[FEATURE] How to set thinking effort with Opus 4.5?

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

I want to set thinking effort to "high" which is presumably the 64000 mentioned in the model card.
If "high" does not mean 64000, then I want to set it to 64000.

The previous env variable MAX_THINKING_TOKENS does not do anything anymore.

Proposed Solution

Allow changing this option in /config or from CLI flags

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_