Blacksmith, a startup that provides cloud infrastructure for continuous integration and automated testing, raised a $45 million Series B led by Peak XV Partners at a $550 million valuation, up nearly tenfold from the roughly $60 million valuation it carried at its Series A less than a year earlier, with existing investors GV and Y Combinator also participating. The company says its customer count has grown from around 700 to more than 5,000 in under a year, and that it reached a $10 million annualized revenue run rate with a team of only about ten people before scaling further. Blacksmith started by offering faster, cheaper CI infrastructure for building and testing code, and has since added Codesmith, an AI agent designed to help diagnose and resolve failed checks automatically. The underlying story here is a useful one for anyone building developer tooling: AI coding assistants such as Cursor, Codex and Claude Code let teams generate code changes far faster than before, but that speed does not remove the need to test and validate that code, it just moves the bottleneck downstream into CI and verification pipelines that were not designed for that volume. That is creating real demand for a second layer of infrastructure built specifically around checking, testing and securing AI-generated code rather than generating it. Teams evaluating their own CI setup, especially ones leaning heavily on AI-assisted coding, may want to watch this category closely, since specialized testing infrastructure is emerging as a distinct, fundable niche rather than a feature bolted onto existing coding assistants.