Respan (formerly Keywords AI)
LLM engineering platform combining a multi-model gateway with tracing, evals, and prompt management.
Pick Respan if you're shipping a production LLM app and want one vendor for gateway routing, tracing, evals, and prompt versioning.
Skip it if you need a self-hostable open-source observability stack or you're happy stitching together Langfuse, Helicone, and your own dashboards.
Respan, previously branded as Keywords AI, is a YC-backed LLM observability and operations platform. It sits in front of your AI app as a unified gateway routing to 500+ models from OpenAI, Anthropic, and others with built-in fallback and error handling, while logging every call for tracing, cost, latency, and error analysis. On top of that runtime data, it layers an evaluation system that mixes rule-based checks, AI judges, and human review into repeatable workflows.
The platform is aimed at teams shipping production LLM features who have outgrown ad-hoc logging and want a single pane for monitoring, prompt versioning, and quality regression testing. It claims to have processed 80 trillion+ tokens across customers, which puts it in the same competitive bracket as LangSmith, Helicone, and Langfuse. There's a free tier and paid plans, with enterprise demos available on request.
SDKs ship for Python and TypeScript, with first-party integrations for LangChain, LlamaIndex, the Vercel AI SDK, and 40+ other frameworks. Not open source, so self-hosting is off the table unless you negotiate an enterprise arrangement.
A credible LangSmith competitor that doubles as a model gateway, which is a genuinely useful combo if you're tired of running observability and routing as separate systems. The rebrand from Keywords AI to Respan is recent enough that some docs and case studies still reference the old name — worth checking pricing and SDK stability before committing.
— The AI Tool Bible editorial team
Pros
- ✅ Unified gateway to 500+ models with fallback and error handling
- ✅ End-to-end loop: trace, evaluate, monitor, version prompts in one UI
- ✅ Eval system mixes rules, AI judges, and human review
- ✅ Broad SDK and framework coverage (LangChain, LlamaIndex, Vercel AI SDK)
- ✅ YC-backed with serious production scale (80T+ tokens claimed)
Cons
- ⚠️ Closed source — no self-host option for most customers
- ⚠️ Paid pricing not transparent on the site
- ⚠️ Recent rebrand from Keywords AI may cause doc and link churn
- ⚠️ Gateway dependency adds a network hop and vendor lock-in
Use cases
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