Langfuse observes.
Runback re-executes.
Langfuse is an open-source observability and prompt-management platform. Traces are read-only — there's no re-execution, policy enforcement, or signed compliance artifact.
| Capability | Langfuse | Runback | Note |
|---|---|---|---|
| Read and search traces | ✓ | ✓ | |
| Prompt versioning and management | ✓ | partial | Runback tracks prompt changes via model diff |
| Open-source, self-hostable | ✓ | ✓ | Both fully self-hostable on Postgres |
| Re-execute any step from captured inputs | ✗ | ✓ | |
| Live policy enforcement — block before it runs | ✗ | ✓ | |
| CI release gate | ✗ | ✓ | |
| Signed, tamper-evident audit export | ✗ | ✓ | |
| Regulatory mappings (EU AI Act · CPS 230 · NIST) | ✗ | ✓ |
Most teams use both — Langfusefor day-to-day trace browsing, Runback for incident replay, CI gating, and the compliance artifact. The two don't overlap until the moment an agent misbehaves in production and someone asks you to prove it.
Try the replay on a real incident.
No signup. Walk a failing production run step by step and see what the model saw.