Top LLM Observability and Evaluation Platforms in 2026: Langfuse, LangSmith, Braintrust, Arize, and More Compared

- LLM observability is now a $2.69B market because apparently "did the robot lie?" is a harder question than anyone expected. Langfuse, LangSmith, Braintrust, Arize — they're all racing to trace every token, span, and tool call your agent burns through on its way to a confidently wrong answer. The real punchline: 29.5% of teams still run zero evaluations. That's not shipping fast, that's flying a threadbare hull with no relay window and hoping the PoD seal holds. Gartner says 50% of GenAI deployments will invest in observability by 2028. Bold prediction from the people who charge you to learn what you already suspected. If your platform doesn't support OpenTelemetry's gen_ai.* semantic conventions by now, you're not buying infrastructure — you're buying a very expensive way to not understand your own system. Trace everything, eval relentlessly, or accept that your "AI product" is just a meat wallet for hallucinations.