[P2][BUG] No agent execution timeout — infinite tool-calling loops run indefinitely and drain API credits

[pratik-saptarshi]

Summary

Probus spawns Claude Code agents via runClaudeAgent() and runChatAgent() with no wall-clock timeout. There is no deadline on how long an agent may run, how many tool calls it may make, or how many tokens it may consume. In pathological cases — adversarial repositories, model misalignment, or complex codebases — an agent can enter an infinite read-edit loop, running indefinitely until the user manually clicks Stop (or the API rate limit kicks in). This drains API credits silently.

Panel verdict: P2, VERIFIED, EXISTING_DEFECT (Completeness Audit finding G-06 / VAL-21).

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Affected Files

File	Lines	Issue
src/claude-agent.ts	L51–L61	No timeout option in Options object
src/server/chat-agent.ts	L50–L59	No timeout option in chat agent Options
src/scanner.ts	L156–L188	runAgent() passes signal? but never creates a timeout signal

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Root Cause — Code Evidence

No timeout in scanner agent options (src/claude-agent.ts, lines 51–61):

const options: Options = {
  cwd,
  model,
  env: { ...process.env, ...env } as Record<string, string | undefined>,
  abortController,
  includePartialMessages: true,
  permissionMode: 'bypassPermissions',
  settingSources: [],
  // ↑ No maxTokens, no timeout, no maxTurns — agent can run forever
};

runAgent() accepts a signal but never creates a timeout one (src/scanner.ts, lines 156–188):

async function* runAgent(
  prompt: string,
  cwd: string,
  model: string,
  signal?: AbortSignal,   // ← caller provides signal, but callers never add a timeout
  logFile?: string,
  stageLabel?: string,
): AsyncGenerator<...> {
  // ...
  for await (const ev of runClaudeAgent({ prompt, cwd, model, env, signal, logFile, stageLabel })) {
    yield ev;
  }
}

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Impact

• Credit drain: A single stuck agent on a complex file can consume $10–$100+ in API credits before the user notices.
• UI freeze: The scan/chat interface shows a perpetual loading state with no timeout indicator.
• Cascading scans: In high-parallelism mode (parallel=16), 16 concurrent agents can all get stuck simultaneously.

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Steps to Reproduce

1. Scan a repository containing a deliberately complex or adversarially crafted source file (e.g. a 10,000-line minified JS bundle).
2. Observe: the agent enters a read-loop trying to process the file, never completing.
3. Wait 10 minutes — the scan is still running with no timeout.

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Remediation

Step 1 — Add per-agent wall-clock timeout using AbortSignal.timeout()

// src/claude-agent.ts — in runClaudeAgent()
const MAX_AGENT_DURATION_MS = 5 * 60 * 1000; // 5 minutes per file scan

// Compose the caller's signal with a timeout signal:
const timeoutSignal = AbortSignal.timeout(MAX_AGENT_DURATION_MS);
const combined = AbortSignal.any([timeoutSignal, ...(signal ? [signal] : [])]);

const options: Options = {
  // ...
  abortController, // use abortController driven by combined signal
};

// Drive abortController from combined signal:
combined.addEventListener('abort', () => abortController.abort(combined.reason), { once: true });

Step 2 — Add a max token budget per agent

If the Claude Code SDK supports a token cap:

const options: Options = {
  // ...
  maxTokens: 50_000,  // cap per-agent invocation
};

Step 3 — Add configurable timeout to scan options

Expose agentTimeoutSeconds in the POST /api/scans body (defaulting to 300s) and thread it through to runAgent():

const agentTimeout = Math.min(body.agentTimeoutSeconds ?? 300, 600) * 1000;
// Pass to scanner as AbortSignal.timeout(agentTimeout)

Step 4 — Show elapsed time in the UI

Display per-file elapsed time in the scan progress view so users can see when an agent is running unusually long and manually abort it.

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References

• AbortSignal.timeout(): https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal/timeout_static
• AbortSignal.any(): https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal/any_static