diff --git a/app/Models/User.php b/app/Models/User.php
index e8f59835b..10303422b 100644
--- a/app/Models/User.php
+++ b/app/Models/User.php
@@ -520,10 +520,14 @@ public function hasSsoIdentity(): bool
 
     /**
      * Check if the user has a password set.
-     * OAuth users are created without passwords.
      */
     public function hasPassword(): bool
     {
         return ! empty($this->password);
     }
+
+    public function requiresPasswordConfirmation(): bool
+    {
+        return $this->hasPassword() && ! $this->hasSsoIdentity();
+    }
 }
diff --git a/app/Services/Auth/OauthLoginService.php b/app/Services/Auth/OauthLoginService.php
index f656fad08..2ec8f88e3 100644
--- a/app/Services/Auth/OauthLoginService.php
+++ b/app/Services/Auth/OauthLoginService.php
@@ -7,6 +7,7 @@
 use App\Models\OauthSetting;
 use App\Models\Team;
 use App\Models\User;
+use Illuminate\Database\UniqueConstraintViolationException;
 use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Support\Facades\Hash;
@@ -35,16 +36,61 @@ public function login(string $provider, object $oauthUser, OauthSetting $oauthSe
 
     private function resolveOauthUser(object $oauthUser, OauthSetting $oauthSetting, string $email): User
     {
-        $user = User::whereEmail($email)->first();
-        if ($user) {
-            return $user;
+        $provider = $oauthSetting->provider;
+        $providerUserId = $oauthUser->id ?? null;
+        if (
+            (! is_string($providerUserId) && ! is_int($providerUserId))
+            || (is_string($providerUserId) && trim($providerUserId) === '')
+        ) {
+            throw new HttpException(403, 'OAuth provider did not return a valid user ID');
         }
+        $providerUserId = (string) $providerUserId;
+        $rawClaims = is_array($oauthUser->user ?? null) ? $oauthUser->user : [];
 
-        if (! $this->canCreateUser($oauthSetting)) {
-            throw new HttpException(403, 'Registration is disabled');
+        $identityKey = [
+            'provider' => $provider,
+            'issuer' => $provider,
+            'provider_user_id' => $providerUserId,
+        ];
+
+        try {
+            return DB::transaction(function () use ($oauthUser, $oauthSetting, $email, $provider, $providerUserId, $rawClaims, $identityKey): User {
+                $identity = OauthIdentity::where($identityKey)->first();
+
+                if ($identity) {
+                    $identity->update([
+                        'email' => $email,
+                        'raw_claims' => $rawClaims,
+                        'last_login_at' => now(),
+                    ]);
+
+                    return $identity->user;
+                }
+
+                $user = User::whereEmail($email)->first();
+                if (! $user) {
+                    if (! $this->canCreateUser($oauthSetting)) {
+                        throw new HttpException(403, 'Registration is disabled');
+                    }
+
+                    $user = $this->createUser($oauthUser->name ?: $email, $email, $oauthSetting);
+                }
+
+                OauthIdentity::create([
+                    'user_id' => $user->id,
+                    'provider' => $provider,
+                    'issuer' => $provider,
+                    'provider_user_id' => $providerUserId,
+                    'email' => $email,
+                    'raw_claims' => $rawClaims,
+                    'last_login_at' => now(),
+                ]);
+
+                return $user;
+            });
+        } catch (UniqueConstraintViolationException $exception) {
+            return OauthIdentity::where($identityKey)->first()?->user ?? throw $exception;
         }
-
-        return $this->createUser($oauthUser->name ?: $email, $email, $oauthSetting);
     }
 
     private function resolveOidcUser(object $oauthUser, OauthSetting $oauthSetting, string $email): User
@@ -68,53 +114,59 @@ private function resolveOidcUser(object $oauthUser, OauthSetting $oauthSetting,
 
         $rawClaims = is_array($oauthUser->user ?? null) ? $oauthUser->user : [];
 
-        return DB::transaction(function () use ($oauthUser, $oauthSetting, $email, $issuer, $subject, $emailVerified, $rawClaims) {
-            $identity = OauthIdentity::where([
-                'provider' => 'oidc',
-                'issuer' => $issuer,
-                'provider_user_id' => $subject,
-            ])->first();
+        $identityKey = [
+            'provider' => 'oidc',
+            'issuer' => $issuer,
+            'provider_user_id' => $subject,
+        ];
 
-            if ($identity) {
-                $identity->update([
+        try {
+            return DB::transaction(function () use ($oauthUser, $oauthSetting, $email, $issuer, $subject, $emailVerified, $rawClaims, $identityKey): User {
+                $identity = OauthIdentity::where($identityKey)->first();
+
+                if ($identity) {
+                    $identity->update([
+                        'email' => $email,
+                        'raw_claims' => $rawClaims,
+                        'last_login_at' => now(),
+                    ]);
+
+                    return $identity->user;
+                }
+
+                $user = User::whereEmail($email)->first();
+
+                // Linking a new OIDC identity to an existing local account by email
+                // is account takeover unless the provider attests the email. This
+                // guard is independent of the require_email_verified toggle, which
+                // only governs the broader login flow.
+                if ($user && ! $emailVerified) {
+                    throw new HttpException(403, 'OIDC provider must verify the email address before linking to an existing account');
+                }
+
+                if (! $user) {
+                    if (! $this->canCreateUser($oauthSetting)) {
+                        throw new HttpException(403, 'Registration is disabled');
+                    }
+
+                    $user = $this->createUser($oauthUser->name ?: $email, $email, $oauthSetting);
+                }
+
+                OauthIdentity::create([
+                    'user_id' => $user->id,
+                    'provider' => 'oidc',
+                    'issuer' => $issuer,
+                    'provider_user_id' => $subject,
                     'email' => $email,
                     'raw_claims' => $rawClaims,
                     'last_login_at' => now(),
                 ]);
 
-                return $identity->user;
-            }
-
-            $user = User::whereEmail($email)->first();
-
-            // Linking a new OIDC identity to an existing local account by email
-            // is account takeover unless the provider attests the email. This
-            // guard is independent of the require_email_verified toggle, which
-            // only governs the broader login flow.
-            if ($user && ! $emailVerified) {
-                throw new HttpException(403, 'OIDC provider must verify the email address before linking to an existing account');
-            }
-
-            if (! $user) {
-                if (! $this->canCreateUser($oauthSetting)) {
-                    throw new HttpException(403, 'Registration is disabled');
-                }
-
-                $user = $this->createUser($oauthUser->name ?: $email, $email, $oauthSetting);
-            }
-
-            OauthIdentity::create([
-                'user_id' => $user->id,
-                'provider' => 'oidc',
-                'issuer' => $issuer,
-                'provider_user_id' => $subject,
-                'email' => $email,
-                'raw_claims' => $rawClaims,
-                'last_login_at' => now(),
-            ]);
-
-            return $user;
-        });
+                return $user;
+            });
+        } catch (UniqueConstraintViolationException $exception) {
+            return OauthIdentity::where($identityKey)->first()?->user ?? throw $exception;
+        }
     }
 
     private function canCreateUser(OauthSetting $oauthSetting): bool
diff --git a/bootstrap/helpers/shared.php b/bootstrap/helpers/shared.php
index cf63c4776..d3cc6d826 100644
--- a/bootstrap/helpers/shared.php
+++ b/bootstrap/helpers/shared.php
@@ -4544,7 +4544,7 @@ function formatContainerStatus(string $status): string
  * Check if password confirmation should be skipped.
  * Returns true if:
  * - Two-step confirmation is globally disabled
- * - User has no password (OAuth users)
+ * - User has no usable local password confirmation (including SSO users)
  *
  * Used by modal-confirmation.blade.php to determine if password step should be shown.
  *
@@ -4557,8 +4557,9 @@ function shouldSkipPasswordConfirmation(): bool
         return true;
     }
 
-    // Skip if user has no password (OAuth users)
-    if (! Auth::user()?->hasPassword()) {
+    // OAuth users may have an unusable generated password, so the linked
+    // identity is the source of truth for whether confirmation is possible.
+    if (! Auth::user()?->requiresPasswordConfirmation()) {
         return true;
     }
 
@@ -4569,7 +4570,7 @@ function shouldSkipPasswordConfirmation(): bool
  * Verify password for two-step confirmation.
  * Skips verification if:
  * - Two-step confirmation is globally disabled
- * - User has no password (OAuth users)
+ * - User has no usable local password confirmation (including SSO users)
  *
  * @param  mixed  $password  The password to verify (may be array if skipped by frontend)
  * @param  Component|null  $component  Optional Livewire component to add errors to
diff --git a/tests/Feature/OauthControllerTest.php b/tests/Feature/OauthControllerTest.php
index 27660a6bb..4671183ae 100644
--- a/tests/Feature/OauthControllerTest.php
+++ b/tests/Feature/OauthControllerTest.php
@@ -1,11 +1,17 @@
 <?php
 
 use App\Models\InstanceSettings;
+use App\Models\OauthIdentity;
 use App\Models\OauthSetting;
 use App\Models\User;
+use App\Services\Auth\OauthLoginService;
+use Illuminate\Database\UniqueConstraintViolationException;
 use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Event;
 use Illuminate\Support\Once;
 use Laravel\Socialite\Facades\Socialite;
+use Symfony\Component\HttpKernel\Exception\HttpException;
 
 uses(RefreshDatabase::class);
 
@@ -50,6 +56,75 @@
     $response->assertRedirect('/');
     $this->assertAuthenticatedAs($user);
     expect(User::count())->toBe(1);
+    expect(OauthIdentity::where([
+        'user_id' => $user->id,
+        'provider' => 'google',
+        'provider_user_id' => 'google-user-id',
+    ])->exists())->toBeTrue();
+});
+
+it('never moves an existing oauth identity when the provider email changes', function () {
+    config()->set('app.maintenance.driver', 'file');
+
+    $identityOwner = User::factory()->create(['email' => 'old@example.com']);
+    $otherUser = User::factory()->create(['email' => 'new@example.com']);
+    $identity = OauthIdentity::create([
+        'user_id' => $identityOwner->id,
+        'provider' => 'google',
+        'issuer' => 'google',
+        'provider_user_id' => 'google-user-id',
+        'email' => 'old@example.com',
+    ]);
+
+    $provider = Mockery::mock();
+    $provider->shouldReceive('setConfig')->once()->andReturnSelf();
+    $provider->shouldReceive('with')->once()->with(['hd' => 'example.com'])->andReturnSelf();
+    $provider->shouldReceive('user')->once()->andReturn((object) [
+        'email' => 'new@example.com',
+        'name' => 'Example User',
+        'id' => 'google-user-id',
+    ]);
+
+    Socialite::shouldReceive('driver')->once()->with('google')->andReturn($provider);
+
+    $this->get(route('auth.callback', 'google'))->assertRedirect('/');
+
+    $this->assertAuthenticatedAs($identityOwner);
+    expect($identity->refresh()->user_id)->toBe($identityOwner->id)
+        ->and($identity->email)->toBe('new@example.com')
+        ->and($identity->user_id)->not->toBe($otherUser->id);
+});
+
+it('continues oauth login when another request creates the identity first', function () {
+    $user = User::factory()->create(['email' => 'race@example.com']);
+    $eventName = 'eloquent.creating: '.OauthIdentity::class;
+
+    Event::listen($eventName, function (OauthIdentity $identity): void {
+        $attributes = $identity->getAttributes();
+
+        DB::afterRollBack(fn () => DB::table('oauth_identities')->insert($attributes));
+
+        throw new UniqueConstraintViolationException(
+            DB::getDefaultConnection(),
+            'insert into oauth_identities',
+            [],
+            new PDOException('duplicate identity'),
+        );
+    });
+
+    try {
+        $resolvedUser = app(OauthLoginService::class)->login('google', (object) [
+            'email' => 'race@example.com',
+            'name' => 'Race User',
+            'id' => 'google-race-id',
+        ], OauthSetting::where('provider', 'google')->firstOrFail());
+    } finally {
+        Event::forget($eventName);
+    }
+
+    expect($resolvedUser->is($user))->toBeTrue()
+        ->and(OauthIdentity::where('provider_user_id', 'google-race-id')->count())->toBe(1);
+    $this->assertAuthenticatedAs($user);
 });
 
 it('rejects oauth logins when the provider does not return an email address', function (?string $providerEmail) {
@@ -83,3 +158,34 @@
     'malformed email' => ['not-an-email'],
     'missing domain' => ['user@'],
 ]);
+
+it('rejects oauth logins when the provider does not return a valid user id', function (mixed $invalidId) {
+    $oauthUser = (object) [
+        'email' => 'user@example.edu',
+        'name' => 'Example User',
+    ];
+
+    if ($invalidId !== 'missing') {
+        $oauthUser->id = $invalidId;
+    }
+
+    try {
+        app(OauthLoginService::class)->login('google', $oauthUser, OauthSetting::where('provider', 'google')->firstOrFail());
+    } catch (HttpException $exception) {
+        expect($exception->getStatusCode())->toBe(403)
+            ->and(OauthIdentity::count())->toBe(0)
+            ->and(User::count())->toBe(0);
+
+        return;
+    }
+
+    $this->fail('Expected an invalid OAuth provider user ID to be rejected.');
+})->with([
+    'null id' => [null],
+    'missing id' => ['missing'],
+    'blank id' => ['   '],
+    'non-scalar id' => [[]],
+    'true id' => [true],
+    'false id' => [false],
+    'float id' => [1.0],
+]);
diff --git a/tests/Feature/OidcOauthControllerTest.php b/tests/Feature/OidcOauthControllerTest.php
index 21b335016..084347f66 100644
--- a/tests/Feature/OidcOauthControllerTest.php
+++ b/tests/Feature/OidcOauthControllerTest.php
@@ -6,7 +6,11 @@
 use App\Models\OauthSetting;
 use App\Models\Team;
 use App\Models\User;
+use App\Services\Auth\OauthLoginService;
+use Illuminate\Database\UniqueConstraintViolationException;
 use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Event;
 use Illuminate\Support\Facades\Log;
 use Illuminate\Support\Once;
 use Laravel\Socialite\Facades\Socialite;
@@ -73,6 +77,44 @@ function fakeOidcProvider(array $claims = []): void
     $this->assertAuthenticatedAs($user);
 });
 
+it('continues oidc login when another request creates the identity first', function () {
+    $user = User::factory()->create(['email' => 'race@example.com']);
+    $eventName = 'eloquent.creating: '.OauthIdentity::class;
+
+    Event::listen($eventName, function (OauthIdentity $identity): void {
+        $attributes = $identity->getAttributes();
+
+        DB::afterRollBack(fn () => DB::table('oauth_identities')->insert($attributes));
+
+        throw new UniqueConstraintViolationException(
+            DB::getDefaultConnection(),
+            'insert into oauth_identities',
+            [],
+            new PDOException('duplicate identity'),
+        );
+    });
+
+    try {
+        $resolvedUser = app(OauthLoginService::class)->login('oidc', (new OidcUser)->setRaw([
+            'iss' => 'https://idp.example.com',
+            'sub' => 'oidc-race-id',
+            'email' => 'race@example.com',
+            'email_verified' => true,
+            'name' => 'Race User',
+        ])->map([
+            'id' => 'oidc-race-id',
+            'name' => 'Race User',
+            'email' => 'race@example.com',
+        ]), OauthSetting::where('provider', 'oidc')->firstOrFail());
+    } finally {
+        Event::forget($eventName);
+    }
+
+    expect($resolvedUser->is($user))->toBeTrue()
+        ->and(OauthIdentity::where('provider_user_id', 'oidc-race-id')->count())->toBe(1);
+    $this->assertAuthenticatedAs($user);
+});
+
 it('creates a new oidc user when provider registration is allowed while normal registration is disabled', function () {
     OauthSetting::where('provider', 'oidc')->update(['allow_registration' => true]);
 
diff --git a/tests/v4/Feature/DangerDeleteResourceTest.php b/tests/v4/Feature/DangerDeleteResourceTest.php
index 7a73f5979..4a275ad48 100644
--- a/tests/v4/Feature/DangerDeleteResourceTest.php
+++ b/tests/v4/Feature/DangerDeleteResourceTest.php
@@ -4,6 +4,7 @@
 use App\Models\Application;
 use App\Models\Environment;
 use App\Models\InstanceSettings;
+use App\Models\OauthIdentity;
 use App\Models\Project;
 use App\Models\Server;
 use App\Models\StandaloneDocker;
@@ -18,7 +19,7 @@
 uses(RefreshDatabase::class);
 
 beforeEach(function () {
-    InstanceSettings::create(['id' => 0]);
+    InstanceSettings::forceCreate(['id' => 0]);
     Queue::fake();
 
     $this->user = User::factory()->create([
@@ -70,6 +71,21 @@
     expect(Application::find($this->application->id))->toBeNull();
 });
 
+test('delete succeeds without password for an oauth user', function () {
+    OauthIdentity::create([
+        'user_id' => $this->user->id,
+        'provider' => 'oidc',
+        'issuer' => 'https://idp.example.com',
+        'provider_user_id' => 'oauth-user-id',
+    ]);
+
+    Livewire::test(Danger::class, ['resource' => $this->application])
+        ->call('delete', '')
+        ->assertHasNoErrors();
+
+    expect(Application::find($this->application->id))->toBeNull();
+});
+
 test('delete applies selectedActions from checkbox state', function () {
     $component = Livewire::test(Danger::class, ['resource' => $this->application])
         ->call('delete', 'test-password', ['delete_configurations', 'docker_cleanup']);