Langfuse is a strong open-source observability and prompt-evaluation platform — tracing, datasets, and prompt experiments, with a real self-host option. What it fundamentally cannot do, by design, is sit in the request path: it observes calls your application already made, after the fact. Wardin is a gateway first — every call passes through it before it reaches a provider — so enforcement (budget, policy, rate limits) is possible in a way a downstream observability tool cannot replicate.
Langfuse's prompt-management and evaluation tooling is more mature than ours — dataset-based experiments and team collaboration workflows that have had longer to develop. It's also genuinely open-source and self-hostable, which we are not. If prompt engineering and evaluation depth is the main workflow you need, Langfuse is ahead there today.
Choose Langfuse if your priority is open-source prompt engineering and evaluation workflows and you don't need in-path enforcement. Choose Wardin if you need a request to actually be stoppable — a budget hard-stop or a policy violation that never reaches the provider, not just a trace of one that already did.