Expose the negotiated HTTP version to request handlers

Sources/NIOHTTPServer/HTTPServerCapability+ConnectionCapabilities.swift

@@ -31,6 +31,16 @@ extension HTTPServerCapability {
         var localAddress: NIOHTTPServer.SocketAddress? { get }
     }
 
+    /// A request-context capability exposing the application-level HTTP version.
+    ///
+    /// Servers whose request context conforms to this capability surface the
+    /// HTTP version in use on the connection carrying the request, whether it
+    /// was negotiated via ALPN or fixed by a plaintext listener.
+    public protocol HTTPVersion: RequestContext {
+        /// The application-level HTTP version in use on the connection.
+        var httpVersion: NIOHTTPServer.HTTPVersion { get }
+    }
+
     /// A request-context capability exposing the validated peer certificate chain.
     ///
     /// Servers whose request context conforms to this capability surface the

Sources/NIOHTTPServer/NIOHTTPServer+ConnectionContext.swift

@@ -40,6 +40,7 @@ extension NIOHTTPServer {
     ///
     /// User code accesses this state via the corresponding ``RequestContext``
     /// capabilities (``HTTPServerCapability/ConnectionInfo``,
+    /// ``HTTPServerCapability/HTTPVersion``,
     /// ``HTTPServerCapability/PeerCertificate``) when handling individual
     /// requests, and directly when implementing an
     /// ``NIOHTTPServerConnectionHandler``.

Sources/NIOHTTPServer/NIOHTTPServer+RequestContext.swift

@@ -22,6 +22,7 @@ extension NIOHTTPServer {
     ///
     /// Conforms to:
     /// - ``HTTPServerCapability/ConnectionInfo`` — peer / local addresses.
+    /// - ``HTTPServerCapability/HTTPVersion`` — HTTP version of the connection.
     /// - ``HTTPServerCapability/PeerCertificate`` — mTLS-validated peer chain.
     ///
     /// Generic library code can constrain on these capabilities to access
@@ -60,6 +61,15 @@ extension NIOHTTPServer.RequestContext: HTTPServerCapability.ConnectionInfo {
     }
 }
 
+@available(anyAppleOS 27.0, *)
+extension NIOHTTPServer.RequestContext: HTTPServerCapability.HTTPVersion {
+    /// The application-level HTTP version in use on the connection carrying
+    /// this request.
+    public var httpVersion: NIOHTTPServer.HTTPVersion {
+        self.connectionContext.httpVersion
+    }
+}
+
 @available(anyAppleOS 27.0, *)
 extension NIOHTTPServer.RequestContext: HTTPServerCapability.PeerCertificate {
     /// The peer's mTLS-validated certificate chain, when available.

Tests/NIOHTTPServerTests/NIOHTTPServerTests.swift

@@ -118,6 +118,43 @@ struct NIOHTTPServerTests {
         }
     }
 
+    @available(anyAppleOS 27.0, *)
+    #if HTTP3
+    @Test(
+        "Request context reports the HTTP version",
+        arguments: [NIOHTTPServer.HTTPVersion.plaintextHTTP1_1, .http1_1, .http2, .http3]
+    )
+    #else
+    @Test(
+        "Request context reports the HTTP version",
+        arguments: [NIOHTTPServer.HTTPVersion.plaintextHTTP1_1, .http1_1, .http2]
+    )
+    #endif
+    func testRequestContextHTTPVersion(httpVersion: NIOHTTPServer.HTTPVersion) async throws {
+        let (server, clientConfiguration) = try TestHelpers.makeServerAndClientConfiguration(
+            for: httpVersion,
+            clientLogger: self.clientLogger,
+            serverLogger: self.serverLogger
+        )
+
+        try await TestHelpers.withClientServerRequestChannel(
+            clientConfiguration: clientConfiguration,
+            server: server,
+            serverHandler: HTTPServerClosureRequestHandler { request, requestContext, reader, responseWriter in
+                #expect(requestContext.httpVersion == httpVersion)
+                try await responseWriter.sendAndFinish(.init(status: .ok))
+            }
+        ) { _, inbound, outbound in
+            try await outbound.write(.testHead(method: .get, for: httpVersion))
+            try await outbound.write(.end(nil))
+
+            var iterator = inbound.makeAsyncIterator()
+            while let part = try await iterator.next() {
+                if case .end = part { break }
+            }
+        }
+    }
+
     @available(anyAppleOS 27.0, *)
     @Test(
         "mTLS request-response with custom verification callback returning peer certificates",