fix(app): close missing child session tabs

packages/app/e2e/regression/subagent-child-navigation.spec.ts

@@ -39,7 +39,9 @@ test("shows the not found fallback when the viewed session is deleted", async ({
   })
 
   await expect(page.getByText("This session cannot be found")).toBeVisible()
-  await expect(page.getByRole("button", { name: "Close Tab" })).toBeVisible()
+  await page.getByRole("button", { name: "Close Tab" }).click()
+  await expect(page).toHaveURL(/\/$/)
+  await expect(page.getByText("This session cannot be found")).toHaveCount(0)
   await expect(page.getByRole("heading", { name: taskDescription })).toHaveCount(0)
 })
 

packages/app/src/context/tabs.tsx

@@ -249,6 +249,16 @@ export const { use: useTabs, provider: TabsProvider } = createSimpleContext({
         removeDraftPersisted(draftID)
       },
       removeTab,
+      // Child routes share their root session's tab, so the route ID cannot
+      // identify the tab once a deleted child falls back to an error page.
+      removeActiveTab(key: ServerConnection.Key) {
+        const index = store.findIndex((tab) => tab.server === key && tabKey(tab) === recentKey())
+        if (index === -1) {
+          navigate("/")
+          return
+        }
+        removeTab(index)
+      },
       // User-initiated close: records the tab so it can be reopened.
       // Cleanup paths (missing sessions, archive, server removal) go through
       // removeTab and friends directly and are not recorded.

packages/app/src/pages/session.tsx

@@ -211,7 +211,7 @@ function SessionErrorFallback(props: { error: unknown; sessionID?: string; serve
   })
   const closeTab = () => {
     if (!props.sessionID) return
-    tabs.removeSessionTab({ server: props.serverKey ?? server.key, sessionId: props.sessionID })
+    tabs.removeActiveTab(props.serverKey ?? server.key)
   }
   if (isCurrentSessionNotFoundError(props.error, props.sessionID)) {
     return (