Add GPT-5.6 Sol Pro as a selectable model in Codex

What variant of Codex are you using?

IDE Extension and CLI

What feature would you like to see?

Please add GPT-5.6 Sol Pro as a selectable model in Codex.

Currently, Codex provides GPT-5.6 Sol with different reasoning/compute modes, including Ultra, while GPT-5.6 Sol Pro is available in ChatGPT but not directly selectable in Codex.

I would like Sol Pro to be available as an additional model option in Codex, especially for difficult software engineering tasks that benefit from deep single-threaded reasoning, such as:

Complex debugging and root-cause analysis
Architecture analysis
Large codebase understanding
Deep code review
Difficult refactoring decisions
Reasoning about legacy system behavior

Ultra is very useful for parallel or multi-agent workflows, but Pro may serve a different use case where one model reasoning deeply about a single difficult problem is preferable.

Ideally, Codex users could choose between standard GPT-5.6 Sol reasoning modes, Ultra, and GPT-5.6 Sol Pro.

Additional information

I use Codex regularly through both the VS Code IDE extension and CLI for real full-stack software engineering work involving frontend, backend, databases, legacy-system comparison, debugging, builds, and testing.

Having access to Sol Pro directly inside Codex would be useful when a task requires maximum reasoning quality rather than parallel multi-agent execution.

It would also be helpful if Pro could use the same Codex tools, terminal access, repository context, and file-editing capabilities as the existing Codex models.

Thank you for considering this feature.

Start by tracing how selectable models are registered in the Codex CLI and VS Code IDE extension, focusing on the existing GPT-5.6 Sol and Ultra options. Determine the integration requirements for adding Sol Pro, then verify that it appears as a selectable model with the same Codex tools, terminal access, repository context, and file-editing capabilities.