fix: remove ensureResponseListener; remove isPageAgentMessage

packages/extension/src/entrypoints/background.ts

@@ -15,7 +15,6 @@ import {
 	type ExtensionMessage,
 	type QueryResponseMessage,
 	type RPCCallMessage,
-	type RPCResponseMessage,
 	type TabEventMessage,
 	generateMessageId,
 	isExtensionMessage,
@@ -42,9 +41,9 @@ chrome.runtime.onMessage.addListener(
 
 		switch (msg.type) {
 			case 'rpc:call':
-				// SidePanel → SW: Forward RPC to content script
+				// SidePanel → SW: Forward RPC to content script, return result via sendResponse
-				handleRPCCall(msg as RPCCallMessage)
+				handleRPCCall(msg as RPCCallMessage, sendResponse)
-				return false // No sync response needed
+				return true // Async response
 
 			case 'cs:query':
 				// ContentScript → SW: Forward query to sidepanel
@@ -59,15 +58,18 @@ chrome.runtime.onMessage.addListener(
 
 /**
  * Forward RPC call from SidePanel to ContentScript
+ * Uses sendResponse to return result directly (MV3 compliant)
  */
-async function handleRPCCall(msg: RPCCallMessage): Promise<void> {
+async function handleRPCCall(
-	const { id, tabId, method, args } = msg
+	msg: RPCCallMessage,
+	sendResponse: (response: { success: boolean; result?: unknown; error?: string }) => void
+): Promise<void> {
+	const { tabId, method, args } = msg
 
 	// Create message for content script
 	const csMessage: CSRPCMessage = {
-		isPageAgentMessage: true,
 		type: 'cs:rpc',
-		id,
+		id: msg.id,
 		method,
 		args,
 	}
@@ -75,27 +77,11 @@ async function handleRPCCall(msg: RPCCallMessage): Promise<void> {
 	try {
 		// Send to content script and wait for response
 		const result = await chrome.tabs.sendMessage(tabId, csMessage)
-
+		sendResponse({ success: true, result })
-		// Forward response back to sidepanel
-		const response: RPCResponseMessage = {
-			isPageAgentMessage: true,
-			type: 'rpc:response',
-			id,
-			success: true,
-			result,
-		}
-		await chrome.runtime.sendMessage(response)
 	} catch (error) {
-		// Forward error back to sidepanel
+		sendResponse({
-		const response: RPCResponseMessage = {
-			isPageAgentMessage: true,
-			type: 'rpc:response',
-			id,
 			success: false,
 			error: error instanceof Error ? error.message : String(error),
-		}
-		await chrome.runtime.sendMessage(response).catch(() => {
-			// Sidepanel may be closed
 		})
 	}
 }
@@ -120,7 +106,6 @@ async function handleCSQuery(
 		// Forward response back to content script
 		if (sender.tab?.id) {
 			const queryResponse: QueryResponseMessage = {
-				isPageAgentMessage: true,
 				type: 'query:response',
 				id,
 				result: response,
@@ -131,7 +116,6 @@ async function handleCSQuery(
 		// Sidepanel not open or no response, return default
 		if (sender.tab?.id) {
 			const queryResponse: QueryResponseMessage = {
-				isPageAgentMessage: true,
 				type: 'query:response',
 				id,
 				result: queryType === 'shouldShowMask' ? false : null,
@@ -150,7 +134,6 @@ async function handleCSQuery(
  */
 chrome.tabs.onRemoved.addListener((tabId) => {
 	const message: TabEventMessage = {
-		isPageAgentMessage: true,
 		type: 'tab:event',
 		id: generateMessageId(),
 		eventType: 'removed',
@@ -169,7 +152,6 @@ chrome.tabs.onUpdated.addListener((tabId, changeInfo) => {
 	if (!changeInfo.status) return
 
 	const message: TabEventMessage = {
-		isPageAgentMessage: true,
 		type: 'tab:event',
 		id: generateMessageId(),
 		eventType: 'updated',
@@ -189,7 +171,6 @@ chrome.tabs.onUpdated.addListener((tabId, changeInfo) => {
  */
 chrome.tabs.onActivated.addListener((activeInfo) => {
 	const message: TabEventMessage = {
-		isPageAgentMessage: true,
 		type: 'tab:event',
 		id: generateMessageId(),
 		eventType: 'activated',
@@ -210,7 +191,6 @@ chrome.windows.onFocusChanged.addListener((windowId) => {
 	// windowId is chrome.windows.WINDOW_ID_NONE (-1) when all windows lose focus
 	const focused = windowId !== chrome.windows.WINDOW_ID_NONE
 	const message: TabEventMessage = {
-		isPageAgentMessage: true,
 		type: 'tab:event',
 		id: generateMessageId(),
 		eventType: 'windowFocusChanged',

packages/extension/src/entrypoints/content.ts

@@ -81,7 +81,6 @@ async function queryShouldShowMask(getController: () => PageController): Promise
 
 	const queryId = generateMessageId()
 	const queryMessage: CSQueryMessage = {
-		isPageAgentMessage: true,
 		type: 'cs:query',
 		id: queryId,
 		queryType: 'shouldShowMask',

packages/extension/src/messaging/protocol.ts

@@ -1,13 +1,13 @@
 /**
  * Message Protocol for PageAgentExt
  *
- * NEW ARCHITECTURE (MV3 compliant):
+ * MV3 Compliant Architecture:
  * - SidePanel hosts the agent, all state lives there
  * - Background (SW) is a stateless message relay
  * - Content Script runs PageController
  *
  * Message flows:
- * 1. RPC: SidePanel → SW → ContentScript → SW → SidePanel (PageController calls)
+ * 1. RPC: SidePanel → SW → ContentScript → sendResponse (PageController calls)
  * 2. Query: ContentScript → SW → SidePanel → SW → ContentScript (mask state check)
  * 3. Events: SW → SidePanel (tab events from chrome.tabs API)
  */
@@ -52,8 +52,7 @@ export interface ScrollHorizontallyOptions {
 
 /** Message type identifier */
 type MessageType =
-	| 'rpc:call' // SidePanel → SW: RPC call to content script
+	| 'rpc:call' // SidePanel → SW: RPC call to content script (response via sendResponse)
-	| 'rpc:response' // SW → SidePanel: RPC response from content script
 	| 'cs:rpc' // SW → ContentScript: Forwarded RPC call
 	| 'cs:query' // ContentScript → SW: Query to sidepanel
 	| 'query:response' // SW → ContentScript: Query response
@@ -61,7 +60,6 @@ type MessageType =
 
 /** Base message structure */
 interface BaseMessage {
-	isPageAgentMessage: true
 	type: MessageType
 	id: string // Unique message ID for request-response matching
 }
@@ -78,14 +76,6 @@ export interface RPCCallMessage extends BaseMessage {
 	args: unknown[]
 }
 
-/** SW → SidePanel: Response from PageController */
-export interface RPCResponseMessage extends BaseMessage {
-	type: 'rpc:response'
-	success: boolean
-	result?: unknown
-	error?: string
-}
-
 /** SW → ContentScript: Forwarded RPC call */
 export interface CSRPCMessage extends BaseMessage {
 	type: 'cs:rpc'
@@ -143,7 +133,6 @@ export interface TabEventMessage extends BaseMessage {
 /** All message types */
 export type ExtensionMessage =
 	| RPCCallMessage
-	| RPCResponseMessage
 	| CSRPCMessage
 	| CSQueryMessage
 	| QueryResponseMessage
@@ -158,12 +147,16 @@ export function generateMessageId(): string {
 	return `${Date.now()}-${Math.random().toString(36).slice(2, 8)}`
 }
 
-/** Type guard for our messages */
+/** Known message types for type guard */
+const MESSAGE_TYPES = new Set<string>([
+	'rpc:call',
+	'cs:rpc',
+	'cs:query',
+	'query:response',
+	'tab:event',
+])
+
+/** Type guard - checks if message has a known type */
 export function isExtensionMessage(msg: unknown): msg is ExtensionMessage {
-	return (
+	return typeof msg === 'object' && msg !== null && MESSAGE_TYPES.has((msg as any).type)
-		typeof msg === 'object' &&
-		msg !== null &&
-		'isPageAgentMessage' in msg &&
-		(msg as any).isPageAgentMessage === true
-	)
 }

packages/extension/src/messaging/rpc.ts

@@ -4,17 +4,18 @@
  * This module provides RPC functionality from SidePanel to ContentScript
  * via the Background (SW) relay.
  *
- * Flow: SidePanel → SW (relay) → ContentScript → SW → SidePanel
+ * Flow: SidePanel → SW (relay) → ContentScript → sendResponse → SidePanel
+ *
+ * MV3 Compliant: Uses chrome.runtime.sendMessage with direct sendResponse,
+ * no pending calls map or custom response listeners needed.
  */
 import {
 	type ActionResult,
 	type BrowserState,
 	type RPCCallMessage,
-	type RPCResponseMessage,
 	type ScrollHorizontallyOptions,
 	type ScrollOptions,
 	generateMessageId,
-	isExtensionMessage,
 } from './protocol'
 
 /** RPC configuration */
@@ -23,52 +24,6 @@ const RPC_CONFIG = {
 	maxRetries: 3,
 	/** Base delay between retries in ms (exponential backoff) */
 	retryDelayMs: 500,
-	/** Timeout for individual RPC call in ms */
-	callTimeoutMs: 30000,
-}
-
-/** Pending RPC calls waiting for response */
-const pendingCalls = new Map<
-	string,
-	{
-		resolve: (value: unknown) => void
-		reject: (error: Error) => void
-		timeout: ReturnType<typeof setTimeout>
-	}
->()
-
-/** Whether the response listener is registered */
-let listenerRegistered = false
-
-/**
- * Register the RPC response listener (called once)
- */
-function ensureResponseListener(): void {
-	if (listenerRegistered) return
-	listenerRegistered = true
-
-	chrome.runtime.onMessage.addListener((message: unknown) => {
-		if (!isExtensionMessage(message)) return
-		if (message.type !== 'rpc:response') return
-
-		const response = message as RPCResponseMessage
-		const pending = pendingCalls.get(response.id)
-		if (!pending) {
-			console.debug('[RPC] Received response for unknown call:', response.id)
-			return
-		}
-
-		pendingCalls.delete(response.id)
-		clearTimeout(pending.timeout)
-
-		if (response.success) {
-			pending.resolve(response.result)
-		} else {
-			pending.reject(new Error(response.error || 'RPC call failed'))
-		}
-	})
-
-	console.debug('[RPC] Response listener registered')
 }
 
 /**
@@ -96,43 +51,40 @@ async function tabExists(tabId: number): Promise<boolean> {
 export class RPCError extends Error {
 	constructor(
 		message: string,
-		public readonly code: 'TAB_CLOSED' | 'CONTENT_SCRIPT_NOT_READY' | 'RPC_FAILED' | 'TIMEOUT'
+		public readonly code: 'TAB_CLOSED' | 'CONTENT_SCRIPT_NOT_READY' | 'RPC_FAILED'
 	) {
 		super(message)
 		this.name = 'RPCError'
 	}
 }
 
+/** Response type from background script */
+interface RPCResponse {
+	success: boolean
+	result?: unknown
+	error?: string
+}
+
 /**
  * Make a single RPC call (no retry)
+ * Uses chrome.runtime.sendMessage which returns the response directly via sendResponse
  */
 async function callOnce(tabId: number, method: string, args: unknown[]): Promise<unknown> {
-	ensureResponseListener()
-
-	const id = generateMessageId()
 	const message: RPCCallMessage = {
-		isPageAgentMessage: true,
 		type: 'rpc:call',
-		id,
+		id: generateMessageId(),
 		tabId,
 		method,
 		args,
 	}
 
-	return new Promise((resolve, reject) => {
+	const response = (await chrome.runtime.sendMessage(message)) as RPCResponse
-		const timeout = setTimeout(() => {
-			pendingCalls.delete(id)
-			reject(new RPCError(`RPC ${method} timed out`, 'TIMEOUT'))
-		}, RPC_CONFIG.callTimeoutMs)
 
-		pendingCalls.set(id, { resolve, reject, timeout })
+	if (response?.success) {
-
+		return response.result
-		chrome.runtime.sendMessage(message).catch((error: Error) => {
+	} else {
-			pendingCalls.delete(id)
+		throw new Error(response?.error || 'RPC call failed')
-			clearTimeout(timeout)
+	}
-			reject(error)
-		})
-	})
 }
 
 /**