Swiss AI has published release notes for Apertus 1.5 on Hugging Face, according to the single source provided. The post is titled "Apertus 1.5 Release Notes" and is hosted on Hugging Face's blog under the Swiss AI account.
The supplied source text is limited to the title and URL, so no architecture, benchmark, or usage details are available for this article. In the absence of those specifics, the main verifiable fact is that the update exists and was announced in this format.
Because there is only one source presented, there are no independent claims to cross-check or differing accounts to reconcile. A fuller comparison of Apertus 1.5 with earlier versions would require the actual contents of the release notes, which were not included in the prompt.