Add emitLastMessage flag to agent.continue()

When calling continue() with emitLastMessage=true, the agent loop
emits message_start/message_end events for the last message in context.
This allows messages added outside the loop (e.g., hook messages via
sendHookMessage) to trigger proper TUI rendering.

Changes across packages:
- packages/ai: agentLoopContinue() accepts emitLastMessage parameter
- packages/agent: Agent.continue(), transports updated to pass flag
- packages/coding-agent: sendHookMessage passes true when triggerTurn

packages/agent/src/agent.ts

@@ -206,7 +206,12 @@ export class Agent {
 	 * Continue from the current context without adding a new user message.
 	 * Used for retry after overflow recovery when context already has user message or tool results.
 	 */
-	async continue() {
+	/**
+	 * Continue from the current context without adding a new user message.
+	 * Used for retry after overflow recovery when context already has user message or tool results.
+	 * @param emitLastMessage If true, emit message_start/message_end for the last message
+	 */
+	async continue(emitLastMessage?: boolean) {
 		const messages = this._state.messages;
 		if (messages.length === 0) {
 			throw new Error("No messages to continue from");
@@ -217,7 +222,7 @@ export class Agent {
 			throw new Error(`Cannot continue from message role: ${lastMessage.role}`);
 		}
 
-		await this._runAgentLoopContinue();
+		await this._runAgentLoopContinue(emitLastMessage);
 	}
 
 	/**
@@ -234,10 +239,10 @@ export class Agent {
 	/**
 	 * Internal: Continue the agent loop from current context.
 	 */
-	private async _runAgentLoopContinue() {
+	private async _runAgentLoopContinue(emitLastMessage?: boolean) {
 		const { llmMessages, cfg } = await this._prepareRun();
 
-		const events = this.transport.continue(llmMessages, cfg, this.abortController!.signal);
+		const events = this.transport.continue(llmMessages, cfg, this.abortController!.signal, emitLastMessage);
 
 		await this._processEvents(events);
 	}

packages/agent/src/transports/AppTransport.ts

@@ -380,7 +380,7 @@ export class AppTransport implements AgentTransport {
 		}
 	}
 
-	async *continue(messages: Message[], cfg: AgentRunConfig, signal?: AbortSignal) {
+	async *continue(messages: Message[], cfg: AgentRunConfig, signal?: AbortSignal, emitLastMessage?: boolean) {
 		const authToken = await this.options.getAuthToken();
 		if (!authToken) {
 			throw new Error("Auth token is required for AppTransport");
@@ -390,7 +390,7 @@ export class AppTransport implements AgentTransport {
 		const context = this.buildContext(messages, cfg);
 		const pc = this.buildLoopConfig(cfg);
 
-		for await (const ev of agentLoopContinue(context, pc, signal, streamFn as any)) {
+		for await (const ev of agentLoopContinue(context, pc, signal, streamFn as any, emitLastMessage)) {
 			yield ev;
 		}
 	}

packages/agent/src/transports/ProviderTransport.ts

@@ -73,12 +73,12 @@ export class ProviderTransport implements AgentTransport {
 		}
 	}
 
-	async *continue(messages: Message[], cfg: AgentRunConfig, signal?: AbortSignal) {
+	async *continue(messages: Message[], cfg: AgentRunConfig, signal?: AbortSignal, emitLastMessage?: boolean) {
 		const model = this.getModel(cfg);
 		const context = this.buildContext(messages, cfg);
 		const pc = this.buildLoopConfig(model, cfg);
 
-		for await (const ev of agentLoopContinue(context, pc, signal)) {
+		for await (const ev of agentLoopContinue(context, pc, signal, undefined, emitLastMessage)) {
 			yield ev;
 		}
 	}

packages/agent/src/transports/types.ts

@@ -28,5 +28,10 @@ export interface AgentTransport {
 	): AsyncIterable<AgentEvent>;
 
 	/** Continue from current context (no new user message) */
-	continue(messages: Message[], config: AgentRunConfig, signal?: AbortSignal): AsyncIterable<AgentEvent>;
+	continue(
+		messages: Message[],
+		config: AgentRunConfig,
+		signal?: AbortSignal,
+		emitLastMessage?: boolean,
+	): AsyncIterable<AgentEvent>;
 }

packages/ai/src/agent/agent-loop.ts

@@ -40,11 +40,18 @@ export function agentLoop(
  * Used for retry after overflow - context already has user message or tool results.
  * Throws if the last message is not a user message or tool result.
  */
+/**
+ * Continue an agent loop from the current context without adding a new message.
+ * Used for retry after overflow - context already has user message or tool results.
+ * Throws if the last message is not a user message or tool result.
+ * @param emitLastMessage If true, emit message_start/message_end for the last message in context
+ */
 export function agentLoopContinue(
 	context: AgentContext,
 	config: AgentLoopConfig,
 	signal?: AbortSignal,
 	streamFn?: typeof streamSimple,
+	emitLastMessage?: boolean,
 ): EventStream<AgentEvent, AgentContext["messages"]> {
 	// Validate that we can continue from this context
 	const lastMessage = context.messages[context.messages.length - 1];
@@ -63,7 +70,12 @@ export function agentLoopContinue(
 
 		stream.push({ type: "agent_start" });
 		stream.push({ type: "turn_start" });
-		// No user message events - we're continuing from existing context
+
+		// Optionally emit events for the last message (used when message was added outside the loop)
+		if (emitLastMessage) {
+			stream.push({ type: "message_start", message: lastMessage });
+			stream.push({ type: "message_end", message: lastMessage });
+		}
 
 		await runLoop(currentContext, newMessages, config, signal, stream, streamFn);
 	})();

packages/coding-agent/src/core/agent-session.ts

@@ -602,8 +602,8 @@ export class AgentSession {
 				message.display,
 				message.details,
 			);
-			// Start a new turn - agent.continue() works because last message is user role
-			await this.agent.continue();
+			// Start a new turn - emit message events for the hook message so TUI can render it
+			await this.agent.continue(true);
 		} else {
 			// Just append to agent state and session, no turn
 			this.agent.appendMessage(appMessage);