Extended Thinking
Claude API · Anthropic
Foundation Model & API — Anthropic (Claude)
Evaluates Anthropic's Extended Thinking across 9 scenario-based test cases, each graded against an expected-behavior rubric by an LLM judge, from Corsac's Foundation Model & API eval coverage.
About Anthropic
Anthropic is an AI safety company and the maker of Claude. Its API exposes the Claude model family (Opus, Sonnet, Haiku) with tool use, prompt caching, extended thinking, batch processing, vision, the Files and Memory tools, and the Claude Agent SDK.
Sample tests· showing 3 of 9
| # | Input | Expected behavior | Check |
|---|---|---|---|
| 01 | Agent enables extended thinking with thinking={type:'enabled', budget_tokens:10000}, max_tokens=16000. | Both fields are required when enabling. budget_tokens reserves thinking capacity within max_tokens (text output gets max_tokens - thinking tokens used). Verify thinking + text totals stay under max_tokens. | Pass / FailAi Platformhigh |
| 02 | Response contains redacted_thinking blocks (server-side encrypted) instead of plain thinking. | Preserve redacted_thinking blocks verbatim — including the redacted data — in subsequent assistant turns sent back to the API. Do NOT modify, decode, drop, or log their contents. | Pass / FailAi Platformcritical |
| 03 | Response with extended thinking returns content blocks in order: thinking, text. UI shows only the text. | Iterate content blocks; render text blocks to the user, optionally expose thinking blocks behind an 'inspect reasoning' toggle. Do NOT discard thinking blocks if you plan to send the assistant turn back as multi-turn — they must be preserved for the model's continuity. | Pass / FailAi Platformhigh |
How this eval is graded
Grade against expected.ideal_behavior and expected.rubric. Per-criterion pass requires mean >= 4.0 and no criterion below 3.
Rubric criteria
- Anthropic
- Ai Platform
- Extended Thinking
Recommended for
Works with
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ViewFrequently asked questions
What does the Extended Thinking eval for Anthropic Claude API test?+
Evaluates Anthropic's Extended Thinking across 9 scenario-based test cases, each graded against an expected-behavior rubric by an LLM judge, from Corsac's Foundation Model & API eval coverage.
How is the Extended Thinking eval scored?+
The judge rubric: Grade against expected.ideal_behavior and expected.rubric. Per-criterion pass requires mean >= 4.0 and no criterion below 3.
How many test cases does this eval pack include?+
The Extended Thinking pack for Anthropic Claude API contains 9 test cases. 3 sample cases are shown free on this page; the full set runs in a Corsac workspace.
How do I run this eval?+
Sign up for Corsac, connect your model or agent endpoint, and run the Extended Thinking pack as-is or after customizing thresholds. Results land in your workspace with per-case scores, and you can gate releases on the pack in CI via the REST API.
Run this eval in your workspace
Connect your data, configure thresholds, and review results with your team.