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.
Model switches now go through a decision check before being applied
You'll notice
Useful3Signal4
Models
Model switches now pass a decision check first and can be rejected with an error.
What's wrong with this entry?
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What
What was already a rejected-switch telemetry path is now fed by a hook-style decision taken before the switch lands: anything other than proceed rejects it with an error, and a rejected system-prompt switch reports separately. Notices from the decision come back with a successful switch.
Details
Always on this code path, not behind a flag.
Evidence
model_switch_rejected
Strings lifted out of the shipped bundle, so the claim above can be checked against them.