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feat(server): expose client implementation and capabilities to handlers #733

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11 changes: 11 additions & 0 deletions ...test/src/jvmTest/kotlin/io/modelcontextprotocol/kotlin/sdk/server/ClientConnectionTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ import io.modelcontextprotocol.kotlin.sdk.types.ElicitationCompleteNotification
import io.modelcontextprotocol.kotlin.sdk.types.ElicitationCompleteNotificationParams
import io.modelcontextprotocol.kotlin.sdk.types.GetPromptRequest
import io.modelcontextprotocol.kotlin.sdk.types.GetPromptRequestParams
import io.modelcontextprotocol.kotlin.sdk.types.Implementation
import io.modelcontextprotocol.kotlin.sdk.types.ListRootsRequest
import io.modelcontextprotocol.kotlin.sdk.types.ListRootsResult
import io.modelcontextprotocol.kotlin.sdk.types.LoggingLevel
Expand Down Expand Up @@ -70,6 +71,8 @@ class ClientConnectionTest : AbstractServerFeaturesTest() {
val pingComplete = CompletableDeferred<Unit>()
val rootsResult = CompletableDeferred<ListRootsResult>()
val sessionId = CompletableDeferred<String>()
val clientImplementation = CompletableDeferred<Implementation?>()
val clientCapabilities = CompletableDeferred<ClientCapabilities?>()
val toolListChanged =
onClientNotification<ToolListChangedNotification>(Method.Defined.NotificationsToolsListChanged)
val resourceListChanged =
Expand Down Expand Up @@ -120,6 +123,12 @@ class ClientConnectionTest : AbstractServerFeaturesTest() {
elicitationComplete.await().params.elicitationId shouldBe "elicit-123"
}
capturedSessionId.shouldNotBeBlank()
withClue("clientImplementation should expose the connected client's name and version") {
clientImplementation.await() shouldBe Implementation(name = "test client", version = "1.0")
}
withClue("clientCapabilities should expose what the client advertised at initialize") {
clientCapabilities.await() shouldBe getClientCapabilities()
}
}
}
}
Expand All @@ -142,6 +151,8 @@ class ClientConnectionTest : AbstractServerFeaturesTest() {
ElicitationCompleteNotification(ElicitationCompleteNotificationParams(elicitationId = "elicit-123")),
)
cap.sessionId.complete(sessionId)
cap.clientImplementation.complete(clientImplementation)
cap.clientCapabilities.complete(clientCapabilities)
}

@Test
Expand Down
2 changes: 2 additions & 0 deletions kotlin-sdk-server/api/kotlin-sdk-server.api
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Expand Up @@ -7,6 +7,8 @@ public abstract interface class io/modelcontextprotocol/kotlin/sdk/server/Client
public static synthetic fun createElicitation$default (Lio/modelcontextprotocol/kotlin/sdk/server/ClientConnection;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Lio/modelcontextprotocol/kotlin/sdk/shared/RequestOptions;Lkotlin/coroutines/Continuation;ILjava/lang/Object;)Ljava/lang/Object;
public abstract fun createMessage (Lio/modelcontextprotocol/kotlin/sdk/types/CreateMessageRequest;Lio/modelcontextprotocol/kotlin/sdk/shared/RequestOptions;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public static synthetic fun createMessage$default (Lio/modelcontextprotocol/kotlin/sdk/server/ClientConnection;Lio/modelcontextprotocol/kotlin/sdk/types/CreateMessageRequest;Lio/modelcontextprotocol/kotlin/sdk/shared/RequestOptions;Lkotlin/coroutines/Continuation;ILjava/lang/Object;)Ljava/lang/Object;
public abstract fun getClientCapabilities ()Lio/modelcontextprotocol/kotlin/sdk/types/ClientCapabilities;
public abstract fun getClientImplementation ()Lio/modelcontextprotocol/kotlin/sdk/types/Implementation;
public abstract fun getSessionId ()Ljava/lang/String;
public abstract fun listRoots (Lio/modelcontextprotocol/kotlin/sdk/types/ListRootsRequest;Lio/modelcontextprotocol/kotlin/sdk/shared/RequestOptions;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
public static synthetic fun listRoots$default (Lio/modelcontextprotocol/kotlin/sdk/server/ClientConnection;Lio/modelcontextprotocol/kotlin/sdk/types/ListRootsRequest;Lio/modelcontextprotocol/kotlin/sdk/shared/RequestOptions;Lkotlin/coroutines/Continuation;ILjava/lang/Object;)Ljava/lang/Object;
Expand Down
19 changes: 19 additions & 0 deletions ...erver/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/server/ClientConnection.kt
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Expand Up @@ -2,6 +2,7 @@ package io.modelcontextprotocol.kotlin.sdk.server

import io.github.oshai.kotlinlogging.KotlinLogging
import io.modelcontextprotocol.kotlin.sdk.shared.RequestOptions
import io.modelcontextprotocol.kotlin.sdk.types.ClientCapabilities
import io.modelcontextprotocol.kotlin.sdk.types.CreateMessageRequest
import io.modelcontextprotocol.kotlin.sdk.types.CreateMessageResult
import io.modelcontextprotocol.kotlin.sdk.types.ElicitRequest
Expand All @@ -11,6 +12,7 @@ import io.modelcontextprotocol.kotlin.sdk.types.ElicitRequestURLParams
import io.modelcontextprotocol.kotlin.sdk.types.ElicitResult
import io.modelcontextprotocol.kotlin.sdk.types.ElicitationCompleteNotification
import io.modelcontextprotocol.kotlin.sdk.types.EmptyResult
import io.modelcontextprotocol.kotlin.sdk.types.Implementation
import io.modelcontextprotocol.kotlin.sdk.types.IncludeContext
import io.modelcontextprotocol.kotlin.sdk.types.ListRootsRequest
import io.modelcontextprotocol.kotlin.sdk.types.ListRootsResult
Expand Down Expand Up @@ -41,6 +43,19 @@ public interface ClientConnection {
*/
public val sessionId: String

/**
* The client's reported [Implementation] (name and version) after initialization.
*/
public val clientImplementation: Implementation?
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@devcrocod devcrocod May 15, 2026

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These could be non-null properties


/**
* The client's reported [ClientCapabilities] after initialization.
*
* Consult before invoking [createMessage], [listRoots], or [createElicitation]
Comment on lines +47 to +54
* to fall back gracefully when a capability is not advertised.
*/
public val clientCapabilities: ClientCapabilities?
Comment on lines +46 to +57

/**
* Sends a server-side notification to the client.
*
Expand Down Expand Up @@ -179,6 +194,10 @@ internal class ClientConnectionImpl(private val session: ServerSession) : Client

override val sessionId: String get() = session.sessionId

override val clientImplementation: Implementation? get() = session.clientVersion

override val clientCapabilities: ClientCapabilities? get() = session.clientCapabilities

private suspend fun <T : RequestResult> request(request: Request, options: RequestOptions? = null): T {
logger.trace { "Sending request to client for session $sessionId: $request" }
return session.request(request, options)
Expand Down
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