The routing contract applies a deterministic order:
- hard constraints and policy denies,
- observed real-world performance,
- benchmark-derived quality,
- declared capability profile,
- neutral defaults.
If scores are tied within epsilon, the baseline tie-break sequence is:
- preferred locality strategy,
- lower estimated cost when cost optimization is active,
- lower p95 latency when latency optimization is active,
- lexicographically stable
endpoint_id.
Every exclusion or selection must emit reason codes so the final RouterDecision is explainable.