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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.

← All of v2.1.219 Home All releases ←olderv2.1.218 v2.1.220newer→
Claude Code v2.1.219

Model-downgrade chain and effort tables know about Opus 5

You'll notice
Useful3 Signal0
Models

Model fallbacks and reasoning-effort settings now handle Opus 5, stepping down to Opus 4.8 when needed.

claude-opus-5
What

The stepwise "older model" resolver and the reasoning-effort tables were extended for Opus 5, so downgrades and effort selection land on the right model.

Details
  • an Opus 5 name now steps down to Opus 4.8
  • a fable-5 name resolves to Opus 5 instead of Opus 4.8
  • the reasoning-effort configuration table gained a claude-opus-5 entry
  • the set of models on the special effort path now contains both claude-opus-4-8 and claude-opus-5
Evidence

if (t.includes("opus-5") || t.includes("opus_5"))

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.219 →