Compare
Langfuse vs three.dev
Short answer: Pick Langfuse if you want LLM observability & analytics; pick three.dev if you want live failure detection & automated fixes for AI agents. Langfuse has a free plan, paid from $29/month; three.dev has a free plan, paid from $79/month.
.png?width=96)
LangfuseOpen Source Observability & Analytics for LLM Apps 🕵️♂️
three.devFind out how your AI agent fails. Before your users do.Which to pick
Pick Langfuse if you want…
- LLM observability & analytics
- The lower starting price: $29/month against $79/month
- Integrations with Python, TypeScript or Go (on Langfuse's list, not three.dev's)
Pick three.dev if you want…
- Live failure detection & automated fixes for AI agents
- Integrations with Gemini, Azure OpenAI or Claude Code (on three.dev's list, not Langfuse's)
Side by side
- What it is
- Langfuse:Langfuse is an open-source platform for tracing, evaluating and monitoring LLM applications and AI agents.
- three.dev:three.dev scores live AI agent traffic, groups failures into modes, and helps coding agents fix them.
- Best for
- Langfuse:LLM observability & analytics
- three.dev:Live failure detection & automated fixes for AI agents
- Who it’s for
- Langfuse:Developers building, debugging and scaling LLM-based apps and agents.
- three.dev:Teams building production AI agents who need to detect and remediate failures.
- Pricing
- Langfuse:Freemium
- three.dev:Freemium
- Starting price
- Langfuse:$29/month (Core)
- three.dev:$79/month (Starter)
- Free plan or trial
- Langfuse:Free plan (Hobby)
- three.dev:Free plan (Free)
- Plans
- Langfuse:Hobby Free · Core $29 per month · Pro $199 per month · Enterprise $2499 per month
- three.dev:Free $0 per month · Starter $79 per month · Pro $249 per month
- Open source
- Langfuse:Yes, 35,097 GitHub stars
- three.dev:Yes, 1 GitHub stars
- Works with
- Langfuse:Python, TypeScript, Go, Java, .NET, Ruby, PHP, Swift
- three.dev:OpenAI, Anthropic, Gemini, Azure OpenAI, Claude Code, Cursor, Codex, MCP server
Langfuse features
- Hierarchical Traces. Capture every LLM call, tool invocation and retrieval step with filters for user, session, cost and latency.
- Prompt Management. Version, fetch, release and cache prompts separately from code with one-click deployments.
- Evaluation Engine. Run LLM-as-judge, heuristic or human-review evaluations on production data or experiments.
- Experiments & Datasets. Define test cases, run experiments and create golden datasets for continuous improvement.
- Dashboards & Alerts. Monitor cost, latency and quality via custom dashboards and automated alerts.
- Human Annotation. Collaborative human-in-the-loop workflows with annotation queues.
- Extensive Integrations. Supports Python, TypeScript, Go, Java, .NET, Ruby, PHP, Swift and 100+ agent frameworks and model providers.
- Self-hosted & Cloud Options. Available as hosted SaaS or self-hosted under MIT license.
three.dev features
- Live traffic scoring. Scores every production request in real-time with no added latency.
- Failure mode grouping. Aggregates similar issues into named failure modes ranked by severity.
- Evidence-backed issues. Each failure includes the exact line or prompt that caused it.
- Coding-agent integration (MCP). Your coding agent can query failure modes and apply fixes automatically.
- Before/after comparison. Compare metrics across two traffic slices to see impact of a fix.
- Chat interface. Ask natural-language questions about traffic and get links to underlying requests.
- Replay & experiment. Test new versions on recorded traffic before releasing to users.
Langfuse vs three.dev FAQ
What is the difference between Langfuse and three.dev?+
Langfuse provides observability for LLM apps but does not auto-fix failures.
Should I use Langfuse or three.dev?+
Pick Langfuse if you want LLM observability & analytics, the lower starting price: $29/month against $79/month or integrations with Python, TypeScript or Go (on Langfuse's list, not three.dev's). Pick three.dev if you want live failure detection & automated fixes for AI agents or integrations with Gemini, Azure OpenAI or Claude Code (on three.dev's list, not Langfuse's).
Is Langfuse or three.dev free?+
Langfuse has a free plan (Hobby); paid plans start at $29/month (Core). three.dev has a free plan; paid plans start at $79/month (Starter).
Which is cheaper, Langfuse or three.dev?+
Langfuse is cheaper to start with: Langfuse's Core plan ($29/month) against three.dev's Starter plan ($79/month).
Is Langfuse or three.dev open source?+
Yes, both are open source: Langfuse (langfuse/langfuse on GitHub) and three.dev (round3ai/skills on GitHub, MIT license).
Do Langfuse and three.dev integrate with the same tools?+
Partly. Both list OpenAI and Anthropic. Langfuse also lists Python, TypeScript, Go, Java and 8 more; three.dev also lists Gemini, Azure OpenAI, Claude Code, Cursor and 2 more.
On DevHunt
Based on each tool's website and DevHunt data. Details may change; check the official sites.