Langfuse vs Flagsmith

Langfuse

Flagsmith

Langfuse · 16 features

• Annotation Queues — Human reviewers rate traces. Unlimited on Pro+.
• Dashboards — Aggregate metrics, cost, quality across projects.
• Datasets — Curate test sets from production traces. Run experiments.
• EU Cloud Region — GDPR-compliant hosting in EU.
• Evaluations — LLM-as-judge, manual scores, custom model-graded evaluators.
• LLM Cost Tracking — Automatic cost calculation per provider/model.
• OpenTelemetry Native — OTel SDK → Langfuse endpoint works out of box.
• Playground — Test prompts + models + variables live.
• Prompt Management — Version, tag, label prompts. Reference from code by label.
• Public API — Full REST API for ingest, query, prompt management.
• Python @observe decorator — One-line decorator to trace any function.
• Self-Hosting — Docker Compose + k8s Helm chart.
• Sessions — Group related traces (conversations, agent runs).
• Tracing — Capture every LLM call, tool call, nested span with inputs/outputs/cost.
• Users Tracking — Segment traces by user ID, track per-user cost.
• Webhooks — Subscribe to trace completion events.

Flagsmith · 14 features

• A/B Testing — Multivariate flag splits.
• Audit Log — Full history of flag changes.
• Change Requests — Approval workflow for flag changes.
• Edge API — Global low-latency flag eval.
• Feature Flags — Boolean + multivariate + JSON flags.
• Local Evaluation — Server SDKs eval flags locally — no per-req API call.
• Percentage Rollouts — Gradual traffic ramp.
• Remote Config — Non-boolean config values.
• Role-Based Access — Fine-grained permissions.
• Scheduled Flags — Time-based flag changes.
• Segments — Rule-based targeting.
• Self-Hosting — Docker/Helm install.
• SSO + SAML — Enterprise SSO.
• Webhooks — Outbound event streaming.