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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 v2.1.238

MCP servers can connect lazily from a cached entry

Not switched on
Useful2 Signal3
MCP Notable

Tool calls to a remembered MCP server could dial it on demand, but the cache behind it is off.

Lazy connect and re-auth cache clearing both require the MCP discovery cache, enabled only by setting MCP_DISCOVERY_CACHE to true.

MCP_DISCOVERY_CACHE/mcp
What

A tool call to a server that exists only as a cached discovery entry can now dial it on demand rather than failing, and /mcp re-authentication clears the cached entry before reconnecting. Both depend on the MCP discovery cache, enabled only by setting MCP_DISCOVERY_CACHE to true or by a server value, and off otherwise.

Details
  • Client-state updates carry an attempt counter and are discarded, with remote connections detached and closed, when the signed-in account moved underneath them.
  • Reconnect callbacks, tool-list-changed handlers and initial-connect retries all re-check that counter before applying anything.
  • The cached client type itself only exists when the cache is on.
Evidence

mcp_call lazy connect

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 v2.1.238 →