We are hitting the wall where prompt engineering stops being a solution and starts being a liability. In production, multi-agent systems do not fail because the LLM is "dumb"; they fail because there is no control plane enforcing boundaries. You cannot prompt your way out of a race condition or a privilege escalation.
Score vendors against the governance gap¶
The pattern that worked for us: buy the observability, build the governance. When we evaluated tools we ignored the feature lists and scored them against the governance gap. LangSmith at $39/seat/mo is excellent for trace-level debugging; AgentOps at $49–$199/mo gives you session replay and cost tracking; Helicone's free tier (10k requests/mo) handles proxy metering. All good tools. All of them answer "what happened," not "was it allowed to."
The missing control layer¶
None sells the actual control layer as one plane: identity-scoped grants, hard-gated human approvals, per-plan spend ceilings that fail closed, hash-linked audit rows. That absence is the product gap — and it is also why the layer is cheap to own: six policies, two schemas, about a 14-day rollout.
Our rules¶
- Do not pay for a platform until we have metered real spend on the free tiers.
- Build the kill switch ourselves.
- Feed the observability tools' data into a control plane we own.
- Revisit paid tiers only when the metered data justifies it.
If you rely solely on vendor-provided safety features, you are renting your compliance. Feed the observability tools' data into a control plane you own. The safety mesh is your IP, not their SaaS feature. The full vendor evaluation matrix, the six policies, and the two schemas are in the Studio Edition playbook.