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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 v2.1.51 23 Feb 2026

Duplicate Permission Response Handling

The structured transport now tracks resolved tool-use IDs and silently ignores duplicate control_response messages, preventing race conditions where a late-arriving permission response could cause errors.

Evidence

"Ignoring duplicate control_response for already-resolved toolUseID=" (search for "Ignoring duplicate control_response")

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

See this entry in the whole of v2.1.51 →