Definition
Plain language
A small piece of ordinary software running alongside the model that keeps an exact record of where things stand.
As stated in the literature
An external deterministic component that parses emitted actions, replays them from the initial state, and computes the true current configuration; used to supply ground-truth state for steering or verification during decoding.
Also called: symbolic trackers, external tracker
Why it matters: It supplies an unarguable ground truth about the current situation, which can be used to catch a model's mistakes as they happen or to check what the model itself believes.
For example, as a model announces each move, a small program replays those moves on its own copy of the puzzle and reports exactly which disk is sitting on which peg right now.
Heard on the show
“So they run an external symbolic tracker alongside decoding.”Episode 237 — The Model Built a Perfect Map of the Puzzle, Then Lost It