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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 subscriptions/listen streams are re-opened after drops

You'll notice
Useful4 Signal0
MCP

MCP notification streams now reconnect after a server drop or redeploy instead of silently going dead.

What

A watcher keeps the subscriptions/listen stream alive on modern-era MCP connections, so a dropped or redeployed server no longer silently ends notification delivery.

Details
  • remote drops are retried on a delay ladder; a graceful server close waits out a redeploy grace window before re-listening
  • gives up once the ladder is exhausted
  • after a successful reopen it re-fetches tools, prompts and resources lists for whichever listChanged capabilities the server advertises
  • tools/list gained a bounded retry loop using cacheMode: "refresh"
  • telemetry event tengu_mcp_listen_reopen reports outcome (opened_from_zero, reopened, budget_exhausted, gave_up), attempt count and trigger
  • the path only runs on modern connections, that is behind the protocol-negotiation gates
Evidence

subscriptions/listen closed gracefully (server shutdown); re-listening after the redeploy grace window

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 →