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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 v2.1.232

An MCP server that stalls during version negotiation now falls back instead of erroring

You'll notice
Useful3 Signal2
MCP

An MCP server that stalls on the version probe is retried as legacy instead of erroring out.

What

If the probe Claude Code sends to work out an MCP server's protocol version times out, the connection is retried with the pinned legacy protocol inside the remaining time budget rather than surfacing as a connection error.

Details
  • The timeout is tagged probe_timeout (distinct from the existing probe_failed) in the disconnect cause, and logged as "version negotiation probe timed out on the ... transport" followed by "reconnecting pinned legacy within the remaining budget".
  • If the pinned-legacy retry then fails with a typed non-auth, non-timeout error, the original timeout classification is preserved so the connect stays eligible for the normal retry ladder.
  • Previously a probe timeout on http or sse transports simply failed the connection.
Evidence

probe_timeout, preserving the timeout classification so the connect stays ladder-retryable

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

See this entry in the whole of v2.1.232 →