There is Aider (aider.chat), and it has been there for couple years now. Great tool.
Alas, you don't install Claude Code or Gemini CLI for the actual CLI tool. You install it because the only way agentic coding makes sense is through subscription billing at the vendor - SOTA models burns through tokens too fast for pay-per-use API billing to make sense here; we're talking literally a day of basic use costing more than a monthly subscription to the Max plan at $200 or so.
Aider is in a sad state. The maintainer does not "maintain" for quite some time now (look at the open PRs and issues). It's not state of the art definitely but one of the first and best ones in the past. A fork was created, Aider CE, from some members of the Discord community https://github.com/dwash96/aider-ce The fork looks and works promising but there is (sadly) so much more development in the other AI CLI tools nowadays.
I came to the same conclusion. It's crickets over there: https://github.com/Aider-AI/aider/graphs/contributors