Meticulous

Meticulous is a software company building what it describes as the world’s first fully autonomous and exhaustive testing platform for frontend codebases. The product is designed to let engineering teams ship fast without breaking things, by automatically verifying the impact of every code change before it is merged. Its stated mission is to enable every engineer to ship code at the speed their AI agents write it.

The platform works by watching how developers and agents actually use a product, turning recorded sessions into thousands of tests, and running those tests against code changes. Meticulous inserts a single line of JavaScript onto a site to record real user sessions, then replays those sessions on the head and base commits of pull requests, captures screenshots at key points, and diffs them to catch visual, logical and behavioral regressions before they reach production. The company says its approach eliminates flaky tests and provides near-exhaustive coverage with zero developer effort.

According to the company, Meticulous tests more than 90,000 pull requests across 1.5 billion snapshots every month. Its customers include Notion, ElevenLabs, Dropbox, Wiz, Mercor, LaunchDarkly and CoreWeave. Meticulous has said these customers often pay more for it than for any other software product in their stack and spontaneously refer the company to others.

Meticulous was founded by brothers Gabriel Spencer-Harper and Quentin Spencer-Harper and grew out of Y Combinator’s S21 batch. It is headquartered in London, at Albert House on Old Street, and has also been building a US presence. The company raised a $15 million Series A led by Chemistry with participation from Menlo Ventures, following earlier backing from investors and angels including Guillermo Rauch, Jason Warner, Scott Belsky, Calvin French-Owen, Jared Friedman and Arash Ferdossi. Meticulous says ARR grew fivefold over the past year as more engineering teams adopted AI coding tools.

The company states that its engineering team includes people who previously worked at Uber, Google, Dropbox, GitHub, Meta, Palantir and Opendoor, and that some of them previously led organizations of more than 100 engineers. Meticulous describes its philosophy as valuing density of talent: it keeps the team small but made up of exceptional individuals, and it is deliberately on-site because it believes speed of iteration and depth of collaboration happen best in person.

Meticulous positions its work as solving a novel set of technical problems at the intersection of browser technology, deterministic replay, distributed systems and testing infrastructure. It says its technology is built on original research rather than transformers or large language models. Public job postings describe building distributed systems that concurrently replay thousands of sessions in seconds, speeding up replay while retaining determinism, and deriving algorithms to identify sessions that cover differing code paths and edge cases.

In its hiring materials, Meticulous asks for technically brilliant people who are delightful to work with, self-aware and strongly motivated to improve, and who are highly supportive of colleagues because the team wins together. The company has been named to Redpoint’s 2026 InfraRed 100 and to AI Disruptors 60, and it says it plans to expand beyond frontend testing into backend and performance testing.