Livewire 3/4 compatibility

Ghostwire supports Livewire 3.6+ and 4.x from the same package. Bridge selection happens at livewire:init, by runtime feature detection — never a version string:

1. typeof Livewire.interceptMessage === 'function' → Livewire 4 bridge
2. else, Livewire.hook present → Livewire 3 bridge
3. neither → the runtime disables itself, with a console warning in development only

Tier matrix

| Tier | Capabilities | |---|---| | A — identical on both lines | Directive and every modifier except .island · #[Ghost] in full (class, method, inheritance, precedence) · synthesis · freeze mode · timing (delay/hold/timeout) · sync-message silence · theme and CSS tokens · accessibility (aria-busy, focus preservation, live region) · learning and export · morph coexistence | | B — degraded on 3.x | Post-paint removal — emulated via two chained requestAnimationFrame calls (costs up to one extra frame of skeleton, never a flash of unpainted content) · finalization — composed from succeed/fail/request.fail, idempotent · cancellation — resolved as finalization · poll detection — heuristic on trigger origin (wire:poll on the element) · per-action interception — filtered at the bridge level, same observable behavior | | C — 4.x only | Island scoping (.island modifier — no-op, documented, on 3.x) · message-skip handling |

What “degraded” means in practice

Nothing in Tier B produces incorrect behavior — it produces the same observable result via a different, 3.x-compatible mechanism. A capability with no 3.x equivalent at all (Tier C) degrades to a documented no-op rather than an error or an emulation built on Livewire’s internal APIs (Ghostwire never reaches into internals to fake a capability that isn’t really there).

CI verification

Both the contract test suite and the full browser test suite run against both Livewire lines on every PR (.github/workflows/tests.yml’s matrix). Behavior that diverges between lines outside this documented matrix is treated as a release-blocking bug.

Detection, not sniffing

Version-string sniffing is explicitly disallowed by the package’s own design (SPEC-INT-20) — a future Livewire patch release that changes internals without changing its public hooks should never require a Ghostwire update just because a string comparison broke.