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mcp: add 2026-07-28 to the supported protocol versions (#1020)

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This PR adds the protocol version `2026-07-28` to the list of supported
protocol versions and fixes legacy tests hardcoding the legacy protocol
version for those use cases.
This commit is contained in:
Guglielmo Colombo 2026-06-24 12:02:56 +02:00 • committed by GitHub
commit 7f4aa4a0ce
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GPG key ID: B5690EEEBB952194
1 changed files with 355 additions and 218 deletions
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16
mcp/shared.go
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@ -35,7 +35,7 @@ const (
//
// It is the version that the client sends in the initialization request, and
// the default version used by the server.
latestProtocolVersion = protocolVersion20251125
latestProtocolVersion = protocolVersion20260728
protocolVersion20260728 = "2026-07-28"
protocolVersion20251125 = "2025-11-25"
protocolVersion20250618 = "2025-06-18"
@ -44,6 +44,7 @@ const (
)
var supportedProtocolVersions = []string{
protocolVersion20260728,
protocolVersion20251125,
protocolVersion20250618,
protocolVersion20250326,
@ -58,8 +59,11 @@ func negotiatedVersion(clientVersion string) string {
//
// This handles the case where a new spec version is released, and the SDK
// does not support it yet.
// Cap the supported versions at the legacy protocolVersion20251125, as this
// method is used by the initialize method which is deprecated in
// version protocolVersion20260728.
if !slices.Contains(supportedProtocolVersions, clientVersion) {
return latestProtocolVersion
return protocolVersion20251125
}
return clientVersion
}
@ -536,7 +540,7 @@ func validateRequestMeta(req *jsonrpc.Request) (*validatedMeta, error) {
Message: fmt.Sprintf("missing or invalid _meta field %q", MetaKeyClientInfo),
}
}
capabilities, ok := decodeMetaValue[*ClientCapabilities](meta, MetaKeyClientCapabilities)
capabilities, ok := decodeMetaValue[*clientCapabilitiesV2](meta, MetaKeyClientCapabilities)
if !ok {
return nil, &jsonrpc.Error{
Code: jsonrpc.CodeInvalidParams,
@ -546,7 +550,7 @@ func validateRequestMeta(req *jsonrpc.Request) (*validatedMeta, error) {
logLevel, _ := decodeMetaValue[LoggingLevel](meta, MetaKeyLogLevel)
return &validatedMeta{usesNewProtocol: true, initializeParams: &InitializeParams{
ProtocolVersion: protocolVersion,
Capabilities: capabilities,
Capabilities: capabilities.toV1(),
ClientInfo: clientInfo,
}, logLevel: logLevel}, nil
}
@ -659,8 +663,8 @@ func (r *ServerRequest[P]) ClientInfo() *Implementation {
// back to the session-level [InitializeParams].
func (r *ServerRequest[P]) ClientCapabilities() *ClientCapabilities {
if m := getRequestMeta(r); m != nil {
if v, ok := decodeMetaValue[*ClientCapabilities](m, MetaKeyClientCapabilities); ok {
return v
if v, ok := decodeMetaValue[*clientCapabilitiesV2](m, MetaKeyClientCapabilities); ok {
return v.toV1()
}
}
if r.Session != nil {