livewire-v4-upgrade

name	livewire-v4-upgrade
description	Walk a developer through upgrading a production Laravel app from Livewire v3 to v4. Use when the user asks to upgrade Livewire, mentions the Livewire 4 upgrade guide, or wants to assess whether an app is ready for Livewire v4. Audit-first - establishes the lay of the land before any dependency changes.

Livewire v3 → v4 Upgrade

Draft v3. Ground-truthed on three production apps: two modern ones (both Laravel 13, Flux Pro 2.14, class components, full-page routes, Pest - full upgrades completed and browser-verified; the second also applied the build-time route:cache fix before the bump rather than discovering it in aftercare) and a long-lived hybrid (Laravel 12, Flux 2.4, 120 components, PHPUnit, much churn - Phases 0-2 plus legacy-binding remediation completed; stopped before the composer bump). Steps marked [extrapolated] have not yet been exercised on a real app - treat them with extra care and update this skill when you learn something.

This skill walks an upgrade in phases. Do not skip the audit phase - it is what tells you whether you're in 20-minute-upgrade territory or two-day-migration territory. The official upgrade guide describes what changed; this skill covers what the guide doesn't: invisible config defaults, layouts with two jobs, stale agent context, and bugs the upgrade surfaces but didn't cause.

Phase 0 — Establish which world you're in

Before anything else, work out which app shape you have. They differ hugely in upgrade surface:

1. Modern shape: full-page Livewire components (Route::get('/x', Component::class)), Flux UI, layout resolved via Livewire's config. The layout question (Phase 2) applies.
2. Hybrid shape (common in long-lived apps that migrated through Blade → Vue → Livewire or similar churn): no full-page component routes - pages are plain Blade consuming the layout as <x-layouts.app>, with Livewire components embedded via <livewire:...> / @livewire(...). Livewire's layout config is never consulted at runtime, so the Phase 2 layout trap does not apply - but a published config/livewire.php makes the v3→v4 config key renames matter (Phase 3).
3. Older shape [extrapolated]: Blade pages using @extends('layouts.app') / @section('content') (or 'main'). Audit greps all apply; layout trap doesn't. Mongrel variant seen in the field: @extends() targeting a component file (@extends('components.layouts.app')) leaves $slot undefined - that's pre-existing breakage, not something the upgrade caused or will fix.

Check: grep -rn "use App\\\\Livewire" routes/ (full-page routes import their component classes, so this is the reliable tell) plus grep -rn "Route::livewire" routes/ and grep -rn "@extends" resources/views/ | head. Do not rely on grepping for the literal word Component in routes - real apps write Route::get('/', HomePage::class) with concrete class names, which returns nothing and nearly misclassifies a fully modern app as hybrid (field-confirmed false negative). When in doubt, read routes/web.php - it's one file. Beware commented-out routes in any grep hits - eyeball them.

Then gather context the docs can't give you:

• Recent git log. A Livewire upgrade often follows hot on the heels of a Laravel upgrade - look for tells like "Composer update to L13" in git log --oneline -10. If found, assume generated agent context is stale (next point).
• CLAUDE.md / Boost guidelines may lie. Verify the framework version from composer.lock, not from CLAUDE.md. (Real example: CLAUDE.md said Laravel 12; the lock file said 13.15.) If Boost is installed, a full php artisan boost:install regenerates the guidelines; boost:update has been observed doing nothing right after a framework upgrade.
• If config/livewire.php is published, read it now. Two keys decide your workload: 'legacy_model_binding' => true is the single biggest blocker this skill knows about (dedicated section below - do not skip it); and the presence of the old 'layout' key means the app leans on a config v4 renames wholesale - plan to re-publish fresh in Phase 3 and carry values across, never hand-rename keys in place.
• Flux compatibility is a lock-file check, not a guess. Flux ≥ 2.14.1 declares "livewire/livewire": "^3.7.4|^4.0". Confirm with: grep -A1 '"name": "livewire/flux"' composer.lock. At or above the floor: no Flux work needed. Below the floor, treat the Flux bump as a sibling task with its own smoke test, not a checkbox: many minor versions of Flux is its own change surface, Flux Pro needs auth against the private composer.fluxui.dev repo (user-run), and long-lived apps may contain views written for a newer Flux than the lock file provides (field case: <flux:button variant="warning"> blowing up Flux 2.4's button with Unhandled match case - two tests failing before any upgrade work began).
• Laravel version constraint. Settle it with a dry run before promising anything: composer require livewire/livewire:^4.0 --dry-run (verified fine against Laravel 13).

Phase 1 — The audit sweep

Run every one of these before touching composer. Most will come back clean on a modern app - the point is knowing, not assuming. (If your shell aborts on grep's no-match exit code, append | cat to each.)

What	Grep	If it hits
Unclosed component tags	grep -rn '<livewire:' resources/views then eyeball each for /> or a closing tag	v4 treats following content as slot content; component silently won't render. Close them.
wire:model modifiers	`grep -rEn 'wire:model.(blur	change)' resources/views`
wire:model on containers	grep -rEn '<(div|section|ul)[^>]*wire:model' resources/views	Behaviour changed silently - see below.
wire:scroll	grep -rn 'wire:scroll' resources/views	Becomes wire:navigate:scroll.
wire:transition modifiers	grep -rn 'wire:transition\.' resources/views	Modifiers removed (now View Transitions API). Bare wire:transition still fine.
JS hooks	grep -rn "Livewire.hook" resources/	commit/request hooks deprecated → interceptors. Still work in v4; note for later.
$js usage	grep -rn '\$js(' resources/	Deprecated syntax; still works. Note for later.
stream()	grep -rn '->stream(' app/	Signature changed: v3 $this->stream(to: '#el', content: 'Hi') becomes v4 $this->stream(content: 'Hi', el: '#el') - to: renamed el:, content now first positionally.
Custom update route	grep -rn 'setUpdateRoute' app/ bootstrap/	Closure gains a $path param carrying the new hashed endpoint.
Hardcoded endpoint URLs	grep -rn '/livewire/' app/ config/ resources/js/	v4 prefix is /livewire-{hash}/. Also flag infra outside the repo: proxy, firewall, CDN rules referencing /livewire/ paths. Ask the user - this is invisible from the repo.
Volt	grep -rn 'Livewire\\\\Volt' app/ composer.json	Follow the Volt section of the official guide.
Legacy model binding	grep -n legacy_model_binding config/livewire.php	If published and true, this is your biggest job - see the dedicated section below.
wire:model.defer	grep -rn 'wire:model.defer' resources/views	v2-era syntax, silently ignored since v3. Harmless, but delete it while you're here - it misleads readers about when the property syncs.

Also inventory: component count (find app/Livewire -name '*.php' | wc -l), test files using Livewire::test (these need no changes - the testing API is unchanged), and any WithFileUploads usage (the upload endpoint moves with the hash prefix but Livewire handles it internally - no action, just smoke-test uploads afterwards).

The wire:model changes, explained

You will not have read the upgrade guide. These two changes are the most dangerous on the list because they are silent: nothing errors, no console warning fires, no test fails. The UI just behaves differently for real users.

1. Modifiers now control client-side sync, not just network timing.

In v3, modifiers like .blur and .change only decided when the network request was sent. The input's value still synced into client-side state ($wire.property) immediately, keystroke by keystroke. In v4 (firmed up in v4.1), those modifiers delay the client-side sync as well - $wire.property doesn't update until the user blurs or the change event fires.

Who gets hurt: anything reading client-side state while the user is mid-typing - Alpine expressions bound to $wire, character counters, live previews, a disabled submit button watching a field. They all go stale until blur. To keep exact v3 behaviour, add .live before the modifier:

v3	v4 equivalent
wire:model.blur="title"	wire:model.live.blur="title"
wire:model.change="status"	wire:model.live.change="status"
wire:model.lazy="note"	unchanged - .lazy is backwards compatible
wire:model / wire:model.live	unchanged

Don't blanket-rewrite: the new behaviour may actually be what the UI wants (it's how you build "only update when the user finishes typing" inputs now). Judge each hit - is anything consuming this property client-side before the sync would fire? If the property is only read server-side on submit, the change is harmless. Concrete check per hit (field-tested - one command per view):

grep -En '\$wire|x-data|x-bind|x-show|x-text' path/to/the-view.blade.php

No matches means nothing reads the property mid-typing; verdict "harmless".

2. wire:model on a container no longer hears its children.

In v3, wire:model on a non-input element (a div wrapping a modal or accordion, say) responded to input/change events bubbling up from form fields inside it. Classic symptom this existed to fix: clearing an input inside a modal would bubble up and close the modal. In v4 the binding only listens for events on the element itself (as if .self were applied). If a container binding relies on hearing its children, add .deep to restore v3 behaviour:

<div wire:model.deep="value">
    <input type="text">
</div>

Standard bindings on actual form controls (inputs, selects, textareas - including via Flux components) are unaffected by both changes; in the ground-truthed app every binding was either .live or a Flux form control, and the answer to both greps was "no hits, nothing to do". That will often be the case - but know, don't assume.

Legacy model binding - the blocker to find early

The v2-era shim letting wire:model write directly into Eloquent model attributes (wire:model="booking.holder_id") lives behind legacy_model_binding in v3 and is gone entirely in v4 - flag and feature both. On a long-lived app this can be the bulk of the whole upgrade (it was, in the field run that added this section). Audit:

1. grep -n legacy_model_binding config/livewire.php. Published and true? Assume trouble until proven otherwise. Unpublished config means the v3 default (false) applies and the app is safe - skip the rest of this section.
2. Find every dot-notation binding: grep -rEln 'wire:model[^=]*="[a-zA-Z_]+\.[a-zA-Z_]' resources/views then triage each root property in its component class - the view alone cannot tell you. Plain arrays ($form, $dates) are fine; Eloquent models are the problem. Untyped public $booking properties need a read of mount() to classify. Expect mostly false alarms (field ratio: 14 views with dot-bindings, only 3 real model bindings).
3. Sneaky variant: a typed ?Collection of Eloquent models with bindings like wire:model="answers.{{ $key }}.body" - the root being a Collection rather than a Model makes it easy to misclassify as a plain array.
4. Tests ride the same synthesizer: grep -rEn "->set\('[a-z_]+\.[a-z_]" tests/ and triage the roots the same way (expect noise from config()->set(...)).
5. Orphaned-view false positives: a view full of model-style bindings may have no component class at all (leftover churn). Verify the class exists before refactoring a view that nothing renders.

Remediation recipes - three patterns covered every real case; all are applied on v3, before any composer bump:

• Model with many bound fields / computed values: keep the model property for id/relations/display; add public array $form = [], fill it in mount(), copy back onto the model in save(). Rename together: view bindings, validation rule keys, @error() keys, and test ->set() paths. And audit the whole element while you're in the view - non-wire:model attributes (a date-picker's value="...") may read the same model attributes you're removing, and no test will catch those.
• Single bound attribute: one plain property, initialised in mount(), copied back on save. Smallest possible diff - prefer this when there's only one binding.
• Collection of models: convert to an array of ['id' => ..., 'field' => ...] rows; actions re-find the model by id ($this->question->answers()->findOrFail($id)) instead of calling ->save() on a bound model.

Expect to write tests first. Code still using magic model binding is old code, and old code is undertested - in the field run, both methods needing refactor had zero coverage. Budget for that; don't refactor blind.

The proof step - cheap, decisive, reversible: after remediating, flip legacy_model_binding => false while still on v3 and run the full suite. The flag exists in v3, so you get v4's behaviour with v3's error messages - CannotBindToModelDataWithoutValidationRuleException names the exact component/property you missed. Green here means this blocker is genuinely cleared before the bump, not hopefully cleared.

Phase 2 — The layout trap (modern shape only)

This is the highest-risk change and the guide undersells it.

If config/livewire.php is not published, the app runs on invisible defaults - and v4 changes the default layout from components.layouts.app to layouts::app (resources/views/layouts/app.blade.php). A bare composer bump breaks every full-page component route at once.

Before deciding to move the layout file, check whether it has two jobs:

grep -rn '<x-layouts\.' resources/views

If anything (commonly auth pages) uses the layout as a Blade anonymous component, its location under resources/views/components/ is load-bearing for Blade, independent of anything in Livewire's config. Moving it then requires Blade::anonymousComponentPath() registration plus edits to every consuming view - a separate PR's worth of churn.

Recommended resolution: keep the file where it is and point v4 at it via config (Phase 3). Smallest diff, no muscle-memory breakage, discoverable by any agent that reads the published config. Do not offer a symlink at the old path - if the layout is Blade-consumed, the symlink is load-bearing while looking optional, which is a trap for whoever tidies up later.

Close the coverage gap while you're here. Plain-Blade pages (login, logged-out) are exactly the pages component tests don't cover and exactly the ones consuming the layout as <x-layouts.app>. If there's no test for them, propose adding one now, before the upgrade, so a layout misresolution is a red test rather than a production surprise:

it('renders the login page', function () {
    $this->get(route('login'))->assertOk();
});

(Hybrid-shape apps: field-confirmed that the layout trap doesn't apply - but run the <x-layouts. grep anyway, because it's how you prove you're in the hybrid shape rather than assume it.)

Phase 3 — Baseline, bump, publish, configure

1. Baseline first - the full suite, before any remediation edits, not just before the bump. A field run baselined only the directly-affected test files, met 36 unrelated failures late, and paid extra attribution work untangling them. A couple of minutes up front is cheaper. Record the failure list, not just the count - pre-existing failures are also your watch-list for Phase 4 (some may be fixed by the upgrade).
2. The user runs the composer commands (agents in sandboxes typically can't, and house permission hooks may block even --dry-run - expect the hand-off to start at the dry-run, not the real bump): composer require livewire/livewire:^4.0.
3. Publish the real config; never hand-write or hand-rename it: php artisan livewire:publish --config (command unchanged from v3). The published file contains options the upgrade guide never mentions (release_token, payload guards, make_command.with) - working from the real file means no guessed keys. If the app already had a published v3 config, still re-publish fresh and carry the old values across by diffing old against new - the v3→v4 key renames are wholesale (layout → component_layout and friends) and hand-renaming in place will miss new keys and changed defaults.
4. Make the deliberate edits to the published file. Team defaults:
   • 'component_layout' => 'components.layouts.app' - dot-notation view names verified working in v4.3.1; keeps the layout where developers expect it (modern shape only).
   • 'make_command' => ['type' => 'class', 'emoji' => false, ...] - we use class-based components and we do not put ⚡ in filenames.
5. php artisan optimize:clear.
6. Full suite again. On the ground-truthed app: 348/348 before and after, including get(route(...))->assertOk() tests that render full pages through the layout - which is what proves the layout config resolves. If your suite has no such test, add one rather than trusting the config edit.

Verified along the way: plain Blade views living in resources/views/livewire/ do not confuse v4's component_locations discovery - class components resolve as before.

Phase 4 — Browser smoke test, console open

Tests can't see everything. Have the user (or a browser tool) walk:

• Login and logged-out pages (the Blade-consumed layout path)
• One full-page component route, poking something interactive (wire:model.live fields)
• A couple of wire:navigate links
• A file upload, if WithFileUploads is used anywhere (exercises the new hashed endpoint)
• Browser console open throughout.

Treat v4's console warnings as a diagnostic, not noise. v4 warns at bind time when wire:model targets a property that doesn't exist on the component. What it surfaces may be an ancient pre-existing bug masquerading as an upgrade regression. Triage:

1. Does the property exist on the component class? (Watch for near-misses like newUserDefaultLocation vs newUserDefaultLocationId.)
2. git log -S 'the-binding-string' - if the mismatch predates the upgrade, it's a surfaced bug, not a regression. Tell the user which it is; the distinction matters.
3. Audit the whole element, not just the property name. Real case: the same select also rendered value="{{ $location->value }}" against an Eloquent model with no value attribute - a copy-paste from an enum options loop. Mistakes travel in pairs.
4. Why tests missed it: Livewire::test()->set() sets properties directly, bypassing the view binding. A component test can pin the binding with ->assertSeeHtml('wire:model="theProperty"'); only a browser test truly exercises it.

Note the binding warnings are also statically findable before the upgrade - the Phase 1 greps plus a read of the component class catch them on v3, where they're silent. And remember the mirror image: some failures on your Phase 3 baseline list may simply vanish after the bump (field case: views written for a newer Flux than the old lock file provided). Anything that goes red → green is worth a line in the upgrade notes too - "fixed by upgrade" is information, not luck.

Phase 5 — Aftercare

• Re-run php artisan boost:install so generated guidelines pick up the livewire/v4 rules instead of coaching future agents in v3 idioms. (Composer's post-update hooks may have already done this - verify the version line in CLAUDE.md rather than assume.) --no-interaction works fine. Field note: recent Boost versions also drop a batch of new skill directories into .claude/skills/, .agents/skills/ and .cursor/skills/ - flag them to the user to review/keep/bin rather than silently committing them.
• The build-time route:cache problem (next bullet) is statically findable in Phase 0 - if you spot it during the audit, fix it before the bump rather than leaving it for aftercare. Field-confirmed: the move-to-app-start fix is a two-line diff, independent of the composer bump, and a good use of the time while waiting for the user to run it. Tell-tale that the build genuinely lacks APP_KEY: a Dockerfile line symlinking .env to /run/secrets/.env (dangling at build time).
• Check the deploy pipeline for build-time route:cache - field-confirmed 404 source. v4's routes embed a hash derived from APP_KEY at route-registration time. If the Dockerfile or CI runs route:cache during image build - where secrets don't exist and APP_KEY is empty or a placeholder - the baked route table holds one hash while rendered pages emit another, and every Livewire asset/endpoint 404s. Audit: grep -rn 'route:cache' Dockerfile docker/ .github/ .gitlab-ci.yml 2>/dev/null. Fix: move route:cache to container start, next to the config:cache that's almost certainly already there (config is env-dependent; v4 made routes env-dependent too). Diagnosis pattern if you meet the 404 live: curl -sI the asset URL to confirm the app (not a proxy) is answering, then php artisan route:list --path=livewire in the container and compare its hash against the page's asset URLs. Treacherous detail from the field: this was invisible on QA because the QA image target happened to run optimize:clear last, wiping the poisoned cache - prod was the only environment that kept it. And it's a latent pre-v4 pattern: v3's static Livewire paths made build-time route caching safe by accident, so expect it across a whole fleet of apps sharing a Dockerfile lineage. A manual route:clear in the running container is a stopgap only - the next deploy or container reschedule restores the stale cache from the image.
• Confirm with the user whether anything outside the repo references /livewire/ paths (proxy/firewall/CDN rules) - the {hash} prefix change breaks those silently.
• Optional, when convenient rather than now: migrate deprecated $js('name', fn) to the v4 form $wire.$js.name = fn, and Livewire.hook('commit'|'request', ...) to the new interceptors (Livewire.interceptMessage(...) / Livewire.interceptRequest(...) - see the v4 JavaScript docs for the callback shapes); consider Route::livewire() for full-page routes. All the old forms still work in v4 - this is tidiness, not necessity.
• Deferred-but-still-true: anything the audit found that "still works in v4" should be recorded somewhere it won't be forgotten (issue tracker), not left as tribal memory.

Field notes for agents (environment gotchas)

• Temp or copied checkouts break Lando: .lando.yml names an app whose container was built for a different directory (chdir to cwd ... no such file or directory). Fallback that worked: bare php artisan test - check whether phpunit.xml already uses in-memory sqlite before assuming you need the container at all.
• CACHE_STORE=array does not cover direct Redis:: facade calls (e.g. a lock acquired in mount()). Field fix: a throwaway docker run -d --rm -p 6379:6379 redis:alpine plus REDIS_HOST=127.0.0.1 prefixed to the test command - works because phpdotenv doesn't override real environment variables. Tell the user about any container you leave running.
• Expect house-style permission hooks - blocked composer commands, blocked raw-database test assertions. They are conventions doing their job, not obstacles: ask the user, never route around them. Also seen: a TDD hook rejecting a Write that contains two tests at once. The Phase 2 safety-net tests aren't really TDD (they're green-on-arrival regression pins), but don't argue with the hook - write one test, run it, then Edit the second in. Same outcome, no friction.

Things this skill does not yet know

Honest gaps, to be filled by future runs:

• Anything past the composer bump on the hybrid shape: v4 runtime there, wire:poll under v4 (five views waiting in the field app), the hashed endpoint behind proxies.
• Whether Flux ≥ 2.14 actually adds the button warning variant - assumed when predicting two pre-existing failures would be fixed by the Flux bump; unconfirmed.
• The pure @extends('layouts.app') older shape end-to-end (everything marked [extrapolated]).
• Apps using islands, lazy/deferred components, or pagination themes under v4 - no real-world observations yet.
• Whether smart_wire_keys => true (new v4 default) bites deeply nested components in practice - neither ground-truth app had issues, but neither nests deeply.