Cerebras API version 2 available for testing, becomes default July 21, 2026

API version 2 is now available for testing via the X-Cerebras-Version-Patch header. This version introduces stricter validation and breaking changes.

Key changes in version 2:

• Structured Outputs - When using strict: true, stricter schema validation requiring additionalProperties: false at all object levels
• Tool Calling - Stricter message validation for multi-turn conversations (tool response completeness, orphan tool messages, tool choice consistency, unique tool call IDs)
• Reasoning Models - Adds a separate reasoning_logprobs field for reasoning token logprobs
• Unicode Fix - Logprobs now reflect partial Unicode tokens as they appear in the model's vocabulary

Timeline:

• January 21, 2026 - Version 2 available for testing via header
• July 21, 2026 - Version 2 becomes the default; older versions end-of-life

Test now by adding extra_headers={"X-Cerebras-Version-Patch": "2"} to your requests. See Versions for migration details.