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Sweep 22 Oct 2026 · 21:04Z Build v2.1.309 528 read Stable v2.1.308 Latest v2.1.308 Next v2.1.309 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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Claude Code v2.1.221 ·

Failure telemetry errorCode is now normalized against a fixed allowlist

MCP connection failure reporting now uses a fixed set of error codes instead of raw values.

Under the hood Internal Changes
JSON All of v2.1.221
Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
0Signal: worth watching, 1 to 5
MCPArea: what it touches
Internal ChangesKind: in v2.1.221,
Internal ChangesSection of the release
What

errorCode on tengu_mcp_server_connection_failed is no longer the raw stringified code.

Details
  • It emits missing when absent, keeps numeric codes, keeps values from a fixed list, and otherwise reports other.
  • The list includes new entries such as ERA_NEGOTIATION_FAILED, LIST_PAGINATION_EXCEEDED, METHOD_NOT_SUPPORTED_BY_PROTOCOL_VERSION and the CLIENT_HTTP_* family.
  • The client-side error code map also gained list_pagination_exceeded plus explicit -32000 and -32001 entries.
Evidence

METHOD_NOT_SUPPORTED_BY_PROTOCOL_VERSION

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 →

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