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Merged
wenshao merged 1 commit into from
Jun 30, 2026
Merged

Stop repeated invalid tool parameter loops in ACP #6076

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81 changes: 81 additions & 0 deletions packages/cli/src/acp-integration/session/Session.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2347,6 +2347,87 @@ describe('Session', () => {
).toContain('Duplicate provider tool call id "shell_1"');
});

it('stops an ACP prompt after repeated invalid tool parameters with fresh ids', async () => {
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mockConfig.getApprovalMode = vi.fn().mockReturnValue(ApprovalMode.YOLO);
const build = vi.fn().mockImplementation(() => {
throw new Error('Parameter "questions" must be an array.');
});
mockToolRegistry.getTool.mockReturnValue({
name: 'ask_user_question',
kind: core.Kind.Other,
displayName: 'Ask User Question',
description: 'Ask user question',
build,
canUpdateOutput: false,
isOutputMarkdown: true,
});

mockChat.sendMessageStream = vi
.fn()
.mockResolvedValueOnce(
createStreamWithChunks([
{
type: core.StreamEventType.CHUNK,
value: {
functionCalls: [
{
id: 'ask_1',
name: 'ask_user_question',
args: { questions: '[{"question":"Continue?"}]' },
},
],
},
},
]),
)
.mockResolvedValueOnce(
createStreamWithChunks([
{
type: core.StreamEventType.CHUNK,
value: {
functionCalls: [
{
id: 'ask_2',
name: 'ask_user_question',
args: { questions: '[{"question":"Continue?"}]' },
},
],
},
},
]),
)
.mockResolvedValueOnce(
createStreamWithChunks([
{
type: core.StreamEventType.CHUNK,
value: {
functionCalls: [
{
id: 'ask_3',
name: 'ask_user_question',
args: { questions: '[{"question":"Continue?"}]' },
},
],
},
},
]),
)
.mockResolvedValueOnce(createEmptyStream());

await session.prompt({
sessionId: 'test-session-id',
prompt: [{ type: 'text', text: 'ask me before continuing' }],
});

expect(build).toHaveBeenCalledTimes(3);
expect(mockChat.sendMessageStream).toHaveBeenCalledTimes(3);
expect(debugLoggerWarnSpy).toHaveBeenCalledWith(
expect.stringContaining(
'Stopping ACP turn after repeated tool parameter errors',
),
);
});

it('clears duplicate provider id tracking between ACP prompts', async () => {
mockConfig.getApprovalMode = vi.fn().mockReturnValue(ApprovalMode.YOLO);
vi.mocked(mockChat.getHistoryFunctionResponseIds).mockReturnValue(
Expand Down
145 changes: 144 additions & 1 deletion packages/cli/src/acp-integration/session/Session.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,9 @@ import {
endToolExecutionSpan,
logConversationFinishedEvent,
ConversationFinishedEvent,
logLoopDetected,
LoopDetectedEvent,
LoopType,
acquireSleepInhibitor,
clearGoalTerminalObserver,
setGoalTerminalObserver,
Expand Down Expand Up @@ -209,11 +212,85 @@ type RunToolResult = {
parts: Part[];
stopAfterPermissionCancel: boolean;
repeatedDuplicateProviderToolCall?: boolean;
loopDetected?: boolean;
};

type DaemonToolLoopState = {
totalToolCalls: number;
invalidToolParamErrors: Map<string, number>;
loopDetected: boolean;
};

const DAEMON_TURN_TOOL_CALL_CAP = 100;
const DAEMON_INVALID_TOOL_PARAMS_THRESHOLD = 3;

const PERMISSION_CANCEL_SKIP_MESSAGE =
'Skipped because a permission request was cancelled before the user answered; user input is required before continuing.';

function createDaemonToolLoopState(): DaemonToolLoopState {
return {
totalToolCalls: 0,
invalidToolParamErrors: new Map(),
loopDetected: false,
};
}

function recordDaemonLoopDetected(
config: Config,
promptId: string,
loopType: LoopType,
message: string,
loopState: DaemonToolLoopState,
): true {
if (!loopState.loopDetected) {
loopState.loopDetected = true;
debugLogger.warn(message);
logLoopDetected(config, new LoopDetectedEvent(loopType, promptId));
}
return true;
}

function recordDaemonToolCalls(
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config: Config,
promptId: string,
loopState: DaemonToolLoopState | undefined,
count: number,
): boolean {
if (!loopState || loopState.loopDetected)
return loopState?.loopDetected ?? false;
loopState.totalToolCalls += count;
if (loopState.totalToolCalls <= DAEMON_TURN_TOOL_CALL_CAP) return false;
return recordDaemonLoopDetected(
config,
promptId,
LoopType.TURN_TOOL_CALL_CAP,
`Stopping ACP turn after ${loopState.totalToolCalls} tool calls in one turn.`,
loopState,
);
}

function recordDaemonInvalidToolParams(
config: Config,
promptId: string,
loopState: DaemonToolLoopState | undefined,
toolName: string,
error: Error,
): boolean {
if (!loopState || loopState.loopDetected)
return loopState?.loopDetected ?? false;
const key = `${toolName}\0${error.message}`;
const count = (loopState.invalidToolParamErrors.get(key) ?? 0) + 1;
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loopState.invalidToolParamErrors.set(key, count);
if (count < DAEMON_INVALID_TOOL_PARAMS_THRESHOLD) return false;
return recordDaemonLoopDetected(
config,
promptId,
LoopType.INVALID_TOOL_PARAMS_STAGNATION,
`Stopping ACP turn after repeated tool parameter errors from ${toolName}: ${error.message}`,
loopState,
);
}

// The drain is served from an in-memory queue, so a conforming client answers
// near-instantly (or rejects with -32601). No response within this window
// means the client silently drops unknown methods; without a deadline the
Expand Down Expand Up @@ -1653,6 +1730,7 @@ export class Session implements SessionContext {

let nextMessage: Content | null = { role: 'user', parts };
let turnCount = 0;
const toolLoopState = createDaemonToolLoopState();

// conversation_finished must fire on every terminal path of the
// turn — the loop below has cancel/abort/no-stream early-returns
Expand Down Expand Up @@ -1820,6 +1898,7 @@ export class Session implements SessionContext {
pendingSend.signal,
promptId,
functionCalls,
toolLoopState,
);
if (toolRun.stopAfterPermissionCancel) {
await this.#preserveCancelledPermissionToolRun(
Expand Down Expand Up @@ -1981,6 +2060,7 @@ export class Session implements SessionContext {
role: 'user',
parts: continueParts,
};
const toolLoopState = createDaemonToolLoopState();
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// Process the follow-up message and any tool calls that result
while (nextMessage !== null) {
Expand Down Expand Up @@ -2096,6 +2176,7 @@ export class Session implements SessionContext {
pendingSend.signal,
promptId,
functionCalls,
toolLoopState,
);
if (toolRun.stopAfterPermissionCancel) {
await this.#preserveCancelledPermissionToolRun(
Expand Down Expand Up @@ -2293,6 +2374,10 @@ export class Session implements SessionContext {
toolRun: RunToolResult,
abortSignal: AbortSignal,
): Promise<Content | null> {
if (toolRun.loopDetected) {
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debugLogger.debug('Stopping ACP turn after daemon loop detection.');
return null;
}
if (toolRun.repeatedDuplicateProviderToolCall) {
debugLogger.debug(
'Stopping ACP turn after dropping repeated duplicate provider tool-call response.',
Expand Down Expand Up @@ -2894,6 +2979,7 @@ export class Session implements SessionContext {
role: 'user',
parts: [...cronReminders, { text: modelText }],
};
const toolLoopState = createDaemonToolLoopState();

while (nextMessage !== null) {
turnCount++;
Expand Down Expand Up @@ -2982,6 +3068,7 @@ export class Session implements SessionContext {
ac.signal,
promptId,
functionCalls,
toolLoopState,
);
if (toolRun.stopAfterPermissionCancel) {
await this.#preserveCancelledPermissionToolRun(
Expand Down Expand Up @@ -3197,6 +3284,7 @@ export class Session implements SessionContext {
role: 'user',
parts: [...notificationReminders, ...notificationParts],
};
const toolLoopState = createDaemonToolLoopState();

while (nextMessage !== null) {
if (ac.signal.aborted) {
Expand Down Expand Up @@ -3297,6 +3385,7 @@ export class Session implements SessionContext {
ac.signal,
promptId,
functionCalls,
toolLoopState,
);
if (toolRun.stopAfterPermissionCancel) {
await this.#preserveCancelledPermissionToolRun(
Expand Down Expand Up @@ -3650,7 +3739,23 @@ export class Session implements SessionContext {
abortSignal: AbortSignal,
promptId: string,
functionCalls: FunctionCall[],
toolLoopState?: DaemonToolLoopState,
): Promise<RunToolResult> {
if (
recordDaemonToolCalls(
this.config,
promptId,
toolLoopState,
functionCalls.length,
)
) {
return {
parts: [],
stopAfterPermissionCancel: false,
loopDetected: true,
};
}

const dedupedFunctionCalls = dedupeToolCallsById(functionCalls);
type ExecutableBatch = {
kind: 'execute';
Expand Down Expand Up @@ -3846,6 +3951,7 @@ export class Session implements SessionContext {
promptId,
calls[idx],
onStopAfterPermissionCancel,
toolLoopState,
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)
.then((r) => {
results[idx] = r;
Expand Down Expand Up @@ -3898,9 +4004,18 @@ export class Session implements SessionContext {
abortSignal.removeEventListener('abort', propagateAbort);
}
let shouldStop = false;
let shouldStopForLoop = false;
for (const r of results) {
parts.push(...r.parts);
shouldStop ||= r.stopAfterPermissionCancel;
shouldStopForLoop ||= r.loopDetected === true;
}
if (shouldStopForLoop) {
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return {
parts,
stopAfterPermissionCancel: false,
loopDetected: true,
};
}
if (shouldStop) {
await appendSkippedAfter(parts, batch.calls[batch.calls.length - 1]);
Expand All @@ -3912,8 +4027,21 @@ export class Session implements SessionContext {
}
} else {
for (const fc of batch.calls) {
const r = await this.runTool(abortSignal, promptId, fc);
const r = await this.runTool(
abortSignal,
promptId,
fc,
undefined,
toolLoopState,
);
parts.push(...r.parts);
if (r.loopDetected) {
return {
parts,
stopAfterPermissionCancel: false,
loopDetected: true,
};
}
if (r.stopAfterPermissionCancel) {
await appendSkippedAfter(parts, fc);
return {
Expand Down Expand Up @@ -3972,6 +4100,7 @@ export class Session implements SessionContext {
promptId: string,
fc: FunctionCall,
onStopAfterPermissionCancel?: () => void,
toolLoopState?: DaemonToolLoopState,
): Promise<RunToolResult> {
const callId = fc.id ?? `${fc.name}-${Date.now()}`;
let args = (fc.args ?? {}) as Record<string, unknown>;
Expand Down Expand Up @@ -4110,8 +4239,10 @@ export class Session implements SessionContext {
// Get approval mode for hook context (defined outside try for catch block access)
const approvalMode = this.config.getApprovalMode();

let toolBuildSucceeded = false;
try {
const invocation = tool.build(args);
toolBuildSucceeded = true;

// Production AgentTool always initializes `eventEmitter` on its
// invocation (`agent.ts:392`). Be defensive about the `undefined`
Expand Down Expand Up @@ -4886,9 +5017,21 @@ export class Session implements SessionContext {
errorType: undefined,
});

const loopDetected =
!activeToolAbortSignal.aborted &&
!toolBuildSucceeded &&
recordDaemonInvalidToolParams(
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this.config,
promptId,
toolLoopState,
toolName,
error,
);

return {
parts: errorResponse(error),
stopAfterPermissionCancel: nestedPermissionCancelled,
loopDetected,
};
}
}); // end runInToolSpanContext
Expand Down
5 changes: 4 additions & 1 deletion packages/cli/src/nonInteractiveCli.ts
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Expand Up @@ -138,6 +138,8 @@ const LOOP_TYPE_LABELS: Record<LoopType, string> = {
'the model alternated between the same two tool calls in a repeating pattern',
[LoopType.TURN_TOOL_CALL_CAP]:
'the model exceeded the maximum number of tool calls allowed in a single turn',
[LoopType.INVALID_TOOL_PARAMS_STAGNATION]:
'the model repeatedly sent invalid tool parameters without correcting them',
};

function formatLoopDetectedMessage(loopType: LoopType | undefined): string {
Expand All @@ -150,7 +152,8 @@ function formatLoopDetectedMessage(loopType: LoopType | undefined): string {
loopType === LoopType.TURN_TOOL_CALL_CAP ||
loopType === LoopType.CONSECUTIVE_IDENTICAL_TOOL_CALLS ||
loopType === LoopType.SHELL_COMMAND_STAGNATION ||
loopType === LoopType.GLOBAL_TOOL_CALL_DUPLICATE;
loopType === LoopType.GLOBAL_TOOL_CALL_DUPLICATE ||
loopType === LoopType.INVALID_TOOL_PARAMS_STAGNATION;
const hint = isAlwaysOn
? ' This is an always-on guard and cannot be disabled via `model.skipLoopDetection`.'
: ' Set the `model.skipLoopDetection` setting to true to disable.';
Expand Down
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