Blacksmith raises $45M Series B: Valuation up nearly 10x in under a year in AI code verification

Funding Amount: $45 million (Series B)

Lead Investor: Peak XV Partners

Valuation: $550 million (up from just $60 million at Series A in September 2025)

Other Investors: GV, Y Combinator

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AI code testing company Blacksmith completed a $45 million Series B round, with its valuation skyrocketing from $60 million less than a year ago to $550 million.

Growth Data:

• Customers grew from ~800 to 6,000+ (including Supabase, Clerk, Ashby, Mercury)
• Annualized revenue reached the "tens of millions of dollars" level; largest customer spends over $1 million annually
• Achieved $10 million ARR with only 10 employees
• CI tasks growing 5%-10% week-over-week

Core Product: Blacksmith CI Cloud, supporting GitHub Actions environments, runs 2x faster and costs 60% less than official GitHub runners. Cache downloads are 4x faster, Docker builds are 40% faster.

New Product codesmith: A cloud coding agent that can diagnose CI failures, auto-fix issues, and keep PRs green—extending from "running tests" to "fixing problems."

Founder's View: "Writing code has never been easier, but verifying it hasn't."—The volume of AI-generated code is exploding, but the verification bottleneck has become even larger.

Signal Value: A 10-person company reaching a $550 million valuation validates the high leverage of "infrastructure layer" tools in the AI era. The more prosperous code generation becomes, the more rigid the demand for the verification layer.

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