dial9 is a microscope for Tokio (and Rust applications in general): its compact binary format can record a log of runtime events so you can reconstruct what actually happened to understand bugs and performance behavior. It runs in production, where bugs have real blast radius.

As much as we attempt to avoid it, dial9 still has bugs. We catch most in CI, some in PR review, and some are discovered by customers.

We use AI to help build dial9, but this presents a challenge: today's models are jagged: strong in one domain, weak in another. Folks are probably familiar with "How many r's are in Strawberry" or "I want to wash my car, the car wash is 50m away. Should I walk or drive?" These are real but don't really capture what this looks like in practice. Here are three examples we hit building dial9.