whats-new-fable-5-1 changedmodels/fable-5-1/whats-new-fable-5-1
Nearest release: v2.1.307, published 2 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.
Recorded here
Lines+1added
Lines−1removed
From line
379
where the diff opens
First seen
1 Sep 2026
this site's first read of the page
Recorded edits18to this page, all time
The whole hunk
from line 379, old and new numbered
/
from line 379
379379* `thinking.display` defaults to `"omitted"`. `"summarized"` is available, and the raw chain of thought is never returned.
380380* Reasoning between tool calls appears in thinking blocks rather than text, and [interleaved thinking](https://platform.claude.com/docs/en/build-with-claude/thinking#interleaved-thinking) is automatic with no beta header.
381381* Prefilling the assistant response returns a 400 error.
382* Non-default `temperature`, `top_p`, or `top_k` values return a 400 error.
382* Setting `temperature`, `top_p`, or `top_k` returns a 400 error.
383383* The minimum cacheable prompt length is 512 tokens.
384384* [Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) and tool changes are supported.
385385
No line in this hunk matches that.