feat: protocol version enum and per-version schema conformance for 2026-07-28 (T1, T2)

client-streaming/client-ox/src/main/scala/chimp/client/transport/ox/OxClientHttpTransport.scala

@@ -237,7 +237,7 @@ object OxClientHttpTransport:
   def apply(
       backend: SyncBackend,
       uri: Uri,
-      protocolVersion: ProtocolVersion = ProtocolVersion.Latest,
+      protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy,
       timeout: FiniteDuration = ClientTransport.defaultTimeout,
       headers: Seq[Header] = Nil
   )(using Ox): OxClientHttpTransport =

client-streaming/client-pekko/src/main/scala/chimp/client/transport/pekko/PekkoClientHttpTransport.scala

@@ -354,7 +354,7 @@ object PekkoClientHttpTransport:
   def apply(
       backend: StreamBackend[Future, PekkoStreams],
       uri: Uri,
-      protocolVersion: ProtocolVersion = ProtocolVersion.Latest,
+      protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy,
       timeout: FiniteDuration = ClientTransport.defaultTimeout,
       reconnectSettings: RestartSettings = defaultReconnectSettings,
       headers: Seq[Header] = Nil

client-streaming/client-pekko/src/test/scala/chimp/client/transport/pekko/PekkoMcpClientHttpIntegrationSpec.scala

@@ -22,5 +22,5 @@ class PekkoMcpClientHttpIntegrationSpec
   override def usingBidirectionalTransport[A](b: StreamBackend[Future, PekkoStreams], uri: Uri, timeout: FiniteDuration)(
       use: ClientBidirectionalTransport[Future] => Future[A]
   ): Future[A] =
-    val transport = PekkoClientHttpTransport(b, uri, ProtocolVersion.Latest, timeout)
+    val transport = PekkoClientHttpTransport(b, uri, ProtocolVersion.LatestLegacy, timeout)
     monad.ensure2(use(transport), transport.close())

client-streaming/client-zio/src/main/scala/chimp/client/transport/zio/ZioClientHttpTransport.scala

@@ -272,7 +272,7 @@ object ZioClientHttpTransport:
   def apply(
       backend: StreamBackend[Task, ZioStreams],
       uri: Uri,
-      protocolVersion: ProtocolVersion = ProtocolVersion.Latest,
+      protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy,
       timeout: FiniteDuration = ClientTransport.defaultTimeout,
       reconnectSchedule: Schedule[Any, Any, Any] = defaultReconnectSchedule,
       headers: Seq[Header] = Nil
@@ -306,7 +306,7 @@ object ZioClientHttpTransport:
   def scoped(
       backend: StreamBackend[Task, ZioStreams],
       uri: Uri,
-      protocolVersion: ProtocolVersion = ProtocolVersion.Latest,
+      protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy,
       timeout: FiniteDuration = ClientTransport.defaultTimeout,
       reconnectSchedule: Schedule[Any, Any, Any] = defaultReconnectSchedule,
       headers: Seq[Header] = Nil
@@ -316,7 +316,7 @@ object ZioClientHttpTransport:
   def layer(
       backend: StreamBackend[Task, ZioStreams],
       uri: Uri,
-      protocolVersion: ProtocolVersion = ProtocolVersion.Latest,
+      protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy,
       timeout: FiniteDuration = ClientTransport.defaultTimeout,
       reconnectSchedule: Schedule[Any, Any, Any] = defaultReconnectSchedule,
       headers: Seq[Header] = Nil

client-streaming/client-zio/src/test/scala/chimp/client/transport/zio/ZioMcpClientHttpIntegrationSpec.scala

@@ -20,4 +20,4 @@ class ZioMcpClientHttpIntegrationSpec extends McpClientStreamingHttpIntegrationS
   override def usingBidirectionalTransport[A](b: StreamBackend[Task, ZioStreams], uri: Uri, timeout: FiniteDuration)(
       use: ClientBidirectionalTransport[Task] => Task[A]
   ): Task[A] =
-    ZIO.scoped(ZioClientHttpTransport.scoped(b, uri, ProtocolVersion.Latest, timeout).flatMap(use))
+    ZIO.scoped(ZioClientHttpTransport.scoped(b, uri, ProtocolVersion.LatestLegacy, timeout).flatMap(use))

client/src/main/scala/chimp/client/McpClient.scala

@@ -127,7 +127,7 @@ object McpClient:
   def apply[F[_]](
       transport: ClientTransport[F],
       clientInfo: Implementation,
-      protocolVersion: ProtocolVersion = ProtocolVersion.Latest
+      protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy
   ): F[McpClient[F]] =
     McpClientImpl.create(transport, clientInfo, protocolVersion)
 
@@ -154,6 +154,6 @@ object McpClient:
       rootsHandler: Option[() => F[ListRootsResult]] = None,
       samplingHandler: Option[CreateMessageRequest => F[CreateMessageResult]] = None,
       elicitationHandler: Option[ElicitRequest => F[ElicitResult]] = None,
-      protocolVersion: ProtocolVersion = ProtocolVersion.Latest
+      protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy
   ): F[BidirectionalMcpClient[F]] =
     McpClientImpl.createBidirectional(transport, clientInfo, protocolVersion, rootsHandler, samplingHandler, elicitationHandler)

client/src/main/scala/chimp/client/transport/ClientHttpTransport.scala

@@ -26,7 +26,7 @@ import scala.util.chaining.*
 final class ClientHttpTransport[F[_]](
     backend: Backend[F],
     uri: Uri,
-    protocolVersion: ProtocolVersion = ProtocolVersion.Latest,
+    protocolVersion: ProtocolVersion = ProtocolVersion.LatestLegacy,
     headers: Seq[Header] = Nil
 ) extends ClientTransport[F]:
 

client/src/test/scala/chimp/client/ClientHttpTransportSpec.scala

@@ -67,4 +67,4 @@ class ClientHttpTransportSpec extends AnyFlatSpec with Matchers:
 
     val request = backend.allInteractions.map { case (request, _) => request }.head
     request.headers.filter(_.is("Accept")) shouldBe List(Header("Accept", "application/json, text/event-stream"))
-    request.header("MCP-Protocol-Version") shouldBe Some(ProtocolVersion.Latest.name)
+    request.header("MCP-Protocol-Version") shouldBe Some(ProtocolVersion.LatestLegacy.name)

client/src/test/scala/chimp/client/integration/McpClientHttpIntegrationSpec.scala

@@ -42,6 +42,6 @@ abstract class McpClientHttpIntegrationSpec[F[_], B]
     toFuture(
       usingBackend: backend =>
         usingTransport(backend, mcpEverythingContainer.mcpUri): transport =>
-          McpClient(transport, clientInfo, ProtocolVersion.Latest).flatMap: client =>
+          McpClient(transport, clientInfo, ProtocolVersion.LatestLegacy).flatMap: client =>
             test(client).flatMap(assertion => client.close().map(_ => assertion))
     )

client/src/test/scala/chimp/client/integration/McpClientStdioIntegrationSpec.scala

@@ -38,7 +38,7 @@ abstract class McpClientStdioIntegrationSpec[F[_]]
     toFuture(
       usingTransport(everythingServerCommand, ClientTransport.defaultTimeout): transport =>
         McpClient
-          .bidirectional[F](transport, clientInfo, rootsHandler, samplingHandler, elicitationHandler, ProtocolVersion.Latest)
+          .bidirectional[F](transport, clientInfo, rootsHandler, samplingHandler, elicitationHandler, ProtocolVersion.LatestLegacy)
           .flatMap: client =>
             test(client).flatMap(assertion => client.close().map(_ => assertion))
     )

client/src/test/scala/chimp/client/integration/McpClientStreamingHttpIntegrationSpec.scala

@@ -42,7 +42,7 @@ abstract class McpClientStreamingHttpIntegrationSpec[F[_], B]
       usingBackend: backend =>
         usingBidirectionalTransport(backend, mcpEverythingContainer.mcpUri, ClientTransport.defaultTimeout): transport =>
           McpClient
-            .bidirectional[F](transport, clientInfo, rootsHandler, samplingHandler, elicitationHandler, ProtocolVersion.Latest)
+            .bidirectional[F](transport, clientInfo, rootsHandler, samplingHandler, elicitationHandler, ProtocolVersion.LatestLegacy)
             .flatMap: client =>
               test(client).flatMap(assertion => client.close().map(_ => assertion))
     )
@@ -57,7 +57,7 @@ abstract class McpClientStreamingHttpIntegrationSpec[F[_], B]
       usingBackend: backend =>
         usingBidirectionalTransport(backend, proxyContainer.mcpUri, timeout): transport =>
           McpClient
-            .bidirectional[F](transport, clientInfo, None, samplingHandler, None, ProtocolVersion.Latest)
+            .bidirectional[F](transport, clientInfo, None, samplingHandler, None, ProtocolVersion.LatestLegacy)
             .flatMap: client =>
               test(proxyContainer, client).flatMap(assertion => client.close().map(_ => assertion))
     )

core/src/main/scala/chimp/protocol/ProtocolVersion.scala

@@ -5,12 +5,18 @@ import io.circe.{Decoder, Encoder, Json}
 enum ProtocolVersion(val name: String):
   case V2025_06_18 extends ProtocolVersion("2025-06-18")
   case V2025_11_25 extends ProtocolVersion("2025-11-25")
+  case V2026_07_28 extends ProtocolVersion("2026-07-28")
 
 object ProtocolVersion:
-  val Latest: ProtocolVersion = V2025_11_25
+  val Latest: ProtocolVersion = V2026_07_28
+  val LatestLegacy: ProtocolVersion = V2025_11_25
 
   def from(s: String): Option[ProtocolVersion] = values.find(_.name == s)
   def negotiate(requested: String): ProtocolVersion = from(requested).getOrElse(Latest)
 
+  given Ordering[ProtocolVersion] = Ordering.by(_.ordinal)
+
+  extension (version: ProtocolVersion) def >=(other: ProtocolVersion): Boolean = version.ordinal >= other.ordinal
+
   given Encoder[ProtocolVersion] = Encoder.instance(v => Json.fromString(v.name))
   given Decoder[ProtocolVersion] = Decoder.decodeString.emap(s => from(s).toRight(s"Unsupported protocol version: $s"))