claude-mythos-preview
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.
Long-context eligibility is now looked up per model, and DISABLE_COMPACT turns off compaction.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.223.
In the changelogs
5Releases whose published page names claude-mythos-preview.
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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
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v2.1.228
More models now show a deprecation date
More models now report a concrete deprecation date, including one named claude-mythos-preview.
named in this entry, found in this entry's text
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v2.1.228
Bundled API client: new endpoints and a stripped request field
The bundled client swapped memory-version endpoints for deployment runs and added a threads resource.
found in this entry's text
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v2.1.223
1M-context and compaction checks now go through model capability lookup
Long-context eligibility is now looked up per model, and DISABLE_COMPACT turns off compaction.
found in this entry's text
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v2.1.168
Extended Thinking Budget for claude-mythos-preview
found in this entry's text
First cited
3The earliest release whose published evidence quoted claude-mythos-preview was v2.1.223, 5 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.
Presence across releases
0The 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.