You don't need a $50k/month enterprise gateway just to keep LLMs from doing something stupid in production. The enforcement layer itself costs zero dollars in licensing fees because the primitives are already solved by standard infrastructure patterns.
If you break down what "governance" actually means at runtime, it's just three things:
- A policy-as-code gate sitting right before the tool-execution boundary. OPA/Rego or an equivalent checking arguments before a Postgres query or a
curlexecution. The model decides; the gate permits or denies before anything mutates. - A transparent reverse proxy in front of the model API. Something like Envoy or a lightweight sidecar handling token-bucket rate limiting, PII redaction on egress, and basic circuit breaking. This is decades-old proxy craft, not a new product category.
- Structured JSON audit logs piped to stdout, ingested by whatever log aggregator you're already paying for. No special pipeline, no new vendor.
None of this requires a proprietary control plane with a glossy SaaS dashboard. You can spin up local validation loops using JSON schema validators and lightweight policy engines directly in your agent's runtime process. If the model tries to invoke a tool with parameters that fail the schema or violate the policy, the execution loop catches it, appends the error to the context window as a feedback message, and lets the model self-correct.
Enterprise sales reps will try to convince you that policy distribution and distributed state management for agents require a specialized commercial mesh. They don't. You just need disciplined Unix-style composability: deterministic validators sitting between probabilistic outputs and state-mutating APIs. Keep the model in a sandbox, make every tool call explicit and typed, and let standard logging handle the rest. Save the budget for compute.
This is the open-source enforcement stack from Section 8 of the Governed Agent Mesh Playbook — the full system for running governed agents without buying a gateway.