fix: prevent overlapping poll cycles in managers

Guarding polling re-entry avoids stacked async polls under slow responses, and unref on pending-call cleanup timer reduces idle wakeups.

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

@@ -0,0 +1,53 @@
+import { describe, test, expect } from "bun:test"
+import { tmpdir } from "node:os"
+import type { PluginInput } from "@opencode-ai/plugin"
+import { BackgroundManager } from "./manager"
+
+function createManagerWithStatus(statusImpl: () => Promise<{ data: Record<string, { type: string }> }>): BackgroundManager {
+  const client = {
+    session: {
+      status: statusImpl,
+      prompt: async () => ({}),
+      promptAsync: async () => ({}),
+      abort: async () => ({}),
+      todo: async () => ({ data: [] }),
+      messages: async () => ({ data: [] }),
+    },
+  }
+
+  return new BackgroundManager({ client, directory: tmpdir() } as unknown as PluginInput)
+}
+
+describe("BackgroundManager polling overlap", () => {
+  test("skips overlapping pollRunningTasks executions", async () => {
+    //#given
+    let activeCalls = 0
+    let maxActiveCalls = 0
+    let statusCallCount = 0
+    let releaseStatus: (() => void) | undefined
+    const statusGate = new Promise<void>((resolve) => {
+      releaseStatus = resolve
+    })
+
+    const manager = createManagerWithStatus(async () => {
+      statusCallCount += 1
+      activeCalls += 1
+      maxActiveCalls = Math.max(maxActiveCalls, activeCalls)
+      await statusGate
+      activeCalls -= 1
+      return { data: {} }
+    })
+
+    //#when
+    const firstPoll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks()
+    await Promise.resolve()
+    const secondPoll = (manager as unknown as { pollRunningTasks: () => Promise<void> }).pollRunningTasks()
+    releaseStatus?.()
+    await Promise.all([firstPoll, secondPoll])
+    manager.shutdown()
+
+    //#then
+    expect(maxActiveCalls).toBe(1)
+    expect(statusCallCount).toBe(1)
+  })
+})

src/features/background-agent/manager.ts

@@ -80,6 +80,7 @@ export class BackgroundManager {
   private client: OpencodeClient
   private directory: string
   private pollingInterval?: ReturnType<typeof setInterval>
+  private pollingInFlight = false
   private concurrencyManager: ConcurrencyManager
   private shutdownTriggered = false
   private config?: BackgroundTaskConfig
@@ -1546,6 +1547,9 @@ Use \`background_output(task_id="${task.id}")\` to retrieve this result when rea
   }
 
   private async pollRunningTasks(): Promise<void> {
+    if (this.pollingInFlight) return
+    this.pollingInFlight = true
+    try {
     this.pruneStaleTasksAndNotifications()
 
     const statusResult = await this.client.session.status()
@@ -1601,6 +1605,9 @@ Use \`background_output(task_id="${task.id}")\` to retrieve this result when rea
     if (!this.hasRunningTasks()) {
       this.stopPolling()
     }
+    } finally {
+      this.pollingInFlight = false
+    }
   }
 
   /**