fix(background-agent): apply smart circuit breaker to manager events

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/features/background-agent/manager-circuit-breaker.test.ts

@@ -0,0 +1,239 @@
+import { describe, expect, test } from "bun:test"
+import type { PluginInput } from "@opencode-ai/plugin"
+import { tmpdir } from "node:os"
+import type { BackgroundTaskConfig } from "../../config/schema"
+import { BackgroundManager } from "./manager"
+import type { BackgroundTask } from "./types"
+
+function createManager(config?: BackgroundTaskConfig): BackgroundManager {
+  const client = {
+    session: {
+      prompt: async () => ({}),
+      promptAsync: async () => ({}),
+      abort: async () => ({}),
+    },
+  }
+
+  const manager = new BackgroundManager({ client, directory: tmpdir() } as unknown as PluginInput, config)
+  const testManager = manager as unknown as {
+    enqueueNotificationForParent: (sessionID: string, fn: () => Promise<void>) => Promise<void>
+    notifyParentSession: (task: BackgroundTask) => Promise<void>
+    tasks: Map<string, BackgroundTask>
+  }
+
+  testManager.enqueueNotificationForParent = async (_sessionID, fn) => {
+    await fn()
+  }
+  testManager.notifyParentSession = async () => {}
+
+  return manager
+}
+
+function getTaskMap(manager: BackgroundManager): Map<string, BackgroundTask> {
+  return (manager as unknown as { tasks: Map<string, BackgroundTask> }).tasks
+}
+
+async function flushAsyncWork() {
+  await new Promise(resolve => setTimeout(resolve, 0))
+}
+
+describe("BackgroundManager circuit breaker", () => {
+  describe("#given the same tool dominates the recent window", () => {
+    test("#when tool events arrive #then the task is cancelled early", async () => {
+      const manager = createManager({
+        circuitBreaker: {
+          windowSize: 20,
+          repetitionThresholdPercent: 80,
+        },
+      })
+      const task: BackgroundTask = {
+        id: "task-loop-1",
+        sessionID: "session-loop-1",
+        parentSessionID: "parent-1",
+        parentMessageID: "msg-1",
+        description: "Looping task",
+        prompt: "loop",
+        agent: "explore",
+        status: "running",
+        startedAt: new Date(Date.now() - 60_000),
+        progress: {
+          toolCalls: 0,
+          lastUpdate: new Date(Date.now() - 60_000),
+        },
+      }
+      getTaskMap(manager).set(task.id, task)
+
+      for (const toolName of [
+        "read",
+        "read",
+        "grep",
+        "read",
+        "edit",
+        "read",
+        "read",
+        "bash",
+        "read",
+        "read",
+        "read",
+        "glob",
+        "read",
+        "read",
+        "read",
+        "read",
+        "read",
+        "read",
+        "read",
+        "read",
+      ]) {
+        manager.handleEvent({
+          type: "message.part.updated",
+          properties: { sessionID: task.sessionID, type: "tool", tool: toolName },
+        })
+      }
+
+      await flushAsyncWork()
+
+      expect(task.status).toBe("cancelled")
+      expect(task.error).toContain("repeatedly called read 16/20 times")
+    })
+  })
+
+  describe("#given recent tool calls are diverse", () => {
+    test("#when the window fills #then the task keeps running", async () => {
+      const manager = createManager({
+        circuitBreaker: {
+          windowSize: 10,
+          repetitionThresholdPercent: 80,
+        },
+      })
+      const task: BackgroundTask = {
+        id: "task-diverse-1",
+        sessionID: "session-diverse-1",
+        parentSessionID: "parent-1",
+        parentMessageID: "msg-1",
+        description: "Healthy task",
+        prompt: "work",
+        agent: "explore",
+        status: "running",
+        startedAt: new Date(Date.now() - 60_000),
+        progress: {
+          toolCalls: 0,
+          lastUpdate: new Date(Date.now() - 60_000),
+        },
+      }
+      getTaskMap(manager).set(task.id, task)
+
+      for (const toolName of [
+        "read",
+        "grep",
+        "edit",
+        "bash",
+        "glob",
+        "read",
+        "lsp_diagnostics",
+        "grep",
+        "edit",
+        "read",
+      ]) {
+        manager.handleEvent({
+          type: "message.part.updated",
+          properties: { sessionID: task.sessionID, type: "tool", tool: toolName },
+        })
+      }
+
+      await flushAsyncWork()
+
+      expect(task.status).toBe("running")
+      expect(task.progress?.toolCalls).toBe(10)
+    })
+  })
+
+  describe("#given the absolute cap is configured lower than the repetition detector needs", () => {
+    test("#when the raw tool-call cap is reached #then the backstop still cancels the task", async () => {
+      const manager = createManager({
+        maxToolCalls: 3,
+        circuitBreaker: {
+          windowSize: 10,
+          repetitionThresholdPercent: 95,
+        },
+      })
+      const task: BackgroundTask = {
+        id: "task-cap-1",
+        sessionID: "session-cap-1",
+        parentSessionID: "parent-1",
+        parentMessageID: "msg-1",
+        description: "Backstop task",
+        prompt: "work",
+        agent: "explore",
+        status: "running",
+        startedAt: new Date(Date.now() - 60_000),
+        progress: {
+          toolCalls: 0,
+          lastUpdate: new Date(Date.now() - 60_000),
+        },
+      }
+      getTaskMap(manager).set(task.id, task)
+
+      for (const toolName of ["read", "grep", "edit"]) {
+        manager.handleEvent({
+          type: "message.part.updated",
+          properties: { sessionID: task.sessionID, type: "tool", tool: toolName },
+        })
+      }
+
+      await flushAsyncWork()
+
+      expect(task.status).toBe("cancelled")
+      expect(task.error).toContain("maximum tool call limit (3)")
+    })
+  })
+
+  describe("#given the same running tool part emits multiple updates", () => {
+    test("#when duplicate running updates arrive #then it only counts the tool once", async () => {
+      const manager = createManager({
+        maxToolCalls: 2,
+        circuitBreaker: {
+          windowSize: 5,
+          repetitionThresholdPercent: 80,
+        },
+      })
+      const task: BackgroundTask = {
+        id: "task-dedupe-1",
+        sessionID: "session-dedupe-1",
+        parentSessionID: "parent-1",
+        parentMessageID: "msg-1",
+        description: "Dedupe task",
+        prompt: "work",
+        agent: "explore",
+        status: "running",
+        startedAt: new Date(Date.now() - 60_000),
+        progress: {
+          toolCalls: 0,
+          lastUpdate: new Date(Date.now() - 60_000),
+        },
+      }
+      getTaskMap(manager).set(task.id, task)
+
+      for (let index = 0; index < 3; index += 1) {
+        manager.handleEvent({
+          type: "message.part.updated",
+          properties: {
+            part: {
+              id: "tool-1",
+              sessionID: task.sessionID,
+              type: "tool",
+              tool: "bash",
+              state: { status: "running" },
+            },
+          },
+        })
+      }
+
+      await flushAsyncWork()
+
+      expect(task.status).toBe("running")
+      expect(task.progress?.toolCalls).toBe(1)
+      expect(task.progress?.countedToolPartIDs).toEqual(["tool-1"])
+    })
+  })
+})

src/features/background-agent/manager.ts

@@ -51,6 +51,11 @@ import { join } from "node:path"
 import { pruneStaleTasksAndNotifications } from "./task-poller"
 import { checkAndInterruptStaleTasks } from "./task-poller"
 import { removeTaskToastTracking } from "./remove-task-toast-tracking"
+import {
+  detectRepetitiveToolUse,
+  recordToolCall,
+  resolveCircuitBreakerSettings,
+} from "./loop-detector"
 import {
   createSubagentDepthLimitError,
   createSubagentDescendantLimitError,
@@ -64,9 +69,11 @@ type OpencodeClient = PluginInput["client"]
 
 
 interface MessagePartInfo {
+  id?: string
   sessionID?: string
   type?: string
   tool?: string
+  state?: { status?: string }
 }
 
 interface EventProperties {
@@ -80,6 +87,19 @@ interface Event {
   properties?: EventProperties
 }
 
+function resolveMessagePartInfo(properties: EventProperties | undefined): MessagePartInfo | undefined {
+  if (!properties || typeof properties !== "object") {
+    return undefined
+  }
+
+  const nestedPart = properties.part
+  if (nestedPart && typeof nestedPart === "object") {
+    return nestedPart as MessagePartInfo
+  }
+
+  return properties as MessagePartInfo
+}
+
 interface Todo {
   content: string
   status: string
@@ -720,6 +740,8 @@ export class BackgroundManager {
 
     existingTask.progress = {
       toolCalls: existingTask.progress?.toolCalls ?? 0,
+      toolCallWindow: existingTask.progress?.toolCallWindow,
+      countedToolPartIDs: existingTask.progress?.countedToolPartIDs,
       lastUpdate: new Date(),
     }
 
@@ -852,8 +874,7 @@ export class BackgroundManager {
     }
 
     if (event.type === "message.part.updated" || event.type === "message.part.delta") {
-      if (!props || typeof props !== "object" || !("sessionID" in props)) return
+      const partInfo = resolveMessagePartInfo(props)
-      const partInfo = props as unknown as MessagePartInfo
       const sessionID = partInfo?.sessionID
       if (!sessionID) return
 
@@ -876,10 +897,50 @@ export class BackgroundManager {
       task.progress.lastUpdate = new Date()
 
       if (partInfo?.type === "tool" || partInfo?.tool) {
+        const countedToolPartIDs = task.progress.countedToolPartIDs ?? []
+        const shouldCountToolCall =
+          !partInfo.id ||
+          partInfo.state?.status !== "running" ||
+          !countedToolPartIDs.includes(partInfo.id)
+
+        if (!shouldCountToolCall) {
+          return
+        }
+
+        if (partInfo.id && partInfo.state?.status === "running") {
+          task.progress.countedToolPartIDs = [...countedToolPartIDs, partInfo.id]
+        }
+
         task.progress.toolCalls += 1
         task.progress.lastTool = partInfo.tool
+        const circuitBreaker = resolveCircuitBreakerSettings(this.config)
+        if (partInfo.tool) {
+          task.progress.toolCallWindow = recordToolCall(
+            task.progress.toolCallWindow,
+            partInfo.tool,
+            circuitBreaker
+          )
 
-        const maxToolCalls = this.config?.maxToolCalls ?? 200
+          const loopDetection = detectRepetitiveToolUse(task.progress.toolCallWindow)
+          if (loopDetection.triggered) {
+            log("[background-agent] Circuit breaker: repetitive tool usage detected", {
+              taskId: task.id,
+              agent: task.agent,
+              sessionID,
+              toolName: loopDetection.toolName,
+              repeatedCount: loopDetection.repeatedCount,
+              sampleSize: loopDetection.sampleSize,
+              thresholdPercent: loopDetection.thresholdPercent,
+            })
+            void this.cancelTask(task.id, {
+              source: "circuit-breaker",
+              reason: `Subagent repeatedly called ${loopDetection.toolName} ${loopDetection.repeatedCount}/${loopDetection.sampleSize} times in the recent tool-call window (${loopDetection.thresholdPercent}% threshold). This usually indicates an infinite loop. The task was automatically cancelled to prevent excessive token usage.`,
+            })
+            return
+          }
+        }
+
+        const maxToolCalls = circuitBreaker.maxToolCalls
         if (task.progress.toolCalls >= maxToolCalls) {
           log("[background-agent] Circuit breaker: tool call limit reached", {
             taskId: task.id,