What
The vendored claude-api skill documents were retargeted from a hardcoded model ID to placeholders resolving to the new Opus, with new guidance on thinking defaults, refusal fallbacks and fast mode.
Details
- Python, Go and Ruby guides, the error-code reference, the managed-agents reference and the top-level skill all replace
claude-opus-4-8with{{OPUS_NAME}}/{{OPUS_ID}}, and add a{{PREV_OPUS_NAME}}/{{PREV_OPUS_ID}}row. - On the new Opus, thinking is on by default, so omitting
thinkingruns adaptive;{type: "disabled"}is accepted only at efforthighor lower and returns 400 atxhighormax. - A new pitfall section covers the two failure modes of disabling thinking.
- Refusal fallbacks gain a scalar form
fallbacks: "default"under beta headerserver-side-fallback-2026-07-01; the array form keeps-2026-06-01and mixing the two returns 400. - Fast mode is documented as new-Opus/4.8 only and Claude API only, with Opus 4.7 fast mode removed rather than deprecated, plus a note that Priority Tier does not cover the new Opus.
- Mid-conversation system messages are documented for several models rather than one.
Evidence
server-side-fallback-2026-07-01
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundle/claude-api