Simulithic

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Introduction

Simulithic starts from the claim that you should not have to describe tests at all. Running simulithic map https://your-app explores the app and maps every user flow on its own.

Each flow is then verified against the browsers, devices, screen sizes and network speeds your users actually have, each run in its own isolated VM: Safari, Chrome and Firefox on macOS and Windows, iOS and Android devices, and network profiles from fast Wi-Fi and Ethernet down to 3G.

It is meant to run at three points. While you code, run simulithic qa in the terminal or let Claude Code or Codex run it before opening a pull request. In CI it is the end-to-end step and comments on the PR with anything that broke, testing each PR on its preview deploy. In production, flows run as often as every 30 minutes and failures go to Slack.

Launch and background: Y Combinator’s company directory lists Simulithic in its Fall 2026 batch, with the one-liner “AI users that test your app on every device and browser”.

Features

1. Automatic flow mapping: simulithic map discovers user flows.
2. Device and network matrix: Browsers, OSes, phones and 3G to Ethernet.
3. Isolated VMs: Each run is sandboxed.
4. Local CLI: simulithic qa before you push.
5. PR comments: CI step on preview deploys.
6. Production checks: Runs up to every 30 minutes with Slack alerts.

Pros

1. Real-world conditions: Network throttling and real devices catch environment bugs.

Cons

1. No public prices: Team and Enterprise plans via sales.
2. Very new: Fall 2026 YC company.
3. Preview deploys needed: PR testing assumes per-PR environments.

Usage and Links (Example)

simulithic map https://acme.dev
simulithic qa

Then add Simulithic as the end-to-end step in CI so it comments on each pull request.

Resources:

• Simulithic website

Pricing

Simulithic lists Team and Enterprise plans: Team tests the journeys a pull request touches, Enterprise tests all journeys on every PR. Prices and credit rates are arranged with the company.

Recommended for?

1. Consumer web apps whose users are spread across devices and networks.
2. Teams with preview deployments on Vercel, Netlify or similar.

Conclusion

Simulithic packs flow discovery, a device and network matrix and production checks into one CLI.

Its Team plan tests the journeys a PR touches, and Enterprise tests all of them.

On CheckOps, Simulithic is filed under the End-to-end & functional, Release & CI gates and Production monitoring & observability stages. Related tools listed here include BrowserStack, LambdaTest, Sauce Labs, Checkly, Momentic and Playwright. Before standardising on one, compare recent maintenance activity, the pricing model as your usage grows, and the integrations you rely on today. Information on this page was verified against the official website, documentation and repository on 11 November 2026.