Fix auto-enable to work without delay by skipping duplicate Target.attachedToTarget

Move auto-create logic from onOpen to Target.setAutoAttach handler so it runs
synchronously in the CDP command flow. Add skipAttachedEvent option to extension's
attachTab to prevent sending Target.attachedToTarget when the relay will send it
via the Target.setAutoAttach response handler.

extension/src/background.ts

@@ -273,7 +273,7 @@ async function handleCommand(msg: ExtensionCommandMessage): Promise<any> {
       if (!tab.id) throw new Error('Failed to create tab')
       logger.debug('Created tab:', tab.id, 'waiting for it to load...')
       await sleep(100)
-      const targetInfo = await attachTab(tab.id)
+      const { targetInfo } = await attachTab(tab.id)
       return { targetId: targetInfo.targetId } satisfies Protocol.Target.CreateTargetResponse
     }
 
@@ -378,7 +378,12 @@ function onDebuggerDetach(source: chrome.debugger.Debuggee, reason: `${chrome.de
   }
 }
 
-async function attachTab(tabId: number): Promise<Protocol.Target.TargetInfo> {
+type AttachTabResult = {
+  targetInfo: Protocol.Target.TargetInfo
+  sessionId: string
+}
+
+async function attachTab(tabId: number, { skipAttachedEvent = false }: { skipAttachedEvent?: boolean } = {}): Promise<AttachTabResult> {
   const debuggee = { tabId }
 
   logger.debug('Attaching debugger to tab:', tabId)
@@ -415,20 +420,22 @@ async function attachTab(tabId: number): Promise<Protocol.Target.TargetInfo> {
     return { tabs: newTabs, connectionState: 'connected', errorText: undefined }
   })
 
-  sendMessage({
-    method: 'forwardCDPEvent',
-    params: {
-      method: 'Target.attachedToTarget',
+  if (!skipAttachedEvent) {
+    sendMessage({
+      method: 'forwardCDPEvent',
       params: {
-        sessionId,
-        targetInfo: { ...targetInfo, attached: true },
-        waitingForDebugger: false,
+        method: 'Target.attachedToTarget',
+        params: {
+          sessionId,
+          targetInfo: { ...targetInfo, attached: true },
+          waitingForDebugger: false,
+        },
       },
-    },
-  })
+    })
+  }
 
-  logger.debug('Tab attached successfully:', tabId, 'sessionId:', sessionId, 'targetId:', targetInfo.targetId)
-  return targetInfo
+  logger.debug('Tab attached successfully:', tabId, 'sessionId:', sessionId, 'targetId:', targetInfo.targetId, 'skipAttachedEvent:', skipAttachedEvent)
+  return { targetInfo, sessionId }
 }
 
 function detachTab(tabId: number, shouldDetachDebugger: boolean): void {
@@ -630,14 +637,32 @@ async function ensureConnection(): Promise<void> {
     }
 
     // Handle createInitialTab - create a new tab when Playwright connects and no tabs exist
+    // We use skipAttachedEvent: true because the relay's Target.setAutoAttach handler will send
+    // Target.attachedToTarget for all targets in connectedTargets. If we also sent it here,
+    // Playwright would receive a duplicate.
+    //
+    // This differs from the normal flow (user clicks extension icon) where:
+    // 1. Extension attaches and sends Target.attachedToTarget to existing Playwright clients
+    // 2. New Playwright clients that connect later get targets via Target.setAutoAttach
+    //
+    // But with createInitialTab, the SAME client that triggered the create is waiting for
+    // Target.setAutoAttach - so we'd send the event twice to the same client.
     if (message.method === 'createInitialTab') {
       try {
         logger.debug('Creating initial tab for Playwright client')
         const tab = await chrome.tabs.create({ url: 'about:blank', active: false })
         if (tab.id) {
-          await connectTab(tab.id)
-          logger.debug('Initial tab created and connected:', tab.id)
-          sendMessage({ id: message.id, result: { success: true, tabId: tab.id } })
+          const { targetInfo, sessionId } = await attachTab(tab.id, { skipAttachedEvent: true })
+          logger.debug('Initial tab created and connected:', tab.id, 'sessionId:', sessionId)
+          sendMessage({
+            id: message.id,
+            result: {
+              success: true,
+              tabId: tab.id,
+              sessionId,
+              targetInfo,
+            }
+          })
         } else {
           throw new Error('Failed to create tab - no tab ID returned')
         }