For several weeks, my daily coding setup was pretty much built around Composer 2.5 running on Grok Build. It was cheap, unbelievably fast, and handled almost everything I threw at it without slowing down my momentum. I eventually switched over to Grok 4.5 for heavier tasks, but I have been waiting to see how Cursor would build on what made Composer 2.5 so practical.
It looks like we might finally get our answer soon. A leak shared on X by Lumina shows that Composer 3 is currently undergoing internal testing inside Cursor under the codename Vega.
🚨 Composer 3 is reportedly being tested inside Cursor under the codename “Vega”
— Lumina (@LuminaXspace) July 20, 2026
The leaked checkpoint appears to include:
• Fast mode
• Medium reasoning
• High reasoning
• XHigh reasoning
• Six internal model variants
• A public release possibly coming very soon
Its… pic.twitter.com/Ocv1xFdPOo
The leaked checkpoint gives us a detailed look at what the Cursor team is working on. It reveals six distinct internal model variants and introduces four separate reasoning modes.
Users will reportedly be able to toggle between Fast mode, Medium reasoning, High reasoning, and an XHigh reasoning setting depending on the task.
This multi-tiered setup is a smart move for real-world development. You do not always need an AI model to pause and overthink a basic script or simple UI change. Fast mode works fine for quick edits. But when you are trying to refactor legacy code or debug tricky state issues across multiple components, having High or XHigh reasoning will give the model the extra room it needs to get things right.
Rumors surrounding the leak claim that Composer 3 delivers coding and agent performance somewhere between GPT 5.4 and GPT 5.5.
If that doesn't sound all that good, you have to keep in mind that Composer 3 will likely be cheaper and faster than those models too. If Cursor can offer reasoning capabilities close to frontier models while maintaining Composer's speeds and low pricing, it will be tough to beat.
According to the leak, a public rollout could happen very soon. Composer 2.5 set a really high bar for speed and value, so I am eager to see how version 3 performs in actual daily use once it drops. If it lives up to these leaked specs, it might just pull me back from Grok 4.5.
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