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[Server][Client] SEP-2575: Stateless protocol (per-request version, server/discover, messages/listen) #340
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2026-07-28All issues and PRs related to the spec release 2026-07-28All issues and PRs related to the spec release 2026-07-28ClientIssues & PRs related to the Client componentIssues & PRs related to the Client componentP0Broken core functionality, security issues, critical missing featureBroken core functionality, security issues, critical missing featureSchemaIssues & PRs related to the Schema componentIssues & PRs related to the Schema componentServerIssues & PRs related to the Server componentIssues & PRs related to the Server componentbreaking changeBreaking the Backwards Compatibility PromiseBreaking the Backwards Compatibility PromiseenhancementRequest for a new feature that's not currently supportedRequest for a new feature that's not currently supportedimproves spec complianceImproves consistency with other SDKs such as TyepScriptImproves consistency with other SDKs such as TyepScriptneeds designValid issue but needs maintainer alignment on design or approachValid issue but needs maintainer alignment on design or approach
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2026-07-28All issues and PRs related to the spec release 2026-07-28All issues and PRs related to the spec release 2026-07-28ClientIssues & PRs related to the Client componentIssues & PRs related to the Client componentP0Broken core functionality, security issues, critical missing featureBroken core functionality, security issues, critical missing featureSchemaIssues & PRs related to the Schema componentIssues & PRs related to the Schema componentServerIssues & PRs related to the Server componentIssues & PRs related to the Server componentbreaking changeBreaking the Backwards Compatibility PromiseBreaking the Backwards Compatibility PromiseenhancementRequest for a new feature that's not currently supportedRequest for a new feature that's not currently supportedimproves spec complianceImproves consistency with other SDKs such as TyepScriptImproves consistency with other SDKs such as TyepScriptneeds designValid issue but needs maintainer alignment on design or approachValid issue but needs maintainer alignment on design or approach
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Implements SEP-2575 for the MCP Spec 2026-07-28 release.
Tracked by umbrella #334.
Spec summary
PHP SDK changes
src/Server/Handler/Request/InitializeHandler.php,src/Schema/Request/InitializeRequest.php,src/Schema/Result/InitializeResult.php— keep working for old clients but make optional; gate on protocol version.src/Server/Protocol.php— drop hard requirement that initialize precedes other calls; routeserver/discoverandmessages/listen.src/Server/Handler/Request/DiscoverHandler.phpandMessagesListenHandler.php; corresponding schemas undersrc/Schema/Request|Result/.src/Server/Transport/Http/Middleware/ProtocolVersionMiddleware.php— extend to also read_meta.protocolVersionfrom JSON-RPC payloads and emitUnsupportedVersionError.src/Server/Transport/StreamableHttpTransport.php— route streaming throughmessages/listenPOST; legacy GET-SSE deprecated.src/Client/Protocol.phpandsrc/Client/Builder.php— skip handshake when negotiating new version; emit per-request capabilities/version; handleUnsupportedVersionErrorretry.Breaking change. Coordinate with deprecation policy (SEP-2596, umbrella #339).
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