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.
MCP WebSocket connection errors now include the list of subprotocols offered by the server when relevant. The message format is (subprotocols: "proto1", "proto2") appended to connection error text.
Evidence
"(subprotocols:" (search for "Nxu")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
