You've shipped your LLM service. Costs climb. Errors appear with no visibility. This is the observability gap.
Three Options
Langfuse — Open-source. Built for cost attribution. Developers saved €400/month discovering waste. Free tier: 100K runs/month.
LangSmith — Anthropic's platform. Integrates into LangChain with zero code changes. Strong root-cause analysis. Price ceiling hits fast: $1200+/mo at scale.
OpenTelemetry — Vendor-independent standard. Maximum control and no lock-in. Trade-off: more instrumentation work.
Real Tradeoffs
- Cost visibility: Langfuse >> others
- Root cause analysis: LangSmith > others
- No vendor lock-in: OpenTelemetry
Based on interviews with five production teams. One LangSmith user hit price ceiling, switched to Langfuse for cost control.
Pick Yours
Using LangChain heavily? LangSmith.
Need per-user cost tracking? Langfuse.
Want maximum freedom? OpenTelemetry.
Ship this week. Run it a month. The data will tell you which fits.
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