Google's AI crawler, Google-Extended, the crawler it uses for Gemini and other related AI services, does render itself and can render JavaScript, just like Googlebot, Google's main web search crawler.
Martin Splitt from Google confirmed this in an interview with Kenichi Suzuki. Martin said, " we don’t share what we see with web search but Google’s, I think it is called Google extended, the AI crawler that Gemini uses, also renders." He explained "it uses WRS but it’s basically like we have a service, Googlebot uses the service and Gemini uses the service as well."
Meaning, both Googlebot and Google-Extended both use Google's Web Rendered Service. Martin said, "So WRS is shared across different Google services, including Web Search and Gemini."
So this lets Google's Gemini service also see content that may be more challenging for other newer AI engines to access. Google generally does an excellent job of crawler and understanding content that is generated using more advanced web languages.
This came up at the 22 second mark in this video interview:
Forum discussion at X.