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Sweep 28 Aug 2026 · 00:00Z Build v2.1.250 478 read Stable v2.1.236 Latest v2.1.250 Next v2.1.251 Feeds RSS JSON llms.txt
Reading a new release v2.1.251 Analysing changes · 2/5 Deeper second pass · 0/5 agents 427 findings $12.75 so far

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

One change

whats-new-sonnet-5

models/sonnet-5/whats-new-sonnet-5

first seen The page's own history The capture it came from

Nearest release: v2.1.246, published 3 hours after this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

models/sonnet-5/whats-new-sonnet-5 Changed · +1 / -1 lines

from line 189
 2. **Extended thinking:** if you still set `budget_tokens`, migrate to [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking). Manual extended thinking (`thinking: {type: "enabled"}`) is not supported and returns a 400 error.
 3. **Sampling parameters:** requests that set sampling parameters (`temperature`, `top_p`, `top_k`) to a non-default value return a 400 error; remove them when migrating. Tool definitions and response shapes are unchanged, and assistant message prefilling was already unsupported on Claude Sonnet 4.6.
 
-See the [Claude Sonnet 5 section of the migration guide](https://platform.claude.com/docs/en/about-claude/models/migration-guide#migrating-from-claude-sonnet-4-6-to-claude-sonnet-5) for details.
+See [Migrating to Claude Sonnet 5 from Claude Sonnet 4.6](https://platform.claude.com/docs/en/models/sonnet-5/migration-guide#migrating-from-claude-sonnet-4-6-to-claude-sonnet-5) for details.
 
 ## Next steps