Hook commands: remove string return, use sendMessage() for prompting

- Command handler now returns Promise<void> instead of Promise<string | undefined>
- To trigger LLM response, use sendMessage() with triggerTurn: true
- Simplify _tryExecuteHookCommand to return boolean

Added example hook and slash command in .pi/:
- .pi/hooks/test-command.ts - /greet command using sendMessage
- .pi/commands/review.md - file-based /review command

.pi/commands/review.md

@@ -0,0 +1,12 @@
+---
+description: Review a file for issues
+---
+Please review the following file for potential issues, bugs, or improvements:
+
+$1
+
+Focus on:
+- Logic errors
+- Edge cases
+- Code style
+- Performance concerns

.pi/hooks/test-command.ts

@@ -0,0 +1,24 @@
+/**
+ * Test hook that registers a /greet command.
+ * Usage: /greet [name]
+ */
+import type { HookAPI } from "@mariozechner/pi-coding-agent/hooks";
+
+export default function (pi: HookAPI) {
+	pi.registerCommand("greet", {
+		description: "Send a greeting message to the LLM",
+		handler: async (ctx) => {
+			const name = ctx.args.trim() || "world";
+
+			// Insert a custom message and trigger LLM response
+			ctx.sendMessage(
+				{
+					customType: "greeting",
+					content: `Hello, ${name}! Please say something nice about them.`,
+					display: true,
+				},
+				true, // triggerTurn - get LLM to respond
+			);
+		},
+	});
+}

packages/coding-agent/docs/session-tree-plan.md

@@ -183,8 +183,7 @@ registerCommand(name: string, options: {
 ```
 
 Handler return:
-- `undefined` - command completed
+- `void` - command completed (use `sendMessage()` with `triggerTurn: true` to prompt LLM)
-- `string` - text to send as prompt (like file-based slash commands)
 
 Wiring (all in AgentSession.prompt()):
 - [x] Add hook commands to autocomplete in interactive-mode

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

@@ -462,15 +462,10 @@ export class AgentSession {
 
 		// Handle hook commands first (if enabled and text is a slash command)
 		if (expandCommands && text.startsWith("/")) {
-			const result = await this._tryExecuteHookCommand(text);
+			const handled = await this._tryExecuteHookCommand(text);
-			if (result.handled) {
+			if (handled) {
-				if (result.prompt) {
+				// Hook command executed, no prompt to send
-					// Hook returned text to use as prompt
+				return;
-					text = result.prompt;
-				} else {
-					// Hook command executed, no prompt to send
-					return;
-				}
 			}
 		}
 
@@ -506,10 +501,10 @@ export class AgentSession {
 	}
 
 	/**
-	 * Try to execute a hook command. Returns whether it was handled and optional prompt text.
+	 * Try to execute a hook command. Returns true if command was found and executed.
 	 */
-	private async _tryExecuteHookCommand(text: string): Promise<{ handled: boolean; prompt?: string }> {
+	private async _tryExecuteHookCommand(text: string): Promise<boolean> {
-		if (!this._hookRunner) return { handled: false };
+		if (!this._hookRunner) return false;
 
 		// Parse command name and args
 		const spaceIndex = text.indexOf(" ");
@@ -517,11 +512,11 @@ export class AgentSession {
 		const args = spaceIndex === -1 ? "" : text.slice(spaceIndex + 1);
 
 		const command = this._hookRunner.getCommand(commandName);
-		if (!command) return { handled: false };
+		if (!command) return false;
 
 		// Get UI context from hook runner (set by mode)
 		const uiContext = this._hookRunner.getUIContext();
-		if (!uiContext) return { handled: false };
+		if (!uiContext) return false;
 
 		// Build command context
 		const cwd = process.cwd();
@@ -541,11 +536,8 @@ export class AgentSession {
 		};
 
 		try {
-			const result = await command.handler(ctx);
+			await command.handler(ctx);
-			if (typeof result === "string") {
+			return true;
-				return { handled: true, prompt: result };
-			}
-			return { handled: true };
 		} catch (err) {
 			// Emit error via hook runner
 			this._hookRunner.emitError({
@@ -553,7 +545,7 @@ export class AgentSession {
 				event: "command",
 				error: err instanceof Error ? err.message : String(err),
 			});
-			return { handled: true };
+			return true;
 		}
 	}
 

packages/coding-agent/src/core/hooks/types.ts

@@ -426,7 +426,7 @@ export interface CommandContext {
 export interface RegisteredCommand {
 	name: string;
 	description?: string;
-	handler: (ctx: CommandContext) => Promise<string | undefined>;
+	handler: (ctx: CommandContext) => Promise<void>;
 }
 
 /**