diff --git a/docs/api/routes/article/set-categories.md b/docs/api/routes/article/set-categories.md
index 269a1ad..a21a064 100644
--- a/docs/api/routes/article/set-categories.md
+++ b/docs/api/routes/article/set-categories.md
@@ -5,8 +5,8 @@ Protected. Requires a valid session cookie (`credentials: 'include'`).
 Replace article categories by SKU
 
 Replace-all the article's category list. Each category must belong to
-the article's company; ids must be unique. Empty array removes the
-article from all categories. Returns the same shape as GET by SKU.
+the article's company; ids must be unique. The article must belong to
+at least one category (empty array is rejected). Returns the same shape as GET by SKU.
 
 
 ## Path parameters
@@ -115,7 +115,7 @@ Updated article detail
 
 | Status | Description |
 |--------|-------------|
-| 400 | Invalid categoryIds — `{"error":"…"}` |
+| 400 | Invalid categoryIds or empty array — `{"error":"…"}` |
 | 401 | Unauthorized — `{"error":"…"}` |
 | 403 | Not authorized — `{"error":"…"}` |
 | 404 | Article not found — `{"error":"…"}` |
diff --git a/src/api/routes/article.js b/src/api/routes/article.js
index 7ff414e..da72d78 100644
--- a/src/api/routes/article.js
+++ b/src/api/routes/article.js
@@ -77,7 +77,7 @@ function articleErrorStatus(error) {
     if (error.message === 'Invalid attributeValueId') return 400;
     if (error.message === 'Invalid weight') return 400;
     if (error.message === 'Invalid track_stock') return 400;
-    if (error.message === 'Invalid categoryIds') return 400;
+    if (error.message === 'Invalid categoryIds' || error.message === 'Article must have at least one category') return 400;
     if (error.message === 'Attribute name not found') return 404;
     if (error.message === 'attributeNameId is required to become a parent article') return 400;
     if (error.message?.includes('already used by an ancestor parent')) return 400;
@@ -1470,8 +1470,8 @@ export function register(app, basePath = '') {
      *     summary: Replace article categories by SKU
      *     description: |
      *       Replace-all the article's category list. Each category must belong to
-     *       the article's company; ids must be unique. Empty array removes the
-     *       article from all categories. Returns the same shape as GET by SKU.
+     *       the article's company; ids must be unique. The article must belong to
+     *       at least one category (empty array is rejected). Returns the same shape as GET by SKU.
      *     security:
      *       - cookieAuth: []
      *     x-signals: [article-<sku>]
@@ -1492,6 +1492,7 @@ export function register(app, basePath = '') {
      *             properties:
      *               categoryIds:
      *                 type: array
+     *                 minItems: 1
      *                 items:
      *                   type: integer
      *             example:
@@ -1507,7 +1508,7 @@ export function register(app, basePath = '') {
      *                 article:
      *                   $ref: '#/components/schemas/ArticleDetail'
      *       400:
-     *         description: Invalid categoryIds
+     *         description: Invalid categoryIds or empty array
      *         content:
      *           application/json:
      *             schema: