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.

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Extended Thinking Budget for claude-mythos-preview

Claude Code now enables extended thinking for models in the "mythos" family (such as claude-mythos-preview) where it was previously disabled. Two distinct thinking budget paths are updated:

  • The always-disabled thinking path ([false, 0]) now returns [undefined, 2048] for mythos-family models, activating thinking with a 2048-token budget.
  • The main thinking configuration path now checks for mythos-family models first and applies a dedicated 2048-token budget constant (Cx4) before falling through to the general thinking settings.

This means users who have claude-mythos-preview configured as their model will now benefit from extended reasoning where Claude thinks through problems more carefully before responding.

Evidence

Model family detection uses ZW_ = ["fruitcake", "macaroon", "mythos"] — search for "mythos" in the source; thinking budget is Cx4 = 2048 (search for "Cx4 = 2048").

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

See this entry in the whole of v2.1.168 →