[Server] Serve both protocol eras from one endpoint (#455)

* [Server] Serve both protocol eras from one endpoint

The two lifecycles share a transport, not a dispatcher. StreamableHttpTransport
classifies each request - a 2026-07-28 envelope, an initialize handshake, or a
session-bound follow-up - through InboundClassifier and routes it to the
dispatcher that owns it, so one URL answers a modern client and a handshake-era
one alike. Builder::build() carries both; withoutModernEra() opts out and
setModernVersions() narrows what the modern leg answers for.

InputRequiredShim lets a handler written for multi round-trip requests also
serve a handshake-era client, by turning each ask into the request/response
exchange that era has - so a handler is written once rather than twice.

The conformance fixture collapses into one server for the same reason: both
legs now hit the same URL.

* Trim redundant comments, fix stale in-memory claim in conformance fixture

* Drop stale json-schema-2020-12 baseline entries

The new fixture tool makes this scenario pass in both eras now.

* Reject handshake revisions in setModernVersions(), warn on unsafe custom middleware

Copilot review: setModernVersions() accepted revisions InboundClassifier
would never route to the modern leg. StreamableHttpTransport now warns
when a custom middleware list carries ProtocolVersionMiddleware, since
it runs before era classification and rejects modern-era traffic by
default. Also fixed a misleading docblock claim on the same middleware.
This commit is contained in:
Christopher Hertel 2026-08-19 01:36:56 +02:00 • committed by GitHub
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@ -28,6 +28,13 @@ set_exception_handler(static function (Throwable $t): never {
});
/**
* The transport every example runs on.
*
* Over HTTP that is one endpoint serving both protocol eras: `StreamableHttpTransport`
* classifies each request and routes it to the lifecycle it belongs to, so every
* example here answers an `initialize` handshake and a 2026-07-28 envelope alike.
* Over stdio there is no such choice to make — that binding carries the handshake era.
*
* @return TransportInterface<int>|TransportInterface<ResponseInterface>
*/
function transport(): TransportInterface