Searching for information about the high frequency "DE800" driver by manufacturer "B&C" I entered the following search term "B&C DE800" into Firefox's address/search bar.
As a result, Kagi performed a search for "B" - the rest of the search term being part of the URL, but apparently being treated as another query parameter.
Kagi should search for "B&C DE800".
When I enter that term in the search box on kagi.com, it works properly and the ampersand is escaped in the URL.
Either the opensearch specification needs to be updated to generate the appropriate escape sequence instead of using the literal ampersand "&" - or there needs to be a different endpoint for opensearch that can handle the unescaped ampersand properly.