You put the whole document into the prompt and ask. Nothing gets chopped into chunks or looked up from a search index; the model reads all of it, up to 512K tokens, which is roughly 350,000 words, a long novel with room to spare. It thinks before it answers, with a per-request dial for how hard: low, medium or high. High is what the makers recommend and it can run long, so a detailed question over a big document takes a while but comes back with the reasoning visible.
It is a general model too, not just a long reader. It handles tool calls for agent work, and IFM, the group behind the LLM360 open-training project, puts it ahead of Gemma 4 12B and Qwen3.5 9B on their long-context reasoning, competition math and software-engineering tests. Those are the makers' own numbers; the technical report is due at the end of September.
The unusual part is how open the release is. Pretraining data, training logs and around fifty intermediate checkpoints are public, from the first pretraining stage through the context extension and the final tuning, so you can load any point in training and watch a capability appear.