The ids are data in constants; no setting, flag or menu exposes them.
What
The model tables shipped in this build carry ids for models that are not part of the current lineup, including a Mythos preview and a family of 5-series entries. They are data in constants and mapping tables only, so nothing here makes the models selectable or reachable, and the build ships no setting, flag or menu entry that turns them on.
Details
- The model constants list ids for Fable 5, Mythos 5, Opus 5 and Sonnet 5, with
claude-opus-4-8positioned as the previous Opus andclaude-sonnet-4-6as the previous Sonnet. - Mythos has full provider id mappings across Bedrock, Vertex, Foundry, Mantle and the gateway, so the routing tables would resolve it if it were ever requested.
- A model list constant includes
claude-mythos-previewandclaude-opus-4-6together, and a separate mapping names a further id. - The bundled Anthropic client's deprecation table now covers
claude-mythos-previewwith an end-of-life date of June 30th, 2026. claude-mythos-previewandclaude-opus-4-6are both in the set that prints a console warning when used with non-adaptive thinking enabled.
Evidence
"claude-mythos-5", "claude-mythos-preview": "June 30th, 2026", ["claude-mythos-preview", "claude-opus-4-6"]
Strings lifted out of the shipped bundle, so the claim above can be checked against them.