Developers just caught a company hiding something inside of their new model.

Developers just caught a company hiding something inside of their new model. The company Cursor released a new coding AI model called Composer 2. It had frontier level coding intelligence. Benchmark charts comparing it to models from companies like Anthropic and OpenAI. They then used those charts and numbers to justify raising more money for the company. But then developers started digging around in the API. Found something very interesting. The internal model ID literally reference Kimi K 2.5, which is an open source AI model built by the Chinese startup Moonshot AI. The new model might actually be Kimi K 2.5 with reinforcement learning added on top. But the crazy part. The discovery happened a day after launch. Developers noticed the model ID ran tokenizer test and started posting the evidence online. The controversy exploded so fast that Cursor eventually admitted that the model was built on top of Kimi's open source base. They said, "Yep, Composer 2 started from an open-source base!" But he said, "Only 1/4 of the compute spent on the final model came from the base, the rest is from our training." As a result, he said Composer 2's performance on various benchmarks is "very different" from Kimi's. Robinson also insisted that Cursor's use of Kimi's was consistent with the terms of its license, a point the Kimi account on X repeated in a subsequent post congratulating Cursor, where it said Cursor used Kimi "as part of an authorized commercial partnership" with Fireworks AI. Only about a compute actually came from the original and the rest from their own training. But the whole situation sparked a bigger debate in the AI world. Are companies actually building new AI models, or are they just taking open source models and putting better training give me a follow. Join the Discord in the link in my bio if you want to keep up with this AI space.