces workflow friction (no manual model switching).
3. Achieves feature parity between /plan and /review.
4. Improves suitability for structured multi-phase engineering
   workflows.

Closing

This feature would significantly improve advanced workflows where
planning and execution have different optimization targets (reasoning
quality vs cost/latency).

Additional information

No response