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Public story · 2026-09-20 · high
The round, led by CRV with Lightspeed and Datadog, adds personal backers from Anthropic, OpenAI and Thinking Machines and brings total funding to $50M.
Why now: Axios Pro reported the round and product on September 16, 2026.
Raindrop raised a $35M Series A led by CRV, with Lightspeed and Datadog joining, per Axios Pro. That brings total funding to $50M after a $15M seed in December 2025. The product it funds matters for anyone shipping agents that touch customers. It catches a regression before the agent goes live, instead of after a support queue fills up.
Simulations replays real production traffic and existing test cases against a proposed agent change before it ships. Then it runs semantic anomaly detection on the results. Researchers and executives at Anthropic, OpenAI and Thinking Machines put money into the round too.
The founders came from fraud detection at Robinhood and Square before starting Raindrop. Axios Pro's report doesn't say how Simulations handles agents with side effects: sending an email, charging a card, writing to a database. Replaying production traffic against a proposed change isn't free to undo for an agent that acts in the world. The report doesn't say whether Raindrop draws that line either.
Each link below shares sources, entities, or timing with this story.
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On September 16, Anthropic folded Cowork into Claude and launched Claude Docs, Claude Slides and Claude Design in beta. One window now routes a request to an inline answer or a long-running agentic task on its own. Slides export to PowerPoint and PDF. Docs supports collaborati...
Led by Lightspeed and Wellington with Goldman Sachs Alternatives, Tiger Global and T. Rowe Price (Temporal). The post frames the raise around agents running for days or weeks that need to survive outages and approval waits without hand-built recovery machinery. Numbers: 1.9 tr...
The SDKs you pip install and npm install every day just changed ownership. Anthropic announced the acquisition of Stainless, the SDK generation company founded by former Stripe engineer Alex Rattray, for over $300 million. That's more than double Stainless's December 2025 valu...
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