claude-code - 💡(How to fix) Fix Opus 4 on Vertex AI fails with thinking.type.enabled error (400) [1 participants]

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":""thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior."},"request_id":"req_vrtx_011CaNV29S9FHHK79mCMmTeC"}

TL;DR

Update the API request to use thinking: { type: "adaptive" } and include output_config.effort to match the Vertex AI Opus 4 endpoint's requirements.

Guidance

• Verify the current API request payload to confirm it's sending thinking: { type: "enabled" }, which is not supported by the Opus 4 endpoint.
• Update the Claude Code configuration to send thinking: { type: "adaptive" } and include a valid output_config.effort value in the API request.
• Test the updated configuration with the Opus 4 model to ensure the 400 error is resolved and the model responds successfully.
• If updating the configuration is not feasible, consider using the Sonnet 4.6 model as a temporary workaround, as mentioned in the issue.

Example

No code snippet is provided, as the issue does not include specific code details.

Notes

The fix relies on updating the API request payload to match the Opus 4 endpoint's requirements. The exact implementation details may vary depending on the Claude Code version and configuration.

Recommendation

Apply workaround: Update the API request to use thinking: { type: "adaptive" } and include output_config.effort, as this is a breaking schema difference between the Vertex Opus 4 endpoint and earlier models.