Merge pull request #2655 from tad-hq/infinite-circuit-target-fix

fix(circuit-breaker): make repetitive detection target-aware and add enabled escape hatch
This commit is contained in:
YeonGyu-Kim
2026-03-18 11:46:06 +09:00
committed by GitHub
8 changed files with 390 additions and 33 deletions

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@@ -3708,6 +3708,9 @@
"circuitBreaker": {
"type": "object",
"properties": {
"enabled": {
"type": "boolean"
},
"maxToolCalls": {
"type": "integer",
"minimum": 10,

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@@ -1,6 +1,7 @@
import { z } from "zod"
const CircuitBreakerConfigSchema = z.object({
enabled: z.boolean().optional(),
maxToolCalls: z.number().int().min(10).optional(),
windowSize: z.number().int().min(5).optional(),
repetitionThresholdPercent: z.number().gt(0).max(100).optional(),

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@@ -9,6 +9,7 @@ export const DEFAULT_MESSAGE_STALENESS_TIMEOUT_MS = 1_800_000
export const DEFAULT_MAX_TOOL_CALLS = 200
export const DEFAULT_CIRCUIT_BREAKER_WINDOW_SIZE = 20
export const DEFAULT_CIRCUIT_BREAKER_REPETITION_THRESHOLD_PERCENT = 80
export const DEFAULT_CIRCUIT_BREAKER_ENABLED = true
export const MIN_RUNTIME_BEFORE_STALE_MS = 30_000
export const MIN_IDLE_TIME_MS = 5000
export const POLLING_INTERVAL_MS = 3000

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@@ -1,5 +1,6 @@
import { describe, expect, test } from "bun:test"
import {
createToolCallSignature,
detectRepetitiveToolUse,
recordToolCall,
resolveCircuitBreakerSettings,
@@ -17,6 +18,17 @@ function buildWindow(
)
}
function buildWindowWithInputs(
calls: Array<{ tool: string; input?: Record<string, unknown> }>,
override?: Parameters<typeof resolveCircuitBreakerSettings>[0]
) {
const settings = resolveCircuitBreakerSettings(override)
return calls.reduce(
(window, { tool, input }) => recordToolCall(window, tool, settings, input),
undefined as ReturnType<typeof recordToolCall> | undefined
)
}
describe("loop-detector", () => {
describe("resolveCircuitBreakerSettings", () => {
describe("#given nested circuit breaker config", () => {
@@ -31,12 +43,90 @@ describe("loop-detector", () => {
})
expect(result).toEqual({
enabled: true,
maxToolCalls: 120,
windowSize: 10,
repetitionThresholdPercent: 70,
})
})
})
describe("#given no enabled config", () => {
test("#when resolved #then enabled defaults to true", () => {
const result = resolveCircuitBreakerSettings({
circuitBreaker: {
maxToolCalls: 100,
windowSize: 5,
repetitionThresholdPercent: 60,
},
})
expect(result.enabled).toBe(true)
})
})
describe("#given enabled is false in config", () => {
test("#when resolved #then enabled is false", () => {
const result = resolveCircuitBreakerSettings({
circuitBreaker: {
enabled: false,
maxToolCalls: 100,
windowSize: 5,
repetitionThresholdPercent: 60,
},
})
expect(result.enabled).toBe(false)
})
})
describe("#given enabled is true in config", () => {
test("#when resolved #then enabled is true", () => {
const result = resolveCircuitBreakerSettings({
circuitBreaker: {
enabled: true,
maxToolCalls: 100,
windowSize: 5,
repetitionThresholdPercent: 60,
},
})
expect(result.enabled).toBe(true)
})
})
})
describe("createToolCallSignature", () => {
test("#given tool with input #when signature created #then includes tool and sorted input", () => {
const result = createToolCallSignature("read", { filePath: "/a.ts" })
expect(result).toBe('read::{"filePath":"/a.ts"}')
})
test("#given tool with undefined input #when signature created #then returns bare tool name", () => {
const result = createToolCallSignature("read", undefined)
expect(result).toBe("read")
})
test("#given tool with null input #when signature created #then returns bare tool name", () => {
const result = createToolCallSignature("read", null)
expect(result).toBe("read")
})
test("#given tool with empty object input #when signature created #then returns bare tool name", () => {
const result = createToolCallSignature("read", {})
expect(result).toBe("read")
})
test("#given same input different key order #when signatures compared #then they are equal", () => {
const first = createToolCallSignature("read", { filePath: "/a.ts", offset: 0 })
const second = createToolCallSignature("read", { offset: 0, filePath: "/a.ts" })
expect(first).toBe(second)
})
})
describe("detectRepetitiveToolUse", () => {
@@ -113,5 +203,56 @@ describe("loop-detector", () => {
})
})
})
describe("#given same tool with different file inputs", () => {
test("#when evaluated #then it does not trigger", () => {
const calls = Array.from({ length: 20 }, (_, i) => ({
tool: "read",
input: { filePath: `/src/file-${i}.ts` },
}))
const window = buildWindowWithInputs(calls, {
circuitBreaker: { windowSize: 20, repetitionThresholdPercent: 80 },
})
const result = detectRepetitiveToolUse(window)
expect(result.triggered).toBe(false)
})
})
describe("#given same tool with identical file inputs", () => {
test("#when evaluated #then it triggers with bare tool name", () => {
const calls = [
...Array.from({ length: 16 }, () => ({ tool: "read", input: { filePath: "/src/same.ts" } })),
{ tool: "grep", input: { pattern: "foo" } },
{ tool: "edit", input: { filePath: "/src/other.ts" } },
{ tool: "bash", input: { command: "ls" } },
{ tool: "glob", input: { pattern: "**/*.ts" } },
]
const window = buildWindowWithInputs(calls, {
circuitBreaker: { windowSize: 20, repetitionThresholdPercent: 80 },
})
const result = detectRepetitiveToolUse(window)
expect(result.triggered).toBe(true)
expect(result.toolName).toBe("read")
expect(result.repeatedCount).toBe(16)
})
})
describe("#given tool calls with no input", () => {
test("#when the same tool dominates #then falls back to name-only detection", () => {
const calls = [
...Array.from({ length: 16 }, () => ({ tool: "read" })),
{ tool: "grep" },
{ tool: "edit" },
{ tool: "bash" },
{ tool: "glob" },
]
const window = buildWindowWithInputs(calls, {
circuitBreaker: { windowSize: 20, repetitionThresholdPercent: 80 },
})
const result = detectRepetitiveToolUse(window)
expect(result.triggered).toBe(true)
expect(result.toolName).toBe("read")
})
})
})
})

View File

@@ -1,5 +1,6 @@
import type { BackgroundTaskConfig } from "../../config/schema"
import {
DEFAULT_CIRCUIT_BREAKER_ENABLED,
DEFAULT_CIRCUIT_BREAKER_REPETITION_THRESHOLD_PERCENT,
DEFAULT_CIRCUIT_BREAKER_WINDOW_SIZE,
DEFAULT_MAX_TOOL_CALLS,
@@ -7,6 +8,7 @@ import {
import type { ToolCallWindow } from "./types"
export interface CircuitBreakerSettings {
enabled: boolean
maxToolCalls: number
windowSize: number
repetitionThresholdPercent: number
@@ -24,6 +26,7 @@ export function resolveCircuitBreakerSettings(
config?: BackgroundTaskConfig
): CircuitBreakerSettings {
return {
enabled: config?.circuitBreaker?.enabled ?? DEFAULT_CIRCUIT_BREAKER_ENABLED,
maxToolCalls:
config?.circuitBreaker?.maxToolCalls ?? config?.maxToolCalls ?? DEFAULT_MAX_TOOL_CALLS,
windowSize: config?.circuitBreaker?.windowSize ?? DEFAULT_CIRCUIT_BREAKER_WINDOW_SIZE,
@@ -36,28 +39,56 @@ export function resolveCircuitBreakerSettings(
export function recordToolCall(
window: ToolCallWindow | undefined,
toolName: string,
settings: CircuitBreakerSettings
settings: CircuitBreakerSettings,
toolInput?: Record<string, unknown> | null
): ToolCallWindow {
const previous = window?.toolNames ?? []
const toolNames = [...previous, toolName].slice(-settings.windowSize)
const previous = window?.toolSignatures ?? []
const signature = createToolCallSignature(toolName, toolInput)
const toolSignatures = [...previous, signature].slice(-settings.windowSize)
return {
toolNames,
toolSignatures,
windowSize: settings.windowSize,
thresholdPercent: settings.repetitionThresholdPercent,
}
}
function sortObject(obj: unknown): unknown {
if (obj === null || obj === undefined) return obj
if (typeof obj !== "object") return obj
if (Array.isArray(obj)) return obj.map(sortObject)
const sorted: Record<string, unknown> = {}
const keys = Object.keys(obj as Record<string, unknown>).sort()
for (const key of keys) {
sorted[key] = sortObject((obj as Record<string, unknown>)[key])
}
return sorted
}
export function createToolCallSignature(
toolName: string,
toolInput?: Record<string, unknown> | null
): string {
if (toolInput === undefined || toolInput === null) {
return toolName
}
if (Object.keys(toolInput).length === 0) {
return toolName
}
return `${toolName}::${JSON.stringify(sortObject(toolInput))}`
}
export function detectRepetitiveToolUse(
window: ToolCallWindow | undefined
): ToolLoopDetectionResult {
if (!window || window.toolNames.length === 0) {
if (!window || window.toolSignatures.length === 0) {
return { triggered: false }
}
const counts = new Map<string, number>()
for (const toolName of window.toolNames) {
counts.set(toolName, (counts.get(toolName) ?? 0) + 1)
for (const signature of window.toolSignatures) {
counts.set(signature, (counts.get(signature) ?? 0) + 1)
}
let repeatedTool: string | undefined
@@ -70,7 +101,7 @@ export function detectRepetitiveToolUse(
}
}
const sampleSize = window.toolNames.length
const sampleSize = window.toolSignatures.length
const minimumSampleSize = Math.min(
window.windowSize,
Math.ceil((window.windowSize * window.thresholdPercent) / 100)
@@ -88,7 +119,7 @@ export function detectRepetitiveToolUse(
return {
triggered: true,
toolName: repeatedTool,
toolName: repeatedTool.split("::")[0],
repeatedCount,
sampleSize,
thresholdPercent: window.thresholdPercent,

View File

@@ -236,4 +236,181 @@ describe("BackgroundManager circuit breaker", () => {
expect(task.progress?.countedToolPartIDs).toEqual(["tool-1"])
})
})
describe("#given same tool reading different files", () => {
test("#when tool events arrive with state.input #then task keeps running", async () => {
const manager = createManager({
circuitBreaker: {
windowSize: 20,
repetitionThresholdPercent: 80,
},
})
const task: BackgroundTask = {
id: "task-diff-files-1",
sessionID: "session-diff-files-1",
parentSessionID: "parent-1",
parentMessageID: "msg-1",
description: "Reading different files",
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 i = 0; i < 20; i++) {
manager.handleEvent({
type: "message.part.updated",
properties: {
part: {
sessionID: task.sessionID,
type: "tool",
tool: "read",
state: { status: "running", input: { filePath: `/src/file-${i}.ts` } },
},
},
})
}
await flushAsyncWork()
expect(task.status).toBe("running")
expect(task.progress?.toolCalls).toBe(20)
})
})
describe("#given same tool reading same file repeatedly", () => {
test("#when tool events arrive with state.input #then task is cancelled with bare tool name in error", async () => {
const manager = createManager({
circuitBreaker: {
windowSize: 20,
repetitionThresholdPercent: 80,
},
})
const task: BackgroundTask = {
id: "task-same-file-1",
sessionID: "session-same-file-1",
parentSessionID: "parent-1",
parentMessageID: "msg-1",
description: "Reading same file repeatedly",
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 i = 0; i < 20; i++) {
manager.handleEvent({
type: "message.part.updated",
properties: {
part: {
sessionID: task.sessionID,
type: "tool",
tool: "read",
state: { status: "running", input: { filePath: "/src/same.ts" } },
},
},
})
}
await flushAsyncWork()
expect(task.status).toBe("cancelled")
expect(task.error).toContain("repeatedly called read")
expect(task.error).not.toContain("::")
})
})
describe("#given circuit breaker enabled is false", () => {
test("#when repetitive tools arrive #then task keeps running", async () => {
const manager = createManager({
circuitBreaker: {
enabled: false,
windowSize: 20,
repetitionThresholdPercent: 80,
},
})
const task: BackgroundTask = {
id: "task-disabled-1",
sessionID: "session-disabled-1",
parentSessionID: "parent-1",
parentMessageID: "msg-1",
description: "Disabled circuit breaker 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 i = 0; i < 20; i++) {
manager.handleEvent({
type: "message.part.updated",
properties: {
sessionID: task.sessionID,
type: "tool",
tool: "read",
},
})
}
await flushAsyncWork()
expect(task.status).toBe("running")
})
})
describe("#given circuit breaker enabled is false but absolute cap is low", () => {
test("#when max tool calls exceeded #then task is still cancelled by absolute cap", async () => {
const manager = createManager({
maxToolCalls: 3,
circuitBreaker: {
enabled: false,
windowSize: 10,
repetitionThresholdPercent: 95,
},
})
const task: BackgroundTask = {
id: "task-cap-disabled-1",
sessionID: "session-cap-disabled-1",
parentSessionID: "parent-1",
parentMessageID: "msg-1",
description: "Backstop task with disabled circuit breaker",
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)")
})
})
})

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@@ -74,7 +74,7 @@ interface MessagePartInfo {
sessionID?: string
type?: string
tool?: string
state?: { status?: string }
state?: { status?: string; input?: Record<string, unknown> }
}
interface EventProperties {
@@ -918,29 +918,32 @@ export class BackgroundManager {
task.progress.lastTool = partInfo.tool
const circuitBreaker = resolveCircuitBreakerSettings(this.config)
if (partInfo.tool) {
task.progress.toolCallWindow = recordToolCall(
task.progress.toolCallWindow,
partInfo.tool,
circuitBreaker
)
task.progress.toolCallWindow = recordToolCall(
task.progress.toolCallWindow,
partInfo.tool,
circuitBreaker,
partInfo.state?.input
)
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
}
if (circuitBreaker.enabled) {
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

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@@ -10,7 +10,7 @@ export type BackgroundTaskStatus =
| "interrupt"
export interface ToolCallWindow {
toolNames: string[]
toolSignatures: string[]
windowSize: number
thresholdPercent: number
}