Apertus 1.5 adds images, reasoning, and 4× longer context

What happened

Apertus released version 1.5 of its open-source language models on July 24, 2026, with 8B and 70B variants. The update adds image understanding, an optional thinking mode for reasoning, a context window extended to 262,144 tokens (four times longer than Apertus 1.0), and improved instruction-following and tool use. The 8B model received 4 trillion tokens of additional training data and the 70B model received 2 trillion tokens.

Why it matters

Apertus publishes its models as fully open — weights, training data, and methodology included — meaning developers can use and modify the software without commercial licensing restrictions. The multimodal and reasoning enhancements make the models more practical for real-world tasks like document analysis and complex problem-solving, while the longer context window allows the models to work with much larger inputs.

What to watch

A technical report with detailed benchmark results, training pipelines, and intermediate checkpoints will be published in the coming weeks. The models are available on Hugging Face, and the team is working with inference providers to make them available on multiple platforms.