fix: handle undefined sessionStatus in pollRunningTasks (#2387)

When a completed session is no longer returned by session.status(),
allStatuses[sessionID] is undefined. Previously this fell through to
a 'still running' log, leaving the task stuck as running forever.

Match the sync-session-poller pattern: only continue (skip completion
check) when sessionStatus EXISTS and is not idle. When undefined,
fall through to validateSessionHasOutput + checkSessionTodos +
tryCompleteTask, same as idle.

src/features/background-agent/manager.polling.test.ts

@@ -2,6 +2,7 @@ import { describe, test, expect } from "bun:test"
 import { tmpdir } from "node:os"
 import type { PluginInput } from "@opencode-ai/plugin"
 import { BackgroundManager } from "./manager"
+import type { BackgroundTask } from "./types"
 
 function createManagerWithStatus(statusImpl: () => Promise<{ data: Record<string, { type: string }> }>): BackgroundManager {
   const client = {
@@ -51,3 +52,105 @@ describe("BackgroundManager polling overlap", () => {
     expect(statusCallCount).toBe(1)
   })
 })
+
+
+function createRunningTask(sessionID: string): BackgroundTask {
+  return {
+    id: `bg_test_${sessionID}`,
+    sessionID,
+    parentSessionID: "parent-session",
+    parentMessageID: "parent-msg",
+    description: "test task",
+    prompt: "test",
+    agent: "explore",
+    status: "running",
+    startedAt: new Date(),
+    progress: { toolCalls: 0, lastUpdate: new Date() },
+  }
+}
+
+function injectTask(manager: BackgroundManager, task: BackgroundTask): void {
+  const tasks = (manager as unknown as { tasks: Map<string, BackgroundTask> }).tasks
+  tasks.set(task.id, task)
+}
+
+function createManagerWithClient(clientOverrides: Record<string, unknown> = {}): BackgroundManager {
+  const client = {
+    session: {
+      status: async () => ({ data: {} }),
+      prompt: async () => ({}),
+      promptAsync: async () => ({}),
+      abort: async () => ({}),
+      todo: async () => ({ data: [] }),
+      messages: async () => ({
+        data: [{
+          info: { role: "assistant", finish: "end_turn", id: "msg-2" },
+          parts: [{ type: "text", text: "done" }],
+        }, {
+          info: { role: "user", id: "msg-1" },
+          parts: [{ type: "text", text: "go" }],
+        }],
+      }),
+      ...clientOverrides,
+    },
+  }
+  return new BackgroundManager({ client, directory: tmpdir() } as unknown as PluginInput)
+}
+
+describe("BackgroundManager pollRunningTasks", () => {
+  describe("#given a running task whose session is no longer in status response", () => {
+    test("#when pollRunningTasks runs #then completes the task instead of leaving it running", async () => {
+      //#given
+      const manager = createManagerWithClient()
+      const task = createRunningTask("ses-gone")
+      injectTask(manager, task)
+
+      //#when
+      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      await poll.call(manager)
+      manager.shutdown()
+
+      //#then
+      expect(task.status).toBe("completed")
+      expect(task.completedAt).toBeDefined()
+    })
+  })
+
+  describe("#given a running task whose session status is idle", () => {
+    test("#when pollRunningTasks runs #then completes the task", async () => {
+      //#given
+      const manager = createManagerWithClient({
+        status: async () => ({ data: { "ses-idle": { type: "idle" } } }),
+      })
+      const task = createRunningTask("ses-idle")
+      injectTask(manager, task)
+
+      //#when
+      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      await poll.call(manager)
+      manager.shutdown()
+
+      //#then
+      expect(task.status).toBe("completed")
+    })
+  })
+
+  describe("#given a running task whose session status is busy", () => {
+    test("#when pollRunningTasks runs #then keeps the task running", async () => {
+      //#given
+      const manager = createManagerWithClient({
+        status: async () => ({ data: { "ses-busy": { type: "busy" } } }),
+      })
+      const task = createRunningTask("ses-busy")
+      injectTask(manager, task)
+
+      //#when
+      const poll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks
+      await poll.call(manager)
+      manager.shutdown()
+
+      //#then
+      expect(task.status).toBe("running")
+    })
+  })
+})