Enforcement requires request-path authority
A system cannot guarantee a model allowlist, budget action, or cache boundary if applications can bypass it. These controls belong in a gateway or another mandatory network and identity boundary.
The gateway should emit a compact durable ledger even if a richer trace is sent elsewhere. Billing and policy evidence must survive changes to the observability vendor.
Observability needs application context
A trace platform can connect model calls with retrieval, tools, user actions, evaluation, and business outcomes. That depth is often better implemented through application instrumentation than inferred from proxy traffic alone.
Use trace IDs to join gateway decisions with application spans. Avoid duplicating full prompt bodies in several systems unless retention and access controls are explicit.
Define a system of record
Choose where model cost, token usage, policy decisions, evaluations, and user outcomes are authoritative. Document how late provider corrections and invoice reconciliation update those records.
A practical split is request and cost ledger in the gateway, rich application trace in observability, and summarized financial records in the FinOps platform.
- Gateway: identity, policy, route, cache, cost estimate
- Observability: trace, prompt version, retrieval, tools, scores
- FinOps: allocation, forecast, budget, invoice reconciliation
- Warehouse: cross-system analytics and retained outcomes
Avoid the feature-checklist trap
A product that offers both proxying and traces may still be weak at one. Evaluate bypass resistance, data ownership, export, failure modes, latency, and which controls remain available if the vendor is down.
Frequently asked questions
Can an observability SDK enforce budgets?
It can trigger actions, but enforcement is incomplete if applications can omit the SDK or call providers directly. A mandatory gateway or identity layer is stronger.
Should the gateway store full prompts?
Only when policy permits and the value justifies the privacy risk. Metadata, hashes, redacted previews, and external trace references are often sufficient for the cost ledger.
Can one vendor provide both?
Yes. Still define which records and controls are authoritative, how data is exported, and how bypass is prevented.
Sources and further reading
FrugalAI uses primary documentation and published research where possible. Product capabilities and prices can change; verify vendor details before procurement or production changes.