Add logout and session/delete agent methods

Implement two stable spec methods across all SDK layers, following the
session/close template:

- logout (clears stored credentials): LogoutRequest/Response, async/sync
  handler interfaces, builder wiring, client methods, @Logout annotation,
  resolver
- session/delete (permanently deletes a stored session): DeleteSession
  Request/Response, handler interfaces, builder wiring, client methods,
  @DeleteSession annotation, resolver; gated on the sessionCapabilities
  .delete flag

Both responses are registered in the DirectResponseHandler whitelist and
covered by handler-invocation and serialization tests.

Author: Mark Pollack

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/AcpAgentSupport.java

@@ -28,10 +28,12 @@
 import com.agentclientprotocol.sdk.agent.support.resolver.CancelNotificationResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.CapabilitiesResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.CloseSessionRequestResolver;
+import com.agentclientprotocol.sdk.agent.support.resolver.DeleteSessionRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.ForkSessionRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.InitializeRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.ListSessionsRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.LoadSessionRequestResolver;
+import com.agentclientprotocol.sdk.agent.support.resolver.LogoutRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.NewSessionRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.PromptContextResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.PromptRequestResolver;
@@ -42,10 +44,12 @@
 import com.agentclientprotocol.sdk.agent.support.resolver.SetSessionModelRequestResolver;
 import com.agentclientprotocol.sdk.annotation.Cancel;
 import com.agentclientprotocol.sdk.annotation.CloseSession;
+import com.agentclientprotocol.sdk.annotation.DeleteSession;
 import com.agentclientprotocol.sdk.annotation.ForkSession;
 import com.agentclientprotocol.sdk.annotation.Initialize;
 import com.agentclientprotocol.sdk.annotation.ListSessions;
 import com.agentclientprotocol.sdk.annotation.LoadSession;
+import com.agentclientprotocol.sdk.annotation.Logout;
 import com.agentclientprotocol.sdk.annotation.NewSession;
 import com.agentclientprotocol.sdk.annotation.Prompt;
 import com.agentclientprotocol.sdk.annotation.ResumeSession;
@@ -201,6 +205,12 @@ private void wireHandlers(AcpAgent.SyncAgentBuilder agentBuilder) {
 					java.util.UUID.randomUUID().toString(), null, null));
 		}
 
+		// Logout handler
+		AcpHandlerMethod logoutHandler = handlers.get("logout");
+		if (logoutHandler != null) {
+			agentBuilder.logoutHandler(req -> invokeHandler(logoutHandler, req, null, null, null));
+		}
+
 		// LoadSession handler
 		AcpHandlerMethod loadSessionHandler = handlers.get("session/load");
 		if (loadSessionHandler != null) {
@@ -241,6 +251,13 @@ private void wireHandlers(AcpAgent.SyncAgentBuilder agentBuilder) {
 					req -> invokeHandler(closeSessionHandler, req, req.sessionId(), null, null));
 		}
 
+		// DeleteSession handler
+		AcpHandlerMethod deleteSessionHandler = handlers.get("session/delete");
+		if (deleteSessionHandler != null) {
+			agentBuilder.deleteSessionHandler(
+					req -> invokeHandler(deleteSessionHandler, req, req.sessionId(), null, null));
+		}
+
 		// ResumeSession handler
 		AcpHandlerMethod resumeSessionHandler = handlers.get("session/resume");
 		if (resumeSessionHandler != null) {
@@ -465,6 +482,10 @@ private void discoverHandlers(Class<?> agentClass, Supplier<Object> beanSupplier
 					handlers.put("initialize", new AcpHandlerMethod(beanSupplier, method, "initialize"));
 					log.debug("Discovered @Initialize handler: {}", method.getName());
 				}
+				if (method.isAnnotationPresent(Logout.class)) {
+					handlers.put("logout", new AcpHandlerMethod(beanSupplier, method, "logout"));
+					log.debug("Discovered @Logout handler: {}", method.getName());
+				}
 				if (method.isAnnotationPresent(NewSession.class)) {
 					handlers.put("session/new", new AcpHandlerMethod(beanSupplier, method, "session/new"));
 					log.debug("Discovered @NewSession handler: {}", method.getName());
@@ -493,6 +514,10 @@ private void discoverHandlers(Class<?> agentClass, Supplier<Object> beanSupplier
 					handlers.put("session/close", new AcpHandlerMethod(beanSupplier, method, "session/close"));
 					log.debug("Discovered @CloseSession handler: {}", method.getName());
 				}
+				if (method.isAnnotationPresent(DeleteSession.class)) {
+					handlers.put("session/delete", new AcpHandlerMethod(beanSupplier, method, "session/delete"));
+					log.debug("Discovered @DeleteSession handler: {}", method.getName());
+				}
 				if (method.isAnnotationPresent(ResumeSession.class)) {
 					handlers.put("session/resume", new AcpHandlerMethod(beanSupplier, method, "session/resume"));
 					log.debug("Discovered @ResumeSession handler: {}", method.getName());
@@ -517,13 +542,15 @@ private void addDefaultResolvers() {
 			// Built-in resolvers (order matters - first match wins)
 			// Custom resolvers added via builder go first
 			argumentResolvers.addResolver(new InitializeRequestResolver());
+			argumentResolvers.addResolver(new LogoutRequestResolver());
 			argumentResolvers.addResolver(new NewSessionRequestResolver());
 			argumentResolvers.addResolver(new LoadSessionRequestResolver());
 			argumentResolvers.addResolver(new PromptRequestResolver());
 			argumentResolvers.addResolver(new SetSessionModeRequestResolver());
 			argumentResolvers.addResolver(new SetSessionModelRequestResolver());
 			argumentResolvers.addResolver(new ListSessionsRequestResolver());
 			argumentResolvers.addResolver(new CloseSessionRequestResolver());
+			argumentResolvers.addResolver(new DeleteSessionRequestResolver());
 			argumentResolvers.addResolver(new ResumeSessionRequestResolver());
 			argumentResolvers.addResolver(new ForkSessionRequestResolver());
 			argumentResolvers.addResolver(new SetSessionConfigOptionRequestResolver());

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/handler/DirectResponseHandler.java

@@ -7,10 +7,12 @@
 import com.agentclientprotocol.sdk.agent.support.AcpInvocationContext;
 import com.agentclientprotocol.sdk.agent.support.AcpMethodParameter;
 import com.agentclientprotocol.sdk.spec.AcpSchema.CloseSessionResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.DeleteSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.ForkSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.InitializeResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.ListSessionsResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.LoadSessionResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.LogoutResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.NewSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.PromptResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.ResumeSessionResponse;
@@ -34,13 +36,15 @@ public class DirectResponseHandler implements ReturnValueHandler {
 	public boolean supportsReturnType(AcpMethodParameter returnType) {
 		Class<?> type = returnType.getParameterType();
 		return InitializeResponse.class.isAssignableFrom(type)
+				|| LogoutResponse.class.isAssignableFrom(type)
 				|| NewSessionResponse.class.isAssignableFrom(type)
 				|| LoadSessionResponse.class.isAssignableFrom(type)
 				|| PromptResponse.class.isAssignableFrom(type)
 				|| SetSessionModeResponse.class.isAssignableFrom(type)
 				|| SetSessionModelResponse.class.isAssignableFrom(type)
 				|| ListSessionsResponse.class.isAssignableFrom(type)
 				|| CloseSessionResponse.class.isAssignableFrom(type)
+				|| DeleteSessionResponse.class.isAssignableFrom(type)
 				|| ResumeSessionResponse.class.isAssignableFrom(type)
 				|| ForkSessionResponse.class.isAssignableFrom(type)
 				|| SetSessionConfigOptionResponse.class.isAssignableFrom(type);

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/resolver/DeleteSessionRequestResolver.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2025-2026 the original author or authors.
+ */
+
+package com.agentclientprotocol.sdk.agent.support.resolver;
+
+import com.agentclientprotocol.sdk.agent.support.AcpInvocationContext;
+import com.agentclientprotocol.sdk.agent.support.AcpMethodParameter;
+import com.agentclientprotocol.sdk.spec.AcpSchema.DeleteSessionRequest;
+
+/**
+ * Resolves {@link DeleteSessionRequest} parameters in delete session handlers.
+ *
+ * @author Mark Pollack
+ * @since 1.0.0
+ */
+public class DeleteSessionRequestResolver implements ArgumentResolver {
+
+	@Override
+	public boolean supportsParameter(AcpMethodParameter parameter) {
+		return DeleteSessionRequest.class.isAssignableFrom(parameter.getParameterType());
+	}
+
+	@Override
+	public Object resolveArgument(AcpMethodParameter parameter, AcpInvocationContext context) {
+		Object request = context.getRequest();
+		if (request instanceof DeleteSessionRequest) {
+			return request;
+		}
+		throw new ArgumentResolutionException(
+				"Expected DeleteSessionRequest but got: " + (request != null ? request.getClass().getName() : "null"));
+	}
+
+}

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/resolver/LogoutRequestResolver.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2025-2026 the original author or authors.
+ */
+
+package com.agentclientprotocol.sdk.agent.support.resolver;
+
+import com.agentclientprotocol.sdk.agent.support.AcpInvocationContext;
+import com.agentclientprotocol.sdk.agent.support.AcpMethodParameter;
+import com.agentclientprotocol.sdk.spec.AcpSchema.LogoutRequest;
+
+/**
+ * Resolves {@link LogoutRequest} parameters in logout handlers.
+ *
+ * @author Mark Pollack
+ * @since 1.0.0
+ */
+public class LogoutRequestResolver implements ArgumentResolver {
+
+	@Override
+	public boolean supportsParameter(AcpMethodParameter parameter) {
+		return LogoutRequest.class.isAssignableFrom(parameter.getParameterType());
+	}
+
+	@Override
+	public Object resolveArgument(AcpMethodParameter parameter, AcpInvocationContext context) {
+		Object request = context.getRequest();
+		if (request instanceof LogoutRequest) {
+			return request;
+		}
+		throw new ArgumentResolutionException(
+				"Expected LogoutRequest but got: " + (request != null ? request.getClass().getName() : "null"));
+	}
+
+}

acp-agent-support/src/test/java/com/agentclientprotocol/sdk/agent/support/AcpAgentSupportTest.java

@@ -12,9 +12,11 @@
 import com.agentclientprotocol.sdk.annotation.AcpAgent;
 import com.agentclientprotocol.sdk.annotation.Cancel;
 import com.agentclientprotocol.sdk.annotation.CloseSession;
+import com.agentclientprotocol.sdk.annotation.DeleteSession;
 import com.agentclientprotocol.sdk.annotation.Initialize;
 import com.agentclientprotocol.sdk.annotation.ListSessions;
 import com.agentclientprotocol.sdk.annotation.LoadSession;
+import com.agentclientprotocol.sdk.annotation.Logout;
 import com.agentclientprotocol.sdk.annotation.NewSession;
 import com.agentclientprotocol.sdk.annotation.Prompt;
 import com.agentclientprotocol.sdk.annotation.ResumeSession;
@@ -25,11 +27,15 @@
 import com.agentclientprotocol.sdk.spec.AcpSchema.CancelNotification;
 import com.agentclientprotocol.sdk.spec.AcpSchema.CloseSessionRequest;
 import com.agentclientprotocol.sdk.spec.AcpSchema.CloseSessionResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.DeleteSessionRequest;
+import com.agentclientprotocol.sdk.spec.AcpSchema.DeleteSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.InitializeRequest;
 import com.agentclientprotocol.sdk.spec.AcpSchema.InitializeResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.ListSessionsRequest;
 import com.agentclientprotocol.sdk.spec.AcpSchema.ListSessionsResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.LoadSessionRequest;
+import com.agentclientprotocol.sdk.spec.AcpSchema.LogoutRequest;
+import com.agentclientprotocol.sdk.spec.AcpSchema.LogoutResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.LoadSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.NewSessionRequest;
 import com.agentclientprotocol.sdk.spec.AcpSchema.NewSessionResponse;
@@ -505,6 +511,85 @@ CloseSessionResponse closeSession(CloseSessionRequest req) {
 		assertThat(resp).isNotNull();
 	}
 
+	@Test
+	void logoutHandlerInvoked() throws Exception {
+		AtomicReference<Boolean> loggedOut = new AtomicReference<>(false);
+
+		@AcpAgent
+		class LogoutAgent {
+
+			@Initialize
+			InitializeResponse init() {
+				return InitializeResponse.ok();
+			}
+
+			@Logout
+			LogoutResponse logout(LogoutRequest req) {
+				loggedOut.set(true);
+				return new LogoutResponse();
+			}
+
+		}
+
+		agentSupport = AcpAgentSupport.create(new LogoutAgent())
+				.transport(transportPair.agentTransport())
+				.requestTimeout(TIMEOUT)
+				.build();
+
+		agentSupport.start();
+		Thread.sleep(100);
+
+		client = AcpClient.async(transportPair.clientTransport())
+				.requestTimeout(TIMEOUT)
+				.build();
+
+		client.initialize(new InitializeRequest(1, null)).block(TIMEOUT);
+		LogoutResponse resp = client.logout(new LogoutRequest()).block(TIMEOUT);
+
+		assertThat(loggedOut.get()).isTrue();
+		assertThat(resp).isNotNull();
+	}
+
+	@Test
+	void deleteSessionHandlerInvoked() throws Exception {
+		AtomicReference<String> deletedSessionId = new AtomicReference<>();
+
+		@AcpAgent
+		class DeleteSessionAgent {
+
+			@Initialize
+			InitializeResponse init() {
+				return InitializeResponse.ok();
+			}
+
+			@DeleteSession
+			DeleteSessionResponse deleteSession(DeleteSessionRequest req) {
+				deletedSessionId.set(req.sessionId());
+				return new DeleteSessionResponse();
+			}
+
+		}
+
+		agentSupport = AcpAgentSupport.create(new DeleteSessionAgent())
+				.transport(transportPair.agentTransport())
+				.requestTimeout(TIMEOUT)
+				.build();
+
+		agentSupport.start();
+		Thread.sleep(100);
+
+		client = AcpClient.async(transportPair.clientTransport())
+				.requestTimeout(TIMEOUT)
+				.build();
+
+		client.initialize(new InitializeRequest(1, null)).block(TIMEOUT);
+		DeleteSessionResponse resp = client.deleteSession(new DeleteSessionRequest("session-to-delete"))
+				.block(TIMEOUT);
+
+		assertThat(deletedSessionId.get()).isEqualTo("session-to-delete");
+		assertThat(resp).isNotNull();
+	}
+
 	@Test
 	void resumeSessionHandlerInvoked() throws Exception {
 		AtomicReference<String> resumedSessionId = new AtomicReference<>();

acp-annotations/src/main/java/com/agentclientprotocol/sdk/annotation/DeleteSession.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2025-2026 the original author or authors.
+ */
+
+package com.agentclientprotocol.sdk.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Marks a method as the handler for deleting ACP sessions.
+ *
+ * <p>The annotated method handles the {@code session/delete} JSON-RPC method,
+ * which is called when a client wants to permanently delete a stored session so
+ * it no longer appears in {@code session/list}.
+ *
+ * <p>Only available if the agent advertises the {@code sessionCapabilities.delete}
+ * capability.
+ *
+ * <p>The method can have the following parameters (all optional):
+ * <ul>
+ *   <li>{@code DeleteSessionRequest} - the delete session request containing the sessionId</li>
+ *   <li>{@code @SessionId String} - the session ID being deleted</li>
+ * </ul>
+ *
+ * <p>The method should return one of:
+ * <ul>
+ *   <li>{@code DeleteSessionResponse} - the delete session response</li>
+ *   <li>{@code Mono<DeleteSessionResponse>} - for async handling</li>
+ *   <li>{@code void} - an empty response is sent automatically</li>
+ * </ul>
+ *
+ * <p>Example usage:
+ * <pre>{@code
+ * @DeleteSession
+ * public DeleteSessionResponse delete(DeleteSessionRequest req) {
+ *     // Permanently remove the stored session
+ *     return new DeleteSessionResponse();
+ * }
+ * }</pre>
+ *
+ * @author Mark Pollack
+ * @since 1.0.0
+ * @see AcpAgent
+ * @see CloseSession
+ */
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface DeleteSession {
+
+}