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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 v2.1.221

list_changed refreshes can be synthesized after a listen stream reopens

Under the hood
Useful2 Signal0
MCP

Claude can now tell whether an MCP tool list refresh came from a reconnect or a server notification.

What

Refresh handlers now know why they ran, so a refetch caused by a reconnect is distinguishable from one caused by a server notification.

Details
  • Tools, prompts and resources refresh handlers take a cause argument.
  • When the refetch came from a listen-stream reopen rather than a notification, the debug log says so.
  • The tengu_mcp_list_changed event carries a new cause field.
  • The prompts and resources events moved: they are now emitted after the refresh completes instead of before it starts.
Evidence

Synthesized tools refetch after listen-stream reopen (no notification received)

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

See this entry in the whole of v2.1.221 →