Observability

Assign a stable operation name and correlation ID at the user-action or route boundary. Record start, terminal outcome, duration, release, and route. Do not log every reactive read or scope write; volume hides causality and changes timing.

performance.mark(`task-save:${id}:start`);
try {
  await repository.save(task);
  record({ operation: 'task.save', outcome: 'success', id });
} catch (error) {
  record({ operation: 'task.save', outcome: classify(error), id });
  throw error;
}

Expected domain and transport failures should produce classified outcomes. Unexpected exceptions should reach $exceptionHandler with their cause. Redact credentials, request bodies, user-entered text, and model snapshots.

Carry one correlation ID through route transition, request, retry, and workflow command. Record cancellation separately from failure. For realtime connections, record state transitions and reconnect exhaustion, not every message.

After deployment, verify release tagging, source-map policy, critical routes, error rate, request latency, and one synthetic path. Every alert needs an owner and actionable threshold.