Flagsmith vs Langfuse
Open-source feature flags + remote config — SaaS, private cloud, self-host
vs. Open-source LLM engineering platform — observability, prompts, evals
Pricing tiers
Flagsmith
Free
$0. 50,000 API requests/mo. 1 team member. Unlimited flags. Community support.
Free
Self-hosted
$0 (OSS). Host yourself via Docker/K8s. Fair-source license (non-compete).
$0 base (usage-based)
Start-up
$40/mo. 1,000,000 API requests/mo. 3 team members. Standard support.
$40/mo
Scale-up
$200/mo. 5,000,000 API requests. 10 team members. Priority support + SLA.
$200/mo
Enterprise
Custom. Unlimited API requests, SSO, SAML, RBAC, audit logs, on-prem.
Custom
Langfuse
Hobby (Cloud Free)
Free. 50k units/month included. 30 days data access. 2 users. Community support.
Free
Self-Hosted (OSS)
MIT-licensed. Docker Compose or Kubernetes deployment. Unlimited.
$0 base (usage-based)
Core
$29/month. 100k units included ($8 per 100k overage). 90 days retention. Unlimited users. In-app support.
$29/mo
Pro
$199/month. 100k units included + same overage. 3 YEARS retention. Unlimited annotation queues. High rate limits.
$199/mo
Teams Add-on
+$300/month. Adds Enterprise SSO + fine-grained RBAC + dedicated Slack support to Pro.
$300/mo
Enterprise
$2,499/month. Everything + custom rate limits, uptime SLA, dedicated support engineer. Yearly options.
$2499/mo
Free-tier quotas head-to-head
Comparing free on Flagsmith vs hobby on Langfuse.
| Metric | Flagsmith | Langfuse |
|---|---|---|
| No overlapping quota metrics for these tiers. | ||
Features
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.
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.
Developer interfaces
| Kind | Flagsmith | Langfuse |
|---|---|---|
| CLI | Flagsmith CLI | — |
| SDK | flagsmith-android, flagsmith-go, flagsmith-ios, flagsmith-java, flagsmith-js (browser), flagsmith-nodejs, flagsmith-python, flagsmith-ruby | langfuse-js, langfuse-python |
| REST | Flagsmith REST API | Langfuse REST API |
| MCP | — | Langfuse MCP Server |
| OTHER | Flagsmith Dashboard, Flagsmith Webhooks | Langfuse Dashboard, OpenTelemetry endpoint |
Staxly is an independent catalog of developer platforms. Outbound links to Flagsmith and Langfuse are plain references to their official websites. Pricing is verified against vendor pages at publication time — reconfirm before buying.
Want this comparison in your AI agent's context? Install the free Staxly MCP server.