2 files changed, 88 insertions, 0 deletions
diff --git a/packages/app/e2e/actions.ts b/packages/app/e2e/actions.ts
index fbb13008b..919a1add8 100644
--- a/packages/app/e2e/actions.ts
+++ b/packages/app/e2e/actions.ts
@@ -445,6 +445,57 @@ export async function seedSessionPermission(
   return { id: result.id }
 }
 
+export async function seedSessionTask(
+  sdk: ReturnType<typeof createSdk>,
+  input: {
+    sessionID: string
+    description: string
+    prompt: string
+    subagentType?: string
+  },
+) {
+  const text = [
+    "Your only valid response is one task tool call.",
+    `Use this JSON input: ${JSON.stringify({
+      description: input.description,
+      prompt: input.prompt,
+      subagent_type: input.subagentType ?? "general",
+    })}`,
+    "Do not output plain text.",
+    "Wait for the task to start and return the child session id.",
+  ].join("\n")
+
+  const result = await seed({
+    sdk,
+    sessionID: input.sessionID,
+    prompt: text,
+    timeout: 90_000,
+    probe: async () => {
+      const messages = await sdk.session.messages({ sessionID: input.sessionID, limit: 50 }).then((x) => x.data ?? [])
+      const part = messages
+        .flatMap((message) => message.parts)
+        .find((part) => {
+          if (part.type !== "tool" || part.tool !== "task") return false
+          if (part.state.input?.description !== input.description) return false
+          return typeof part.state.metadata?.sessionId === "string" && part.state.metadata.sessionId.length > 0
+        })
+
+      if (!part) return
+      const id = part.state.metadata?.sessionId
+      if (typeof id !== "string" || !id) return
+      const child = await sdk.session
+        .get({ sessionID: id })
+        .then((x) => x.data)
+        .catch(() => undefined)
+      if (!child?.id) return
+      return { sessionID: id }
+    },
+  })
+
+  if (!result) throw new Error("Timed out seeding task tool")
+  return result
+}
+
 export async function seedSessionTodos(
   sdk: ReturnType<typeof createSdk>,
   input: {
diff --git a/packages/app/e2e/session/session-child-navigation.spec.ts b/packages/app/e2e/session/session-child-navigation.spec.ts
new file mode 100644
index 000000000..ac2dca33c
--- /dev/null
+++ b/packages/app/e2e/session/session-child-navigation.spec.ts
@@ -0,0 +1,37 @@
+import { seedSessionTask, withSession } from "../actions"
+import { test, expect } from "../fixtures"
+
+test("task tool child-session link does not trigger stale show errors", async ({ page, sdk, gotoSession }) => {
+  test.setTimeout(120_000)
+
+  const errs: string[] = []
+  const onError = (err: Error) => {
+    errs.push(err.message)
+  }
+  page.on("pageerror", onError)
+
+  await withSession(sdk, `e2e child nav ${Date.now()}`, async (session) => {
+    const child = await seedSessionTask(sdk, {
+      sessionID: session.id,
+      description: "Open child session",
+      prompt: "Search the repository for AssistantParts and then reply with exactly CHILD_OK.",
+    })
+
+    try {
+      await gotoSession(session.id)
+
+      const link = page
+        .locator("a.subagent-link")
+        .filter({ hasText: /open child session/i })
+        .first()
+      await expect(link).toBeVisible({ timeout: 30_000 })
+      await link.click()
+
+      await expect(page).toHaveURL(new RegExp(`/session/${child.sessionID}(?:[/?#]|$)`), { timeout: 30_000 })
+      await page.waitForTimeout(1000)
+      expect(errs).toEqual([])
+    } finally {
+      page.off("pageerror", onError)
+    }
+  })
+})