From f74053b118e0f91bb368c751a8131923239ef876 Mon Sep 17 00:00:00 2001
From: Paulo Castellano <paulo@castellanos.llc>
Date: Sat, 11 Jul 2026 10:34:57 -0300
Subject: [PATCH] Extract alt-text truncation onto MediaItem and close test
 gaps

Centralize the per-platform mb_substr truncation that every publisher was
repeating into MediaItem::altTextFor(Platform), delete each publisher's
private altFor() helper, and clarify the Platform::altTextMaxLength()
docblock so it doesn't imply Instagram's documented 1000-char cap is a
guess. Add the assertions review flagged as missing: LinkedInPage/
InstagramFacebook alt-text caps, non-string and literal-"0" alt_text
normalization, altTextFor() truncation/unsupported-platform behavior,
Mastodon's no-description-part case, and the public API's accept/reject
path for media.*.meta.alt_text.
---
 app/DataTransferObjects/MediaItem.php         | 18 +++++
 app/Enums/SocialAccount/Platform.php          |  8 ++-
 .../Social/AbstractLinkedInPublisher.php      | 17 +----
 app/Services/Social/BlueskyPublisher.php      | 18 +----
 .../Social/Discord/DiscordPublisher.php       |  4 +-
 app/Services/Social/FacebookPublisher.php     | 15 +----
 app/Services/Social/InstagramPublisher.php    | 17 +----
 app/Services/Social/MastodonPublisher.php     |  4 +-
 app/Services/Social/PinterestPublisher.php    |  4 +-
 app/Services/Social/ThreadsPublisher.php      | 16 +----
 app/Services/Social/XPublisher.php            |  4 +-
 tests/Feature/Api/PostMediaApiTest.php        | 66 +++++++++++++++++++
 .../Services/Social/MastodonPublisherTest.php | 65 ++++++++++++++++++
 tests/Unit/MediaItemAltTextTest.php           | 21 ++++++
 tests/Unit/PlatformAltTextTest.php            |  4 ++
 15 files changed, 196 insertions(+), 85 deletions(-)

diff --git a/app/DataTransferObjects/MediaItem.php b/app/DataTransferObjects/MediaItem.php
index a81b0ae7..60718a1d 100644
--- a/app/DataTransferObjects/MediaItem.php
+++ b/app/DataTransferObjects/MediaItem.php
@@ -6,6 +6,7 @@
 
 use App\Enums\Media\Source;
 use App\Enums\Media\Type;
+use App\Enums\SocialAccount\Platform;
 
 class MediaItem
 {
@@ -75,6 +76,23 @@ public function altText(): ?string
         return $alt === '' ? null : $alt;
     }
 
+    /**
+     * The alt text truncated to the given platform's cap, or null when no alt
+     * text is set or the platform doesn't support it. Single place that applies
+     * the per-platform cap so publishers don't each repeat the truncation.
+     */
+    public function altTextFor(Platform $platform): ?string
+    {
+        $alt = $this->altText();
+        $max = $platform->altTextMaxLength();
+
+        if ($alt === null || $max === null) {
+            return null;
+        }
+
+        return mb_substr($alt, 0, $max);
+    }
+
     /**
      * @param  array<string, mixed>  $data
      */
diff --git a/app/Enums/SocialAccount/Platform.php b/app/Enums/SocialAccount/Platform.php
index 73629c8f..64db3849 100644
--- a/app/Enums/SocialAccount/Platform.php
+++ b/app/Enums/SocialAccount/Platform.php
@@ -129,9 +129,11 @@ public function maxImages(): int
 
     /**
      * Character cap the platform's API accepts for image alt text (accessibility
-     * description), or null when the platform has no alt-text field. Facebook and
-     * Threads document no limit, so a defensive 1000 is used. Single source of
-     * truth — publishers truncate to this value, never a literal.
+     * description), or null when the platform has no alt-text field. X, LinkedIn,
+     * Instagram, Pinterest, and Discord use documented API maxes. Facebook,
+     * Threads, Mastodon, and Bluesky document no limit, so a defensive cap is
+     * used instead. Single source of truth — publishers truncate to this value,
+     * never a literal.
      */
     public function altTextMaxLength(): ?int
     {
diff --git a/app/Services/Social/AbstractLinkedInPublisher.php b/app/Services/Social/AbstractLinkedInPublisher.php
index 6922e876..4fba3190 100644
--- a/app/Services/Social/AbstractLinkedInPublisher.php
+++ b/app/Services/Social/AbstractLinkedInPublisher.php
@@ -4,7 +4,6 @@
 
 namespace App\Services\Social;
 
-use App\DataTransferObjects\MediaItem;
 use App\Enums\Media\Type as MediaType;
 use App\Enums\SocialAccount\Platform;
 use App\Exceptions\Social\ErrorCategory;
@@ -127,7 +126,7 @@ private function publishPost(?string $content, $media): array
             if ($mediaUrn) {
                 $payload['content'] = ['media' => array_filter([
                     'id' => $mediaUrn,
-                    'altText' => $this->altFor($media->first()),
+                    'altText' => $media->first()->altTextFor($this->platform()),
                 ], fn ($v) => $v !== null)];
             }
         }
@@ -149,7 +148,7 @@ private function publishCarousel(?string $content, $media): array
             if ($imageUrn) {
                 $images[] = array_filter([
                     'id' => $imageUrn,
-                    'altText' => $this->altFor($item),
+                    'altText' => $item->altTextFor($this->platform()),
                 ], fn ($v) => $v !== null);
             }
         }
@@ -247,18 +246,6 @@ private function resolveDocumentTitle(PostPlatform $postPlatform): string
         return $postPlatform->post->mediaItems->first(fn ($media) => $media->isDocument())?->original_filename ?? 'Document';
     }
 
-    /**
-     * The accessibility description to send for an uploaded image, capped to
-     * what the platform accepts. Null when the user hasn't set one, so the
-     * caller can omit the `altText` key entirely rather than sending it empty.
-     */
-    private function altFor(MediaItem $media): ?string
-    {
-        $alt = $media->altText();
-
-        return $alt === null ? null : mb_substr($alt, 0, $this->platform()->altTextMaxLength());
-    }
-
     private function uploadMedia($mediaItem): ?string
     {
         return match (true) {
diff --git a/app/Services/Social/BlueskyPublisher.php b/app/Services/Social/BlueskyPublisher.php
index ae418c3e..f45f541c 100644
--- a/app/Services/Social/BlueskyPublisher.php
+++ b/app/Services/Social/BlueskyPublisher.php
@@ -4,7 +4,6 @@
 
 namespace App\Services\Social;
 
-use App\DataTransferObjects\MediaItem;
 use App\Enums\Media\Type as MediaType;
 use App\Enums\SocialAccount\Platform;
 use App\Exceptions\Social\BlueskyPublishException;
@@ -64,7 +63,7 @@ public function publish(PostPlatform $postPlatform): array
                     $blob = $this->uploadBlob($account, $service, $media->url, $media->mime_type);
                     if ($blob) {
                         $images[] = [
-                            'alt' => $this->altFor($media),
+                            'alt' => $media->altTextFor(Platform::Bluesky) ?? '',
                             'image' => $blob,
                         ];
                     }
@@ -702,21 +701,6 @@ private function buildPostUrl(string $handle, string $postId): string
         return "{$webApp}/profile/{$handle}/post/{$postId}";
     }
 
-    /**
-     * Bluesky requires `alt` on every image, so this returns '' (never null)
-     * when the user set no description, and the capped description otherwise.
-     */
-    private function altFor(MediaItem $media): string
-    {
-        $alt = $media->altText();
-
-        if ($alt === null) {
-            return '';
-        }
-
-        return mb_substr($alt, 0, Platform::Bluesky->altTextMaxLength());
-    }
-
     private function handleApiError(Response $response): never
     {
         throw BlueskyPublishException::fromApiResponse($response);
diff --git a/app/Services/Social/Discord/DiscordPublisher.php b/app/Services/Social/Discord/DiscordPublisher.php
index f4d88a60..3cbbb4c4 100644
--- a/app/Services/Social/Discord/DiscordPublisher.php
+++ b/app/Services/Social/Discord/DiscordPublisher.php
@@ -129,10 +129,10 @@ private function sendWithMedia(string $channelId, array $payload, Collection $me
 
                 $attachment = ['id' => $index, 'filename' => $filename];
 
-                $alt = $item->altText();
+                $alt = $item->altTextFor(Platform::Discord);
 
                 if ($alt !== null) {
-                    $attachment['description'] = mb_substr($alt, 0, Platform::Discord->altTextMaxLength());
+                    $attachment['description'] = $alt;
                 }
 
                 $attachments[] = $attachment;
diff --git a/app/Services/Social/FacebookPublisher.php b/app/Services/Social/FacebookPublisher.php
index 6386bb1b..64a7e1a2 100644
--- a/app/Services/Social/FacebookPublisher.php
+++ b/app/Services/Social/FacebookPublisher.php
@@ -4,7 +4,6 @@
 
 namespace App\Services\Social;
 
-use App\DataTransferObjects\MediaItem;
 use App\Enums\PostPlatform\ContentType;
 use App\Enums\SocialAccount\Platform;
 use App\Exceptions\Social\ErrorCategory;
@@ -136,7 +135,7 @@ private function publishSingleImagePost(string $pageId, string $accessToken, ?st
             $payload['message'] = $content;
         }
 
-        $alt = $this->altFor($media);
+        $alt = $media->altTextFor(Platform::Facebook);
 
         if ($alt !== null) {
             $payload['alt_text_custom'] = $alt;
@@ -177,7 +176,7 @@ private function publishMultiImagePost(string $pageId, string $accessToken, ?str
                 'access_token' => $accessToken,
             ];
 
-            $alt = $this->altFor($media);
+            $alt = $media->altTextFor(Platform::Facebook);
 
             if ($alt !== null) {
                 $uploadPayload['alt_text_custom'] = $alt;
@@ -428,16 +427,6 @@ private function handleApiError(Response $response): never
         throw FacebookPublishException::fromApiResponse($response);
     }
 
-    /**
-     * User-provided alt text for the image, capped to Facebook's accepted length.
-     */
-    private function altFor(MediaItem $media): ?string
-    {
-        $alt = $media->altText();
-
-        return $alt === null ? null : mb_substr($alt, 0, Platform::Facebook->altTextMaxLength());
-    }
-
     protected function cropFailureException(string $message): SocialPublishException
     {
         return new FacebookPublishException(
diff --git a/app/Services/Social/InstagramPublisher.php b/app/Services/Social/InstagramPublisher.php
index 2fe669f6..79aafc4e 100644
--- a/app/Services/Social/InstagramPublisher.php
+++ b/app/Services/Social/InstagramPublisher.php
@@ -4,7 +4,6 @@
 
 namespace App\Services\Social;
 
-use App\DataTransferObjects\MediaItem;
 use App\Enums\PostPlatform\ContentType;
 use App\Enums\SocialAccount\Platform;
 use App\Exceptions\Social\ErrorCategory;
@@ -89,7 +88,7 @@ private function publishSingleImage(string $instagramId, string $accessToken, ?s
             'access_token' => $accessToken,
         ];
 
-        $alt = $this->altFor($media);
+        $alt = $media->altTextFor(Platform::Instagram);
 
         if ($alt !== null) {
             $params['alt_text'] = $alt;
@@ -217,7 +216,7 @@ private function publishCarousel(string $instagramId, string $accessToken, ?stri
             } else {
                 $params['image_url'] = $this->cropImageForAspectRatio($media->url, $aspectRatio);
 
-                $alt = $this->altFor($media);
+                $alt = $media->altTextFor(Platform::Instagram);
 
                 if ($alt !== null) {
                     $params['alt_text'] = $alt;
@@ -371,16 +370,4 @@ private function handleApiError(Response $response): never
     {
         throw InstagramPublishException::fromApiResponse($response);
     }
-
-    /**
-     * User-provided alt text for the image, capped to Instagram's accepted
-     * length. Instagram only accepts `alt_text` on image containers/children,
-     * never on video/reel containers.
-     */
-    private function altFor(MediaItem $media): ?string
-    {
-        $alt = $media->altText();
-
-        return $alt === null ? null : mb_substr($alt, 0, Platform::Instagram->altTextMaxLength());
-    }
 }
diff --git a/app/Services/Social/MastodonPublisher.php b/app/Services/Social/MastodonPublisher.php
index 8edc58b7..ec5799df 100644
--- a/app/Services/Social/MastodonPublisher.php
+++ b/app/Services/Social/MastodonPublisher.php
@@ -33,7 +33,7 @@ public function publish(PostPlatform $postPlatform): array
 
         // Upload media first (max 4)
         foreach ($medias->take(4) as $media) {
-            $mediaId = $this->uploadMedia($account, $instance, $media->url, $media->original_filename, $media->altText());
+            $mediaId = $this->uploadMedia($account, $instance, $media->url, $media->original_filename, $media->altTextFor(Platform::Mastodon));
             if ($mediaId) {
                 $mediaIds[] = $mediaId;
             }
@@ -105,7 +105,7 @@ private function uploadMedia(SocialAccount $account, string $instance, string $u
                 ->attach('file', $stream, $name);
 
             if ($altText !== null) {
-                $request = $request->attach('description', mb_substr($altText, 0, Platform::Mastodon->altTextMaxLength()));
+                $request = $request->attach('description', $altText);
             }
 
             $response = $request->post("{$instance}/api/v1/media");
diff --git a/app/Services/Social/PinterestPublisher.php b/app/Services/Social/PinterestPublisher.php
index 8e7b087f..2d97128d 100644
--- a/app/Services/Social/PinterestPublisher.php
+++ b/app/Services/Social/PinterestPublisher.php
@@ -119,10 +119,10 @@ private function publishImagePin(PostPlatform $postPlatform, ?string $content):
             $payload['link'] = data_get($postPlatform->meta, 'link');
         }
 
-        $alt = $postPlatform->post->mediaItems->first(fn ($m) => $m->isImage())?->altText();
+        $alt = $postPlatform->post->mediaItems->first(fn ($m) => $m->isImage())?->altTextFor(Platform::Pinterest);
 
         if ($alt !== null) {
-            $payload['alt_text'] = mb_substr($alt, 0, Platform::Pinterest->altTextMaxLength());
+            $payload['alt_text'] = $alt;
         }
 
         $response = $this->socialHttp()->withToken($account->access_token)
diff --git a/app/Services/Social/ThreadsPublisher.php b/app/Services/Social/ThreadsPublisher.php
index 89f87cfc..593567ec 100644
--- a/app/Services/Social/ThreadsPublisher.php
+++ b/app/Services/Social/ThreadsPublisher.php
@@ -4,7 +4,6 @@
 
 namespace App\Services\Social;
 
-use App\DataTransferObjects\MediaItem;
 use App\Enums\SocialAccount\Platform;
 use App\Exceptions\Social\ErrorCategory;
 use App\Exceptions\Social\ThreadsPublishException;
@@ -109,7 +108,7 @@ private function publishImagePost(string $userId, string $accessToken, ?string $
             'access_token' => $accessToken,
         ];
 
-        $alt = $this->altFor($media);
+        $alt = $media->altTextFor(Platform::Threads);
 
         if ($alt !== null) {
             $params['alt_text'] = $alt;
@@ -195,7 +194,7 @@ private function publishCarousel(string $userId, string $accessToken, ?string $c
                 $params['media_type'] = 'IMAGE';
                 $params['image_url'] = $media->url;
 
-                $alt = $this->altFor($media);
+                $alt = $media->altTextFor(Platform::Threads);
 
                 if ($alt !== null) {
                     $params['alt_text'] = $alt;
@@ -347,15 +346,4 @@ private function handleApiError(Response $response): never
     {
         throw ThreadsPublishException::fromApiResponse($response);
     }
-
-    /**
-     * User-provided alt text for the image, capped to Threads' accepted
-     * length. Scoped to image containers/children only.
-     */
-    private function altFor(MediaItem $media): ?string
-    {
-        $alt = $media->altText();
-
-        return $alt === null ? null : mb_substr($alt, 0, Platform::Threads->altTextMaxLength());
-    }
 }
diff --git a/app/Services/Social/XPublisher.php b/app/Services/Social/XPublisher.php
index 5b794ac5..61b7e3bd 100644
--- a/app/Services/Social/XPublisher.php
+++ b/app/Services/Social/XPublisher.php
@@ -114,7 +114,7 @@ private function getHttpClient(): PendingRequest
      */
     private function uploadAltText(string $mediaId, MediaItem $mediaItem): void
     {
-        $alt = $mediaItem->altText();
+        $alt = $mediaItem->altTextFor(Platform::X);
 
         if ($alt === null) {
             return;
@@ -124,7 +124,7 @@ private function uploadAltText(string $mediaId, MediaItem $mediaItem): void
             'id' => $mediaId,
             'metadata' => [
                 'alt_text' => [
-                    'text' => mb_substr($alt, 0, Platform::X->altTextMaxLength()),
+                    'text' => $alt,
                 ],
             ],
         ]);
diff --git a/tests/Feature/Api/PostMediaApiTest.php b/tests/Feature/Api/PostMediaApiTest.php
index daa7c3eb..4bc81781 100644
--- a/tests/Feature/Api/PostMediaApiTest.php
+++ b/tests/Feature/Api/PostMediaApiTest.php
@@ -446,3 +446,69 @@
 
     expect($this->post->fresh()->media)->toBe($original);
 });
+
+it('accepts and persists media alt text on create', function () {
+    $this->socialAccount->update(['is_active' => true]);
+    Http::preventStrayRequests();
+
+    $this->withHeaders(['Authorization' => 'Bearer '.$this->plainToken])
+        ->postJson(route('api.posts.store'), [
+            'content' => 'Alt text post',
+            'media' => [[
+                'id' => 'media-1',
+                'path' => 'assets/foo.jpg',
+                'url' => 'https://cdn.trypost.test/assets/foo.jpg',
+                'type' => 'image',
+                'meta' => ['alt_text' => 'A description of the photo'],
+            ]],
+            'platforms' => [
+                ['social_account_id' => $this->socialAccount->id, 'content_type' => 'linkedin_post'],
+            ],
+        ])
+        ->assertCreated();
+
+    $media = Post::where('content', 'Alt text post')->firstOrFail()->media;
+
+    expect(data_get($media, '0.meta.alt_text'))->toBe('A description of the photo');
+});
+
+it('accepts and persists media alt text on update', function () {
+    $this->withHeaders(['Authorization' => 'Bearer '.$this->plainToken])
+        ->putJson(route('api.posts.update', $this->post), [
+            'status' => 'draft',
+            'media' => [[
+                'id' => 'media-1',
+                'path' => 'assets/foo.jpg',
+                'url' => 'https://cdn.trypost.test/assets/foo.jpg',
+                'type' => 'image',
+                'meta' => ['alt_text' => 'Updated alt text'],
+            ]],
+        ])
+        ->assertOk();
+
+    expect(data_get($this->post->fresh()->media, '0.meta.alt_text'))->toBe('Updated alt text');
+});
+
+it('rejects media alt text over 2000 characters', function () {
+    $this->socialAccount->update(['is_active' => true]);
+    Http::preventStrayRequests();
+
+    $this->withHeaders(['Authorization' => 'Bearer '.$this->plainToken])
+        ->postJson(route('api.posts.store'), [
+            'content' => 'Alt text too long post',
+            'media' => [[
+                'id' => 'media-1',
+                'path' => 'assets/foo.jpg',
+                'url' => 'https://cdn.trypost.test/assets/foo.jpg',
+                'type' => 'image',
+                'meta' => ['alt_text' => str_repeat('a', 2001)],
+            ]],
+            'platforms' => [
+                ['social_account_id' => $this->socialAccount->id, 'content_type' => 'linkedin_post'],
+            ],
+        ])
+        ->assertUnprocessable()
+        ->assertJsonValidationErrors(['media.0.meta.alt_text']);
+
+    expect(Post::where('content', 'Alt text too long post')->exists())->toBeFalse();
+});
diff --git a/tests/Feature/Services/Social/MastodonPublisherTest.php b/tests/Feature/Services/Social/MastodonPublisherTest.php
index aee4120c..5ac8087c 100644
--- a/tests/Feature/Services/Social/MastodonPublisherTest.php
+++ b/tests/Feature/Services/Social/MastodonPublisherTest.php
@@ -196,6 +196,71 @@
     @unlink($optimizedFile);
 });
 
+test('mastodon publisher sends no description part when image has no alt text', function () {
+    // Minimal 1x1 JPEG bytes so mime_content_type() detects image/jpeg
+    $minimalJpeg = "\xFF\xD8\xFF\xE0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00"
+        ."\xFF\xDB\x00\x43\x00\x08\x06\x06\x07\x06\x05\x08\x07\x07\x07\x09\x09\x08\x0A\x0C"
+        ."\x14\x0D\x0C\x0B\x0B\x0C\x19\x12\x13\x0F\x14\x1D\x1A\x1F\x1E\x1D\x1A\x1C\x1C\x20"
+        ."\xFF\xC0\x00\x0B\x08\x00\x01\x00\x01\x01\x01\x11\x00\xFF\xC4\x00\x1F\x00\x00\x01"
+        ."\x05\x01\x01\x01\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x01\x02\x03\x04\x05"
+        ."\xFF\xDA\x00\x08\x01\x01\x00\x00\x3F\x00\xFB\xD3\xFF\xD9";
+
+    $optimizedFile = tempnam(sys_get_temp_dir(), 'masto_no_alt_opt_');
+    file_put_contents($optimizedFile, str_repeat('x', 1024));
+
+    $this->post->update([
+        'media' => [
+            [
+                'id' => 'test-media-id',
+                'path' => 'media/2026-01/test-image.jpg',
+                'url' => 'https://example.com/media/2026-01/test-image.jpg',
+                'mime_type' => 'image/jpeg',
+                'original_filename' => 'test.jpg',
+            ],
+        ],
+    ]);
+
+    $this->mock(MediaOptimizer::class)
+        ->shouldReceive('optimizeImage')
+        ->once()
+        ->with(Mockery::any(), Platform::Mastodon)
+        ->andReturn($optimizedFile);
+
+    Http::fake(function ($request) use ($minimalJpeg) {
+        $url = $request->url();
+
+        if (str_contains($url, '/api/v1/media')) {
+            return Http::response([
+                'id' => 'media-no-alt-123',
+                'type' => 'image',
+                'url' => 'https://mastodon.social/media/image.jpg',
+            ], 200);
+        }
+
+        if (str_contains($url, '/api/v1/statuses')) {
+            return Http::response([
+                'id' => '109876543210',
+                'url' => 'https://mastodon.social/@testuser/109876543210',
+            ], 200);
+        }
+
+        // Media download: return valid JPEG so mime_content_type() detects image/jpeg
+        return Http::response($minimalJpeg, 200, ['Content-Type' => 'image/jpeg']);
+    });
+
+    $this->publisher->publish($this->postPlatform);
+
+    Http::assertSent(function ($request) {
+        if (! str_contains($request->url(), '/api/v1/media')) {
+            return false;
+        }
+
+        return collect($request->data())->firstWhere('name', 'description') === null;
+    });
+
+    @unlink($optimizedFile);
+});
+
 test('mastodon publisher includes media ids in post', function () {
     Http::fake([
         'https://mastodon.social/api/v1/statuses' => Http::response([
diff --git a/tests/Unit/MediaItemAltTextTest.php b/tests/Unit/MediaItemAltTextTest.php
index 599db824..d9e20cc5 100644
--- a/tests/Unit/MediaItemAltTextTest.php
+++ b/tests/Unit/MediaItemAltTextTest.php
@@ -3,6 +3,7 @@
 declare(strict_types=1);
 
 use App\DataTransferObjects\MediaItem;
+use App\Enums\SocialAccount\Platform;
 
 test('altText returns the trimmed meta alt_text', function () {
     $item = MediaItem::fromArray(['id' => 'a', 'path' => 'p.jpg', 'url' => 'u', 'meta' => ['alt_text' => '  a cat  ']]);
@@ -14,3 +15,23 @@
     expect(MediaItem::fromArray(['id' => 'a', 'path' => 'p.jpg', 'url' => 'u'])->altText())->toBeNull()
         ->and(MediaItem::fromArray(['id' => 'a', 'path' => 'p.jpg', 'url' => 'u', 'meta' => ['alt_text' => '   ']])->altText())->toBeNull();
 });
+
+test('altText is null when meta alt_text is not a string', function () {
+    expect(MediaItem::fromArray(['id' => 'a', 'path' => 'p.jpg', 'url' => 'u', 'meta' => ['alt_text' => 123]])->altText())->toBeNull()
+        ->and(MediaItem::fromArray(['id' => 'a', 'path' => 'p.jpg', 'url' => 'u', 'meta' => ['alt_text' => ['x']]])->altText())->toBeNull();
+});
+
+test('altText keeps the literal string "0"', function () {
+    $item = MediaItem::fromArray(['id' => 'a', 'path' => 'p.jpg', 'url' => 'u', 'meta' => ['alt_text' => '0']]);
+
+    expect($item->altText())->toBe('0');
+});
+
+test('altTextFor truncates to the platform cap and is null for an unsupported platform', function () {
+    $longAlt = str_repeat('a', Platform::X->altTextMaxLength() + 50);
+    $item = MediaItem::fromArray(['id' => 'a', 'path' => 'p.jpg', 'url' => 'u', 'meta' => ['alt_text' => $longAlt]]);
+
+    expect($item->altTextFor(Platform::X))->toBe(mb_substr($longAlt, 0, Platform::X->altTextMaxLength()))
+        ->and(mb_strlen($item->altTextFor(Platform::X)))->toBe(Platform::X->altTextMaxLength())
+        ->and($item->altTextFor(Platform::TikTok))->toBeNull();
+});
diff --git a/tests/Unit/PlatformAltTextTest.php b/tests/Unit/PlatformAltTextTest.php
index c5777903..8a060273 100644
--- a/tests/Unit/PlatformAltTextTest.php
+++ b/tests/Unit/PlatformAltTextTest.php
@@ -9,7 +9,9 @@
         ->and(Platform::X->altTextMaxLength())->toBe(1000)
         ->and(Platform::Mastodon->altTextMaxLength())->toBe(1500)
         ->and(Platform::LinkedIn->altTextMaxLength())->toBe(4086)
+        ->and(Platform::LinkedInPage->altTextMaxLength())->toBe(4086)
         ->and(Platform::Instagram->altTextMaxLength())->toBe(1000)
+        ->and(Platform::InstagramFacebook->altTextMaxLength())->toBe(1000)
         ->and(Platform::Pinterest->altTextMaxLength())->toBe(500)
         ->and(Platform::Discord->altTextMaxLength())->toBe(1024)
         ->and(Platform::Facebook->altTextMaxLength())->toBe(1000)
@@ -24,5 +26,7 @@
 
 test('supportsAltText mirrors altTextMaxLength', function () {
     expect(Platform::Bluesky->supportsAltText())->toBeTrue()
+        ->and(Platform::LinkedInPage->supportsAltText())->toBeTrue()
+        ->and(Platform::InstagramFacebook->supportsAltText())->toBeTrue()
         ->and(Platform::TikTok->supportsAltText())->toBeFalse();
 });