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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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claude-mythos-5

model never mined JSON

A Claude Code model, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.

The model picker now colours Fable 5, Mythos 5 and Sonnet 5 in its list.

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.221.

First seen — never in a mined build
Last seen — never in a mined build
Builds0 / 149on this box, as of v2.1.308
Written about v2.1.170 first named in a changelog, 9 Jun 2026

In the changelogs

7

Releases whose published page names claude-mythos-5.

  1. v2.1.284
    /loop has most models schedule the next run before confirming

    When /loop paces itself, most models are now told to decide and schedule the next run first and write their confirmation afterwards

    found in this entry's text

  2. v2.1.267
    fable_5_mitigations gate can now explicitly turn off mitigations for claude-mythos-5

    The fable_5_mitigations flag can now explicitly disable mitigations for claude-mythos-5, not just enable them

    found in this entry's text

  3. v2.1.248
    Unreleased Mythos and next-generation model ids in the bundled tables

    Model tables carry ids for a Mythos preview and a 5-series family, not selectable.

    found in this entry's text

  4. v2.1.221
    Model picker colours the new model names

    The model picker now colours Fable 5, Mythos 5 and Sonnet 5 in its list.

    named in this entry, found in this entry's text

  5. v2.1.201
  6. v2.1.174
    Advisor Model Capability Enforcement

    found in this entry's text

  7. v2.1.170
    Claude Fable 5 Model Support

    found in this entry's text

First cited

1

The earliest release whose published evidence quoted claude-mythos-5 was v2.1.248, 27 Aug 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.

ReleaseDateThe span that was quoted
v2.1.24827 Aug 2026"claude-mythos-5"

Presence across releases

0

The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.

Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the model does. All models.

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