Segment the workload
Classification, extraction, summarization, tool selection, planning, and final prose need different quality signals. Evaluate and route them separately; a single 'best model' ranking throws away the structure that makes optimization safe.
Include risk. A support-ticket label and a financial action should not share the same threshold.
Define eligibility before preference
A model is eligible only if it supports the required capability and clears task-specific success, schema, safety, and latency thresholds. Among eligible models, rank by cost, speed, availability, or a weighted score.
This ordering prevents a cheap route from being chosen for a workload it has never demonstrated it can handle.
Escalate on observable signals
Escalation triggers can include invalid schema, missing citation, tool failure, low verifier score, explicit user risk, or a deterministic rule. Avoid relying only on self-reported model confidence; it is not consistently calibrated.
For some tasks, generate with an efficient model and verify with a separate model or programmatic check. The combined cost can remain below always using the premium model.
Learn from outcomes
Connect user corrections, task completion, retries, and human review back to model and route. Re-run evaluations when the feedback shows a new failure mode.
Use canaries and holdouts to confirm that an optimization transfers from offline tests to real traffic.
