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Cursor Composer 2 is just Kimi K2.5 with RL
- Sammi 7mo agoAs a paying customer, it just doesn't feel good that they are trying to pass off someone else's model as their own. I mean I guess this is what businesses do all the time. There's a term for it even, it's called white-labeling. But is this all that Cursor have? They pass of VS Code as their own, they pass off Kimi as their own... What do Cursor even do? What do I need them for?
- jstanley 7mo agoAs a paying customer, I don't care where the model comes from, I only care how good it is.
- Sammi 7mo agoSure, and also at what price point. But can I rely on Cursor to be able to keep delivering, when they aren't the one's doing the work themselves?
- 827a 7mo agoCan you ensure that Notion is able to keep delivering given they don't develop their own models? Lovable? OpenCode? Should we be worried that Discord might disappear because they don't run their own data centers? Personally, I'm very concerned that one day Google might just have to close up shop, because while they do design their own chips, they don't fabricate them in-house; and don't get me started on TSMC and their critical dependency on ASML, they might as well just lock the doors.
- acmj 7mo agoWell, they can keep stealing as long as someone open weight their models.
- manojlds 7mo agoAnd how cheap it is
- khuey 7mo agoWhite-labeling may be slightly dishonest to the consumer but the manufacturer and distributor are honest with each other. That doesn't appear to be the case here (Kimi's license requires publicly acknowledging Kimi is used for anyone operating at Cursor's scale).
- justindotdev 7mo agoim pretty sure this is in violation of moonshot's ToS. this is going to be fun to watch unfold
- deleted 7mo ago[deleted]
- gillesjacobs 7mo agoThey probably licensed it. Still a bit deceptive not to mention it on the model card/blog post, but companies whitelabel all the time without mentioning. It goes against the ML community ethos to obscure it, but is common branding practice.
- deaux 7mo agoNo they didn't [0][1]. With this leak they're probably negotiating as we speak, which could be why they've deleted the posts. [0] https://chainthink.cn/zh-CN/news/113784276696010804 https://chainthink.cn/zh-CN/news/113784276696010804 [1] https://pbs.twimg.com/media/HD2Ky9jW4AAAe0Y?format=jpg&name=medium https://pbs.twimg.com/media/HD2Ky9jW4AAAe0Y?format=jpg&name=...
- gillesjacobs 7mo agoI stand corrected, that is pretty scummy. I bet Moonshot is going to make them open their wallets to avoid legal trouble.
- charcircuit 7mo agoKimi K2.5 was released under a modified MIT license (100M+ MAU or $20M+ MRR has to prominently display Kimi K2.5). It will be fine.
- antirez 7mo agoBasically this is true for most startups in the world BUT Cursor, so here you are kinda inverting the logic of the matter. Cursor is at a size that, if they wanted to use K2.5, they could clearly state that it was K2.5 or get a license to avoid saying it.
- rvz 7mo agoHonestly I don't think this leak is any good for Cursor. Not only this appears as a violation to Moonshot's ToS, this may also be in fact enough evidence for Anthropic to ban Cursor from using their models, just like they are doing to OpenCode. Why? As I said before, Anthropic mentions Moonshot AI (Maker of the Kimi models) as one of the AI labs that were part of this alleged "distillation attack" [0] campaign and will use that reason to cut off Cursor, Just like they did to OpenAI, xAI and OpenCode. Let's see if the market thinks Composor 2 is really that good without the Claude models helping Cursor. (If Anthropic cuts them off). [0] https://www.anthropic.com/news/detecting-and-preventing-distillation-attacks https://www.anthropic.com/news/detecting-and-preventing-dist...
- charcircuit 7mo agoKimi K2.5 is an open source model. It is intended for people to make derivative models.
- Majromax 7mo ago> this may also be in fact enough evidence for Anthropic to ban Cursor from using their models, just like they are doing to OpenCode. The Anthropic ban on OpenCode isn't an Anthropic ban on OpenCode, it's a ban on using a Calude Code subscription with OpenCode. That's justified (or not) under various ToS arguments, but one can still use OpenCode with the more expensive API access. Anthropic's complaint about distillation attacks is a distinct prong, one not levied against OpenCode. Additionally, the distillation activities described in your link don't describe Cursor's routine use of Anthropic's models. There, the model outputs are a primary product (e.g. the autocompleted code), and any learning signals provided are incidental.
- zozbot234 7mo agoAnthropic's complaint about "distillation" attacks (obligatory scare quotes because training on glorified chat logs is a far cry from actually distilling from model weights you have real access to) is also about ToS violations. Anthropic's ToS, like OpenAI's, forbids you from exploiting interactions with their model for the purpose of building a competitor, even though rumor has it that the AI industry has been doing exactly this for a long time anyway.
- gillesjacobs 7mo agoCursor is mostly an IDE / coding-agent harness company. So it probably makes sense for them not to train their own base model, but instead license something like Kimi and fine-tune it for their own harness and workflows. Their moat looks pretty thin. A VSCode fork with an open-source LLM fork on top. In the fast-moving coding-agent market, it’s not obvious they keep their massive valuation forever.
- jstummbillig 7mo agoThere is a plausible scenario in which software engineering requires a very finite amount of intelligence, in which sota models will be used mainly for other things and where for coding the harness will become increasingly more important than the model.
- merlindru 7mo agoi've kinda had this thought before but never could express it ("you only need up to a certain level of smartness to express most coding concepts correctly") but it never occurred to me that, if true, of course the harness becomes increasingly more important. which feels absolutely correct of course. not sure if the hypothesis is even true though.
- NitpickLawyer 7mo ago> Their moat looks pretty thin. Their value is in the data they've collected and are collecting. Usage, acceptance rate, and all the connected signals. Plus having a large userbase where they can A / B test any finetune they create.
- _puk 7mo agoThere were conversations in the team yesterday about how Cursor's cloud agents are still ahead of Claude from a UX perspective. Obviously we're running both, using the right tool for the job. There is stickiness there from being early. That will be hard to replicate.
- CharlieDigital 7mo ago
- agluszak 7mo agoA hyped startup providing zero added value, burning investor money only to repackage somebody else's work? That's new... /s
- DeathArrow 7mo agoIt depends on what you consider value. People are using it so they find some value.
- genthree 7mo agoIncompetently repackaging. They started with VSCode so nearly all the work was already done, but still managed to make it leak memory like it's infinite. The power of AI slop! Their product is an anti-advertisement for the core concept of itself, which is kind of impressive.
- merlindru 7mo agoI like Cursor's AI projects a lot. Cursor Tab is truly impressive. But you couldn't be more right. I just downloaded VSCode again today after Cursor's latest update dropped my editor to 5 FPS or so (legitimately unusable. not hyperbole.) and holy shit it feels snappy. Completely forgot what it's like.
- deaux 7mo agoLooks like two Moonshot employees confirmed that it's not licensed before Moonshot made the decision to get out of the debate and delete their posts [0][1]. [0] https://chainthink.cn/zh-CN/news/113784276696010804 https://chainthink.cn/zh-CN/news/113784276696010804 - may have originally been https://x.com/apples_jimmy/status/2034920082602864990 https://x.com/apples_jimmy/status/2034920082602864990 [1] https://pbs.twimg.com/media/HD2Ky9jW4AAAe0Y?format=jpg&name=medium https://pbs.twimg.com/media/HD2Ky9jW4AAAe0Y?format=jpg&name=...
- lmc 7mo agoThis is on their website... "Is Kimi K2.5 open source?" "Yes, Kimi K2.5 is an open source AI model. Developers and researchers can explore its architecture, build new solutions, and experiment openly. Model weights and code are publicly available on Hugging Face and the official GitHub repository." https://www.kimi.com/ai-models/kimi-k2-5 https://www.kimi.com/ai-models/kimi-k2-5
- saidmukhamad 7mo ago4th paragraph in license block Our only modification part is that, if the Software (or any derivative works thereof) is used for any of your commercial products or services that have more than 100 million monthly active users, or more than 20 million US dollars (or equivalent in other currencies) in monthly revenue, you shall prominently display "Kimi K2.5" on the user interface of such product or service.
- lossolo 7mo agoTheir first model was also based on an open source Chinese base model. They never fully trained their own model.
- todteera 7mo ago[flagged]
- mohsen1 7mo agoCursor Composer 1 was Qwen and this is Kimi. IDE is based on VSCode. The entire company is build on packaging open source and reselling it. Ollama is also doing this. There is so much money to be made repackaging open source these days. So funny to see Twitter go wild saying "a 50 person team just beat Anthropic" blah blah.
- NitpickLawyer 7mo ago> packaging open source and reselling it. It's a bit more than that. They have plenty of data to inform any finetunes they make. I don't know how much of a moat it will turn out to be in practice, but it's something. There's a reason every big provider made their own coding harness.
- pbowyer 7mo agoCan anyone enlighten me how having a coding harness when for most customers you say "we won't train on your code" helps you do RL? What's the data that they rely on? Is it the prompts and their responses?
- rubymamis 7mo agoI guess they rely on many people not toggling privacy-mode on?
- victorbjorklund 7mo agoI doubt the majority does that. I bet the majority is using the defaults.
- __mharrison__ 7mo agoDoes "code" include the prompt? Seems like the prompts would be the goldmines. Hook those up to rl an open weight model...
- doctorpangloss 7mo agoIt doesn't matter what your privacy setting is, with any savvy vendor. Your data is used to train by paraphrasing it, and the paraphrasing makes it impossible to prove it was your data (it is stored at rest paraphrased). Of course the paraphrasing stores all the salient information, like your goals and guidance to the bot to the answer, even if it has no PII.
- olejorgenb 7mo agoTo be fair, is "with RL", "just"? They should have disclosed it though. If they didn't it's a bad look for sure.
- mono442 7mo agoThis whole ai stuff feels like a big bubble especially with the oil price soon at $200 and guaranteed recession.
- koakuma-chan 7mo agoCursor can't compete with Claude Code's subsidized pricing, so they are trying to gaslight people that their cheap model is good enough.
- vachina 7mo agoA question. I’m due for a yearly Cursor subscription renewal, how does the credit limit look like? Currently I’ve not hit any of the limits despite using it quite rigorously, I wonder if this will change with a renewal?
- thewhitetulip 7mo agoBut you have to buy into it right? If you don't have a limit then what did your contract look like?
- vachina 7mo agoI signed up last year when the limits were a lot more generous.
- thewhitetulip 7mo agoInteresting. I wasn't aware that cursor also has a free tier!
- DeathArrow 7mo agoI whish it was GLM 5.0.
- prodigycorp 7mo agoThere are many reasons to make fun of Cursor. However, one of the things get right is their autocomplete model. Are there any open models that come close? Why doesnt OAI or Anthropic dedicate some resources to blowing Cursor's model out of the water? Cursor's completion model is a sticking point for a lot of users.
- olejorgenb 7mo agoThe model is great. The UX is ~~horrible~~ annoying...
- Tadpole9181 7mo agoDon't get me started. For every half-decent choice, there's a multitude of insane choices. After all this time they still don't have side-by-side review. Equally as annoying, the break from VSCode is horrible. Having to use a separate registry, not having basic settings sync, the delay behind mainline VSCode updates. Then, it's just plain buggier than others. The agent terminal just doesn't work semi-regularly, it doesn't like listing directories in the @, the SSH plugin crashes every other time it tries to connect, undoing agent work undoes edits I made in unrelated files sometimes. Sometimes updates just regress performance hard for seemingly no reason. I also noticed the token use is wildly less efficient than CC or Codex these days. After almost no time at all it's up to 100,000 tokens and they're charging $1 per request for Sonnet. Side-by-side, Cursor spent $17 in the same time CC spent $4. Which is bizarre to me, since they advertise how their indexing and semantic search is more token efficient? The autocomplete model was the only reason I stayed as long as I did. I wish there was a VSCode equivalent.
- olejorgenb 7mo agoWell, the UI as a whole is ok to me (except the parts which is way too volatile). I was talking about the UX of the autocomplete model. The model are very often spot on and fast, but it's impossible to properly configure it to be less in your face. Making it basically useless for day-to-day development.
- 7mo ago
- heliumtera 7mo agoFor all the muh productivity guys that like to claim they can turn invisible when no one is looking, an produce 600k lock over 6 weeks, well...cursor is useless now. We know kimi K2.5 won't make you 100 trillion times faster. Cursor is killed for this market.
- cbg0 7mo agoScores higher than Opus 4.6 on their in-house benchmark? Sounds legit.
- HeavyStorm 7mo agoThere's no "just" in RL. Fine tuning is very important and could make a lot of difference.
- merlindru 7mo agoapparently GPT-5 uses the same pretrain as 4o did, hah
- lukaslalinsky 7mo agoIndeed, this is quite obvious on Claude models vs Gemini. I fully believe Gemini is more powerful model, but the post training process is nowhere near what Anthropic does, which results in Gemini being horrible at coding sessions, while Claude is excellent.
- chvid 7mo agoMoonshot is raising money at a 10B usd valuation, cursor/anysphere is at a 30B usd valuation.
- taytus 7mo agoYC is back at it again.
- simonw 7mo agoI'm annoyed that we still don't know for certain which base model they used for Cursor 1. This feels really rude to me. I have no problem with them fine-tuning open weight models to create their own - they are getting great results, and Cursor's research term should be respected for that. But deliberately hiding the base model they use is disrespectful of the researchers who created that model.
- enraged_camel 7mo agoSimon, sorry to hijack the thread, but what is a good way of contacting you? I'd love to pick your brain on an AI talk I'm supposed to be giving soon.
- leerob 7mo agoWe used a Kimi base, with midtraining and RL on top. Going forward, we'll include the base used in our blog posts, that was a miss. Also, the license is through Fireworks: https://x.com/Kimi_Moonshot/status/2035074972943831491 https://x.com/Kimi_Moonshot/status/2035074972943831491
- simonw 7mo agoThanks for sharing this, I saw Cursor are committed to publishing this now which is great to see.
- EugeneOZ 7mo agoI don't know - it works okay (yet to be tested whether it is actually smarter than Opus 4.6), but it is not bad at all. So far, it works quite fine (I'm not testing the "fast" version).
- deleted 7mo ago[deleted]
- 827a 7mo agoThis is exactly what Cursor should be doing, within the obvious bounds of the law and such. Not everyone needs a pristine foundation model. What a waste of compute. Anthropic & OpenAI need product-level competition to knock them off their $25/Mtok horse.
- coreyburnsdev 7mo agois this the model used on free mode?
- chaosprint 7mo agoThis is actually becoming a path dependency, a dependence on the supply chain.
- granitepail 7mo ago"Just" Kimi K2.5 with RL—people really misunderstand how difficult it is to achieve these reults with RL. Cursor's research team is highly respected within the industry, and what they've done is quite impressive. Before people go jumping to conclusions about model theft, it's worth considering the possibility that they did reach an agreement with Moonshot which their researchers were not aware of. That would certainly explain the deleted tweets. Until Moonshot makes an official statement, I'm not particularly concerned.
- halJordan 7mo agoThe amount of angst people feel the need to have against ai is incredible. We all seemed to want open weights, but it's time to take offense when open weights are used as intended?
- granitepail 7mo agoHey, what do you know—Moonshot came out and explained that Cursor was operating within the licensing agreement. https://x.com/kimi_moonshot/status/2035074972943831491 https://x.com/kimi_moonshot/status/2035074972943831491
- Aurornis 7mo agoEarlier their employees were Tweeting that Cursor did not have a license ( https://pbs.twimg.com/media/HD2Ky9jW4AAAe0Y?format=jpg&name=medium https://pbs.twimg.com/media/HD2Ky9jW4AAAe0Y?format=jpg&name=... ) so Moonshot employees are partially to blame for the outrage.
- jeany2s 7mo agoYou should realize the number/comparison they released is based on CursorBench... I don't have to emphasize more how sus this kind of self-defined closed-source benchmark can be
- ajitid 7mo agoCould you explain how much improvement RL+fine tuning has given to Composer 2.0 over Kimi K2.5? I don't fully grasp the work Cursor model has done here and why it is difficult to achieve these results with RL.
- rockmeamedee 7mo agoWhat does this mean, that you can take Kimi and RL finetune it a little more and blow the big AI shops out of the water? Would this have been extensively fine tuned, beyond what Anthropic/OAI would do themselves? I guess this is Cursor's own benchmark, so you can finetune on your own dataset and get better results on your own specific tasks I guess.
- ryguz 7mo ago[flagged]
- htrp 7mo agoThe cursor investor pitch was we're training our own models to do coding. If your amazing model is just an RL repack, you need a new pitch to justify your 50bn valuation https://www.bloomberg.com/news/articles/2026-03-12/ai-coding-startup-cursor-in-talks-for-about-50-billion-valuation https://www.bloomberg.com/news/articles/2026-03-12/ai-coding...
- simplyluke 7mo agoAny investor who believed a team their size and with their capital was training a SOTA base model doesn't understand the space. I fully believe that was some of their investors, but people acting like RL + fine tuning based on their massive user base that's producing qualitatively better outputs than the base model is meaningless aren't understanding what the company is doing.
- ajitid 7mo agoCould you explain how much improvement RL+fine tuning can give with respect to Composer 2.0 model over Kimi K2.5? I don't fully grasp the work Cursor model has done here.
- __alexs 7mo agoAdvertising your model with some obviously home grown benchmark is a bold play. It doesn't matter how good your model is, I immediately trust it less.
- catbot_dev 7mo ago[dead]
- granzymes 7mo agoThey’re pretty upfront in their release post that they took an open source model and improved it with their own coding data. They mention “continued pretraining” (on top of the base model) and RL. Cursor never claimed to have done a full pretraining run. More to the point, beating Opus 4.6 at coding and coming within striking distance of gpt-5.4 is impressive! The benchmarks outperform raw Kimi K2.5. It’s particularly impressive given larger labs like Meta are struggling to catch up to OpenAI/Anthropic.
- deleted 7mo ago[deleted]
- QubridAI 7mo agoHonestly, this is pretty much how most of the new models operate nowadays: a base model combined with RL and some product-layer magic.
- odst 7mo agoWhat do people like about cursor? I've been using it for the past couple days, and I just don't see many positive things about it. It seems people like the autocomplete so I'll have to give that a try. There's just too many "features" the ux ends up being all over the place. I thought having the browser inside of the editor would be great for design, but it's not that much better than just having your browser open along with your editor.
- varispeed 7mo agoI noticed something strange with Cursor lately. When I am using Opus 4.6, sometimes it is giving ridiculously dumb answers as if they were actually using something like Qwen with a prompt to present itself as Opus. I have to close the session and start again hoping I'll get actual Opus.
- merlindru 7mo agoThere's no shot they're doing that. Would be suicide as soon as anyone notices, and by the looks of it, they didn't even clean up the URL here to "hide" the fact that this is Kimi K2.5 so i doubt there's any grand conspiracy here. What's way more likely is that Opus has been quantized by anthropic or something similar. Or that Opus was updated and didn't work well with Cursor's harness after. Or a token caching issue. Etc.
- varispeed 7mo agoWell, I noticed. Though I am too busy to make a fuss about it.
- 827a 7mo agoFYI: Someone from Cursor has responded to this https://x.com/leerob/status/2035035355364081694 https://x.com/leerob/status/2035035355364081694 I think there's a reason why the people from Moonshot deleted their tweets; they're probably just researchers who got yelled at by the people who actually knew what was going on at Moonshot.
- manojlds 7mo agoBut that makes no sense - what are inference partner terms?
- 827a 7mo agoHere you go: https://x.com/Kimi_Moonshot/status/2035074972943831491 https://x.com/Kimi_Moonshot/status/2035074972943831491 People need to seriously stop it with the whole reddit-esque Boston Marathon Bomber investigation-style low-info crusades. Its extremely unhealthy for both your own mental state and the state of discourse on the internet. Even if Cursor misbehaved (they did not): Your life is not materially changed whether they did or did not. Use it, or don't use it; these things are a matter that lies exclusively between Cursor and Moonshot.
- manojlds 7mo agoAgain, I was not questioning Cursor here, but inference partner terms makes no real sense and that is what I wanted explained.
- MangoCoffee 7mo agocursor copy open source software repack it as closed source and made massive money. i don't want to hear anything on how Chinese is stealing and copying when the west is doing it themselves.
- nreece 7mo agoPartnership confirmed by Moonshot: Cursor accesses Kimi-k2.5 via FireworksAI_HQ hosted RL and inference platform as part of an authorized commercial partnership. https://x.com/Kimi_Moonshot/status/2035074972943831491 https://x.com/Kimi_Moonshot/status/2035074972943831491 Cursor teams take: Only ~1/4 of the compute spent on the final model came from the base, the rest is from our training. This is why evals are very different. https://x.com/leerob/status/2035035355364081694 https://x.com/leerob/status/2035035355364081694