Refactor: shared exec utility, rename CustomMessageRenderer to HookMessageRenderer

- Extract execCommand to src/core/exec.ts, shared by hooks and custom-tools
- Rename CustomMessageRenderer -> HookMessageRenderer
- Rename registerCustomMessageRenderer -> registerMessageRenderer
- Renderer now receives HookMessage instead of CustomMessageEntry
- CustomMessageComponent now has setExpanded() and responds to Ctrl+E toggle
- Re-export ExecOptions/ExecResult from exec.ts for backward compatibility

packages/coding-agent/CHANGELOG.md

@@ -34,9 +34,9 @@
   - `pi.send(text, attachments?)` replaced with `pi.sendMessage(message, triggerTurn?)` which creates `CustomMessageEntry` instead of user messages
   - New `pi.appendEntry(customType, data?)` to persist hook state (does NOT participate in LLM context)
   - New `pi.registerCommand(name, options)` to register custom slash commands
-  - New `pi.registerCustomMessageRenderer(customType, renderer)` to register custom renderers for `CustomMessageEntry`
+  - New `pi.registerMessageRenderer(customType, renderer)` to register custom renderers for hook messages
   - New `pi.exec(command, args, options?)` to execute shell commands (moved from `HookEventContext`/`HookCommandContext`)
-  - `CustomMessageRenderer` type: `(entry, options, theme) => Component | null`
+  - `HookMessageRenderer` type: `(message: HookMessage, options, theme) => Component | null`
   - Renderers return inner content; the TUI wraps it in a styled Box
   - New types: `HookMessage<T>`, `RegisteredCommand`, `HookCommandContext`
   - Handler types renamed: `SendHandler` → `SendMessageHandler`, new `AppendEntryHandler`

packages/coding-agent/src/core/custom-tools/loader.ts

@@ -7,7 +7,6 @@
  * for custom tools that depend on pi packages.
  */
 
-import { spawn } from "node:child_process";
 import * as fs from "node:fs";
 import { createRequire } from "node:module";
 import * as os from "node:os";
@@ -15,15 +14,10 @@ import * as path from "node:path";
 import { fileURLToPath } from "node:url";
 import { createJiti } from "jiti";
 import { getAgentDir, isBunBinary } from "../../config.js";
+import type { ExecOptions } from "../exec.js";
+import { execCommand } from "../exec.js";
 import type { HookUIContext } from "../hooks/types.js";
-import type {
-	CustomToolFactory,
-	CustomToolsLoadResult,
-	ExecOptions,
-	ExecResult,
-	LoadedCustomTool,
-	ToolAPI,
-} from "./types.js";
+import type { CustomToolFactory, CustomToolsLoadResult, LoadedCustomTool, ToolAPI } from "./types.js";
 
 // Create require function to resolve module paths at runtime
 const require = createRequire(import.meta.url);
@@ -87,88 +81,6 @@ function resolveToolPath(toolPath: string, cwd: string): string {
 	return path.resolve(cwd, expanded);
 }
 
-/**
- * Execute a command and return stdout/stderr/code.
- * Supports cancellation via AbortSignal and timeout.
- */
-async function execCommand(command: string, args: string[], cwd: string, options?: ExecOptions): Promise<ExecResult> {
-	return new Promise((resolve) => {
-		const proc = spawn(command, args, {
-			cwd,
-			shell: false,
-			stdio: ["ignore", "pipe", "pipe"],
-		});
-
-		let stdout = "";
-		let stderr = "";
-		let killed = false;
-		let timeoutId: NodeJS.Timeout | undefined;
-
-		const killProcess = () => {
-			if (!killed) {
-				killed = true;
-				proc.kill("SIGTERM");
-				// Force kill after 5 seconds if SIGTERM doesn't work
-				setTimeout(() => {
-					if (!proc.killed) {
-						proc.kill("SIGKILL");
-					}
-				}, 5000);
-			}
-		};
-
-		// Handle abort signal
-		if (options?.signal) {
-			if (options.signal.aborted) {
-				killProcess();
-			} else {
-				options.signal.addEventListener("abort", killProcess, { once: true });
-			}
-		}
-
-		// Handle timeout
-		if (options?.timeout && options.timeout > 0) {
-			timeoutId = setTimeout(() => {
-				killProcess();
-			}, options.timeout);
-		}
-
-		proc.stdout.on("data", (data) => {
-			stdout += data.toString();
-		});
-
-		proc.stderr.on("data", (data) => {
-			stderr += data.toString();
-		});
-
-		proc.on("close", (code) => {
-			if (timeoutId) clearTimeout(timeoutId);
-			if (options?.signal) {
-				options.signal.removeEventListener("abort", killProcess);
-			}
-			resolve({
-				stdout,
-				stderr,
-				code: code ?? 0,
-				killed,
-			});
-		});
-
-		proc.on("error", (err) => {
-			if (timeoutId) clearTimeout(timeoutId);
-			if (options?.signal) {
-				options.signal.removeEventListener("abort", killProcess);
-			}
-			resolve({
-				stdout,
-				stderr: stderr || err.message,
-				code: 1,
-				killed,
-			});
-		});
-	});
-}
-
 /**
  * Create a no-op UI context for headless modes.
  */

packages/coding-agent/src/core/custom-tools/types.ts

@@ -9,6 +9,7 @@ import type { AgentTool, AgentToolResult, AgentToolUpdateCallback } from "@mario
 import type { Component } from "@mariozechner/pi-tui";
 import type { Static, TSchema } from "@sinclair/typebox";
 import type { Theme } from "../../modes/interactive/theme/theme.js";
+import type { ExecOptions, ExecResult } from "../exec.js";
 import type { HookUIContext } from "../hooks/types.js";
 import type { SessionEntry } from "../session-manager.js";
 
@@ -18,22 +19,8 @@ export type ToolUIContext = HookUIContext;
 /** Re-export for custom tools to use in execute signature */
 export type { AgentToolUpdateCallback };
 
-export interface ExecResult {
-	stdout: string;
-	stderr: string;
-	code: number;
-	/** True if the process was killed due to signal or timeout */
-	killed?: boolean;
-}
-
-export interface ExecOptions {
-	/** AbortSignal to cancel the process */
-	signal?: AbortSignal;
-	/** Timeout in milliseconds */
-	timeout?: number;
-	/** Working directory */
-	cwd?: string;
-}
+// Re-export for backward compatibility
+export type { ExecOptions, ExecResult } from "../exec.js";
 
 /** API passed to custom tool factory (stable across session changes) */
 export interface ToolAPI {

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

@@ -0,0 +1,104 @@
+/**
+ * Shared command execution utilities for hooks and custom tools.
+ */
+
+import { spawn } from "node:child_process";
+
+/**
+ * Options for executing shell commands.
+ */
+export interface ExecOptions {
+	/** AbortSignal to cancel the command */
+	signal?: AbortSignal;
+	/** Timeout in milliseconds */
+	timeout?: number;
+	/** Working directory */
+	cwd?: string;
+}
+
+/**
+ * Result of executing a shell command.
+ */
+export interface ExecResult {
+	stdout: string;
+	stderr: string;
+	code: number;
+	killed: boolean;
+}
+
+/**
+ * Execute a shell command and return stdout/stderr/code.
+ * Supports timeout and abort signal.
+ */
+export async function execCommand(
+	command: string,
+	args: string[],
+	cwd: string,
+	options?: ExecOptions,
+): Promise<ExecResult> {
+	return new Promise((resolve) => {
+		const proc = spawn(command, args, {
+			cwd,
+			shell: false,
+			stdio: ["ignore", "pipe", "pipe"],
+		});
+
+		let stdout = "";
+		let stderr = "";
+		let killed = false;
+		let timeoutId: NodeJS.Timeout | undefined;
+
+		const killProcess = () => {
+			if (!killed) {
+				killed = true;
+				proc.kill("SIGTERM");
+				// Force kill after 5 seconds if SIGTERM doesn't work
+				setTimeout(() => {
+					if (!proc.killed) {
+						proc.kill("SIGKILL");
+					}
+				}, 5000);
+			}
+		};
+
+		// Handle abort signal
+		if (options?.signal) {
+			if (options.signal.aborted) {
+				killProcess();
+			} else {
+				options.signal.addEventListener("abort", killProcess, { once: true });
+			}
+		}
+
+		// Handle timeout
+		if (options?.timeout && options.timeout > 0) {
+			timeoutId = setTimeout(() => {
+				killProcess();
+			}, options.timeout);
+		}
+
+		proc.stdout?.on("data", (data) => {
+			stdout += data.toString();
+		});
+
+		proc.stderr?.on("data", (data) => {
+			stderr += data.toString();
+		});
+
+		proc.on("close", (code) => {
+			if (timeoutId) clearTimeout(timeoutId);
+			if (options?.signal) {
+				options.signal.removeEventListener("abort", killProcess);
+			}
+			resolve({ stdout, stderr, code: code ?? 0, killed });
+		});
+
+		proc.on("error", (_err) => {
+			if (timeoutId) clearTimeout(timeoutId);
+			if (options?.signal) {
+				options.signal.removeEventListener("abort", killProcess);
+			}
+			resolve({ stdout, stderr, code: 1, killed });
+		});
+	});
+}

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

@@ -13,8 +13,8 @@ export type {
 	AgentEndEvent,
 	AgentStartEvent,
 	BashToolResultEvent,
-	CustomMessageRenderer,
-	CustomMessageRenderOptions,
+	HookMessageRenderer,
+	HookMessageRenderOptions,
 	CustomToolResultEvent,
 	EditToolResultEvent,
 	ExecOptions,

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

@@ -11,11 +11,11 @@ import { createJiti } from "jiti";
 import { getAgentDir } from "../../config.js";
 import { execCommand } from "./runner.js";
 import type {
-	CustomMessageRenderer,
 	ExecOptions,
 	HookAPI,
 	HookFactory,
 	HookMessage,
+	HookMessageRenderer,
 	RegisteredCommand,
 } from "./types.js";
 
@@ -73,8 +73,8 @@ export interface LoadedHook {
 	resolvedPath: string;
 	/** Map of event type to handler functions */
 	handlers: Map<string, HandlerFn[]>;
-	/** Map of customType to custom message renderer */
-	customMessageRenderers: Map<string, CustomMessageRenderer>;
+	/** Map of customType to hook message renderer */
+	messageRenderers: Map<string, HookMessageRenderer>;
 	/** Map of command name to registered command */
 	commands: Map<string, RegisteredCommand>;
 	/** Set the send message handler for this hook's pi.sendMessage() */
@@ -136,7 +136,7 @@ function createHookAPI(
 	cwd: string,
 ): {
 	api: HookAPI;
-	customMessageRenderers: Map<string, CustomMessageRenderer>;
+	messageRenderers: Map<string, HookMessageRenderer>;
 	commands: Map<string, RegisteredCommand>;
 	setSendMessageHandler: (handler: SendMessageHandler) => void;
 	setAppendEntryHandler: (handler: AppendEntryHandler) => void;
@@ -147,7 +147,7 @@ function createHookAPI(
 	let appendEntryHandler: AppendEntryHandler = () => {
 		// Default no-op until mode sets the handler
 	};
-	const customMessageRenderers = new Map<string, CustomMessageRenderer>();
+	const messageRenderers = new Map<string, HookMessageRenderer>();
 	const commands = new Map<string, RegisteredCommand>();
 
 	// Cast to HookAPI - the implementation is more general (string event names)
@@ -164,8 +164,8 @@ function createHookAPI(
 		appendEntry<T = unknown>(customType: string, data?: T): void {
 			appendEntryHandler(customType, data);
 		},
-		registerCustomMessageRenderer<T = unknown>(customType: string, renderer: CustomMessageRenderer<T>): void {
-			customMessageRenderers.set(customType, renderer as CustomMessageRenderer);
+		registerMessageRenderer<T = unknown>(customType: string, renderer: HookMessageRenderer<T>): void {
+			messageRenderers.set(customType, renderer as HookMessageRenderer);
 		},
 		registerCommand(name: string, options: { description?: string; handler: RegisteredCommand["handler"] }): void {
 			commands.set(name, { name, ...options });
@@ -177,7 +177,7 @@ function createHookAPI(
 
 	return {
 		api,
-		customMessageRenderers,
+		messageRenderers,
 		commands,
 		setSendMessageHandler: (handler: SendMessageHandler) => {
 			sendMessageHandler = handler;
@@ -212,7 +212,7 @@ async function loadHook(hookPath: string, cwd: string): Promise<{ hook: LoadedHo
 
 		// Create handlers map and API
 		const handlers = new Map<string, HandlerFn[]>();
-		const { api, customMessageRenderers, commands, setSendMessageHandler, setAppendEntryHandler } = createHookAPI(
+		const { api, messageRenderers, commands, setSendMessageHandler, setAppendEntryHandler } = createHookAPI(
 			handlers,
 			cwd,
 		);
@@ -225,7 +225,7 @@ async function loadHook(hookPath: string, cwd: string): Promise<{ hook: LoadedHo
 				path: hookPath,
 				resolvedPath,
 				handlers,
-				customMessageRenderers,
+				messageRenderers,
 				commands,
 				setSendMessageHandler,
 				setAppendEntryHandler,

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

@@ -2,17 +2,14 @@
  * Hook runner - executes hooks and manages their lifecycle.
  */
 
-import { spawn } from "node:child_process";
 import type { ModelRegistry } from "../model-registry.js";
 import type { SessionManager } from "../session-manager.js";
 import type { AppendEntryHandler, LoadedHook, SendMessageHandler } from "./loader.js";
 import type {
-	CustomMessageRenderer,
-	ExecOptions,
-	ExecResult,
 	HookError,
 	HookEvent,
 	HookEventContext,
+	HookMessageRenderer,
 	HookUIContext,
 	RegisteredCommand,
 	SessionEvent,
@@ -32,78 +29,8 @@ const DEFAULT_TIMEOUT = 30000;
  */
 export type HookErrorListener = (error: HookError) => void;
 
-/**
- * Execute a command and return stdout/stderr/code.
- * Supports cancellation via AbortSignal and timeout.
- */
-export async function execCommand(
-	command: string,
-	args: string[],
-	cwd: string,
-	options?: ExecOptions,
-): Promise<ExecResult> {
-	return new Promise((resolve) => {
-		const proc = spawn(command, args, { cwd, shell: false });
-
-		let stdout = "";
-		let stderr = "";
-		let killed = false;
-		let timeoutId: NodeJS.Timeout | undefined;
-
-		const killProcess = () => {
-			if (!killed) {
-				killed = true;
-				proc.kill("SIGTERM");
-				// Force kill after 5 seconds if SIGTERM doesn't work
-				setTimeout(() => {
-					if (!proc.killed) {
-						proc.kill("SIGKILL");
-					}
-				}, 5000);
-			}
-		};
-
-		// Handle abort signal
-		if (options?.signal) {
-			if (options.signal.aborted) {
-				killProcess();
-			} else {
-				options.signal.addEventListener("abort", killProcess, { once: true });
-			}
-		}
-
-		// Handle timeout
-		if (options?.timeout && options.timeout > 0) {
-			timeoutId = setTimeout(() => {
-				killProcess();
-			}, options.timeout);
-		}
-
-		proc.stdout?.on("data", (data) => {
-			stdout += data.toString();
-		});
-
-		proc.stderr?.on("data", (data) => {
-			stderr += data.toString();
-		});
-
-		proc.on("close", (code) => {
-			if (timeoutId) clearTimeout(timeoutId);
-			if (options?.signal) {
-				options.signal.removeEventListener("abort", killProcess);
-			}
-			resolve({ stdout, stderr, code: code ?? 0, killed });
-		});
-
-		proc.on("error", (_err) => {
-			if (timeoutId) clearTimeout(timeoutId);
-			if (options?.signal) {
-				options.signal.removeEventListener("abort", killProcess);
-			}
-			resolve({ stdout, stderr, code: 1, killed });
-		});
-	});
-}
+// Re-export execCommand for backward compatibility
+export { execCommand } from "../exec.js";
 
 /**
  * Create a promise that rejects after a timeout.
@@ -241,12 +168,12 @@ export class HookRunner {
 	}
 
 	/**
-	 * Get a custom message renderer for the given customType.
+	 * Get a message renderer for the given customType.
 	 * Returns the first renderer found across all hooks, or undefined if none.
 	 */
-	getCustomMessageRenderer(customType: string): CustomMessageRenderer | undefined {
+	getMessageRenderer(customType: string): HookMessageRenderer | undefined {
 		for (const hook of this.hooks) {
-			const renderer = hook.customMessageRenderers.get(customType);
+			const renderer = hook.messageRenderers.get(customType);
 			if (renderer) {
 				return renderer;
 			}

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

@@ -10,6 +10,7 @@ import type { ImageContent, Model, TextContent, ToolResultMessage } from "@mario
 import type { Component } from "@mariozechner/pi-tui";
 import type { Theme } from "../../modes/interactive/theme/theme.js";
 import type { CompactionPreparation, CompactionResult } from "../compaction.js";
+import type { ExecOptions, ExecResult } from "../exec.js";
 import type { ModelRegistry } from "../model-registry.js";
 import type { CompactionEntry, CustomMessageEntry, SessionManager } from "../session-manager.js";
 import type { EditToolDetails } from "../tools/edit.js";
@@ -21,29 +22,8 @@ import type {
 	ReadToolDetails,
 } from "../tools/index.js";
 
-// ============================================================================
-// Execution Context
-// ============================================================================
-
-/**
- * Result of executing a command via ctx.exec()
- */
-export interface ExecResult {
-	stdout: string;
-	stderr: string;
-	code: number;
-	/** True if the process was killed due to signal or timeout */
-	killed?: boolean;
-}
-
-export interface ExecOptions {
-	/** AbortSignal to cancel the process */
-	signal?: AbortSignal;
-	/** Timeout in milliseconds */
-	timeout?: number;
-	/** Working directory */
-	cwd?: string;
-}
+// Re-export for backward compatibility
+export type { ExecOptions, ExecResult } from "../exec.js";
 
 /**
  * UI context for hooks to request interactive UI from the harness.
@@ -372,26 +352,26 @@ export type HookHandler<E, R = void> = (event: E, ctx: HookEventContext) => Prom
 /**
  * Options passed to custom message renderers.
  */
-export interface CustomMessageRenderOptions {
+/**
+ * Message type for hooks to send. Creates CustomMessageEntry in the session.
+ */
+export type HookMessage<T = unknown> = Pick<CustomMessageEntry<T>, "customType" | "content" | "display" | "details">;
+
+export interface HookMessageRenderOptions {
 	/** Whether the view is expanded */
 	expanded: boolean;
 }
 
 /**
- * Renderer for custom message entries.
- * Hooks register these to provide custom TUI rendering for their CustomMessageEntry types.
+ * Renderer for hook messages.
+ * Hooks register these to provide custom TUI rendering for their message types.
  */
-export type CustomMessageRenderer<T = unknown> = (
-	entry: CustomMessageEntry<T>,
-	options: CustomMessageRenderOptions,
+export type HookMessageRenderer<T = unknown> = (
+	message: HookMessage<T>,
+	options: HookMessageRenderOptions,
 	theme: Theme,
 ) => Component | null;
 
-/**
- * Message type for hooks to send. Creates CustomMessageEntry in the session.
- */
-export type HookMessage<T = unknown> = Pick<CustomMessageEntry<T>, "customType" | "content" | "display" | "details">;
-
 /**
  * Context passed to hook command handlers.
  */
@@ -483,7 +463,7 @@ export interface HookAPI {
 	 * The renderer is called when rendering the entry in the TUI.
 	 * Return null to use the default renderer.
 	 */
-	registerCustomMessageRenderer<T = unknown>(customType: string, renderer: CustomMessageRenderer<T>): void;
+	registerMessageRenderer<T = unknown>(customType: string, renderer: HookMessageRenderer<T>): void;
 
 	/**
 	 * Register a custom slash command.

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

@@ -340,7 +340,7 @@ function createFactoryFromLoadedHook(loaded: LoadedHook): HookFactory {
 function createLoadedHooksFromDefinitions(definitions: Array<{ path?: string; factory: HookFactory }>): LoadedHook[] {
 	return definitions.map((def) => {
 		const handlers = new Map<string, Array<(...args: unknown[]) => Promise<unknown>>>();
-		const customMessageRenderers = new Map<string, any>();
+		const messageRenderers = new Map<string, any>();
 		const commands = new Map<string, any>();
 		let sendMessageHandler: (message: any, triggerTurn?: boolean) => void = () => {};
 		let appendEntryHandler: (customType: string, data?: any) => void = () => {};
@@ -357,8 +357,8 @@ function createLoadedHooksFromDefinitions(definitions: Array<{ path?: string; fa
 			appendEntry: (customType: string, data?: any) => {
 				appendEntryHandler(customType, data);
 			},
-			registerCustomMessageRenderer: (customType: string, renderer: any) => {
-				customMessageRenderers.set(customType, renderer);
+			registerMessageRenderer: (customType: string, renderer: any) => {
+				messageRenderers.set(customType, renderer);
 			},
 			registerCommand: (name: string, options: any) => {
 				commands.set(name, { name, ...options });
@@ -371,7 +371,7 @@ function createLoadedHooksFromDefinitions(definitions: Array<{ path?: string; fa
 			path: def.path ?? "<inline>",
 			resolvedPath: def.path ?? "<inline>",
 			handlers,
-			customMessageRenderers,
+			messageRenderers,
 			commands,
 			setSendMessageHandler: (handler: (message: any, triggerTurn?: boolean) => void) => {
 				sendMessageHandler = handler;

packages/coding-agent/src/modes/interactive/components/custom-message.ts

@@ -1,6 +1,6 @@
 import type { TextContent } from "@mariozechner/pi-ai";
 import { Box, Container, Markdown, Spacer, Text } from "@mariozechner/pi-tui";
-import type { CustomMessageRenderer } from "../../../core/hooks/types.js";
+import type { HookMessage, HookMessageRenderer } from "../../../core/hooks/types.js";
 import type { CustomMessageEntry } from "../../../core/session-manager.js";
 import { getMarkdownTheme, theme } from "../theme/theme.js";
 
@@ -9,21 +9,49 @@ import { getMarkdownTheme, theme } from "../theme/theme.js";
  * Uses distinct styling to differentiate from user messages.
  */
 export class CustomMessageComponent extends Container {
-	constructor(entry: CustomMessageEntry, customRenderer?: CustomMessageRenderer) {
+	private entry: CustomMessageEntry;
+	private customRenderer?: HookMessageRenderer;
+	private box: Box;
+	private _expanded = false;
+
+	constructor(entry: CustomMessageEntry, customRenderer?: HookMessageRenderer) {
 		super();
+		this.entry = entry;
+		this.customRenderer = customRenderer;
 
 		this.addChild(new Spacer(1));
 
 		// Create box with purple background
-		const box = new Box(1, 1, (t) => theme.bg("customMessageBg", t));
+		this.box = new Box(1, 1, (t) => theme.bg("customMessageBg", t));
+		this.addChild(this.box);
+
+		this.rebuild();
+	}
+
+	setExpanded(expanded: boolean): void {
+		if (this._expanded !== expanded) {
+			this._expanded = expanded;
+			this.rebuild();
+		}
+	}
+
+	private rebuild(): void {
+		this.box.clear();
+
+		// Convert entry to HookMessage for renderer
+		const message: HookMessage = {
+			customType: this.entry.customType,
+			content: this.entry.content,
+			display: this.entry.display,
+			details: this.entry.details,
+		};
 
 		// Try custom renderer first
-		if (customRenderer) {
+		if (this.customRenderer) {
 			try {
-				const component = customRenderer(entry, { expanded: false }, theme);
+				const component = this.customRenderer(message, { expanded: this._expanded }, theme);
 				if (component) {
-					box.addChild(component);
-					this.addChild(box);
+					this.box.addChild(component);
 					return;
 				}
 			} catch {
@@ -32,27 +60,25 @@ export class CustomMessageComponent extends Container {
 		}
 
 		// Default rendering: label + content
-		const label = theme.fg("customMessageLabel", `\x1b[1m[${entry.customType}]\x1b[22m`);
-		box.addChild(new Text(label, 0, 0));
-		box.addChild(new Spacer(1));
+		const label = theme.fg("customMessageLabel", `\x1b[1m[${this.entry.customType}]\x1b[22m`);
+		this.box.addChild(new Text(label, 0, 0));
+		this.box.addChild(new Spacer(1));
 
 		// Extract text content
 		let text: string;
-		if (typeof entry.content === "string") {
-			text = entry.content;
+		if (typeof this.entry.content === "string") {
+			text = this.entry.content;
 		} else {
-			text = entry.content
+			text = this.entry.content
 				.filter((c): c is TextContent => c.type === "text")
 				.map((c) => c.text)
 				.join("\n");
 		}
 
-		box.addChild(
+		this.box.addChild(
 			new Markdown(text, 0, 0, getMarkdownTheme(), {
 				color: (text: string) => theme.fg("customMessageText", text),
 			}),
 		);
-
-		this.addChild(box);
 	}
 }

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -1028,7 +1028,7 @@ export class InteractiveMode {
 					parentId: null,
 					timestamp: new Date().toISOString(),
 				};
-				const renderer = this.session.hookRunner?.getCustomMessageRenderer(message.customType);
+				const renderer = this.session.hookRunner?.getMessageRenderer(message.customType);
 				this.chatContainer.addChild(new CustomMessageComponent(entry, renderer));
 			}
 		} else if (message.role === "user") {
@@ -1077,7 +1077,7 @@ export class InteractiveMode {
 			// Check if this is a custom_message entry
 			if (entry?.type === "custom_message") {
 				if (entry.display) {
-					const renderer = this.session.hookRunner?.getCustomMessageRenderer(entry.customType);
+					const renderer = this.session.hookRunner?.getMessageRenderer(entry.customType);
 					this.chatContainer.addChild(new CustomMessageComponent(entry, renderer));
 				}
 				continue;
@@ -1271,6 +1271,8 @@ export class InteractiveMode {
 				child.setExpanded(this.toolOutputExpanded);
 			} else if (child instanceof BashExecutionComponent) {
 				child.setExpanded(this.toolOutputExpanded);
+			} else if (child instanceof CustomMessageComponent) {
+				child.setExpanded(this.toolOutputExpanded);
 			}
 		}
 		this.ui.requestRender();

packages/coding-agent/test/compaction-hooks.test.ts

@@ -63,7 +63,7 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 			path: "test-hook",
 			resolvedPath: "/test/test-hook.ts",
 			handlers,
-			customMessageRenderers: new Map(),
+			messageRenderers: new Map(),
 			commands: new Map(),
 			setSendMessageHandler: () => {},
 			setAppendEntryHandler: () => {},
@@ -240,7 +240,7 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 					],
 				],
 			]),
-			customMessageRenderers: new Map(),
+			messageRenderers: new Map(),
 			commands: new Map(),
 			setSendMessageHandler: () => {},
 			setAppendEntryHandler: () => {},
@@ -286,7 +286,7 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 					],
 				],
 			]),
-			customMessageRenderers: new Map(),
+			messageRenderers: new Map(),
 			commands: new Map(),
 			setSendMessageHandler: () => {},
 			setAppendEntryHandler: () => {},
@@ -311,7 +311,7 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 					],
 				],
 			]),
-			customMessageRenderers: new Map(),
+			messageRenderers: new Map(),
 			commands: new Map(),
 			setSendMessageHandler: () => {},
 			setAppendEntryHandler: () => {},