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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 3 Aug 2026

Startup MCP wait is SDK-aware

You'll notice

Useful3 Signal0

MCP

Startup waits less for MCP servers in some setups, only holding for local and deferred ones.

What

The startup wait for MCP servers takes a computed deadline and an options object instead of fixed arguments.

Details

With an explicit MCP config flag it waits up to the MCP timeout.
When running against an sdkUrl, outside bridge environments and not in coordinator mode, it waits only for local servers.
Deferrable servers are always waited for.

Evidence

waitForDeferrable

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 →