Follow Discord

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.

← All of v2.1.221 Home All releases ←olderv2.1.220 v2.1.222newer→

Claude Code v2.1.221 3 Aug 2026

MCP connection-failure telemetry normalizes the error code

Under the hood

Useful1 Signal0

MCP

MCP failure codes are now cleaned up before reporting, so odd server values don't leak through.

What

The error code attached to MCP connection failures is now classified before being reported, so arbitrary values from a server do not reach telemetry verbatim.

Details

Emits missing when there is no code, the numeric value when it is an integer, a known code from an allow-list, or other as the fallback.
Applies to every tengu_mcp_server_connection_failed report; no gate.

Evidence

tengu_mcp_server_connection_failed

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 →