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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

MCP client constructed with a JSON Schema validator and explicit listChanged settings

You'll notice
Useful2 Signal0
MCP

MCP servers announcing tool or prompt list changes will not cause Claude to refetch them.

What

Client construction and request-handler registration were reworked, and server list-changed notifications explicitly do not trigger refetching.

Details
  • The Client is created with jsonSchemaValidator, the negotiation config, and a listChanged block setting autoRefresh: !1, debounceMs: 0 with no-op onChanged for tools, prompts and resources.
  • Request handlers are registered by method-name strings ("roots/list", "elicitation/create") rather than schema objects.
  • A set of recognised JSON Schema draft URIs, draft-04 through 2019-09 plus the unversioned ones, is now kept in the module.
Evidence

jsonSchemaValidator

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 →