LangSmith vs Langfuse vs Helicone vs DriftWatch — I Compared All Four So You Don't Have To

I spent the last two weeks evaluating every major LLM monitoring tool on the market. Here's my honest take on when each one actually makes sense. The short version Tool Best for What it misses LangSmith Tracing + prompt management Proactive drift detection Langfuse Open-source observability Baseline comparison over time Helicone Cost/latency analytics via proxy Behavioral monitoring DriftWatch Behavioral drift alerting Full request logging None of these tools do the same thing.