You asked about Reinforcement Learning
407 people built something like it. 56 are gone.
That is 16% of the ones whose fate we could settle, against 23% across the whole register. 47 were acquired.
| Launched | What it was | Today |
|---|---|---|
| 2019-01-01 | YCrct AI build AI NPCs · rct.ai | still up |
| 2024-06-01 | YCSepal AI Data Development for Advanced AI · sepalai.com | acquired |
| 2025-01-01 | YCHUD Platform for building RL environments and evals · hud.ai | still up |
| 2016-01-01 | YCPathmind Pathmind helps industrial engineers and simulation modelers achieve… · pathmind.com | gone |
| 2025-06-01 | YCidler Hill-climb any benchmark, for any model, in any domain. · idler.ai | still up |
| 2024-06-01 | Open-Source Reinforcement Learning (RL) & Fine-tuning for LLMs. · unsloth.ai | still up |
| 2025-01-01 | Reasoning Fine-Tuning · trainloop.ai | still up |
| 2024-01-01 | Autonomously scaling environments · vibrantlabs.com | still up |
| 2025-01-01 | YCOsmosis Reinforcement Learning (RL) for AI Agents · osmosis.ai | still up |
| 2026-06-01 | We turn company data into training data · ooakdata.com | still up |
| 2024-01-01 | YCJustAI Agentic Marketing Platform · getjust.ai | still up |
| 2025-09-01 | Training Data for Recursive Self-Improvement · hillclimb.com | still up |
| 2025-09-01 | Large-scale real-world robot & human data for embodied AI · cortexrobot.ai | still up |
| 2026-01-01 | Robot Cowboys that Herd Cattle with AI Drones · brumby | still up |
| 2023-01-01 | YCVelos Platform to automate manual back-office work · tryvelos.com | still up |
| 2026-06-01 | Turns real businesses into robotics data vendors · praxisrobotics.io | still up |
| 2026-06-01 | YCCueBench RL post-training for science reasoning and performance engineering · cuebench.dev | still up |
| 2025-06-01 | YCMonte Continual Learning for Agents · trymonte.ai | still up |
| 2026-06-01 | YCCoArena The biggest crowdsourced benchmark for Computer-Use · coarena.ai | still up |
| 2023-01-01 | YCAtmeto We develop ML that optimizes how batteries in the grid store energy · atmeto.com | still up |
| 2026-06-01 | Training the world's best AI model for quantitative finance. · prodigy.markets | still up |
| 2026-06-01 | Building multi-agent simulations for model evals and training. · olamlabs.ai | still up |
| 2024-09-01 | YCSynth Prompt and Context Optimization for Coding Agents · usesynth.ai | still up |
| 2025-06-01 | YCNuntius Making Models Follow Rules. · nuntius.ai | gone |
| 2024-01-01 | Self-improving content bank for marketing · useresonance.com | acquired |
| 2026-06-01 | YCFabraix The world's frontier hacker of AI agents. · fabraix.com | still up |
| 2025-06-01 | Physics-based foundation models for CAD optimization. · topological.com | still up |
| 2025-09-01 | YCSylvian Specialized AI Agents. · sylvian.ai | gone |
| 2026-06-01 | Open source AI gateway that turns your traffic into a better model · experientiallabs.ai | still up |
| 2025-01-01 | AI Agents that automate enterprise software processes · agentin.ai | still up |
| 2026-01-01 | YCAshr Enterprise post-training, monitoring, and continual learning platform · ashr.io | still up |
| 2026-06-01 | YCEdotEnv Quant Neolab building self-improving agents from quant data · edotenv.com | still up |
| 2026-06-01 | YCMarkov Expert computer-use data for frontier AI labs · markovstudios.com | still up |
| 2026-06-01 | YChiloop Autoresearch as a service: we solve your hardest measurable problems · hiloop.ai | still up |
| 2026-06-01 | YCEnact Real-world RL environments for robotics models · enact.company | still up |
| 2026-01-01 | Evals for frontier research agents · buildwithglue.com | still up |
| 2026-06-01 | YCMagma Monetize your agent's traces. · magmahq.ai | still up |
| 2026-01-01 | YCTraverse Research lab solving non-verifiable work · traverse.so | still up |
| 2026-06-01 | YCRiften Earned intelligence for every company · riften.ai | still up |
| 2014-01-01 | YCCruise Self-driving cars. · getcruise.com | acquired |
| 2019-01-01 | Online engineering college for India. Learn technical skills & get… · skill-lync.com | still up |
| 2016-01-01 | Building humanity’s multiplanetary future. · relativityspace.com | still up |
| 2017-06-01 | The first public safety operating system that eliminates crime. · flocksafety.com | still up |
| 2015-01-01 | Rebuilding healthcare with AI at the core · akidolabs.com | still up |
| 2015-06-01 | YCGo1 A learning platform that enables you to train your staff or customers. · go1.com | still up |
| 2016-06-01 | YCScale AI Data-centric infrastructure to accelerate the development of AI · scale.com | still up |
| 2019-06-01 | YCTRM Labs TRM is building a safer world for billions of people. · trmlabs.com | still up |
| 2006-06-01 | YCScribd World's largest online library. · scribd.com | still up |
| 2018-06-01 | YCUBITS Learning Hub for companies in Latam · ubits.com | still up |
| 2021-01-01 | Effective and accessible online live education. · coderhouse.com | still up |
| 2011-06-01 | The leading online learning platform for technical skills. · codecademy.com | acquired |
| 2021-01-01 | YCKiwify Create & sell online courses · kiwify.com.br | still up |
| 2021-06-01 | YCNovatr Online cohort based courses for architects, engineers and designers… · novatr.com | still up |
| 2021-01-01 | The online language school for Latam, with groups led by an instructor · poliglota.org | still up |
| 2016-01-01 | Building the Operating System for B&M Retail using Deep Learning · focal.systems | still up |
| 2015-01-01 | YCTempo Live home fitness training powered by computer vision. · tempo.fit | still up |
| 2021-06-01 | YCBaubap Smart micro financing for everyone · baubap.com | still up |
| 2020-06-01 | YCTaktile Transform your decision-making with reliable AI agents in weeks, not… · taktile.com | still up |
| 2021-01-01 | YCEncord The data layer for physical AI · encord.com | still up |
| 2015-01-01 | YCMashgin Self-Checkout using Computer Vision. · mashgin.com | still up |
How this compares
Older launches have had longer to die, so this slope is expected. A year that broke it would mean something is wrong with the checking.
The register re-probes every domain it holds. Some that answered last month stop answering. We send that list — what went quiet, and what it was — once a month. Nothing else.
How this was made. Show HN entries are every post from 2021 to 2023 with at least five points that linked to its own domain; code hosts and free hosting are excluded, because a repository outlives the effort behind it. Product Hunt entries needed 100 votes — a far higher bar, so they are the promoted top slice rather than a like-for-like sample. Both are judged by asking the domain whether it still answers: gone means it no longer resolves, refuses the connection, serves a parking page, or says plainly that it shut down. An HTTP error is not counted as gone — a server answering 404 is one somebody still pays for, and an audit of 25 gone-calls found two such sites alive with only a moved homepage. Y Combinator entries use the status YC publishes itself, which is why only those can say acquired. Squatted domains — a lapsed name now serving somebody else's site — are not detected, so these figures run slightly low.