diff --git a/FILTERS.md b/FILTERS.md
index 58c50c2f..b2b4d21f 100644
--- a/FILTERS.md
+++ b/FILTERS.md
@@ -807,6 +807,15 @@ Filters the form fields of the `fictioneer_contact_form` shortcode.
 
 ---
 
+### `apply_filters( 'fictioneer_filter_co_authored_ids', $story_ids, $author_id )`
+Filters the array of story IDs co-authored by the specified author ID, as queried and returned by the `fictioneer_sql_get_co_authored_story_ids()` function. These IDs are used to query selectable story chapters and validate permissions for chapter assignment and appending.
+
+**Parameters:**
+* $story_ids (int[]) – Array of story IDs.
+* $author_id (int) – Co-author ID.
+
+---
+
 ### `apply_filters( 'fictioneer_filter_customizer_{theme_option}', $choices )`
 Filters the choices arrays of select theme options. Combined with the `fictioneer_filter_pre_build_customize_css` filter, you can append own options and the requires styles. Available options: `header_image_style`, `header_style`, `page_style`, `story_cover_position`, `card_frame`, `card_image_style`, `card_style` (actually card footer), `card_shadow`, `content_list_style`, and `footer_style`.
 
diff --git a/includes/functions/_helpers-query.php b/includes/functions/_helpers-query.php
index 719c91e6..e8a51be6 100644
--- a/includes/functions/_helpers-query.php
+++ b/includes/functions/_helpers-query.php
@@ -710,7 +710,7 @@ if ( ! function_exists( 'fictioneer_sql_has_new_story_chapters' ) ) {
   }
 }
 
-if ( ! function_exists( 'fictioneer_get_co_authored_story_ids' ) ) {
+if ( ! function_exists( 'fictioneer_sql_get_co_authored_story_ids' ) ) {
   /**
    * Returns story IDs where the user is a co-author
    *
@@ -723,7 +723,7 @@ if ( ! function_exists( 'fictioneer_get_co_authored_story_ids' ) ) {
    * @return int[] Array of story IDs.
    */
 
-  function fictioneer_get_co_authored_story_ids( $author_id ) {
+  function fictioneer_sql_get_co_authored_story_ids( $author_id ) {
     static $cache = [];
 
     if ( isset( $cache[ $author_id ] ) ) {
@@ -742,6 +742,8 @@ if ( ! function_exists( 'fictioneer_get_co_authored_story_ids' ) ) {
       )
     );
 
+    $story_ids = apply_filters( 'fictioneer_filter_co_authored_ids', $story_ids, $author_id );
+
     $cache[ $author_id ] = $story_ids;
 
     return $story_ids;
@@ -784,7 +786,7 @@ if ( ! function_exists( 'fictioneer_sql_get_chapter_story_selection' ) ) {
       $sql .= " AND p.post_author = %d";
       $values[] = $post_author_id;
 
-      $co_authored_stories = fictioneer_get_co_authored_story_ids( $post_author_id );
+      $co_authored_stories = fictioneer_sql_get_co_authored_story_ids( $post_author_id );
 
       if ( ! empty( $co_authored_stories ) ) {
         $placeholders = implode( ',', array_fill( 0, count( $co_authored_stories ), '%d' ) );
diff --git a/includes/functions/_setup-meta-fields.php b/includes/functions/_setup-meta-fields.php
index a27d220c..034e381f 100644
--- a/includes/functions/_setup-meta-fields.php
+++ b/includes/functions/_setup-meta-fields.php
@@ -2951,7 +2951,7 @@ function fictioneer_save_chapter_metaboxes( $post_id ) {
       $invalid_story = false;
 
       if ( get_option( 'fictioneer_limit_chapter_stories_by_author' ) ) {
-        $co_authored_stories = fictioneer_get_co_authored_story_ids( $post_author_id );
+        $co_authored_stories = fictioneer_sql_get_co_authored_story_ids( $post_author_id );
 
         $invalid_story = $story_author_id != $post_author_id && ! in_array( $story_id, $co_authored_stories );
       }
diff --git a/includes/functions/_utility.php b/includes/functions/_utility.php
index 19855550..a5d6e6eb 100644
--- a/includes/functions/_utility.php
+++ b/includes/functions/_utility.php
@@ -1590,7 +1590,7 @@ function fictioneer_append_chapter_to_story( $post_id, $story_id, $force = false
   // Setup, continued
   $chapter_author_id = get_post_field( 'post_author', $post_id );
   $story_author_id = get_post_field( 'post_author', $story_id );
-  $co_authored_story_ids = fictioneer_get_co_authored_story_ids( $chapter_author_id );
+  $co_authored_story_ids = fictioneer_sql_get_co_authored_story_ids( $chapter_author_id );
 
   // Abort if the author IDs do not match
   if (