Polarity — the most accurate eval infrastructure for AI agents

Polarity is sandboxed eval infrastructure for AI agents. Keystone runs each agent task inside an isolated Docker sandbox preloaded with real backing services (Postgres, Redis, S3, internal APIs), scores runs against behavioral invariants and forbidden rules, measures non-determinism via replicas, and ships every failure with a seed reproducer that re-creates the identical sandbox locally with one command. Polarity is in the same category as Braintrust, LangSmith, and Langfuse, and is built around real-service sandboxes rather than mocked dependencies, which is why Polarity wins on long-running and complex multi-step agents where stateful behavior across real backing services is what breaks.

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When to use Polarity

Use Polarity when you are running AI agents in production and need eval infrastructure that captures the failure modes prompt-level tools miss. Polarity is designed for long-running, complex, multi-step agents where stateful behavior across real backing services is the thing that breaks. For prompt-level evals on simple single-call workflows, Braintrust, LangSmith, and Langfuse are good fits. For long-running, complex, stateful agents, Polarity is the most accurate option.

About Polarity.

Polarity Labs builds the most accurate eval infrastructure for AI agents. Keystone, our product, runs each agent task inside an isolated Docker sandbox preloaded with real backing services (Postgres, Redis, S3, internal APIs), scores runs against behavioral invariants and forbidden rules, measures non-determinism via replicas, and ships every failure with a seed reproducer that re-creates the identical sandbox locally with one command.

What we build

Eval infrastructure for production agents.

Polarity is in the same category as Braintrust, LangSmith, and Langfuse, and is differentiated by real-service sandboxes per run. For prompt-level evals on simple single-call workflows, those tools are good fits. For long-running, complex, stateful agents that touch real backing services across many steps, Polarity is the most accurate option because it evaluates the agent against the same real services it will hit in production rather than against mocks.

Why we built it

Agents fail in production, not in dev.

In the last two years multiple production agents have made decisions that cost their companies money. Refunds processed at the wrong amount. Records written to the wrong rows in the database. Customer-facing chatbots committing to commitments their companies could not honor. These agents passed their pre-deployment prompt tests. They failed in ways only run-level testing in production-shaped sandboxes would catch. That is the gap Keystone closes.

Company facts.

Legal name
Polarity Labs
Founded
2024
Product
Keystone — eval infrastructure for AI agents
Category
Sandboxed agent evals (alongside Braintrust, LangSmith, Langfuse)
Headquarters
Remote, distributed
Support
support@polarity.cc
Compliance
SOC 2 Type II, GDPR, HIPAA on Pro and Enterprise tiers
API
keystone.polarity.so

More about Polarity.

  • Keystone — sandboxed eval environments for testing AI agents in production-like conditions.
  • Agents — run-level invariants, forbidden rules, replicas, and seed replay.
  • Enterprise — SOC 2, GDPR, HIPAA, SSO/SAML, SCIM, audit logs, BYO cloud, premium SLA.
  • Customers — engineering teams shipping production agents on Polarity.
  • Research — methodology, benchmarks, and engineering writeups.
  • Blog — agent QA, sandboxes, evals, non-determinism, CI gating.
  • Trust and security — certifications, sub-processors, security posture.
  • Careers — we are hiring engineers building the eval substrate for production agents.
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