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Langfuse vs Respan
Teams shipping LLM agents need to see what every call did, and these two answer that in different ways. Langfuse is an open-source platform for tracing, prompts, and evaluations that you can self-host or buy as a cloud service. Respan, formerly Keywords AI, is a hosted platform that adds a model gateway to tracing, monitoring, and evaluations.
| What buyers compare | Langfuse | Respan |
|---|---|---|
| Price per monthSources 3, 4 | Self-hosted: free. Cloud: Hobby free, Core $29, Pro $199, Enterprise $2,499 | Free. Team $199, billed yearly. Enterprise: quote |
| Free plan or trialSources 3, 4 | Hobby: free, 50k units a month, 30 days of data, 2 users. Self-hosting is free | Free: 100k logs, 1k scores, 5 datasets, 5 prompts, 2 evaluators, and 7 days of retention |
| How usage is countedSources 3, 4 | Units per month: 50k on Hobby, 100k on Core, Pro, and Enterprise, then $8 per 100k | Logs and scores: 100k logs and 10k scores on Team, then $8 per 100k logs and $1 per 1k scores |
| Integrations and featuresSources 3, 4 | Tracing for agents, sessions, and users. Prompt management, datasets, LLM-as-judge evaluators, annotation queues, dashboards, and alerts. Python and JavaScript SDKs and OpenTelemetry | Agent tracing, alerts, dashboards, prompts, datasets, and LLM-as-judge evaluators. AI gateway to 1,000+ models with a key vault, caching, retries, fallbacks, and load balancing |
| Security and deploymentSources 3, 4 | Self-host with Docker Compose, Kubernetes, or Terraform. Cloud regions in the US, EU, and JP. Pro: SOC 2 Type II and ISO 27001 reports and a HIPAA-ready region | Cloud on Free and Team, with a SOC 2 report on Team. Enterprise: self-hosted deployment, SAML SSO, and a HIPAA BAA |
| Best forSources 1, 2 | AI engineering teams that want LLM tracing, prompt management, and evals with the option to self-host | Startups and product teams shipping AI agents that want one API for model access plus tracing, alerts, and evaluations, with a free plan to start and a team plan at $199 a month |
List prices in US dollars per month before tax, as published on each vendor's site on October 29, 2026, billed monthly unless the cell says otherwise. "Quote" means the vendor sets the price through its sales team.
Which one fits
Langfuse is the open-source option you can run yourself, while Respan bundles a model gateway with tracing in one hosted service.
Choose Langfuse if
- You want to host the observability layer yourself. Langfuse self-hosts with Docker Compose, Kubernetes, or Terraform.
- You want tracing, prompt management, and evaluations as separate pillars. Core costs $29 a month with 100k units.
- You need audit logs, SCIM, and a support SLA. Enterprise includes them at $2,499 a month.
Choose Respan if
- You want model routing and observability from one vendor. The gateway reaches 1,000+ models with caching, retries, and fallbacks.
- You want one flat team price. Team is $199 a month, billed yearly, with unlimited datasets, evaluators, and prompts.
- You may want to run the gateway yourself. Respan's gateway code is open source under Apache-2.0.
What buyers say
“Consider using a service like Keywords AI OR langfuse OR similar. Many such tools have prompt management features you can use.”
vasily_sl · Reddit r/AI_Agents, on managing prompts across a project (Keywords AI is now Respan) · · source
“Didn't know about keywordsai. I use mainly langfuse”
Time-Plum-7893 · Reddit r/LocalLLaMA, replying to feedback on an AI agent library (keywordsai is now Respan) · · source
Verdict
Langfuse (7.9 out of 10, Recommend) is the choice when the team wants to own the observability layer, since it self-hosts, covers tracing, prompts, and evaluations, and starts at $29 a month on cloud. Respan (7.6 out of 10, Recommend) is the choice when the team wants a gateway and tracing from one hosted vendor, with a free plan and $199 a month for Team. Respan is the younger company, so buyers who want a long track record may lean toward Langfuse.
Methodology
We read the Langfuse and Respan pricing pages on October 29, 2026 and recorded every published price, limit, and plan feature. A cell reads "Not published" when the vendor does not state that detail on its site.
Scores and best-fit notes come from the AIR reviews of each product. Buyer quotes come from public forum posts that name both products.