GitHub Copilot Desktop v1.1.32: latest Claude models fail with thinking.type.enabled 400 error

[Teja-ssnc]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Copilot in GitHub

Body

Error message:

streaming inference failed: bedrock returned 400 (ValidationException): 
The model returned the following errors: "thinking.type.enabled" is not supported for this model. 
Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.

Environment

• GitHub Copilot Desktop App Version: 1.1.32
• Provider: Anthropic (BYOK)
• Models Affected: Claude Opus 4.7, Claude Opus 4.8, Claude Sonnet 5.x, Claude Haiku 5.5, Claude Fable 5
• Operating System: Windows 11

Steps to Reproduce

1. Open the GitHub Copilot desktop app (v1.1.32).
2. Configure an Anthropic BYOK provider with your API key.
3. Select Claude Opus 4.7 or any newer Claude model that requires adaptive thinking.
4. Try to use the model in chat.
5. Observe the 400 error.

Root Cause Analysis

This is a client-side API compatibility issue. The GitHub Copilot desktop app's request-building code has a hardcoded list of models that support adaptive thinking. Models not on this list still receive the deprecated thinking.type.enabled format, which Anthropic rejects on Claude 4.7+ models.

Reference: https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting/

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[rstropek]

My workaround is a proxy in Docker rewriting the outgoing requests. Works for me for Haiku 5.5 and Opus 5.5. Scripts see https://gist.github.com/rstropek/36d8af5d36108ea6e4abfa2188cbe34c