Coach definition, not a live verdict. These pages show how the X-ray Coach defines this concept and where its thresholds sit, sourced from the coach's own code. Unlike the tactic pages, nothing here runs a live detector — example boards illustrate the rule, they don't execute it.
What it means
- Measures the quality of your play through the opening phase, judged against other players in your rating band — not against engine perfection.
- Two signals feed it: how often you blunder in the opening, and where your evaluation stands once the opening is over.
The exact rule the X-ray Coach applies
- Opening-blunder rate: share of opening-phase moves that are blunders (see the Blunders page for the blunder definition).
- Eval at ply 30: your engine evaluation at move 15 (ply 30), clipped to ±500 cp, as a continuous measure of how the opening turned out.
How it's scored
- Scored peer-relative: your rates are mapped through calibrated anchor tables (267-player benchmark, ≥30 games each) so 100 = top of band, 0 = bottom.
Why it matters
A bad opening start compounds — it sets the eval you then have to defend or convert for the rest of the game.