diff --git a/acp-ktor-test/src/commonTest/kotlin/com/agentclientprotocol/FeaturesTest.kt b/acp-ktor-test/src/commonTest/kotlin/com/agentclientprotocol/FeaturesTest.kt
index d80f757..6ca2b83 100644
--- a/acp-ktor-test/src/commonTest/kotlin/com/agentclientprotocol/FeaturesTest.kt
+++ b/acp-ktor-test/src/commonTest/kotlin/com/agentclientprotocol/FeaturesTest.kt
@@ -192,6 +192,37 @@ abstract class FeaturesTest(protocolDriver: ProtocolDriver) : ProtocolDriver by
 
 
 
+    @Test
+    fun `authenticate returns null when agent returns null`() = testWithProtocols { clientProtocol, agentProtocol ->
+        val client = Client(protocol = clientProtocol)
+
+        val agentSupport = object : AgentSupport {
+            override suspend fun initialize(clientInfo: ClientInfo): AgentInfo {
+                return AgentInfo(clientInfo.protocolVersion)
+            }
+
+            override suspend fun authenticate(methodId: AuthMethodId, _meta: JsonElement?): AuthenticateResponse? {
+                // Return null to simulate {"jsonrpc":"2.0","id":3,"result":null} response
+                return null
+            }
+
+            override suspend fun createSession(sessionParameters: SessionCreationParameters): AgentSession {
+                return TestAgentSession()
+            }
+
+            override suspend fun loadSession(sessionId: SessionId, sessionParameters: SessionCreationParameters): AgentSession {
+                return TestAgentSession()
+            }
+        }
+        Agent(agentProtocol, agentSupport)
+
+        client.initialize(ClientInfo())
+
+        // This should correctly handle the null response without throwing an exception
+        val result = client.authenticate(AuthMethodId("test-auth"))
+        assertNull(result, "authenticate should return null when agent returns null")
+    }
+
 //    @Test
 //    fun `call agent extension from client`(): TestResult = testWithProtocols { clientProtocol, agentProtocol ->
 //
diff --git a/acp-model/api/acp-model.api b/acp-model/api/acp-model.api
index 3ab25c3..3bb4a89 100644
--- a/acp-model/api/acp-model.api
+++ b/acp-model/api/acp-model.api
@@ -30,6 +30,12 @@ public class com/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod :
 	public final fun getResponseSerializer ()Lkotlinx/serialization/KSerializer;
 }
 
+public class com/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod : com/agentclientprotocol/model/AcpMethod {
+	public fun <init> (Ljava/lang/String;Lkotlinx/serialization/KSerializer;Lkotlinx/serialization/KSerializer;)V
+	public final fun getRequestSerializer ()Lkotlinx/serialization/KSerializer;
+	public final fun getResponseSerializer ()Lkotlinx/serialization/KSerializer;
+}
+
 public class com/agentclientprotocol/model/AcpMethod$AcpSessionNotificationMethod : com/agentclientprotocol/model/AcpMethod$AcpNotificationMethod {
 	public fun <init> (Ljava/lang/String;Lkotlinx/serialization/KSerializer;)V
 }
@@ -38,11 +44,15 @@ public class com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseMe
 	public fun <init> (Ljava/lang/String;Lkotlinx/serialization/KSerializer;Lkotlinx/serialization/KSerializer;)V
 }
 
+public class com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseNullableMethod : com/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod {
+	public fun <init> (Ljava/lang/String;Lkotlinx/serialization/KSerializer;Lkotlinx/serialization/KSerializer;)V
+}
+
 public final class com/agentclientprotocol/model/AcpMethod$AgentMethods {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$AgentMethods;
 }
 
-public final class com/agentclientprotocol/model/AcpMethod$AgentMethods$Authenticate : com/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod {
+public final class com/agentclientprotocol/model/AcpMethod$AgentMethods$Authenticate : com/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$AgentMethods$Authenticate;
 }
 
@@ -66,11 +76,11 @@ public final class com/agentclientprotocol/model/AcpMethod$AgentMethods$SessionP
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$AgentMethods$SessionPrompt;
 }
 
-public final class com/agentclientprotocol/model/AcpMethod$AgentMethods$SessionSetMode : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseMethod {
+public final class com/agentclientprotocol/model/AcpMethod$AgentMethods$SessionSetMode : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseNullableMethod {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$AgentMethods$SessionSetMode;
 }
 
-public final class com/agentclientprotocol/model/AcpMethod$AgentMethods$SessionSetModel : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseMethod {
+public final class com/agentclientprotocol/model/AcpMethod$AgentMethods$SessionSetModel : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseNullableMethod {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$AgentMethods$SessionSetModel;
 }
 
@@ -82,7 +92,7 @@ public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$FsReadT
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$ClientMethods$FsReadTextFile;
 }
 
-public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$FsWriteTextFile : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseMethod {
+public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$FsWriteTextFile : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseNullableMethod {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$ClientMethods$FsWriteTextFile;
 }
 
@@ -98,7 +108,7 @@ public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$Termina
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalCreate;
 }
 
-public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalKill : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseMethod {
+public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalKill : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseNullableMethod {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalKill;
 }
 
@@ -106,11 +116,11 @@ public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$Termina
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalOutput;
 }
 
-public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalRelease : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseMethod {
+public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalRelease : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseNullableMethod {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalRelease;
 }
 
-public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalWaitForExit : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseMethod {
+public final class com/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalWaitForExit : com/agentclientprotocol/model/AcpMethod$AcpSessionRequestResponseNullableMethod {
 	public static final field INSTANCE Lcom/agentclientprotocol/model/AcpMethod$ClientMethods$TerminalWaitForExit;
 }
 
diff --git a/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Methods.kt b/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Methods.kt
index e39fb2a..d1ceaf7 100644
--- a/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Methods.kt
+++ b/acp-model/src/commonMain/kotlin/com/agentclientprotocol/model/Methods.kt
@@ -20,12 +20,24 @@ public open class AcpMethod(public val methodName: MethodName) {
         public val responseSerializer: KSerializer<TResponse>
     ) : AcpMethod(MethodName(method))
 
+    public open class AcpRequestResponseNullableMethod<TRequest: AcpRequest, TResponse: AcpResponse>(
+        method: String,
+        public val requestSerializer: KSerializer<TRequest>,
+        public val responseSerializer: KSerializer<TResponse>
+    ) : AcpMethod(MethodName(method))
+
     public open class AcpSessionRequestResponseMethod<TRequest, TResponse: AcpResponse>(method: String,
                                                                                         requestSerializer: KSerializer<TRequest>,
                                                                                         responseSerializer: KSerializer<TResponse>
     ) : AcpRequestResponseMethod<TRequest, TResponse>(method, requestSerializer, responseSerializer)
             where TRequest : AcpRequest, TRequest : AcpWithSessionId
 
+    public open class AcpSessionRequestResponseNullableMethod<TRequest, TResponse: AcpResponse>(method: String,
+                                                                                        requestSerializer: KSerializer<TRequest>,
+                                                                                        responseSerializer: KSerializer<TResponse>
+    ) : AcpRequestResponseNullableMethod<TRequest, TResponse>(method, requestSerializer, responseSerializer)
+            where TRequest : AcpRequest, TRequest : AcpWithSessionId
+
     public open class AcpNotificationMethod<TNotification: AcpNotification>(
         method: String,
         public val serializer: KSerializer<TNotification>,
@@ -43,16 +55,16 @@ public open class AcpMethod(public val methodName: MethodName) {
     public object AgentMethods {
         // Agent-side operations (methods that agents can call on clients)
         public object Initialize : AcpRequestResponseMethod<InitializeRequest, InitializeResponse>("initialize", InitializeRequest.serializer(), InitializeResponse.serializer())
-        public object Authenticate : AcpRequestResponseMethod<AuthenticateRequest, AuthenticateResponse>("authenticate", AuthenticateRequest.serializer(), AuthenticateResponse.serializer())
+        public object Authenticate : AcpRequestResponseNullableMethod<AuthenticateRequest, AuthenticateResponse>("authenticate", AuthenticateRequest.serializer(), AuthenticateResponse.serializer())
         public object SessionNew : AcpRequestResponseMethod<NewSessionRequest, NewSessionResponse>("session/new", NewSessionRequest.serializer(), NewSessionResponse.serializer())
         public object SessionLoad : AcpRequestResponseMethod<LoadSessionRequest, LoadSessionResponse>("session/load", LoadSessionRequest.serializer(), LoadSessionResponse.serializer())
 
         // session specific
         public object SessionPrompt : AcpSessionRequestResponseMethod<PromptRequest, PromptResponse>("session/prompt", PromptRequest.serializer(), PromptResponse.serializer())
         public object SessionCancel : AcpSessionNotificationMethod<CancelNotification>("session/cancel", CancelNotification.serializer())
-        public object SessionSetMode : AcpSessionRequestResponseMethod<SetSessionModeRequest, SetSessionModeResponse>("session/set_mode", SetSessionModeRequest.serializer(), SetSessionModeResponse.serializer())
+        public object SessionSetMode : AcpSessionRequestResponseNullableMethod<SetSessionModeRequest, SetSessionModeResponse>("session/set_mode", SetSessionModeRequest.serializer(), SetSessionModeResponse.serializer())
         @UnstableApi
-        public object SessionSetModel : AcpSessionRequestResponseMethod<SetSessionModelRequest, SetSessionModelResponse>("session/set_model", SetSessionModelRequest.serializer(), SetSessionModelResponse.serializer())
+        public object SessionSetModel : AcpSessionRequestResponseNullableMethod<SetSessionModelRequest, SetSessionModelResponse>("session/set_model", SetSessionModelRequest.serializer(), SetSessionModelResponse.serializer())
     }
 
     public object ClientMethods {
@@ -62,12 +74,12 @@ public open class AcpMethod(public val methodName: MethodName) {
 
         // extensions
         public object FsReadTextFile : AcpSessionRequestResponseMethod<ReadTextFileRequest, ReadTextFileResponse>("fs/read_text_file", ReadTextFileRequest.serializer(), ReadTextFileResponse.serializer())
-        public object FsWriteTextFile : AcpSessionRequestResponseMethod<WriteTextFileRequest, WriteTextFileResponse>("fs/write_text_file", WriteTextFileRequest.serializer(), WriteTextFileResponse.serializer())
+        public object FsWriteTextFile : AcpSessionRequestResponseNullableMethod<WriteTextFileRequest, WriteTextFileResponse>("fs/write_text_file", WriteTextFileRequest.serializer(), WriteTextFileResponse.serializer())
         public object TerminalCreate : AcpSessionRequestResponseMethod<CreateTerminalRequest, CreateTerminalResponse>("terminal/create", CreateTerminalRequest.serializer(), CreateTerminalResponse.serializer())
         public object TerminalOutput : AcpSessionRequestResponseMethod<TerminalOutputRequest, TerminalOutputResponse>("terminal/output", TerminalOutputRequest.serializer(), TerminalOutputResponse.serializer())
-        public object TerminalRelease : AcpSessionRequestResponseMethod<ReleaseTerminalRequest, ReleaseTerminalResponse>("terminal/release", ReleaseTerminalRequest.serializer(), ReleaseTerminalResponse.serializer())
-        public object TerminalWaitForExit : AcpSessionRequestResponseMethod<WaitForTerminalExitRequest, WaitForTerminalExitResponse>("terminal/wait_for_exit", WaitForTerminalExitRequest.serializer(), WaitForTerminalExitResponse.serializer())
-        public object TerminalKill : AcpSessionRequestResponseMethod<KillTerminalCommandRequest, KillTerminalCommandResponse>("terminal/kill", KillTerminalCommandRequest.serializer(), KillTerminalCommandResponse.serializer())
+        public object TerminalRelease : AcpSessionRequestResponseNullableMethod<ReleaseTerminalRequest, ReleaseTerminalResponse>("terminal/release", ReleaseTerminalRequest.serializer(), ReleaseTerminalResponse.serializer())
+        public object TerminalWaitForExit : AcpSessionRequestResponseNullableMethod<WaitForTerminalExitRequest, WaitForTerminalExitResponse>("terminal/wait_for_exit", WaitForTerminalExitRequest.serializer(), WaitForTerminalExitResponse.serializer())
+        public object TerminalKill : AcpSessionRequestResponseNullableMethod<KillTerminalCommandRequest, KillTerminalCommandResponse>("terminal/kill", KillTerminalCommandRequest.serializer(), KillTerminalCommandResponse.serializer())
     }
 
 
diff --git a/acp/api/acp.api b/acp/api/acp.api
index f75626e..21a5ad5 100644
--- a/acp/api/acp.api
+++ b/acp/api/acp.api
@@ -272,6 +272,7 @@ public final class com/agentclientprotocol/protocol/Protocol : com/agentclientpr
 	public fun sendRequestRaw-TF-lsE4 (Ljava/lang/String;Lkotlinx/serialization/json/JsonElement;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public fun setNotificationHandlerRaw (Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
 	public fun setRequestHandlerRaw (Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
+	public fun setRequestHandlerRaw (Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
 	public final fun start ()V
 	public fun toString ()Ljava/lang/String;
 }
@@ -293,13 +294,17 @@ public final class com/agentclientprotocol/protocol/Protocol_extensionsKt {
 	public static final fun getJsonRpcRequest (Lkotlin/coroutines/CoroutineContext;)Lcom/agentclientprotocol/rpc/JsonRpcRequest;
 	public static final fun invoke (Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpNotification;)V
 	public static final fun invoke (Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpRequest;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+	public static final fun invoke (Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpRequest;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun sendNotification (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lcom/agentclientprotocol/model/AcpNotification;)V
 	public static synthetic fun sendNotification$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lcom/agentclientprotocol/model/AcpNotification;ILjava/lang/Object;)V
 	public static final fun sendRequest (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lcom/agentclientprotocol/model/AcpRequest;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+	public static final fun sendRequestNullable (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lcom/agentclientprotocol/model/AcpRequest;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun setNotificationHandler (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
 	public static synthetic fun setNotificationHandler$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
 	public static final fun setRequestHandler (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
+	public static final fun setRequestHandler (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
 	public static synthetic fun setRequestHandler$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
+	public static synthetic fun setRequestHandler$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
 }
 
 public abstract interface class com/agentclientprotocol/protocol/RpcMethodsOperations {
@@ -310,7 +315,9 @@ public abstract interface class com/agentclientprotocol/protocol/RpcMethodsOpera
 	public abstract fun setNotificationHandlerRaw (Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
 	public static synthetic fun setNotificationHandlerRaw$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
 	public abstract fun setRequestHandlerRaw (Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
+	public abstract fun setRequestHandlerRaw (Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)V
 	public static synthetic fun setRequestHandlerRaw$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
+	public static synthetic fun setRequestHandlerRaw$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
 }
 
 public final class com/agentclientprotocol/protocol/RpcMethodsOperations$DefaultImpls {
@@ -318,6 +325,7 @@ public final class com/agentclientprotocol/protocol/RpcMethodsOperations$Default
 	public static synthetic fun sendRequestRaw-TF-lsE4$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Ljava/lang/String;Lkotlinx/serialization/json/JsonElement;Lkotlin/coroutines/Continuation;ILjava/lang/Object;)Ljava/lang/Object;
 	public static synthetic fun setNotificationHandlerRaw$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpNotificationMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
 	public static synthetic fun setRequestHandlerRaw$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
+	public static synthetic fun setRequestHandlerRaw$default (Lcom/agentclientprotocol/protocol/RpcMethodsOperations;Lcom/agentclientprotocol/model/AcpMethod$AcpRequestResponseNullableMethod;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)V
 }
 
 public abstract class com/agentclientprotocol/transport/BaseTransport : com/agentclientprotocol/transport/Transport {
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/AgentSupport.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/AgentSupport.kt
index 4bd99b0..3e6c437 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/AgentSupport.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/AgentSupport.kt
@@ -9,7 +9,7 @@ import kotlinx.serialization.json.JsonElement
 
 public interface AgentSupport {
     public suspend fun initialize(clientInfo: ClientInfo): AgentInfo
-    public suspend fun authenticate(methodId: AuthMethodId, _meta: JsonElement?): AuthenticateResponse = AuthenticateResponse()
+    public suspend fun authenticate(methodId: AuthMethodId, _meta: JsonElement?): AuthenticateResponse? = AuthenticateResponse()
     public suspend fun createSession(sessionParameters: SessionCreationParameters): AgentSession
     public suspend fun loadSession(sessionId: SessionId, sessionParameters: SessionCreationParameters): AgentSession
 }
\ No newline at end of file
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/RemoteClientSessionOperations.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/RemoteClientSessionOperations.kt
index 947fb66..503b8e3 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/RemoteClientSessionOperations.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/agent/RemoteClientSessionOperations.kt
@@ -36,7 +36,7 @@ internal class RemoteClientSessionOperations(private val rpc: RpcMethodsOperatio
         path: String,
         content: String,
         _meta: JsonElement?,
-    ): WriteTextFileResponse {
+    ): WriteTextFileResponse? {
         if (clientCapabilities.fs?.writeTextFile != true) error("Client does not support fs.writeTextFile capability")
         return AcpMethod.ClientMethods.FsWriteTextFile(rpc, WriteTextFileRequest(sessionId, path, content, _meta))
     }
@@ -64,7 +64,7 @@ internal class RemoteClientSessionOperations(private val rpc: RpcMethodsOperatio
     override suspend fun terminalRelease(
         terminalId: String,
         _meta: JsonElement?,
-    ): ReleaseTerminalResponse {
+    ): ReleaseTerminalResponse? {
         if (!clientCapabilities.terminal) error("Client does not support terminal capability")
         return AcpMethod.ClientMethods.TerminalRelease(rpc, ReleaseTerminalRequest(sessionId, terminalId, _meta))
     }
@@ -72,7 +72,7 @@ internal class RemoteClientSessionOperations(private val rpc: RpcMethodsOperatio
     override suspend fun terminalWaitForExit(
         terminalId: String,
         _meta: JsonElement?,
-    ): WaitForTerminalExitResponse {
+    ): WaitForTerminalExitResponse? {
         if (!clientCapabilities.terminal) error("Client does not support terminal capability")
         return AcpMethod.ClientMethods.TerminalWaitForExit(rpc, WaitForTerminalExitRequest(sessionId, terminalId, _meta))
     }
@@ -80,7 +80,7 @@ internal class RemoteClientSessionOperations(private val rpc: RpcMethodsOperatio
     override suspend fun terminalKill(
         terminalId: String,
         _meta: JsonElement?,
-    ): KillTerminalCommandResponse {
+    ): KillTerminalCommandResponse? {
         if (!clientCapabilities.terminal) error("Client does not support terminal capability")
         return AcpMethod.ClientMethods.TerminalKill(rpc, KillTerminalCommandRequest(sessionId, terminalId, _meta))
     }
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/client/Client.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/client/Client.kt
index 0841b58..e180bc1 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/client/Client.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/client/Client.kt
@@ -148,7 +148,7 @@ public class Client(
      * Performs authentication of the agent with the specified [methodId].
      * The method may throw an exception if the authentication fails.
      */
-    public suspend fun authenticate(methodId: AuthMethodId, _meta: JsonElement? = null): AuthenticateResponse {
+    public suspend fun authenticate(methodId: AuthMethodId, _meta: JsonElement? = null): AuthenticateResponse? {
         return AcpMethod.AgentMethods.Authenticate(protocol, AuthenticateRequest(methodId, _meta))
     }
 
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSession.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSession.kt
index 0c2564e..ca03429 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSession.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSession.kt
@@ -49,7 +49,7 @@ public interface ClientSession {
     /**
      * Changes the session mode to the specified mode. The real change will be reported by an agent via [currentMode] and [ClientSessionOperations.notify].
      */
-    public suspend fun setMode(modeId: SessionModeId, _meta: JsonElement? = null): SetSessionModeResponse
+    public suspend fun setMode(modeId: SessionModeId, _meta: JsonElement? = null): SetSessionModeResponse?
 
     /**
      * The flag indicates whether the agent supports the session model changing.
@@ -75,5 +75,5 @@ public interface ClientSession {
      * Changes the session model to the specified model. The real change will be reported by an agent via [currentModel] and [ClientSessionOperations.notify].
      */
     @UnstableApi
-    public suspend fun setModel(modelId: ModelId, _meta: JsonElement? = null): SetSessionModelResponse
+    public suspend fun setModel(modelId: ModelId, _meta: JsonElement? = null): SetSessionModelResponse?
 }
\ No newline at end of file
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSessionImpl.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSessionImpl.kt
index bd2135e..a5b4d23 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSessionImpl.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/client/ClientSessionImpl.kt
@@ -96,7 +96,7 @@ internal class ClientSessionImpl(
         get() = _currentMode
 
 
-    override suspend fun setMode(modeId: SessionModeId, _meta: JsonElement?): SetSessionModeResponse {
+    override suspend fun setMode(modeId: SessionModeId, _meta: JsonElement?): SetSessionModeResponse? {
         return AcpMethod.AgentMethods.SessionSetMode(protocol, SetSessionModeRequest(sessionId, modeId, _meta))
     }
 
@@ -113,7 +113,7 @@ internal class ClientSessionImpl(
         get() = _currentModel
 
     @UnstableApi
-    override suspend fun setModel(modelId: ModelId, _meta: JsonElement?): SetSessionModelResponse {
+    override suspend fun setModel(modelId: ModelId, _meta: JsonElement?): SetSessionModelResponse? {
         return AcpMethod.AgentMethods.SessionSetModel(protocol, SetSessionModelRequest(sessionId, modelId, _meta))
     }
 
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/common/FileSystemOperations.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/common/FileSystemOperations.kt
index 262124a..7840589 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/common/FileSystemOperations.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/common/FileSystemOperations.kt
@@ -13,7 +13,7 @@ public interface FileSystemOperations {
     }
     public suspend fun fsWriteTextFile(path: String,
                                        content: String,
-                                       _meta: JsonElement? = null): WriteTextFileResponse {
+                                       _meta: JsonElement? = null): WriteTextFileResponse? {
         throw NotImplementedError("Must be implemented by client when advertising fs.writeTextFile capability")
     }
 }
\ No newline at end of file
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/common/TerminalOperations.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/common/TerminalOperations.kt
index c170456..9af9e8c 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/common/TerminalOperations.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/common/TerminalOperations.kt
@@ -19,17 +19,17 @@ public interface TerminalOperations {
     }
 
     public suspend fun terminalRelease(terminalId: String,
-                                      _meta: JsonElement? = null): ReleaseTerminalResponse {
+                                      _meta: JsonElement? = null): ReleaseTerminalResponse? {
         throw NotImplementedError("Must be implemented by client when advertising terminal capability")
     }
 
     public suspend fun terminalWaitForExit(terminalId: String,
-                                      _meta: JsonElement? = null): WaitForTerminalExitResponse {
+                                      _meta: JsonElement? = null): WaitForTerminalExitResponse? {
         throw NotImplementedError("Must be implemented by client when advertising terminal capability")
     }
 
     public suspend fun terminalKill(terminalId: String,
-                                      _meta: JsonElement? = null): KillTerminalCommandResponse {
+                                      _meta: JsonElement? = null): KillTerminalCommandResponse? {
         throw NotImplementedError("Must be implemented by client when advertising terminal capability")
     }
 }
\ No newline at end of file
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.extensions.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.extensions.kt
index cb488de..533622e 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.extensions.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.extensions.kt
@@ -7,6 +7,7 @@ import com.agentclientprotocol.model.AcpResponse
 import com.agentclientprotocol.rpc.ACPJson
 import com.agentclientprotocol.rpc.JsonRpcRequest
 import kotlinx.serialization.json.JsonNull
+import kotlinx.serialization.json.buildJsonObject
 import kotlinx.serialization.json.decodeFromJsonElement
 import kotlinx.serialization.json.encodeToJsonElement
 import kotlin.coroutines.AbstractCoroutineContextElement
@@ -26,6 +27,16 @@ public suspend fun <TRequest : AcpRequest, TResponse : AcpResponse> RpcMethodsOp
     return ACPJson.decodeFromJsonElement(method.responseSerializer, responseJson)
 }
 
+public suspend fun <TRequest : AcpRequest, TResponse : AcpResponse> RpcMethodsOperations.sendRequestNullable(
+    method: AcpMethod.AcpRequestResponseNullableMethod<TRequest, TResponse>,
+    request: TRequest?
+): TResponse? {
+    val params = request?.let { ACPJson.encodeToJsonElement(method.requestSerializer, request) }
+    val responseJson = this.sendRequestRaw(method.methodName, params)
+    if (responseJson is JsonNull) return null
+    return ACPJson.decodeFromJsonElement(method.responseSerializer, responseJson)
+}
+
 /**
  * Send a notification (no response expected).
  */
@@ -51,6 +62,21 @@ public fun<TRequest : AcpRequest, TResponse : AcpResponse> RpcMethodsOperations.
         ACPJson.encodeToJsonElement(method.responseSerializer, responseObject)
     }
 }
+
+/**
+ * Register a handler for incoming requests.
+ */
+public fun<TRequest : AcpRequest, TResponse : AcpResponse> RpcMethodsOperations.setRequestHandler(
+    method: AcpMethod.AcpRequestResponseNullableMethod<TRequest, TResponse>,
+    additionalContext: CoroutineContext = EmptyCoroutineContext,
+    handler: suspend (TRequest) -> TResponse?
+) {
+    this.setRequestHandlerRaw(method, additionalContext) { request ->
+        val requestParams = ACPJson.decodeFromJsonElement(method.requestSerializer, request.params ?: JsonNull)
+        val responseObject = handler(requestParams)
+        responseObject?.let { ACPJson.encodeToJsonElement(method.responseSerializer, responseObject) } ?: JsonNull
+    }
+}
 /**
  * Register a handler for incoming notifications.
  */
@@ -69,6 +95,10 @@ public suspend operator fun <TRequest: AcpRequest, TResponse: AcpResponse> AcpMe
     return rpc.sendRequest(this, request)
 }
 
+public suspend operator fun <TRequest: AcpRequest, TResponse: AcpResponse> AcpMethod.AcpRequestResponseNullableMethod<TRequest, TResponse>.invoke(rpc: RpcMethodsOperations, request: TRequest): TResponse? {
+    return rpc.sendRequestNullable(this, request)
+}
+
 public operator fun <TNotification : AcpNotification> AcpMethod.AcpNotificationMethod<TNotification>.invoke(rpc: RpcMethodsOperations, notification: TNotification) {
     return rpc.sendNotification(this, notification)
 }
diff --git a/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.kt b/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.kt
index b372ab5..334c9eb 100644
--- a/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.kt
+++ b/acp/src/commonMain/kotlin/com/agentclientprotocol/protocol/Protocol.kt
@@ -87,6 +87,12 @@ public interface RpcMethodsOperations {
         handler: suspend (JsonRpcRequest) -> JsonElement?
     )
 
+    public fun setRequestHandlerRaw(
+        method: AcpMethod.AcpRequestResponseNullableMethod<*, *>,
+        additionalContext: CoroutineContext = EmptyCoroutineContext,
+        handler: suspend (JsonRpcRequest) -> JsonElement?
+    )
+
     public fun setNotificationHandlerRaw(
         method: AcpMethod.AcpNotificationMethod<*>,
         additionalContext: CoroutineContext = EmptyCoroutineContext,
@@ -264,6 +270,22 @@ public class Protocol(
         method: AcpMethod.AcpRequestResponseMethod<*, *>,
         additionalContext: CoroutineContext,
         handler: suspend (JsonRpcRequest) -> JsonElement?
+    ) {
+        doSetRequestHandlerRaw(method, additionalContext, handler)
+    }
+
+    override fun setRequestHandlerRaw(
+        method: AcpMethod.AcpRequestResponseNullableMethod<*, *>,
+        additionalContext: CoroutineContext,
+        handler: suspend (JsonRpcRequest) -> JsonElement?
+    ) {
+        doSetRequestHandlerRaw(method, additionalContext, handler)
+    }
+
+    private fun doSetRequestHandlerRaw(
+        method: AcpMethod,
+        additionalContext: CoroutineContext,
+        handler: suspend (JsonRpcRequest) -> JsonElement?
     ) {
         requestHandlers.update {
             it.put(method.methodName) { params ->
diff --git a/build.gradle.kts b/build.gradle.kts
index b011328..fe7cdd7 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -7,7 +7,7 @@ plugins {
 private val buildNumber: String? = System.getenv("GITHUB_RUN_NUMBER")
 private val isReleasePublication = System.getenv("RELEASE_PUBLICATION")?.toBoolean() ?: false
 
-private val baseVersion = "0.10.2"
+private val baseVersion = "0.10.3"
 
 allprojects {
     group = "com.agentclientprotocol"
diff --git a/samples/kotlin-acp-client-sample/src/main/kotlin/com/agentclientprotocol/samples/SimpleAgentSupport.kt b/samples/kotlin-acp-client-sample/src/main/kotlin/com/agentclientprotocol/samples/SimpleAgentSupport.kt
index a77b3a1..b3ed8a5 100644
--- a/samples/kotlin-acp-client-sample/src/main/kotlin/com/agentclientprotocol/samples/SimpleAgentSupport.kt
+++ b/samples/kotlin-acp-client-sample/src/main/kotlin/com/agentclientprotocol/samples/SimpleAgentSupport.kt
@@ -180,7 +180,7 @@ class SimpleAgentSession(
 
             emit(Event.SessionUpdateEvent(
                 SessionUpdate.AgentMessageChunk(
-                    ContentBlock.Text("\nTerminal output: ${outputResponse.output} (exit code: ${exitResponse.exitCode})")
+                    ContentBlock.Text("\nTerminal output: ${outputResponse.output} (exit code: ${exitResponse?.exitCode})")
                 )
             ))
         } catch (e: Exception) {