Rules overview

Every rule exists because the bug shipped. Each is pinned against the markup of the failure it claims to catch — a rule that cannot fail its own fixture is decoration.

The rules htmx-contract enforces. Each has a narrative page under Rules.

Rule	Summary
empty-after-oob	A response empty after out-of-band extraction, without HX-Reswap: none — outerHTML deletes the target.
duplicate-id	The same id twice in one document; htmx swaps the first match.
duplicate-field-in-form	Two controls sharing a name inside one form; htmx lets the form override the element.
target-identity-lost	An outerHTML swap whose replacement does not keep the target id.
unbounded-poll	hx-trigger=“every …” with no declared bound.
dead-target	hx-target points at an id that is not in the document.
dead-oob	An out-of-band node whose target is missing, or which names no target.

Expanded pages live under each rule name in the sidebar. When you add a rule: implement it, add it to RULES, pin a fixture, expand its page, run bun run docs:sync.