diff --git a/openapi/spec/paths/api@register.yaml b/openapi/spec/paths/api@register.yaml
index 3cd039930c0..2790cf40a4c 100644
--- a/openapi/spec/paths/api@register.yaml
+++ b/openapi/spec/paths/api@register.yaml
@@ -59,7 +59,17 @@ post:
             - email_marketing
   responses:
     '200':
-      description: User registered successfully
+      description: |
+        Invitation-based registration where the user is auto-confirmed.
+        Returns session credentials so the client can log in immediately.
+      content:
+        application/json:
+          schema:
+            $ref: ../components/schemas/userAuth.yaml
+    '204':
+      description: |
+        Open registration completed. The account requires email confirmation
+        before the user can log in.
     '400':
       $ref: ../components/responses/400.yaml
     '401':
diff --git a/server/api/routes/invitation.go b/server/api/routes/invitation.go
index 56cd106942c..17c97ec5676 100644
--- a/server/api/routes/invitation.go
+++ b/server/api/routes/invitation.go
@@ -44,7 +44,7 @@ func (h *Handler) RegisterUser(c *gateway.Context) error {
 		return c.JSON(http.StatusOK, authInfo)
 	}
 
-	return c.NoContent(http.StatusOK)
+	return c.NoContent(http.StatusNoContent)
 }
 
 // ResolveInvitation serves what an invite code stands for, so the accept page can route the