checkField in packages/validation/src/index.ts (and its browser mirror in runtime.ts) treated any string other than "true"/"on" as false with no error, so typos like "treu" or values like "yes"/"1"/"TRUE" silently passed as false. Now: - true/false booleans pass through unchanged - recognised true strings (case-insensitive, trimmed): true, on, 1, yes - recognised false strings: false, off, 0, no - numeric 1/0 coerce (JSON payloads) - undefined/null/"" still coerce to false (unchecked-checkbox semantics) - anything else is now a type error (desc.typeMessage or "Must be true or false") instead of a silent false Locked-in behaviours preserved: a required boolean given false still errors, and parseEnv DEBUG: "true" coercion still works. Added coverage for recognised strings, numeric 1/0, the type-error regression guard, absent/empty handling, the required+false case, and a client/server parity test driving both checkField and the browser runtime through the same inputs. Blast radius: searched packages/, examples/, services/ for v.boolean() usage; all existing call sites (auth consent/rememberDevice, db 'active' default, example consent checkboxes) feed true/false/'on'/absent values, none of which change behavior. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>