{"version":"2.1.219","anchor":"bundled-claude-api-skill-docs-rewritten-around-opus-5","canonical_anchor":"bundled-claude-api-skill-docs-rewritten-around-opus-5","heading":"Bundled Claude API skill docs rewritten around Opus 5","tier":"notice","area":"Skills","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.219\/e\/bundled-claude-api-skill-docs-rewritten-around-opus-5","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.219","markdown":"### Bundled Claude API skill docs rewritten around Opus 5\n\nThe bundled Claude API skill docs now target the new Opus, covering thinking defaults, fallbacks and fast mode.\n\n**What**\n\nThe 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.\n\n**Details**\n\n- Python, Go and Ruby guides, the error-code reference, the managed-agents reference and the top-level skill all replace `claude-opus-4-8` with `{{OPUS_NAME}}`\/`{{OPUS_ID}}`, and add a `{{PREV_OPUS_NAME}}`\/`{{PREV_OPUS_ID}}` row.\n- On the new Opus, thinking is on by default, so omitting `thinking` runs adaptive; `{type: \"disabled\"}` is accepted only at effort `high` or lower and returns 400 at `xhigh` or `max`.\n- A new pitfall section covers the two failure modes of disabling thinking.\n- Refusal fallbacks gain a scalar form `fallbacks: \"default\"` under beta header `server-side-fallback-2026-07-01`; the array form keeps `-2026-06-01` and mixing the two returns 400.\n- 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.\n- Mid-conversation system messages are documented for several models rather than one.\n\n**Evidence**\n\n`server-side-fallback-2026-07-01`\n\n- Area: Skills\n- Names: `\/claude-api`\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 0\/5"}