Dual rail

Computing a published value twice by two routes that share as little logic as possible: once by where it sits in the file, once by the label beside it. Both must agree within a tolerance written down in advance. Disagreement is a refusal to publish, never a warning to dismiss.

Principle 2 · Two independent reads beat one careful one

Where does Dual rail come from?

Principle 2 of the Kymira doctrine, Two independent reads beat one careful one. Dual rail is the name the doctrine gives to what that principle requires in practice.

What failure is Dual rail named after?

The wrong column that reconciles. Read the wrong column with the right shape and every total still ties. The number is internally perfect and means the wrong thing.

What does it look like on a real file?

The figure is read once by position and once by label, and the page prints which degree of independence it actually earned.

Not for

Not for two readers of the same cell. That proves placement, not value, and the page states which degree of independence a figure earned.

Nearest terms

Both rails from one blueprintThe failure where a two rail check builds both rails from the same field list, the same parse,...Tolerance creepWidening the allowed difference between two reads until they stop disagreeing Reconciliation anchorA total the source file states about itself, a printed grand total, a totals row, a stated...

Last updated 2026-09-02 · Dylan, founder · one of 40 terms in the Kymira glossary, each one named after something we watched go wrong in a real build or in our own audits.

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