An MCP server needs to support clients running both the 2025-03-26 and — MCP Professional Practice — Claude Cert Academy

An MCP server needs to support clients running both the 2025-03-26 and 2025-11-25 protocol versions. How does the handshake handle this?

• The server rejects clients that do not support the latest version
• The client declares its version in initialize; the server replies with the nearest version it supports; the client decides whether to proceed
• The server automatically upgrades the client to the latest version
• Both sides must use identical versions or the session fails

Answer: The client declares its version in initialize; the server replies with the nearest version it supports; the client decides whether to proceed

Protocol version negotiation happens during the initialization handshake. The client declares its protocolVersion in the initialize request. If the server does not support that exact version, it replies with the nearest version it does support. The client then decides whether the negotiated version is acceptable. Automatic upgrades are not part of the protocol.

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