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.

Describe what to test.
Paragon handles the rest.

Write tests in plain English. Paragon generates, executes, and iterates on end-to-end, integration, and unit tests — in isolated cloud environments.

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Paragon Testing Dashboard

Every layer of testing, covered.

From unit tests to full E2E flows — generated, executed, and verified automatically.

test the checkout flow
Read playwright.config.ts
Ran terminal command
$ npx playwright test
Running 5 tests...
checkout › navigates to /products
checkout › adds item to cart
checkout › submits payment
✓ 5 passed in 6.1s
All tests passed. Ready to merge?

End-to-End Testing

Describe user flows in plain English. Paragon writes and runs Playwright tests against your app, iterating until they pass.

Auth service contractJan 8
Payment API v2Jan 12
Inventory syncJan 18
Order fulfillmentYesterday
Webhook delivery3h ago
Rate limit headers1h ago
Deploy stagingNow

Integration Testing

Validates API contracts, service boundaries, and data flows between components. Catches breakage where systems connect.

// Calculate prorated amount for partial billing periods
export const prorateCharge = (
amount: number,
daysUsed: number
): number => Math.round(amount * daysUsed / 30);
import { prisma, type Invoice } from "@/lib/db";
import { type Stripe } from "stripe";
export const getInvoicesByCustomer = (customer
prisma.invoice.findMany({ where: { customerId
export const getInvoice = (id: string): Promis
prisma.invoice.findUnique({
where: { id },
include: { lineItems: true, customer: true,
});
export const updateInvoiceStatus = (
id: string,
status: InvoiceStatus
): Promise<Invoice> =>
prisma.invoice.update({
where: { id },
data: { status, updatedAt:

Unit Testing

Generates targeted unit tests for functions, edge cases, and error paths. Covers the code your team didn't have time to test.

AgentDashboard
Today
Load test /api/checkout
Spawning users · benchmarks
Stress test WebSocket
Planning next moves · api-core
Profile DB queries
3 models · api-core
Optimize image pipeline
4 Files +89 -31 · cdn-service
This Week

Performance Testing

Monitors response times, throughput, and resource usage under load. Identifies bottlenecks before your users do.

Paragon natural language testing

Tests from plain English.

Describe what you want to test — “user signs up, adds an item to cart, and checks out” — and Paragon writes Playwright tests, runs them, and iterates until they pass. No boilerplate, no brittle selectors.

Read about Autotest

Isolated cloud environments.

Every test suite runs in its own sandboxed environment with your dependencies, network access, and permissions. Clean state every time — no flaky tests from shared infrastructure.

Explore environments
Paragon sandboxed testing environments
Paragon automated testing pipeline

Runs on every PR, automatically.

Trigger test suites on pull requests, schedules, or webhooks. Paragon runs end-to-end in the background and reports results back — no manual intervention required.

Set up automations

Head of QA, Global 100 Company

“Paragon does 3 weeks worth of testing, in 3 hours.”
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87%

Reduction in manual testing effort with Paragon Autotest.

89%

Test accuracy — outperforming Cursor, Claude, and Codex agents.

<5min

Average bug detection time from PR open to flagged.

Enterprise-ready.

Compliant, certified, and trusted by Fortune 500 companies.

★★★★★★★★★★★★GDPR
SOC 2
Fortune
500
W3C®

Try Polarity today.

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