Lemma

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Introduction

Lemma targets silent failures, the cases where an agent returns success but does the wrong thing. It audits every trace against your agent’s instructions and groups recurring failures into issues. The homepage example shows an agent inventing placeholder customer IDs instead of asking, then filing tickets against them, in 33 of the last 50 runs.

Lemma triages issues and alerts you in Slack, and its MCP server lets you pull the context into your coding agent to fix the problem. After you deploy the fix, it creates an online eval so a regression is caught immediately.

Launch and background: Y Combinator’s company directory lists Lemma in its Fall 2025 batch, with the one-liner “Production Monitoring for AI agents”.

Features

1. Instruction audits: Each trace checked against the agent’s instructions.
2. Issue grouping: Recurring failures clustered with example traces.
3. Slack alerts: Triage and notify.
4. Lemma MCP: Bring context into coding agents.
5. Online evals: Auto-created after a fix.

Pros

1. Finds unknown unknowns: No need to predefine failure modes.

Cons

1. Pricing not public: Contact the team.
2. Young product: Fall 2025 batch.

Usage and Links (Example)

1. Send agent traces to Lemma.
2. Review grouped issues and their representative traces.
3. Fix via your coding agent with Lemma MCP, then watch the online eval.

Resources:

• Lemma website

Pricing

Prices were not listed on the website when checked on 11 November 2026; contact the vendor for plans.

Recommended for?

1. Teams with customer-facing agents where silent errors are costly.

Conclusion

Lemma is a sharp tool for catching agents that fail while looking successful.

It works best alongside a general tracing platform.

On CheckOps, Lemma is filed under the Production monitoring & observability stage. Related tools listed here include Langfuse, LangSmith, Arize Phoenix, Helicone, Laminar and AgentOps. When comparing them, weigh the licence, the languages and platforms each supports, whether it is self-hosted or managed, and how cleanly it slots into your existing CI pipeline. Details on this page were checked against the official website, documentation and repository on 11 November 2026.