Best AI Cost Observability Tools in 2026

In short: AI cost observability tools track token usage, latency, and spend at the model or request level, then attribute that spend to a team, feature, or customer. They fall into four categories: gateway/proxy tools (LiteLLM, Helicone), trace-level tools (Langfuse, LangSmith), billing-based platforms (Finout, CloudZero, Vantage), and full-stack FinOps platforms with AI coverage. The right category depends on whether you need real-time request control, prompt-level debugging, or financial allocation and governance across your whole cloud and AI stack.