Is there a way to have the model inside of codex to make use of chunkhound instead of its “built in” search/explore functionality with rg? Whenever I spin up a new agent using xhigh thinking it spins its wheels for a while to get up to speed — wondering if chunkhound can make this process faster.

That's what the MCP is for, if you can get the LLM to use it. Sometimes they just like to do it their own way :)