I am on this trajectory too; opencode got me started but I tried to understand the way it is working and to do that I would normally read the source code, but the source code is really not fun.
I generally view the kind of code in projects like OpenCode to be the same as binary machine code, and the harness that works on it is the compiler. The source code is the prompts (I guess), except we live in a weird state now we use the existing machine code + more prompts to make even more machine code.