Harden chat stream transition handling

apps/sim/app/workspace/[workspaceId]/home/home.tsx

@@ -218,8 +218,9 @@ export function Home({ chatId, userName, userId, tableViewsEnabled }: HomeProps)
   activeResourceParamRef.current = activeResourceParam
 
   function handleResourceEvent(resourceId: string, options?: ResourceEventOptions) {
-    // Agent work makes the resource surface available without replacing an
-    // existing selection. Explicit user navigation can request activation.
+    // Agent work surfaces the resource and switches to it as it is created or
+    // edited; only the browser session stays in the background behind an
+    // existing selection (see shouldActivateResourceEvent).
     if (isResourceCollapsedRef.current) setIsResourceCollapsed(false)
 
     const activeResourceId = activeResourceParamRef.current

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.test.ts

@@ -33,17 +33,27 @@ vi.mock('next/navigation', () => ({
 }))
 
 describe('shouldActivateResourceEvent', () => {
-  it('keeps background agent activity from replacing another selected resource', () => {
+  it('keeps background browser activity from replacing another selected resource', () => {
     expect(shouldActivateResourceEvent('file-1', 'browser-session')).toBe(false)
   })
 
-  it('allows an explicit user action to replace another selected resource', () => {
+  it('allows an explicit user action to surface the browser over another selection', () => {
     expect(
       shouldActivateResourceEvent('file-1', 'browser-session', {
         activate: true,
       })
     ).toBe(true)
   })
+
+  it('activates the browser when nothing else is selected', () => {
+    expect(shouldActivateResourceEvent(null, 'browser-session')).toBe(true)
+    expect(shouldActivateResourceEvent('browser-session', 'browser-session')).toBe(true)
+  })
+
+  it('activates a non-browser resource even when another resource is selected', () => {
+    expect(shouldActivateResourceEvent('file-1', 'workflow-1')).toBe(true)
+    expect(shouldActivateResourceEvent('browser-session', 'terminal-session')).toBe(true)
+  })
 })
 
 describe('shouldQueueOutgoingMessage', () => {

apps/sim/app/workspace/[workspaceId]/home/hooks/use-chat.ts

@@ -1195,12 +1195,20 @@ export interface ResourceEventOptions {
 
 export type ResourceEventHandler = (resourceId: string, options?: ResourceEventOptions) => void
 
+/**
+ * Whether a streamed resource event should activate its tab. Resources switch
+ * into view as the agent creates or edits them; only the background browser
+ * session declines to replace an existing selection (it gets an attention
+ * marker instead), unless the event explicitly requests activation.
+ */
 export function shouldActivateResourceEvent(
   activeResourceId: string | null,
   resourceId: string,
   options?: ResourceEventOptions
 ): boolean {
-  return options?.activate === true || !activeResourceId || activeResourceId === resourceId
+  if (options?.activate === true) return true
+  if (resourceId !== BROWSER_SESSION_RESOURCE_ID) return true
+  return !activeResourceId || activeResourceId === resourceId
 }
 
 /**