Source Intelligence

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.248 Home All releases olderv2.1.247 v2.1.250newer
Claude Code v2.1.248

Opus 5, Fable and Mythos in the version and alias tables

Not switched on
Useful3 Signal5
Models Notable

Naming tables list Opus 4.8, Sonnet 5, Fable 5 and Mythos 5 with aliases.

These are naming and alias tables only, and two task-model maps disagree with each other.

What

The family and version table now lists opus 4.8, sonnet 5, fable 5 and mythos 5; display names gain "Fable"; and aliases map fable-5, mythos-5 and opus-5 to full ids. These are naming tables, not availability. Two task-model maps in the same build disagree, one selecting Opus 5 where the other selects Opus 4.8.

Evidence

["fable-5", "claude-fable-5"]

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.248 →