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Sweep 22 Sep 2026 · 17:19Z Build v2.1.280 501 read Stable v2.1.267 Latest v2.1.280 Next v2.1.280 Feeds RSS JSON llms.txt Unofficial
Claude Code v2.1.257 ·

claude-fable-5-1 model added, gated behind renamed fable51 flag

The gate controlling whether the fable model is added to opus and haiku lists was renamed from fable5 to fable51.

TierUnder the hoodhow much it should matter to you
Useful2my rating, 1 to 5
Signal3worth watching, 1 to 5
AreaModelswhat it touches
KindInternal Changesin v2.1.257,
Group of 2 Under the hood Nothing to try yet No documentation found

The gate controlling whether the fable model is added to opus and haiku lists was renamed from fable5 to fable51.

A new model id claude-fable-5-1 and its Vertex region constant VERTEX_REGION_CLAUDE_FABLE_5_1 were added. The opus/haiku fallback-list builders now check feature gate fable51 (replacing the previous fable5 check) before appending the model via WZe().

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Names in the bundlefable51

See this entry in the whole of v2.1.257 →

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