claude-code - 💡(How to fix) Fix [BUG] REGRESSION: Cannot switch between Opus and Sonnet mid-thread in Cowork after April 15 desktop redesign [1 participants]

TL;DR

The most likely fix for the broken mid-thread model switching in Cowork is to revert or modify the changes introduced in the April 15, 2026 desktop app redesign.

Guidance

• Review the code changes made during the April 14-15 desktop redesign to identify the specific modifications that removed the mid-thread model switching capability.
• Compare the current implementation with the previous version to understand what was changed or removed, focusing on the differences in handling model switching within Cowork threads.
• Investigate the relationship between this issue and the regression reported in #40095, as understanding the root cause of the automatic model switching issue might provide insights into fixing the manual switching problem.
• Consider temporarily reverting the redesign changes related to model switching in Cowork to restore the previous functionality while a more permanent solution is developed.

Example

No specific code snippet can be provided without access to the actual codebase, but the investigation should involve comparing the model switching logic before and after the April 15 update.

Notes

The solution may involve backporting the model switching functionality from the pre-redesign version or re-implementing it in a way that is compatible with the new desktop app design. The exact approach will depend on the specifics of the code changes made during the redesign.

Recommendation

Apply a workaround by reverting the specific changes related to model switching in Cowork, as this is likely to restore the previous functionality until a more integrated solution can be developed and tested.