Observed 20 September 2026

Anthropic added three new Claude "Mythos" models to its deprecation schedule, one already deprecated and two set for retirement no earlier than 2027.

what changed matterssummary written by a model — check it against the diff below

1 line of binding language were added — this changes what someone is permitted or required to do.

+3 · a83189d → c36bd21 · c36bd2113bc8 · live page

anthropic/model-deprecations.txt20 Sept 2026

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Current and recently retired models are listed in the following table with their status:
API model name Current state Deprecated Tentative retirement date
claude-fable-5-1 Active N/A Not sooner than September 1, 2027
claude-mythos-5-1 Active N/A Not sooner than September 1, 2027
claude-fable-5 Active N/A Not sooner than June 9, 2027
claude-mythos-5 Active N/A Not sooner than June 9, 2027
claude-mythos-preview Deprecated June 9, 2026 To be announced
claude-opus-5 Active N/A Not sooner than July 24, 2027
claude-opus-4-8 Active N/A Not sooner than May 28, 2027
claude-opus-4-7 Active N/A Not sooner than April 16, 2027
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