fix: prevent infinite restart loop that causes runaway API costs

[ajbmachon]

Problem

When memorySessionId is null (due to a race condition during session initialization), the generator enters an infinite restart loop:

1. Generator starts → Calls LLM API ✅ (tokens charged)
2. processAgentResponse() → throws "memorySessionId not yet captured" ❌
3. .finally() sees pendingCount > 0 → Restarts generator after 1 second
4. Go to step 1 (NO RETRY LIMIT!)

Real-World Impact

I experienced $402 in wasted API costs before my OpenRouter key limit stopped it. The logs showed:

[ERROR] ✗ OpenRouter agent error - Cannot store observations: memorySessionId not yet captured
[INFO ] Restarting generator after crash/exit with pending work {pendingCount=429}

This repeated 24,219 times in a single day. Each restart made another LLM call that succeeded (cost tokens) but then failed to store the result.

Solution

1. Add Restart Limit (Primary Fix)

// SessionRoutes.ts
const MAX_CONSECUTIVE_RESTARTS = 3;

if (session.consecutiveRestarts > MAX_CONSECUTIVE_RESTARTS) {
  logger.error('SESSION', 'CRITICAL: Generator restart limit exceeded - stopping to prevent runaway costs');
  session.abortController.abort();
  return;
}

2. Add Exponential Backoff

// Backoff: 1s → 2s → 4s
const backoffMs = Math.min(1000 * Math.pow(2, session.consecutiveRestarts - 1), 8000);

3. Fail Fast - Check Before LLM Call (Defensive)

// OpenRouterAgent.ts and GeminiAgent.ts
if (!session.memorySessionId) {
  throw new Error('Cannot process observations: memorySessionId not yet captured');
}
// THEN call expensive LLM
await this.queryOpenRouterMultiTurn(...);

This check happens before the LLM call, preventing token waste.

Files Changed

File	Change
worker-types.ts	Add consecutiveRestarts: number to ActiveSession
SessionManager.ts	Initialize consecutiveRestarts: 0
SessionRoutes.ts	Add restart limit (3), exponential backoff, reset on success
OpenRouterAgent.ts	Check memorySessionId before LLM calls
GeminiAgent.ts	Same defensive check

Testing

1. Build succeeds: npm run build ✅
2. Logic verified against original logs showing the infinite loop pattern
3. Fix preserves legitimate crash recovery for transient failures (3 retries)

Notes

• The root cause (why memorySessionId isn't captured in some sessions) may still need investigation
• This fix is a safety guardrail to prevent catastrophic costs regardless of root cause
• Consider adding alerting/monitoring for when the restart limit is hit

[denjzs]

Related Issue:

• v9.0.0: Crash-recovery loop when memory_session_id is not captured #623
• OpenRouter agent fails to capture memorySessionId for sessions with empty prompt history #591
• OpenRouter provider fails to create observations (obsCount=0) #677
• Resolution: PostToolUse hook not creating observations - switch to claude provider #678

PR:

• fix: generate memorySessionId for stateless providers #615