Add complete annotation set for Phase 5B.1

New annotations:
- @LoadSession - handler for session/load requests
- @cancel - handler for session/cancel notifications
- @SetSessionMode - handler for session/set_mode requests
- @SetSessionModel - handler for session/set_model requests
- @AcpExceptionHandler - method-level exception handling (annotation only)

New argument resolvers:
- LoadSessionRequestResolver
- SetSessionModeRequestResolver
- SetSessionModelRequestResolver
- CancelNotificationResolver

Updated DirectResponseHandler to support all response types.
Updated AcpAgentSupport to discover and wire new handlers.

Added tests for @LoadSession, @SetSessionMode, and @cancel annotations.

Author: Mark Pollack

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

@@ -26,23 +26,38 @@
 import com.agentclientprotocol.sdk.agent.support.interceptor.InterceptorChain;
 import com.agentclientprotocol.sdk.agent.support.resolver.ArgumentResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.ArgumentResolverComposite;
+import com.agentclientprotocol.sdk.agent.support.resolver.CancelNotificationResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.CapabilitiesResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.InitializeRequestResolver;
+import com.agentclientprotocol.sdk.agent.support.resolver.LoadSessionRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.NewSessionRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.PromptContextResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.PromptRequestResolver;
 import com.agentclientprotocol.sdk.agent.support.resolver.SessionIdResolver;
+import com.agentclientprotocol.sdk.agent.support.resolver.SetSessionModeRequestResolver;
+import com.agentclientprotocol.sdk.agent.support.resolver.SetSessionModelRequestResolver;
+import com.agentclientprotocol.sdk.annotation.Cancel;
 import com.agentclientprotocol.sdk.annotation.Initialize;
+import com.agentclientprotocol.sdk.annotation.LoadSession;
 import com.agentclientprotocol.sdk.annotation.NewSession;
 import com.agentclientprotocol.sdk.annotation.Prompt;
+import com.agentclientprotocol.sdk.annotation.SetSessionMode;
+import com.agentclientprotocol.sdk.annotation.SetSessionModel;
 import com.agentclientprotocol.sdk.capabilities.NegotiatedCapabilities;
 import com.agentclientprotocol.sdk.spec.AcpAgentTransport;
+import com.agentclientprotocol.sdk.spec.AcpSchema.CancelNotification;
 import com.agentclientprotocol.sdk.spec.AcpSchema.InitializeRequest;
 import com.agentclientprotocol.sdk.spec.AcpSchema.InitializeResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.LoadSessionRequest;
+import com.agentclientprotocol.sdk.spec.AcpSchema.LoadSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.NewSessionRequest;
 import com.agentclientprotocol.sdk.spec.AcpSchema.NewSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.PromptRequest;
 import com.agentclientprotocol.sdk.spec.AcpSchema.PromptResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.SetSessionModeRequest;
+import com.agentclientprotocol.sdk.spec.AcpSchema.SetSessionModeResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.SetSessionModelRequest;
+import com.agentclientprotocol.sdk.spec.AcpSchema.SetSessionModelResponse;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -188,6 +203,12 @@ private void wireHandlers(AcpAgent.SyncAgentBuilder agentBuilder) {
 					java.util.UUID.randomUUID().toString(), null, null));
 		}
 
+		// LoadSession handler
+		AcpHandlerMethod loadSessionHandler = handlers.get("session/load");
+		if (loadSessionHandler != null) {
+			agentBuilder.loadSessionHandler(req -> invokeHandler(loadSessionHandler, req, req.sessionId(), null, null));
+		}
+
 		// Prompt handler
 		AcpHandlerMethod promptHandler = handlers.get("session/prompt");
 		if (promptHandler != null) {
@@ -196,6 +217,26 @@ private void wireHandlers(AcpAgent.SyncAgentBuilder agentBuilder) {
 				return invokeHandler(promptHandler, req, req.sessionId(), syncContext, caps);
 			});
 		}
+
+		// SetSessionMode handler
+		AcpHandlerMethod setModeHandler = handlers.get("session/set_mode");
+		if (setModeHandler != null) {
+			agentBuilder.setSessionModeHandler(req -> invokeHandler(setModeHandler, req, req.sessionId(), null, null));
+		}
+
+		// SetSessionModel handler
+		AcpHandlerMethod setModelHandler = handlers.get("session/set_model");
+		if (setModelHandler != null) {
+			agentBuilder.setSessionModelHandler(req -> invokeHandler(setModelHandler, req, req.sessionId(), null, null));
+		}
+
+		// Cancel handler
+		AcpHandlerMethod cancelHandler = handlers.get("session/cancel");
+		if (cancelHandler != null) {
+			agentBuilder.cancelHandler(notification -> {
+				invokeHandler(cancelHandler, notification, notification.sessionId(), null, null);
+			});
+		}
 	}
 
 	@SuppressWarnings("unchecked")
@@ -396,10 +437,26 @@ private void discoverHandlers(Class<?> agentClass, Supplier<Object> beanSupplier
 					handlers.put("session/new", new AcpHandlerMethod(beanSupplier, method, "session/new"));
 					log.debug("Discovered @NewSession handler: {}", method.getName());
 				}
+				if (method.isAnnotationPresent(LoadSession.class)) {
+					handlers.put("session/load", new AcpHandlerMethod(beanSupplier, method, "session/load"));
+					log.debug("Discovered @LoadSession handler: {}", method.getName());
+				}
 				if (method.isAnnotationPresent(Prompt.class)) {
 					handlers.put("session/prompt", new AcpHandlerMethod(beanSupplier, method, "session/prompt"));
 					log.debug("Discovered @Prompt handler: {}", method.getName());
 				}
+				if (method.isAnnotationPresent(SetSessionMode.class)) {
+					handlers.put("session/set_mode", new AcpHandlerMethod(beanSupplier, method, "session/set_mode"));
+					log.debug("Discovered @SetSessionMode handler: {}", method.getName());
+				}
+				if (method.isAnnotationPresent(SetSessionModel.class)) {
+					handlers.put("session/set_model", new AcpHandlerMethod(beanSupplier, method, "session/set_model"));
+					log.debug("Discovered @SetSessionModel handler: {}", method.getName());
+				}
+				if (method.isAnnotationPresent(Cancel.class)) {
+					handlers.put("session/cancel", new AcpHandlerMethod(beanSupplier, method, "session/cancel"));
+					log.debug("Discovered @Cancel handler: {}", method.getName());
+				}
 			}
 		}
 
@@ -408,7 +465,11 @@ private void addDefaultResolvers() {
 			// Custom resolvers added via builder go first
 			argumentResolvers.addResolver(new InitializeRequestResolver());
 			argumentResolvers.addResolver(new NewSessionRequestResolver());
+			argumentResolvers.addResolver(new LoadSessionRequestResolver());
 			argumentResolvers.addResolver(new PromptRequestResolver());
+			argumentResolvers.addResolver(new SetSessionModeRequestResolver());
+			argumentResolvers.addResolver(new SetSessionModelRequestResolver());
+			argumentResolvers.addResolver(new CancelNotificationResolver());
 			argumentResolvers.addResolver(new PromptContextResolver());
 			argumentResolvers.addResolver(new SessionIdResolver());
 			argumentResolvers.addResolver(new CapabilitiesResolver());

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

@@ -7,14 +7,18 @@
 import com.agentclientprotocol.sdk.agent.support.AcpInvocationContext;
 import com.agentclientprotocol.sdk.agent.support.AcpMethodParameter;
 import com.agentclientprotocol.sdk.spec.AcpSchema.InitializeResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.LoadSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.NewSessionResponse;
 import com.agentclientprotocol.sdk.spec.AcpSchema.PromptResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.SetSessionModeResponse;
+import com.agentclientprotocol.sdk.spec.AcpSchema.SetSessionModelResponse;
 
 /**
  * Handles direct protocol response types that need no conversion.
  *
  * <p>Supports {@link InitializeResponse}, {@link NewSessionResponse},
- * and {@link PromptResponse}.
+ * {@link LoadSessionResponse}, {@link PromptResponse}, {@link SetSessionModeResponse},
+ * and {@link SetSessionModelResponse}.
  *
  * @author Mark Pollack
  * @since 1.0.0
@@ -26,7 +30,10 @@ public boolean supportsReturnType(AcpMethodParameter returnType) {
 		Class<?> type = returnType.getParameterType();
 		return InitializeResponse.class.isAssignableFrom(type)
 				|| NewSessionResponse.class.isAssignableFrom(type)
-				|| PromptResponse.class.isAssignableFrom(type);
+				|| LoadSessionResponse.class.isAssignableFrom(type)
+				|| PromptResponse.class.isAssignableFrom(type)
+				|| SetSessionModeResponse.class.isAssignableFrom(type)
+				|| SetSessionModelResponse.class.isAssignableFrom(type);
 	}
 
 	@Override

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/resolver/CancelNotificationResolver.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.CancelNotification;
+
+/**
+ * Resolves {@link CancelNotification} parameters in cancel handlers.
+ *
+ * @author Mark Pollack
+ * @since 1.0.0
+ */
+public class CancelNotificationResolver implements ArgumentResolver {
+
+	@Override
+	public boolean supportsParameter(AcpMethodParameter parameter) {
+		return CancelNotification.class.isAssignableFrom(parameter.getParameterType());
+	}
+
+	@Override
+	public Object resolveArgument(AcpMethodParameter parameter, AcpInvocationContext context) {
+		Object request = context.getRequest();
+		if (request instanceof CancelNotification) {
+			return request;
+		}
+		throw new ArgumentResolutionException("Expected CancelNotification but got: "
+				+ (request != null ? request.getClass().getName() : "null"));
+	}
+
+}

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/resolver/LoadSessionRequestResolver.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.LoadSessionRequest;
+
+/**
+ * Resolves {@link LoadSessionRequest} parameters in load session handlers.
+ *
+ * @author Mark Pollack
+ * @since 1.0.0
+ */
+public class LoadSessionRequestResolver implements ArgumentResolver {
+
+	@Override
+	public boolean supportsParameter(AcpMethodParameter parameter) {
+		return LoadSessionRequest.class.isAssignableFrom(parameter.getParameterType());
+	}
+
+	@Override
+	public Object resolveArgument(AcpMethodParameter parameter, AcpInvocationContext context) {
+		Object request = context.getRequest();
+		if (request instanceof LoadSessionRequest) {
+			return request;
+		}
+		throw new ArgumentResolutionException(
+				"Expected LoadSessionRequest but got: " + (request != null ? request.getClass().getName() : "null"));
+	}
+
+}

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/resolver/SetSessionModeRequestResolver.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.SetSessionModeRequest;
+
+/**
+ * Resolves {@link SetSessionModeRequest} parameters in set session mode handlers.
+ *
+ * @author Mark Pollack
+ * @since 1.0.0
+ */
+public class SetSessionModeRequestResolver implements ArgumentResolver {
+
+	@Override
+	public boolean supportsParameter(AcpMethodParameter parameter) {
+		return SetSessionModeRequest.class.isAssignableFrom(parameter.getParameterType());
+	}
+
+	@Override
+	public Object resolveArgument(AcpMethodParameter parameter, AcpInvocationContext context) {
+		Object request = context.getRequest();
+		if (request instanceof SetSessionModeRequest) {
+			return request;
+		}
+		throw new ArgumentResolutionException("Expected SetSessionModeRequest but got: "
+				+ (request != null ? request.getClass().getName() : "null"));
+	}
+
+}

acp-agent-support/src/main/java/com/agentclientprotocol/sdk/agent/support/resolver/SetSessionModelRequestResolver.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.SetSessionModelRequest;
+
+/**
+ * Resolves {@link SetSessionModelRequest} parameters in set session model handlers.
+ *
+ * @author Mark Pollack
+ * @since 1.0.0
+ */
+public class SetSessionModelRequestResolver implements ArgumentResolver {
+
+	@Override
+	public boolean supportsParameter(AcpMethodParameter parameter) {
+		return SetSessionModelRequest.class.isAssignableFrom(parameter.getParameterType());
+	}
+
+	@Override
+	public Object resolveArgument(AcpMethodParameter parameter, AcpInvocationContext context) {
+		Object request = context.getRequest();
+		if (request instanceof SetSessionModelRequest) {
+			return request;
+		}
+		throw new ArgumentResolutionException("Expected SetSessionModelRequest but got: "
+				+ (request != null ? request.getClass().getName() : "null"));
+	}
+
+}