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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 v2.1.248

MCP protocol versions listed in negotiation order

Under the hood
Useful2 Signal3
MCP

The MCP client lists its supported protocol versions in descending preference, including two newer symbolic ones.

What

The MCP client now carries an explicit list of the protocol versions it supports, "2025-06-18", "2025-03-26", "2024-11-05", "2024-10-07", preceded by two newer symbolic versions, giving a clear descending preference order when negotiating with a server.

Evidence

"2025-06-18", "2025-03-26", "2024-11-05", "2024-10-07"

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

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.248 →