[Feature]: Add Claude Mythos 5.1 (claude-mythos-5-1) to the Claude model catalog #17780

Summary

Please add Claude Mythos 5.1 (API model ID claude-mythos-5-1) to the Claude provider's model list, next to Claude Fable 5.1.

Details

• Label: Claude Mythos 5.1
• Model ID: claude-mythos-5-1 (also anthropic.claude-mythos-5-1 on Bedrock)
• Released: September 1, 2026
• Specs and pricing match Claude Fable 5.1: 1M context, 128K max output, $10 / $50 per MTok, adaptive thinking (always on), default effort high
• Reasoning options should mirror Fable 5.1 in the current catalog (low, medium, high, xhigh, max, ultracode, ultrathink)

Access

Mythos 5.1 is not generally available. Per the docs, it is limited to organizations verified through Anthropic's verification programs, such as the Cyber Verification Program. Requests without that access will fail at the API. Adding it as a selectable model is still useful for verified users. If the catalog can flag it as verification-gated, that would help.

Precedent

Fable 5.1 was added to the catalog in #9088 (now closed) for the same reason.

Sources

• Official docs: https://platform.claude.com/docs/en/models/mythos-5-1/overview
• Announcement: https://www.anthropic.com/claude-fable-and-mythos-5-1

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