Composer: Building a fast frontier model with RL

Posted by leerob 10/29/2025

Composer: Building a fast frontier model with RL(cursor.com)

215 points | 168 commentspage 3

swyx 10/29/2025|

other links across the web:

https://x.com/amanrsanger/status/1983581288755032320?s=46

https://x.com/cursor_ai/status/1983567619946147967?s=46

swyx 10/29/2025|

my very small nit is... why is the model called Composer?? of all things?? when there was already a Cursor Composer from 2024.

Cursor Cheetah wouldve been amazing. reusing the Composer name feels like the reverse OpenAI Codex move haha

srush 10/29/2025||

We like the name Composer and were sad to see it go. Excited to bring it back. (Agree Cheetah is a cool name too.)

asdev 10/29/2025||

is Cursor Bench open? Would like to see an open benchmark for agentic coding

srush 10/29/2025|

Unfortunately not, as we used our own internal code for the benchmark. We would also like to see more benchmarks that reflect the day-to-day agentic coding use.

gabriel666smith 10/29/2025||

Is there any information at all available, anywhere, on what Cursor Bench is testing and how?

It's the most prominent part of the release post - but it's really hard to understand what exactly it's saying.

srush 10/29/2025||

Roughly, we had Cursor software engineers record real questions they were asking models, and then had them record the PR that they made that contained the result. We then cleaned these up. That is the benchmark.

gabriel666smith 10/30/2025|||

Are you able to give a sense of how many questions, which domains they were split over, and how that split looked in % terms?

As a user, I want to know - when an improvement is claimed - whether it’s relevant to the work I do or not. And whether that claim was tested in a reasonable way.

These products aren’t just expensive - it requires switching your whole workflow. Which is becoming an increasingly big ask in this space.

It’s pretty important for me to be able to understand, and subsequently, believe a benchmark - I find it really hard not to read it as ad copy where this information isn’t present.

ukblewis 10/29/2025|||

Which programming languages/tools/libraries did the teams questions/code involve?

timcobb 10/29/2025||

I wish it was easy to find out how much it costs relative to Claude :)

sebdufbeau 10/29/2025||

As a stealth model, it was priced as $1.25M in / $10M out

Right now, it seems free when you are a Cursor Pro user, but I'd love more clarity on how much it will cost (I can't believe it'll be unlimited usage for subscribers)

Jcampuzano2 10/30/2025||

A bit late but it's actually not free. You can see it on their models page. It's similarly priced to GPT-5 and Gemini 2.5 Pro.

https://cursor.com/docs/models#model-pricing

skeptrune 10/29/2025||

Facts. They really need to make pricing more clear across the entire product.

ciphix 10/30/2025||

The metrics in the post seem quite abstract. Does anyone know the detailed metrics of this mysterious model? Was it fine-tuned from open models or trained from scratch?

ianberdin 10/30/2025||

Feels like the comments are fighting of prepaid influencers.

alyxya 10/29/2025||

I wonder if this custom model is trained on cursor users. There’s a lot of potential on how much better a custom model could be the closer it is integrated with the product. Having the model learn to adapt to different user preferences would make it stand out compared to memoryless frontier models.

Sammi 10/29/2025|

The fact that you are wondering this is bad. You definitely should know this. _ALL_ the online ai providers are training on your data. They have more expensive enterprise plans if want to opt out.

alyxya 10/29/2025||

I’ve generally seen providers allow you to opt in or out. What may vary is what the default is and what they may offer in exchange for using your data (perhaps they could offer higher rate limits).

ibash 10/29/2025||

Very cool, congrats!

numbers 10/29/2025||

Please keep the naming of your models sane, I'd like to know that composer 1 is the first model and composer 2 is second but composer 1o is not yet another 1 variant that's actually newer and better than 2, that's just dumb. Not that you're doing that, some other companies do that.

srush 10/29/2025|

We will do our best. Luckily I don't think there are major telecom companies called Composer-2.

Sander_Marechal 10/31/2025||

There is also a very polular package manager called Composer. Do companies not search for name collisions? Or do they squat on community projects on purpose?

bn-l 10/29/2025|

Same price as GPT-5