Custom models cannot select a thinking level.

[cppcoffee]

Description

Configuring custom models on the UI doesn't allow toggling 'Reasoning' or setting the 'Context Size'. As a result, the model can't operate at its full capacity, causing it to underperform.

Plugins

No response

OpenCode version

1.17.18 (1.17.18)

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

MacOS 26.5.2 (25F84)

Terminal

No response

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [FEATURE]: expose provider-specific reasoning/thinking field schemas for custom models #33013: Feature request to expose provider-specific reasoning/thinking field schemas for custom models — very similar in scope (reasoning/thinking toggle for custom models)
• [FEATURE]: Feature Request / Bug: Cannot set context window limits for local models via GUI/TUI (Defaults to 0) #31433: Feature request / bug about not being able to set context window limits for custom models in the GUI/TUI — directly overlaps the "Context Size" part of this issue

If your issue is different from those, please add more detail explaining how it differs.