Agents no, LLMs yes. Not for generating code per se, but for answering questions. Common Lisp doesn't seem to have a strong influx of n00bs like me, and even though there's pretty excellent documentation, I find it sometimes hard to know what I'm looking for. LLMs definitely helped me a few times by answering my n00b questions I would have otherwise had to ask online.
Vibe coding Common Lisp could probably work well with additional tool support. Even a good documentation lookup and search tool, exposed in an AGENTS.md file, could significantly improve the problem Joe ran into of having the code generate bogus symbols. If you provide a small MCP server or other tool to introspect a running image containing your application, it could be even better.
LLMs can handle the syntax of basically any language, but the library knowledge is significantly improved by having a larger corpus of code than Common Lisp tends to have publicly available.