diff --git a/app/Rules/ContentTypeMatchesPlatform.php b/app/Rules/ContentTypeMatchesPlatform.php
index 56e945c24..fd0da853d 100644
--- a/app/Rules/ContentTypeMatchesPlatform.php
+++ b/app/Rules/ContentTypeMatchesPlatform.php
@@ -40,7 +40,7 @@ public function validate(string $attribute, mixed $value, Closure $fail): void
         $parentKey = Str::beforeLast($attribute, '.');
         $accountId = data_get($this->data, $parentKey.'.social_account_id');
 
-        if (! $accountId) {
+        if (! $accountId || ! Str::isUuid((string) $accountId)) {
             return;
         }
 
diff --git a/tests/Unit/Rules/ContentTypeMatchesPlatformTest.php b/tests/Unit/Rules/ContentTypeMatchesPlatformTest.php
index c3fe5352a..e5a6dedda 100644
--- a/tests/Unit/Rules/ContentTypeMatchesPlatformTest.php
+++ b/tests/Unit/Rules/ContentTypeMatchesPlatformTest.php
@@ -67,6 +67,14 @@ function runMatchesPlatformRule(string $contentType, ?string $accountId, array $
     expect(runMatchesPlatformRule(ContentType::XPost->value, null))->toBe([]);
 });
 
+test('skips validation without querying the database when social_account_id is not a uuid', function () {
+    // Regression: a non-uuid social_account_id (e.g. an MCP client sending a
+    // placeholder string) must not reach SocialAccount::find(), which throws
+    // a QueryException on Postgres for invalid uuid input instead of
+    // returning no rows.
+    expect(runMatchesPlatformRule(ContentType::XPost->value, 'threads-account'))->toBe([]);
+});
+
 test('skips validation when content_type is not a known enum value', function () {
     $workspace = Workspace::factory()->create();
     $linkedin = SocialAccount::factory()->create([