Platform & Safety
LLM observability & evals
Tracing, prompt management and evaluation for LLM apps and agents.
What it is
Observability platforms record every LLM call and agent step (prompt, response, tokens, cost, latency, tool calls) as traces so you can debug failures, track cost and quality, manage prompt versions and run evaluations (LLM-as-judge, human review, regression datasets) before and after release.
How pricing works
Usually a platform subscription (often per seat or flat) that includes some volume, then usage overage per 100K traces/events or per GB of data. We normalise to the lowest paid plan carrying 1M traced events per month, with one small team; seats, retention upgrades and add-ons are extra.
We compare everything in one unit: USD per month at 1M traced events.
Typical uses
- Debugging agent runs step by step
- Tracking cost and latency per feature or customer
- Prompt versioning and A/B tests
- Offline evaluation on datasets and online scoring of production traffic
- Human annotation and feedback queues
What to compare
- Trace volume included and overage rate
- Data retention
- Evaluation features (datasets, judges, experiments)
- Framework integrations (OpenTelemetry, SDKs)
- Self-hosting option
Watch out for
- 'Events', 'units', 'traces' and 'logs' are not the same: one agent run can create dozens of events, so compare on your own trace shape.
- Retention limits can force an upgrade just to look back a few months.
- Storing full prompts can include personal data; check redaction and region options.
All 4 APIs, cheapest first
Free to browse| API | $ / mo · 1M events | Evaluations | Prompt management | Open source | Quality | Price data | Compare |
|---|---|---|---|---|---|---|---|
| Helicone (Pro) Helicone | $79.00 | Yes | Yes | Yes | – | Unverified sample | |
| Langfuse Cloud (Core) Langfuse | $101.00 | Yes | Yes | Yes | – | Verified Oct 6, 2026 | |
| Braintrust (Pro) Braintrust | $280.00 | Yes | Yes | No | – | Unverified sample | |
| LangSmith (Plus) LangChain (LangSmith) | $450.00 | Yes | Yes | No | – | Unverified sample |