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mcp: handle the Mcp-Protocol-Version header correctly

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Handle the protocol version header according to section 2.7 of the spec
(and the other SDKs).

Fixes #198
This commit is contained in:
Rob Findley 2025-08-20 14:54:21 +00:00 • committed by Robert Findley
commit 79f063bc98
1 changed files with 192 additions and 65 deletions
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34
mcp/shared.go
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@ -27,14 +27,36 @@ import (
"github.com/modelcontextprotocol/go-sdk/jsonrpc"
)
// latestProtocolVersion is the latest protocol version that this version of the SDK supports.
// It is the version that the client sends in the initialization request.
const latestProtocolVersion = "2025-06-18"
const (
// latestProtocolVersion is the latest protocol version that this version of
// the SDK supports.
//
// It is the version that the client sends in the initialization request, and
// the default version used by the server.
latestProtocolVersion = protocolVersion20250618
protocolVersion20250618 = "2025-06-18"
protocolVersion20250326 = "2025-03-26"
protocolVersion20251105 = "2024-11-05"
)
var supportedProtocolVersions = []string{
latestProtocolVersion,
"2025-03-26",
"2024-11-05",
protocolVersion20250618,
protocolVersion20250326,
protocolVersion20251105,
}
// negotiatedVersion returns the effective protocol version to use, given a
// client version.
func negotiatedVersion(clientVersion string) string {
// In general, prefer to use the clientVersion, but if we don't support the
// client's version, use the latest version.
//
// This handles the case where a new spec version is released, and the SDK
// does not support it yet.
if !slices.Contains(supportedProtocolVersions, clientVersion) {
return latestProtocolVersion
}
return clientVersion
}
// A MethodHandler handles MCP messages.