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    Raindrop announces Series A and early-access Simulations for AI agents

    Raindrop says Simulations creates test environments to check agent changes before deployment. Investor Lightspeed says the Series A brings the company’s total funding to $50 million.

    Garry TanGT
    Y CombinatorYC
    SoleioSO
    35 Sources, ,

    TLDR

    Raindrop announced its Series A and early access to Simulations on September 17, 2026. The company says CRV led the round, with participation from researchers and leaders at Anthropic, Thinking Machines and OpenAI. Investor Lightspeed says the round brings total funding to $50 million.

    Raindrop says Simulations automatically creates test environments with simulated services and databases for every pull request—a proposed code change. Lightspeed describes the product as a research preview that replays real production traffic and existing test cases against proposed agent changes to look for unexpected behavior before deployment.

    Combined views

    290.2K

    35 Sources, first seen 20d ago

    Combined views

    290.2K

    35 Sources, first seen 20d ago

    2K likes
    20d ago
    first seen 20d ago
    2K likes
    302 comments
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    281 reposts
    302 comments
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    281 reposts

    Sentiment

    Positive91.2%8.8%Negative

    Summary

    Many accounts congratulated Raindrop on its Series A for building a safety layer that detects AI agent failures, while a few replies argued its synthetic simulations and non-deterministic checks add little value over real traces.

    Based on 37 sentiment-bearing replies from 34 accounts across 5 conversations.

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    35 Sources

    ben hylak@benhylakOur Series A funding was led by @CRV, with participation from researchers/leaders at @AnthropicAI, @thinkymachines, and @OpenAI. Below, i talk a little about how we got here + the road ahead.20d
    Ben Aguilera@ben_aguileraWe're on a mission to protect the world from agent failures. Come join us!20d
    Matt Brockman@badphilosopherthis is cool. test suites for model/prompt changes let you know if something's gonna blow up ahead of time.20d
    Y Combinator@ycombinatorRaindrop (@raindrop_ai) is building the safety layer for AI agents. As agents get more capable and take on more complex work, Raindrop detects when they go wrong in production, from failed tool calls and hallucinations to problems companies didn’t even know to look for. Now they’re launching Raindrop Simulations, which brings that same approach earlier in the development process to catch failures before agents reach production. Already used by companies including Vercel, Clay, Framer, and Speak, Raindrop just raised a Series A bringing its total funding to $50 million. In this episode of Founder Firesides, founders @snarkyzk, @benhylak, and @alexisgauba sat down with @sdianahu to share how a tool they originally built to debug their own coding agent became the company, and why better AI agents actually create more ways for things to go wrong. 00:05 — What Raindrop Does 01:32 — Why Better AI Agents Create More Problems 03:25 — Finding the Failures Evals Miss 04:38 — How Raindrop Got Started 06:32 — Why They Kept Going 07:58 — Catching Agent Failures Before Production20d
    Hamel Husain@HamelHusainExcited about this! I've been impressed with raindrop so far. It helps you look at your data 🥰 and generate data (via simulations) to help you find errors.20d
    Brie Wolfson@zebriezA fun question I’m always asking myself about startups is “do I want to live in the world where this company is wildly successful?” No easier yes rn than @raindrop_ai20d
    alexis@alexisgaubainsane year @raindrop_ai it truly feels like we're working on "applied ai safety". agents are getting more capable, stakes are getting higher. we're hiring, dm me.20d
    CRV@CRVWe led Raindrop's $50M Series A because they’re quickly becoming the leader of agent observability. @reidRMC @brittwalker_ and team are thrilled to back the company that is improving agents at Fortune 100s and startups alike. @raindrop_ai @snarkyzk @alexisgauba @benhylak20d
    Nix 🕊@startingfromnixIt's been a warning shot summer, and Raindrop is a mighty crew with a mission: protecting the world from agent failures. Excited to share a behind the scenes in-depth interview with the founders of @raindrop_ai - @snarkyzk, @Benhylak, and @alexisgauba (+ congrats on the A raise, bringing total funding to $50m from @CRV / @lightspeedvp) for New Ontologies. We talk about 1. The Hugging Face incident as a canary in the coal mine 2. Chain of thought monitoring and simulation, including the simulations product Raindrop is announcing 3. How agents fail in the long tail 4. Working with your best friends20d
    Diana@sdianahuCongrats to @snarkyzk ,@alexisgauba and @benhylak on @raindrop_ai's Series A led by CRV, bringing their total funding to $50M they detect failures in AI agents, such as tool call failures and decision errors (Vercel, Clay, and Speak uses them) 1/7 how they got started as a terminal and now solving the rise and fall of agent civilizations with Simulations20d

    35 Sources

    ben hylak@benhylakOur Series A funding was led by @CRV, with participation from researchers/leaders at @AnthropicAI, @thinkymachines, and @OpenAI. Below, i talk a little about how we got here + the road ahead.20d
    Ben Aguilera@ben_aguileraWe're on a mission to protect the world from agent failures. Come join us!20d
    Matt Brockman@badphilosopherthis is cool. test suites for model/prompt changes let you know if something's gonna blow up ahead of time.20d
    Y Combinator@ycombinatorRaindrop (@raindrop_ai) is building the safety layer for AI agents. As agents get more capable and take on more complex work, Raindrop detects when they go wrong in production, from failed tool calls and hallucinations to problems companies didn’t even know to look for. Now they’re launching Raindrop Simulations, which brings that same approach earlier in the development process to catch failures before agents reach production. Already used by companies including Vercel, Clay, Framer, and Speak, Raindrop just raised a Series A bringing its total funding to $50 million. In this episode of Founder Firesides, founders @snarkyzk, @benhylak, and @alexisgauba sat down with @sdianahu to share how a tool they originally built to debug their own coding agent became the company, and why better AI agents actually create more ways for things to go wrong. 00:05 — What Raindrop Does 01:32 — Why Better AI Agents Create More Problems 03:25 — Finding the Failures Evals Miss 04:38 — How Raindrop Got Started 06:32 — Why They Kept Going 07:58 — Catching Agent Failures Before Production20d
    Hamel Husain@HamelHusainExcited about this! I've been impressed with raindrop so far. It helps you look at your data 🥰 and generate data (via simulations) to help you find errors.20d
    Brie Wolfson@zebriezA fun question I’m always asking myself about startups is “do I want to live in the world where this company is wildly successful?” No easier yes rn than @raindrop_ai20d
    alexis@alexisgaubainsane year @raindrop_ai it truly feels like we're working on "applied ai safety". agents are getting more capable, stakes are getting higher. we're hiring, dm me.20d
    CRV@CRVWe led Raindrop's $50M Series A because they’re quickly becoming the leader of agent observability. @reidRMC @brittwalker_ and team are thrilled to back the company that is improving agents at Fortune 100s and startups alike. @raindrop_ai @snarkyzk @alexisgauba @benhylak20d
    Nix 🕊@startingfromnixIt's been a warning shot summer, and Raindrop is a mighty crew with a mission: protecting the world from agent failures. Excited to share a behind the scenes in-depth interview with the founders of @raindrop_ai - @snarkyzk, @Benhylak, and @alexisgauba (+ congrats on the A raise, bringing total funding to $50m from @CRV / @lightspeedvp) for New Ontologies. We talk about 1. The Hugging Face incident as a canary in the coal mine 2. Chain of thought monitoring and simulation, including the simulations product Raindrop is announcing 3. How agents fail in the long tail 4. Working with your best friends20d
    Diana@sdianahuCongrats to @snarkyzk ,@alexisgauba and @benhylak on @raindrop_ai's Series A led by CRV, bringing their total funding to $50M they detect failures in AI agents, such as tool call failures and decision errors (Vercel, Clay, and Speak uses them) 1/7 how they got started as a terminal and now solving the rise and fall of agent civilizations with Simulations20d

    Sentiment

    Positive91.2%8.8%Negative

    Summary

    Many accounts congratulated Raindrop on its Series A for building a safety layer that detects AI agent failures, while a few replies argued its synthetic simulations and non-deterministic checks add little value over real traces.

    Based on 37 sentiment-bearing replies from 34 accounts across 5 conversations.