LLM Router Readiness Checklist (2026)

Use this to assess whether you have a real routing layer (policy + instrumentation + fallbacks), not just multiple model SDKs.

1) Interface & Ownership
- All model calls go through a single gateway/service (not scattered across app code).
- The gateway API is stable: app code doesn’t mention specific model names.
- Prompt/tool configs are versioned artifacts (reviewable diffs, rollbacks).

2) Routing Signals (inputs to decisions)
- You classify requests by task type (chat, extraction, summarization, code, moderation, etc.).
- You detect sensitive data (PII/secrets) before any external API call.
- You tag interactions by risk tier (low-stakes vs regulated or user-harm sensitive).
- You measure provider health (latency, error rate) and feed it into routing.

3) Guardrails That Actually Enforce
- Structured outputs: schemas validated strictly; failures trigger retries or fallbacks.
- Tool calling: arguments validated; tool errors are handled explicitly (not dumped back to the model blindly).
- Retrieval grounding (if using RAG): citations required for claims; spot checks verify quotes exist in retrieved text.

4) Fallback Design
- You have failure-type fallbacks (e.g., JSON parse failure → retry with stricter schema model; provider timeout → switch provider).
- Fallbacks are bounded (max retries, max time, explicit degrade behavior).
- You can degrade features intentionally (shorter answers, no tools, async completion) rather than failing hard.

5) Evals & Regression Control
- You maintain a small “golden set” of representative conversations/tasks.
- Every change to model, prompt, tools, or routing rules re-runs the golden set.
- You track eval results over time and can pinpoint regressions by version.
- You separate deterministic checks (schemas, constraints) from model-graded checks (tone, helpfulness) and audit the latter.

6) Telemetry & Auditability
- Per request, you log: route chosen, model/provider, prompt version, tools invoked, latency, errors.
- You can trace a user-visible failure to a specific route decision and config version.
- You can answer: “What percent of traffic used fallback X last week?” without manual log archaeology.

7) Cost & Rate Controls
- Budgets exist per org/user/feature with deny/downgrade behavior.
- You have batch/async paths for non-interactive workloads.
- You can switch bulk work to smaller/self-hosted models without product changes.

If you fail more than 5 items above, don’t fine-tune. Build the router layer first.