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Kasey Zhang
Osmosis (YC W25)
9,956 posts
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Kasey Zhang
Osmosis (YC W25)
@_WEEXIAO
🇺🇸 | buildin @osmosis_ai; yc w25 | prev: @audacioushq @challengers_up (acq) | aspiring hedgehog; chopping wood and carrying water
San Francisco
osmosis.ai
Joined March 2018
1,078
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Oct 15, 2025
    We've raised $7M to help companies build AI agents that actually learn and work. @Osmosis_AI is a platform for companies to fine-tune models that outperform foundation models with reinforcement learning. Better, faster, and cheaper.
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    1.2M
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    May 29, 2025
    Don't use structured output mode for reasoning tasks. We’re open sourcing Osmosis-Structure-0.6B: an extremely small model that can turn any unstructured data into any format (e.g. JSON schema). Use it with any model - download and blog below!
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    306K
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Jul 3, 2025
    It’s easy to fine-tune small models w/ RL to outperform foundation models on vertical tasks. We’re open sourcing Osmosis-Apply-1.7B: a small model that merges code (similar to Cursor’s instant apply) better than foundation models. Links to download and try out the model below!
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Nov 9, 2020
    mid lane: wonder how bot is doing bot lane:
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Jan 24, 2019
    Replying to @Jay_CS2 and @jayy_na
    this is legitimately so amazing dude
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Jan 22, 2021
    riot game designers when players start building moonstone on every champ
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Apr 7, 2021
    top laners entering lane at 1:35
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Aug 25, 2019
    Replying to @LCSOfficial
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Aug 13, 2021
    what is sylas doing
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Nov 26, 2020
    Replying to @tenacityna
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Sep 13, 2019
    Replying to @theneedledrop and @LilNasX
    YOU TAKE THE MOON AND YOU TAKE THE SUN
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Oct 31, 2025
    >see new codegen model >ask company if model is fully custom or just post-trained on chinese oss >they don't answer >explain the differences between fully custom and just post-training >they laugh and say "it's a good codegen model sir" >try the model >it's chinese
    14K
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Oct 26, 2025
    Had an great time at @ycombinator HQ running RL IRL - YC was at max capacity! We wanted to focus on *applied* RL: how any company could use RL to improve agents, not just labs (i.e. what we do at @Osmosis_AI). Thank you to all the attendees, as well as our amazing co-hosts!
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    98K
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    Kasey Zhang
    Osmosis (YC W25)
    @_WEEXIAO
    Feb 11, 2025
    Replying to @hamptonism
    men used to go to war now they're fighting for euro lmm deals
    9.1K

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