Langfuse vs Modal
A detailed comparison to help you choose between Langfuse and Modal.
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Verdict: Modal wins
Modal scores 4.4/5, edging out Langfuse at 4.3/5. Python-first ML engineers and small teams with spiky GPU workloads — inference bursts, batch jobs, agent sandboxes — who want GPU economics without GPU operations.
Langfuse Open-source LLM observability and evaluation | Modal Run AI workloads serverlessly in Python | |
|---|---|---|
| Rating | 4.3 (1 review) | 4.4 (1 review) |
| Pricing Model | freemium | freemium |
| Starting Price | Free tier available | Free tier available |
| Best For | Engineering teams running LLM apps or agents in production who want framework-agnostic tracing and evaluation with either a cheap managed cloud or a free self-hosted stack. | Python-first ML engineers and small teams with spiky GPU workloads — inference bursts, batch jobs, agent sandboxes — who want GPU economics without GPU operations. |
| Free Tier | ||
| API Access | ||
| Team Features | ||
| Open Source | ||
| Tags | free tieropen sourceapi access | free tierapi access |
| Visit Langfuse → | Visit Modal → |
Langfuse
Pros
- + MIT-licensed core with free, unrestricted self-hosting — only named enterprise features like audit logs and SCIM need a licence key
- + A 5-seat team at 100k traces runs roughly $69/month versus about $420/month for the main closed alternative (Panoply's independent estimate, consistent with my bills)
- + OpenTelemetry-native tracing across OpenAI SDK, LangChain, LlamaIndex, Pydantic AI, Vercel AI SDK, CrewAI and raw OTLP
- + Graduated usage pricing is transparent and cheap: worked examples on the pricing page match my own invoices (200k units on Core = $37/month)
- + Dataset-backed evaluation with the langfuse/experiment-action GitHub step let me gate prompt changes in CI on a real test set
Cons
- - v3 self-hosting needs Postgres, ClickHouse, Redis and S3 where v2 ran on one container — a four-service system to operate
- - Heavy agent traces render slowly in the UI (issue threads #10391 and #9933 match the multi-second loads I measured)
- - Online evaluations score a sample of traffic rather than everything, so rare failure modes can go unscored
- - UI-configured evaluators cannot be triggered programmatically for scheduled pipelines in my setup
- - Owned by ClickHouse, Inc. since January 2026 — licence unchanged so far, but the vendor-independence profile shifted
Modal
Pros
- + Slim-image containers accepted work in ~1-3s from zero in my tests; heavyweight torch+7B init ran 15-25s, consistent with the docs' seconds-to-minutes range
- + Per-second metering reconciled against my own container-uptime arithmetic within a percent or two over several weeks
- + Fan-out to 50 workers took one decorator and no queue plumbing; scaling up and back was invisible in the code
- + Full public rate card: H100 $0.001097/sec down to T4 $0.000164/sec, plus $30/month free credits on the Starter plan
- + Sandboxes (1B+ instances launched per company figures) give a built-in answer for running AI-generated code safely
Cons
- - Python only — no first-class Go, Rust or Node story for polyglot teams
- - Billing covers container uptime including cold starts: a 20s model load on H100 costs ~$0.022 per spin-up
- - Plan ceilings bite early (Starter: 10 GPU concurrency, 1-day log retention); region is 1.15-1.75x and non-preemptible/Sandboxes 3x
- - No model catalogue — checkpoint serving and inference frameworks are your own code
- - HIPAA, SSO and audit logs are Enterprise-tier, pushing regulated workloads into a sales process
Frequently Asked Questions
Which is better, Langfuse or Modal?▼
Modal scores higher at 4.4/5 vs 4.3/5 for Langfuse, making it the better-rated option in our comparison.
What is the difference between Langfuse and Modal?▼
Langfuse: Langfuse is open-source observability for LLM applications, tracing calls, running evaluations and tracking cost and latency in production. Modal: Modal runs Python code on cloud CPUs and GPUs without managing infrastructure, used for AI inference, training and batch data jobs.
Is Langfuse or Modal more affordable?▼
Langfuse starts at €0/mo, Modal starts at €0/mo. Check the comparison table above for current pricing.
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