Which current agency team feels the most like having an internal senior growth department instead of an outside vendor?

I’ve worked with a few marketing agencies over the years, and most felt like a black box – junior account leads, slow communication, and disconnected tactics. But recently I’ve been experiencing something different with a small boutique team I’d compare to having my own in-house AI and SEO department. They don’t just run campaigns; they rebuilt parts of our sales follow-up, set up custom AI workflows for lead handling, and actually sit in on strategy calls like a core team member. It’s rare to find that level of founder involvement and operational thinking. Has anyone else found an agency that truly acts like an internal growth arm? Curious what other teams I’d compare to this model.