Where do you see source instrumentation? I see Rust-specific details so for sure it's language-specific, but I didn't see any mention of altering the source code.

I didn't look at it very closely but it seems like you need to add fire::dbg! macros to your code if you want anything beyond function parameters/return values.

Oh so it can't stop at a breakpoint and inspect local variables? Weeird.

Is it like just a trace viewer fed data by debugger-style mechanisms?

Seems like it drives lldb with automation and fills up a database with a dynamic call graph and the data that crosses function call boundaries.

https://firedbg.sea-ql.org/blog/2023-12-11-architecture-of-f...