Swap model & limits

swap.ts is a model of htmx 2’s response path, not of htmx. It stands in for a browser so tests can assert on the page after an interaction. Re-read MODELLED when you bump public/htmx.min.js.

MODELLED

• hx-swap-oob extraction before the main swap
• hx-swap-oob values: true, a bare swap style, and <style>:<selector>
• HX-Reswap overriding hx-swap, including none
• HX-Retarget overriding hx-target
• Swap styles: innerHTML, outerHTML, beforebegin, afterbegin, beforeend, afterend, delete, none
• Default swap style innerHTML when none is given
• 4xx responses swapping only when the application opts in (allowErrorSwap, default true to match a layout htmx:beforeSwap that swaps error toasts)

Non-goals

Not modelled: CSS, focus, htmx:* event handlers, settling, transitions, or anything a stylesheet or script does after the swap. Relative targets (this, closest …, find …, …) are also out of scope for dead-target — they cannot be resolved without a live DOM.

If a bug lives outside this list, the checker will not see it. That is intentional: the rules catch failures that shipped in this stack, not a full simulator.