Cheap triage for all PRs, then deep review only when risk score crosses a threshold. Route to larger reasoning model + tools. This is how you survive 5000 concurrency.
| Signal | Threshold | Weight |
|---|---|---|
| Files changed | > 20 files | High |
| Security-sensitive paths | auth/, crypto/, payment/ | Critical |
| Test coverage delta | < 0% | Medium |
| New dependencies | Any | Medium |
| API surface changes | Public exports modified | High |
| Historical defect rate | > 2 per month in path | Medium |
Mode B represents the best balance on the Pareto frontier for production workloads. It routes 85% of PRs through the cheap path while ensuring high-risk changes get the attention they need. This is the only mode that can handle 5000 concurrent PRs without either bankrupting you or missing critical issues.