Zespan is an AI agent observability and engineering platform. It traces every agent decision, tool call, handoff, and delegation in production. It also provides prompt versioning, built-in LLM-as-judge evaluations, guardrails, cost optimization, and an AI ops assistant called ZespanPilot.

How do I instrument my AI agent with Zespan?

Zespan requires 2 lines of code. Import zespan and call zespan.init({ apiKey: process.env.LT_KEY }). This auto-patches OpenAI, Anthropic, Gemini, Bedrock, and Mistral. For framework-level tracing, add one handler: ZespanCallbackHandler for LangChain, ZespanCrewAIListener for CrewAI, or ZespanADKHandler for Google ADK.

Does Zespan support prompt versioning?

Yes. Zespan includes prompt management with versioning, a playground for iteration, and A/B testing to compare prompt versions against each other in production.

What evaluations does Zespan support?

Zespan ships 12 built-in LLM-as-judge evaluation templates including faithfulness, relevance, toxicity, groundedness, and more. Evaluations run automatically on every trace with no custom scoring functions required.

How does Zespan compare to Langfuse?

Zespan is agent-native: every span carries agent identity, delegations are first-class trace events, and an agent map is built automatically. Langfuse was built for LLM pipelines and extended to agents later. Zespan also ships 12 built-in eval templates (Langfuse has none), includes an AI cost optimizer, and ZespanPilot for AI ops. Langfuse has open-source self-hosting; Zespan does not.

What is the free tier for Zespan?

The free tier includes 10,000 traces per month, 14-day retention, 2 projects, and 1 seat. No credit card required.

Compare

Zespan vs Langfuse

Zespan vs Langfuse — cloud-native vs open-source observability.

Langfuse is well-regarded open-source observability that fully open-sourced in June 2025 and was acquired by ClickHouse in January 2026. It covers the basics — traces, evals, datasets — but lacks agent-first features like health scoring, AI cost optimization, guardrails, and a conversational copilot. Self-hosting is 'free' but requires a ClickHouse cluster ($200–800/month infra cost). Zespan is cloud-native, agent-first, and fully managed.

Capability comparison: Zespan vs Langfuse
Capability	Zespan	Langfuse
Free tier	10K traces/month	100K units/month (with limits)
Starting price	$39/month	$29/month (Core)
Managed cloud	✓ Fully managed	Cloud or self-host
Self-host infra cost	Not available	ClickHouse: $200–800/month
Agent auto-discovery	✓ Zero config	Not available
Agent health scoring	✓ A–F composite score	Not available
Multi-agent delegation graph	Yes	Agent Graphs (Nov 2025)
AI cost optimizer	✓ Forecast + recs	Not available
Guardrails	✓ 7 types, pre/post	Not available
LLM-as-judge auto-evals	✓ 12 templates, automatic	Custom only, manual
Natural language query	✓ ZespanPilot NLQ	Not available
Incident management	✓ Full state machine	Not available
OpenTelemetry native	Yes	Yes

Pick Zespan when…

You want fully managed — no ClickHouse cluster to operate.
You need guardrails, runtime safety, or PII redaction in production.
You want agent health scoring, cost forecasting, and anomaly detection.
Your team builds on multiple frameworks, not just LangChain.
You want an AI copilot for querying observability data.

Pick Langfuse when…

Open-source license is a hard requirement for compliance or vendor policy reasons.
You want full data sovereignty and are willing to operate ClickHouse yourself.
You're already in the ClickHouse ecosystem and the ClickHouse acquisition is a feature, not a risk.

Frequently asked

Is Langfuse's self-hosted option actually free?

The software license is free (MIT), but you still need to operate a ClickHouse cluster, which runs $200–800/month on most cloud providers. For small teams, Zespan's $39/month managed plan is often cheaper total.

How does Zespan compare on evaluations?

Both platforms support evaluations and datasets. Zespan's auto-evaluators run automatically on every new trace using 12 built-in LLM-as-judge templates — no manual setup. Langfuse's evaluations require manual configuration and trigger.

Does Zespan support agent graphs like Langfuse does?

Yes. Zespan has had first-class multi-agent delegation graphs since launch. The delegation graph shows which agents hand off to which, with cost and latency per hop. Langfuse added Agent Graphs in November 2025.

What happened to Langfuse after the ClickHouse acquisition?

Langfuse was acquired by ClickHouse in January 2026. The long-term product roadmap and pricing independence are now tied to ClickHouse's plans. Zespan is independent.

Try Zespan — free, no card needed

10K traces/month free. Setup takes under 5 minutes. See why teams switch from Langfuse.

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