You'll noticeTier: how much it should matter to you
3Useful: my rating, 1 to 5
0Signal: worth watching, 1 to 5
ModelsArea: what it touches
ImprovementsKind: in v2.1.219,
ImprovementsSection of the release
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.
