AI Code-Testing Startup Blacksmith Hits $1B Valuation in 17x Leap

Blacksmith, a San Francisco startup that runs continuous-integration (CI) jobs on servers it owns rather than general-purpose cloud infrastructure, closed a $66 million Series C at a $1 billion valuation this week, with Sequoia Capital leading the round. The raise, announced October 21, lands just over two months after an August Series B valued the three-year-old company at $550 million — meaning its valuation has roughly doubled in ten weeks and climbed nearly 17-fold since its Series A thirteen months ago.

The speed of the markup is notable even by this cycle's standards. Blacksmith's Series A, a $10 million check led by GV, priced the company at $60 million in September 2025. A $45 million Series B led by Peak XV Partners pushed that to $550 million in August 2026. Sequoia's Series C, joined by Premji Invest alongside existing backers Peak XV, GV and Y Combinator, now puts total funding at $125 million against a $1 billion price tag.

The Pitch: Infrastructure for AI-Written Code

Blacksmith's core claim is that it can run the automated build-and-test checks every code change triggers roughly twice as fast and at about 60% lower cost than standard cloud CI, by operating its own hardware rather than renting general-purpose compute. For teams already on GitHub Actions, the company says switching requires changing a single line in a workflow file. Co-founder and CEO Aditya Jayaprakash, previously of marketplace company Faire, said the company exists to make CI 'less painful' — a problem he argues is intensifying as AI tools generate an increasing share of the code that needs checking.

That framing lines up with what the company says is driving its growth. Blacksmith reports its customers' weekly CI job volume rose from roughly 5 million in January to more than 90 million now, with its customer count growing from about 800 at the time of its Series A to more than 10,000 today. Named customers include fintech Mercury, meeting-notes startup Granola, recruiting platform Handshake, and developer tools LangChain and Supabase. Annual recurring revenue grew 17-fold, though the company has not disclosed an absolute revenue figure.

Part of a Broader AI-Infrastructure Financing Wave

Blacksmith's jump is one of several rapid-fire valuations among companies building the plumbing underneath AI-assisted software development this month. Developer-sandbox startup Daytona crossed a $1 billion valuation on October 20, and Modal raised $750 million at a $15.75 billion valuation on October 14. Anthropic itself has cited similar pressure internally, reporting in September that its own CI job volume rose 25-fold over six months as Claude came to write roughly 80% of the code its engineers ship — a data point Blacksmith and competitors point to as evidence that verification infrastructure, not just model capability, is becoming a bottleneck worth funding.

Blacksmith faces competition on multiple fronts: GitHub Actions and the major cloud providers' native testing services on one side, and AI-coding tools themselves — including validation features built into OpenAI's Codex and Anthropic's Claude Code, plus startups like Cursor Automations — on the other. The company says it will use the new capital to expand headcount in New York and San Francisco and to grow its data-center footprint, which currently draws just under 10 megawatts across the US and Europe, by roughly fivefold in 2027.

For investors, the back-to-back markups reflect a bet that as AI models write more code, the systems that test and verify that code at scale become their own durable business — one where usage volume, not just subscriber counts, is the growth metric that matters.