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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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Claude Code v2.1.239

Requesting a model you are not permitted to use can now step down instead of failing

You'll notice
Useful3 Signal3
Models

Switching to a model you aren't allowed to use now falls back to a substitute instead of failing.

What

When a program switches models mid-session through the control channel, a name that is recognized but not permitted no longer just gets blocked; a substitute model is picked instead.

Details
  • The requested name is classified as default, unrecognized, allowed, blocked or stepped down.
  • An unrecognized name still returns the shape it expected plus a suggestion, and is reported as tengu_set_model_unrecognized.
Evidence

steppedDown

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 v2.1.239 →