diff --git a/extensions/mentions/src/Formatter/FormatGroupMentions.php b/extensions/mentions/src/Formatter/FormatGroupMentions.php
index b6ad163170..be8bddcd63 100644
--- a/extensions/mentions/src/Formatter/FormatGroupMentions.php
+++ b/extensions/mentions/src/Formatter/FormatGroupMentions.php
@@ -27,9 +27,7 @@ public function __invoke(Renderer $renderer, mixed $context, string $xml): strin
         return Utils::replaceAttributes($xml, 'GROUPMENTION', function ($attributes) use ($context) {
             /** @var Group|null $group */
             $group = match (true) {
-                $context instanceof AbstractModel && $context->isRelation('mentionsGroups') => $context->relationLoaded('mentionsGroups')
-                    ? $context->mentionsGroups->find($attributes['id']) // @phpstan-ignore-line
-                    : $context->mentionsGroups()->find($attributes['id']), // @phpstan-ignore-line
+                $context instanceof AbstractModel && $context->relationLoaded('mentionsGroups') => $context->mentionsGroups->find($attributes['id']), // @phpstan-ignore-line
                 default => Group::query()->find($attributes['id']),
             };
 
diff --git a/extensions/mentions/src/Formatter/FormatPostMentions.php b/extensions/mentions/src/Formatter/FormatPostMentions.php
index 75a20ba368..9140d74fca 100644
--- a/extensions/mentions/src/Formatter/FormatPostMentions.php
+++ b/extensions/mentions/src/Formatter/FormatPostMentions.php
@@ -33,9 +33,7 @@ public function __invoke(Renderer $renderer, mixed $context, string $xml): strin
         return Utils::replaceAttributes($xml, 'POSTMENTION', function ($attributes) use ($context) {
             /** @var Post|null $post */
             $post = match (true) {
-                $context instanceof AbstractModel && $context->isRelation('mentionsPosts') => $context->relationLoaded('mentionsPosts')
-                    ? $context->mentionsPosts->find($attributes['id']) // @phpstan-ignore-line
-                    : $context->mentionsPosts()->find($attributes['id']), // @phpstan-ignore-line
+                $context instanceof AbstractModel && $context->relationLoaded('mentionsPosts') => $context->mentionsPosts->find($attributes['id']), // @phpstan-ignore-line
                 default => Post::query()->find($attributes['id']),
             };
 
diff --git a/extensions/mentions/src/Formatter/FormatTagMentions.php b/extensions/mentions/src/Formatter/FormatTagMentions.php
index 6cad73ca6c..ca64181786 100644
--- a/extensions/mentions/src/Formatter/FormatTagMentions.php
+++ b/extensions/mentions/src/Formatter/FormatTagMentions.php
@@ -22,9 +22,7 @@ public function __invoke(Renderer $renderer, mixed $context, string $xml, ?Reque
         return Utils::replaceAttributes($xml, 'TAGMENTION', function ($attributes) use ($context) {
             /** @var Tag|null $tag */
             $tag = match (true) {
-                $context instanceof AbstractModel && $context->isRelation('mentionsTags') => $context->relationLoaded('mentionsTags')
-                    ? $context->mentionsTags->find($attributes['id']) // @phpstan-ignore-line
-                    : $context->mentionsTags()->find($attributes['id']), // @phpstan-ignore-line
+                $context instanceof AbstractModel && $context->relationLoaded('mentionsTags') => $context->mentionsTags->find($attributes['id']), // @phpstan-ignore-line
                 default => Tag::query()->find($attributes['id']),
             };
 
diff --git a/extensions/mentions/src/Formatter/FormatUserMentions.php b/extensions/mentions/src/Formatter/FormatUserMentions.php
index fbbbe28f73..9658b98e1e 100644
--- a/extensions/mentions/src/Formatter/FormatUserMentions.php
+++ b/extensions/mentions/src/Formatter/FormatUserMentions.php
@@ -29,9 +29,7 @@ public function __invoke(Renderer $renderer, mixed $context, string $xml): strin
         return Utils::replaceAttributes($xml, 'USERMENTION', function ($attributes) use ($context) {
             /** @var User|null $user */
             $user = match (true) {
-                $context instanceof AbstractModel && $context->isRelation('mentionsUsers') => $context->relationLoaded('mentionsUsers')
-                    ? $context->mentionsUsers->find($attributes['id']) // @phpstan-ignore-line
-                    : $context->mentionsUsers()->find($attributes['id']), // @phpstan-ignore-line
+                $context instanceof AbstractModel && $context->relationLoaded('mentionsUsers') => $context->mentionsUsers->find($attributes['id']), // @phpstan-ignore-line
                 default => User::query()->find($attributes['id']),
             };
 
diff --git a/extensions/mentions/src/Formatter/UnparsePostMentions.php b/extensions/mentions/src/Formatter/UnparsePostMentions.php
index ee9f0d24d4..d1a59d5bf4 100644
--- a/extensions/mentions/src/Formatter/UnparsePostMentions.php
+++ b/extensions/mentions/src/Formatter/UnparsePostMentions.php
@@ -40,9 +40,7 @@ protected function updatePostMentionTags(mixed $context, string $xml): string
         return Utils::replaceAttributes($xml, 'POSTMENTION', function ($attributes) use ($context) {
             /** @var Post|null $post */
             $post = match (true) {
-                $context instanceof AbstractModel && $context->isRelation('mentionsPosts') => $context->relationLoaded('mentionsPosts')
-                    ? $context->mentionsPosts->find($attributes['id']) // @phpstan-ignore-line
-                    : $context->mentionsPosts()->find($attributes['id']), // @phpstan-ignore-line
+                $context instanceof AbstractModel && $context->relationLoaded('mentionsPosts') => $context->mentionsPosts->find($attributes['id']), // @phpstan-ignore-line
                 default => Post::query()->find($attributes['id']),
             };
 
diff --git a/extensions/mentions/src/Formatter/UnparseTagMentions.php b/extensions/mentions/src/Formatter/UnparseTagMentions.php
index 8623f47985..d4a19c71dd 100644
--- a/extensions/mentions/src/Formatter/UnparseTagMentions.php
+++ b/extensions/mentions/src/Formatter/UnparseTagMentions.php
@@ -34,9 +34,7 @@ protected function updateTagMentionTags(mixed $context, string $xml): string
         return Utils::replaceAttributes($xml, 'TAGMENTION', function (array $attributes) use ($context) {
             /** @var Tag|null $tag */
             $tag = match (true) {
-                $context instanceof AbstractModel && $context->isRelation('mentionsTags') => $context->relationLoaded('mentionsTags')
-                    ? $context->mentionsTags->find($attributes['id']) // @phpstan-ignore-line
-                    : $context->mentionsTags()->find($attributes['id']), // @phpstan-ignore-line
+                $context instanceof AbstractModel && $context->relationLoaded('mentionsTags') => $context->mentionsTags->find($attributes['id']), // @phpstan-ignore-line
                 default => Tag::query()->find($attributes['id']),
             };
 
diff --git a/extensions/mentions/src/Formatter/UnparseUserMentions.php b/extensions/mentions/src/Formatter/UnparseUserMentions.php
index b40b1a5615..14bc1834dc 100644
--- a/extensions/mentions/src/Formatter/UnparseUserMentions.php
+++ b/extensions/mentions/src/Formatter/UnparseUserMentions.php
@@ -40,9 +40,7 @@ protected function updateUserMentionTags(mixed $context, string $xml): string
         return Utils::replaceAttributes($xml, 'USERMENTION', function ($attributes) use ($context) {
             /** @var User|null $user */
             $user = match (true) {
-                $context instanceof AbstractModel && $context->isRelation('mentionsUsers') => $context->relationLoaded('mentionsUsers')
-                    ? $context->mentionsUsers->find($attributes['id']) // @phpstan-ignore-line
-                    : $context->mentionsUsers()->find($attributes['id']), // @phpstan-ignore-line
+                $context instanceof AbstractModel && $context->relationLoaded('mentionsUsers') => $context->mentionsUsers->find($attributes['id']), // @phpstan-ignore-line
                 default => User::query()->find($attributes['id']),
             };
 
diff --git a/extensions/mentions/tests/integration/api/MentionsDuringSavingTest.php b/extensions/mentions/tests/integration/api/MentionsDuringSavingTest.php
new file mode 100644
index 0000000000..9562c275e4
--- /dev/null
+++ b/extensions/mentions/tests/integration/api/MentionsDuringSavingTest.php
@@ -0,0 +1,121 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Mentions\Tests\integration\api;
+
+use Carbon\Carbon;
+use Flarum\Discussion\Discussion;
+use Flarum\Extend;
+use Flarum\Post\Event\Saving;
+use Flarum\Post\Post;
+use Flarum\Testing\integration\RetrievesAuthorizedUsers;
+use Flarum\Testing\integration\TestCase;
+use Flarum\User\User;
+use PHPUnit\Framework\Attributes\Test;
+
+/**
+ * Regression tests for https://github.com/flarum/framework/issues/4823.
+ *
+ * When `$post->content` is read during the `Saving` lifecycle event (before
+ * the post's mention pivot tables have been populated), the mention
+ * formatters must still resolve the mentioned entity by its own existence
+ * rather than the not-yet-synced pivot — otherwise the mention is wrongly
+ * unparsed to the `[deleted]` / `[unknown]` fallback text.
+ */
+class MentionsDuringSavingTest extends TestCase
+{
+    use RetrievesAuthorizedUsers;
+
+    /**
+     * Content observed by the Saving listener, captured for assertion.
+     */
+    protected ?string $observedContent = null;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->extension('flarum-mentions');
+
+        $this->extend(
+            (new Extend\Event())
+                ->listen(Saving::class, function (Saving $event) {
+                    // Reading content here triggers unparse() while the post's
+                    // mention pivots are not yet synced — the #4823 scenario.
+                    $this->observedContent = $event->post->content;
+                })
+        );
+
+        $this->prepareDatabase([
+            User::class => [
+                $this->normalUser(),
+                ['id' => 3, 'username' => 'mentioned_user', 'email' => 'mentioned_user@machine.local', 'is_email_confirmed' => 1],
+            ],
+            Discussion::class => [
+                ['id' => 1, 'title' => 'Test discussion', 'created_at' => Carbon::now(), 'last_posted_at' => Carbon::now(), 'user_id' => 1, 'first_post_id' => 1, 'comment_count' => 1],
+            ],
+            Post::class => [
+                ['id' => 1, 'number' => 1, 'discussion_id' => 1, 'created_at' => Carbon::now(), 'user_id' => 1, 'type' => 'comment', 'content' => '<t><p>Original</p></t>'],
+            ],
+        ]);
+    }
+
+    #[Test]
+    public function user_mention_resolves_during_saving_of_a_new_post(): void
+    {
+        $response = $this->send(
+            $this->request('POST', '/api/posts', [
+                'authenticatedAs' => 1,
+                'json' => [
+                    'data' => [
+                        'attributes' => [
+                            'content' => '@"mentioned_user"#3',
+                        ],
+                        'relationships' => [
+                            'discussion' => ['data' => ['type' => 'discussions', 'id' => '1']],
+                        ],
+                    ],
+                ],
+            ])
+        );
+
+        $this->assertEquals(201, $response->getStatusCode(), $response->getBody()->getContents());
+
+        // The Saving listener must have seen the real mention, NOT the deleted
+        // fallback — this is the regression from #4823.
+        $this->assertNotNull($this->observedContent);
+        $this->assertStringContainsString('mentioned_user', $this->observedContent);
+        $this->assertStringNotContainsString('[deleted]', $this->observedContent);
+        $this->assertStringNotContainsString('[unknown]', $this->observedContent);
+    }
+
+    #[Test]
+    public function user_mention_resolves_during_saving_when_editing_a_post(): void
+    {
+        $response = $this->send(
+            $this->request('PATCH', '/api/posts/1', [
+                'authenticatedAs' => 1,
+                'json' => [
+                    'data' => [
+                        'attributes' => [
+                            'content' => '@"mentioned_user"#3 edited',
+                        ],
+                    ],
+                ],
+            ])
+        );
+
+        $this->assertEquals(200, $response->getStatusCode(), $response->getBody()->getContents());
+
+        $this->assertNotNull($this->observedContent);
+        $this->assertStringContainsString('mentioned_user', $this->observedContent);
+        $this->assertStringNotContainsString('[deleted]', $this->observedContent);
+        $this->assertStringNotContainsString('[unknown]', $this->observedContent);
+    }
+}
diff --git a/extensions/mentions/tests/integration/api/PostMentionsTest.php b/extensions/mentions/tests/integration/api/PostMentionsTest.php
index 0b9cd9c8e1..c07a77089a 100644
--- a/extensions/mentions/tests/integration/api/PostMentionsTest.php
+++ b/extensions/mentions/tests/integration/api/PostMentionsTest.php
@@ -480,7 +480,7 @@ public function editing_a_post_with_deleted_author_that_has_a_mention_works()
                     'data' => [
                         'type' => 'posts',
                         'attributes' => [
-                            'content' => '@"Bad _ User"#p9',
+                            'content' => '@"Bad _ User"#p9 edited',
                         ],
                     ],
                 ],
@@ -494,7 +494,7 @@ public function editing_a_post_with_deleted_author_that_has_a_mention_works()
         $response = json_decode($body, true);
 
         $this->assertStringContainsString('Bad "#p6 User', $response['data']['attributes']['contentHtml']);
-        $this->assertEquals('@"Bad _ User"#p9', $response['data']['attributes']['content']);
+        $this->assertEquals('@"Bad _ User"#p9 edited', $response['data']['attributes']['content']);
         $this->assertStringContainsString('PostMention', $response['data']['attributes']['contentHtml']);
         $this->assertNotNull(CommentPost::find($response['data']['id'])->mentionsPosts->find(9));
     }
diff --git a/extensions/mentions/tests/integration/api/TagMentionsTest.php b/extensions/mentions/tests/integration/api/TagMentionsTest.php
index 3515e1045e..5134f748f4 100644
--- a/extensions/mentions/tests/integration/api/TagMentionsTest.php
+++ b/extensions/mentions/tests/integration/api/TagMentionsTest.php
@@ -40,7 +40,7 @@ protected function setUp(): void
             ],
             Post::class => [
                 ['id' => 4, 'number' => 2, 'discussion_id' => 2, 'created_at' => Carbon::now(), 'user_id' => 3, 'type' => 'comment', 'content' => '<r><TAGMENTION id="1" slug="test_old_slug" tagname="TestOldName">#test_old_slug</TAGMENTION></r>'],
-                ['id' => 7, 'number' => 5, 'discussion_id' => 2, 'created_at' => Carbon::now(), 'user_id' => 2021, 'type' => 'comment', 'content' => '<r><TAGMENTION id="3" slug="support" tagname="Support">#deleted_relation</TAGMENTION></r>'],
+                ['id' => 7, 'number' => 5, 'discussion_id' => 2, 'created_at' => Carbon::now(), 'user_id' => 2021, 'type' => 'comment', 'content' => '<r><TAGMENTION id="999" slug="support" tagname="Support">#deleted_relation</TAGMENTION></r>'],
                 ['id' => 8, 'number' => 6, 'discussion_id' => 2, 'created_at' => Carbon::now(), 'user_id' => 4, 'type' => 'comment', 'content' => '<r><TAGMENTION id="2020" slug="i_am_a_deleted_tag" tagname="i_am_a_deleted_tag">#i_am_a_deleted_tag</TAGMENTION></r>'],
                 ['id' => 10, 'number' => 11, 'discussion_id' => 2, 'created_at' => Carbon::now(), 'user_id' => 4, 'type' => 'comment', 'content' => '<r><TAGMENTION id="5" slug="laravel">#laravel</TAGMENTION></r>'],
             ],
diff --git a/extensions/mentions/tests/integration/api/UserMentionsTest.php b/extensions/mentions/tests/integration/api/UserMentionsTest.php
index 962eb59df8..db0b3983d4 100644
--- a/extensions/mentions/tests/integration/api/UserMentionsTest.php
+++ b/extensions/mentions/tests/integration/api/UserMentionsTest.php
@@ -465,7 +465,7 @@ public function editing_a_post_with_deleted_author_that_has_a_mention_works()
                     'data' => [
                         'type' => 'posts',
                         'attributes' => [
-                            'content' => '@"Bad _ User"#5',
+                            'content' => '@"Bad _ User"#5 edited',
                         ],
                     ],
                 ],
@@ -479,7 +479,7 @@ public function editing_a_post_with_deleted_author_that_has_a_mention_works()
         $response = json_decode($body, true);
 
         $this->assertStringContainsString('Bad "#p6 User', $response['data']['attributes']['contentHtml']);
-        $this->assertEquals('@"Bad _ User"#5', $response['data']['attributes']['content']);
+        $this->assertEquals('@"Bad _ User"#5 edited', $response['data']['attributes']['content']);
         $this->assertStringContainsString('UserMention', $response['data']['attributes']['contentHtml']);
         $this->assertNotNull(CommentPost::find($response['data']['id'])->mentionsUsers->find(5));
     }