diff --git a/app/Livewire/Project/Service/Domains.php b/app/Livewire/Project/Service/Domains.php
index dae2642825..6029e17bce 100644
--- a/app/Livewire/Project/Service/Domains.php
+++ b/app/Livewire/Project/Service/Domains.php
@@ -112,6 +112,8 @@ class Domains extends Component
 
     public ?int $requiredPort = null;
 
+    public ?int $requestedPort = null;
+
     public bool $isCheckingDns = false;
 
     #[Locked]
@@ -1603,10 +1605,10 @@ class Domains extends Component
         if ($checkPorts && ! $this->forceRemovePort) {
             $requiredPort = $app->getRequiredPort();
             if ($requiredPort !== null && $domainString) {
-                $previousFqdn = $app->getOriginal('fqdn');
                 foreach ($this->splitDomains($domainString) as $fqdn) {
-                    if ($app->portRequiresConfirmation($fqdn, $requiredPort, is_string($previousFqdn) ? $previousFqdn : null)) {
+                    if ($app->portRequiresConfirmation($fqdn, $requiredPort)) {
                         $this->requiredPort = $requiredPort;
+                        $this->requestedPort = ServiceApplication::extractPortFromUrl($fqdn);
                         $this->showPortWarningModal = true;
                         $app->refresh();
 
diff --git a/app/Livewire/Project/Service/Index.php b/app/Livewire/Project/Service/Index.php
index edfc3c0e97..43bf885457 100644
--- a/app/Livewire/Project/Service/Index.php
+++ b/app/Livewire/Project/Service/Index.php
@@ -84,6 +84,8 @@ class Index extends Component
 
     public $requiredPort = null;
 
+    public ?int $requestedPort = null;
+
     public ?string $fqdn = null;
 
     public bool $isGzipEnabled = false;
@@ -630,7 +632,6 @@ class Index extends Component
             $persistedApplication = $this->serviceApplication->fresh();
             $previousDnsHostnames = app(ManagedDnsRecordCleanup::class)->hostnamesOf($persistedApplication);
             $previousServiceDnsHostnames = array_keys(app(ResourceDnsRecords::class)->hostnameUsers($this->service));
-            $previousEditableUrls = $persistedApplication->url;
             $previousFqdn = $persistedApplication->fqdn;
             $previousPortOverrides = $persistedApplication->domain_port_overrides;
             $this->authorize('update', $this->serviceApplication);
@@ -669,8 +670,9 @@ class Index extends Component
                             continue;
                         }
 
-                        if ($this->serviceApplication->portRequiresConfirmation($fqdn, $requiredPort, $previousEditableUrls)) {
+                        if ($this->serviceApplication->portRequiresConfirmation($fqdn, $requiredPort)) {
                             $this->requiredPort = $requiredPort;
+                            $this->requestedPort = ServiceApplication::extractPortFromUrl($fqdn);
                             $this->showPortWarningModal = true;
                             $this->serviceApplication->fqdn = $previousFqdn;
                             $this->serviceApplication->domain_port_overrides = $previousPortOverrides;
diff --git a/app/Models/ServiceApplication.php b/app/Models/ServiceApplication.php
index 5f737459ab..d180d9790a 100644
--- a/app/Models/ServiceApplication.php
+++ b/app/Models/ServiceApplication.php
@@ -275,7 +275,7 @@ class ServiceApplication extends BaseModel
     /**
      * True when saving this URL should confirm that it does not use the required template port.
      */
-    public function portRequiresConfirmation(string $fqdn, ?int $requiredPort, ?string $previousFqdn = null): bool
+    public function portRequiresConfirmation(string $fqdn, ?int $requiredPort): bool
     {
         if ($requiredPort === null) {
             return false;
@@ -286,28 +286,14 @@ class ServiceApplication extends BaseModel
             return false;
         }
 
-        $canonical = DomainPortOverrides::withoutPort($fqdn);
         $explicit = self::extractPortFromUrl($fqdn);
 
-        if ($explicit === $requiredPort) {
+        // A domain without a port routes to the required port.
+        if ($explicit === null || $explicit === $requiredPort) {
             return false;
         }
 
-        if ($explicit === null) {
-            $previous = collect(explode(',', (string) $previousFqdn))
-                ->filter();
-            $previousUrl = $previous->first(
-                fn (string $url): bool => DomainPortOverrides::withoutPort(trim($url)) === $canonical
-            );
-
-            if (is_string($previousUrl) && self::extractPortFromUrl($previousUrl) !== null) {
-                return true;
-            }
-
-            return $previousUrl === null;
-        }
-
-        $existingOverride = $this->domain_port_overrides[$canonical] ?? null;
+        $existingOverride = $this->domain_port_overrides[DomainPortOverrides::withoutPort($fqdn)] ?? null;
 
         return (int) $existingOverride !== $explicit;
     }
diff --git a/bootstrap/helpers/domains.php b/bootstrap/helpers/domains.php
index 176a4e1153..488c04b261 100644
--- a/bootstrap/helpers/domains.php
+++ b/bootstrap/helpers/domains.php
@@ -79,7 +79,10 @@ function domainConflictKey(string $domain): string
         ? str($domain)->beforeLast('/')->toString()
         : $domain;
 
-    return preg_replace('#^https?://#i', '', $domain) ?? $domain;
+    $domain = preg_replace('#^https?://#i', '', $domain) ?? $domain;
+
+    // The URL port is the container port. The public address does not include it.
+    return preg_replace('#^([^/:\[]+|\[[^\]]+\]):\d+#', '$1', $domain) ?? $domain;
 }
 
 /**
diff --git a/resources/views/livewire/project/service/domains.blade.php b/resources/views/livewire/project/service/domains.blade.php
index c2170ae160..98e34e5f37 100644
--- a/resources/views/livewire/project/service/domains.blade.php
+++ b/resources/views/livewire/project/service/domains.blade.php
@@ -336,18 +336,18 @@
                         <div class="application-settings-section-body">
                             <x-callout type="warning" title="Port requirement" class="mb-4">
                                 This service requires port <strong>{{ $requiredPort }}</strong> to function correctly.
-                                One or more of your domains use a different port, or none.
+                                One or more of your domains use port <strong>{{ $requestedPort }}</strong>.
                             </x-callout>
 
                             <div class="mt-4 flex flex-wrap justify-end gap-2 border-t border-neutral-200 pt-4 dark:border-white/[0.08]">
+                                <x-forms.button type="button" wire:click="confirmRemovePort"
+                                    @click="modalOpen = false" isError>
+                                    Use port {{ $requestedPort }} anyway
+                                </x-forms.button>
                                 <x-forms.button type="button"
                                     wire:click="cancelRemovePort"
                                     @click="modalOpen = false">
-                                    Keep required port
-                                </x-forms.button>
-                                <x-forms.button type="button" wire:click="confirmRemovePort"
-                                    @click="modalOpen = false" isError>
-                                    Use this port anyway
+                                    Keep port {{ $requiredPort }}
                                 </x-forms.button>
                             </div>
                         </div>
diff --git a/resources/views/livewire/project/service/index.blade.php b/resources/views/livewire/project/service/index.blade.php
index ff31e43c50..35709eb641 100644
--- a/resources/views/livewire/project/service/index.blade.php
+++ b/resources/views/livewire/project/service/index.blade.php
@@ -141,7 +141,7 @@
                                         <div class="application-settings-section-body">
                                             <x-callout type="warning" title="Port requirement" class="mb-4">
                                                 This service requires port <strong>{{ $requiredPort }}</strong> to function correctly.
-                                                One or more of your domains use a different port, or none.
+                                                One or more of your domains use port <strong>{{ $requestedPort }}</strong>.
                                             </x-callout>
 
                                             <x-callout type="danger" title="What will happen if you continue?" class="mb-4">
@@ -154,13 +154,13 @@
                                             </x-callout>
 
                                             <div class="mt-4 flex flex-wrap justify-end gap-2 border-t border-neutral-200 pt-4 dark:border-white/[0.08]">
-                                                <x-forms.button @click="modalOpen = false; $wire.call('cancelRemovePort')"
-                                                    class="w-auto">
-                                                    Keep required port
-                                                </x-forms.button>
                                                 <x-forms.button wire:click="confirmRemovePort" @click="modalOpen = false" class="w-auto"
                                                     isError>
-                                                    Use this port anyway
+                                                    Use port {{ $requestedPort }} anyway
+                                                </x-forms.button>
+                                                <x-forms.button @click="modalOpen = false; $wire.call('cancelRemovePort')"
+                                                    class="w-auto">
+                                                    Keep port {{ $requiredPort }}
                                                 </x-forms.button>
                                             </div>
                                         </div>
diff --git a/resources/views/livewire/project/service/partials/domain-table.blade.php b/resources/views/livewire/project/service/partials/domain-table.blade.php
index 1e8496e985..922ea2b41e 100644
--- a/resources/views/livewire/project/service/partials/domain-table.blade.php
+++ b/resources/views/livewire/project/service/partials/domain-table.blade.php
@@ -56,7 +56,7 @@
             $faviconUrl = $isSuggested || $serviceApplication?->hasProxyBasicAuth() ? null : \App\Support\DomainFavicon::url($publicUrl, $row['dns_status'] ?? null, $row['expected_ip'] ?? null);
             $domainKey = hash('sha256', $row['url'].'|'.($row['service_application_id'] ?? ''));
             $editingParts = \App\Support\DomainUrlParts::split($row['url']);
-            if ($row['has_port_override'] ?? false) {
+            if (filled($row['internal_port'] ?? null)) {
                 $editingParts['port'] = (string) $row['internal_port'];
             }
         @endphp
diff --git a/tests/Feature/ServiceDomainsTest.php b/tests/Feature/ServiceDomainsTest.php
index 4aca098a61..a3addc19e0 100644
--- a/tests/Feature/ServiceDomainsTest.php
+++ b/tests/Feature/ServiceDomainsTest.php
@@ -755,7 +755,7 @@ YAML,
         ->assertDispatched('success');
 });
 
-it('saves after confirming both a domain conflict and a missing required port', function () {
+it('saves after confirming both a domain conflict and a different port', function () {
     $this->service->update([
         'docker_compose_raw' => <<<'YAML'
 services:
@@ -770,7 +770,9 @@ YAML,
 
     $component = Livewire::test(Domains::class, ['service' => $this->service->fresh(['applications', 'server'])])
         ->set('newServiceApplicationId', $this->webApp->id)
-        ->set('newDomain', 'https://api.example.com')
+        ->set('newDomainParts.host', 'api.example.com')
+        ->set('newDomainParts.port', '3000')
+        ->set('newDomainPartsChanged', true)
         ->call('addDomain')
         ->assertSet('showDomainConflictModal', true)
         ->call('confirmDomainUsage')
@@ -778,8 +780,8 @@ YAML,
         ->assertSet('showPortWarningModal', true)
         ->assertSet('forceSaveDomains', true)
         ->assertSee('Use a different port?')
-        ->assertSee('Keep required port')
-        ->assertSee('Use this port anyway');
+        ->assertSee('Keep port 8000')
+        ->assertSee('Use port 3000 anyway');
 
     $component
         ->call('confirmRemovePort')
@@ -790,7 +792,28 @@ YAML,
         ->assertDispatched('success');
 
     expect(explode(',', (string) $this->webApp->fresh()->fqdn))
-        ->toBe(['https://api.example.com']);
+        ->toBe(['https://api.example.com'])
+        ->and($this->webApp->fresh()->domain_port_overrides)->toBe(['https://api.example.com' => 3000]);
+});
+
+it('does not warn about the port when a domain with an empty port is renamed', function () {
+    $this->service->update([
+        'docker_compose_raw' => "services:\n  api:\n    image: node:alpine\n    environment:\n      - SERVICE_URL_API_8080\n  web:\n    image: nginx:alpine\n",
+    ]);
+    $this->apiApp->update(['fqdn' => 'https://api.example.com']);
+
+    Livewire::test(Domains::class, ['service' => $this->service->fresh(['applications', 'server'])])
+        ->call('startEdit', 0)
+        ->set('editingDomainParts.host', 'renamed.example.com')
+        ->set('editingDomainParts.port', '')
+        ->set('editingDomainPartsChanged', true)
+        ->call('updateDomain')
+        ->assertSet('showPortWarningModal', false)
+        ->assertDispatched('success');
+
+    $this->apiApp->refresh();
+    expect($this->apiApp->fqdn)->toBe('https://renamed.example.com')
+        ->and($this->apiApp->domain_port_overrides)->toBeNull();
 });
 
 it('loads persisted dns status for service applications', function () {