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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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Claude Code v2.1.221 ·

MCP servers can start from a discovery cache and connect lazily

Startup no longer dials cached HTTP or SSE MCP servers; they restore from cache and connect on first use.

You'll notice Notable New Features
JSON All of v2.1.221
You'll noticeTier: how much it should matter to you
4Useful: my rating, 1 to 5
0Signal: worth watching, 1 to 5
MCPArea: what it touches
New FeaturesKind: in v2.1.221,
What probably matters to youSection of the release
What

An http or sse MCP server with a saved discovery entry is no longer dialed at startup. Its tools, commands, prompts, resources, templates, instructions and serverInfo are restored from the cache and the real connection is deferred until something actually uses the server.

Details
  • A new client lifecycle state type: "cached" joins connected, pending, needs-auth and failed; restored entries carry cacheSavedAt.
  • Fresh entries are used directly; stale entries are used immediately and revalidated in the background under the context "MCP discovery-cache stale refresh".
  • A new tengu_mcp_discovery_source event reports where a server came from: cache_fresh, cache_stale, miss_expired, miss_corrupt, miss_strike, miss_no_fingerprint.
  • Entries whose capabilities are skills-capable or channel-capable are deliberately forced to a live connection ({ kind: "miss", reason: "skills-capable" }).
  • Eligibility checks that can send a server live instead: "env-disabled", "kill-switch", "transport", "cli-owned", "env-placeholder". The cache is also skipped when a live connection already exists.
  • Gated on tengu_mcp_discovery_cache with in-source fallback true, so the real value comes from remote config; setting the MCP_DISCOVERY_CACHE env var to false disables it. The persistence file mcp-discovery-cache and the env switch shipped in 2.1.220, but nothing consumed an entry into a client until now.
Evidence

tengu_mcp_discovery_source, tengu_mcp_discovery_cache, MCP discovery-cache stale refresh

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

Read from
Names in the bundleMCP_DISCOVERY_CACHE
Feature flag
tengu_mcp_discovery_cache Not enough to say

Nothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.

This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.221: on

These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.

Read once, for one account on one subscription tier, against v2.1.221. It isn't a statement about your account. What a flag value here can and cannot tell you

How sure we are
One source agreesOne thing we can check says the same as this entry.
The name it cites is new in this buildNew in this build: tengu_mcp_discovery_cache

See this entry in the whole of v2.1.221 →

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