diff --git a/server/auth_audit_test.go b/server/auth_audit_test.go
index bcee600..5ea0890 100644
--- a/server/auth_audit_test.go
+++ b/server/auth_audit_test.go
@@ -75,6 +75,12 @@ func TestMessageQuerySpecsExposeAdminFields(t *testing.T) {
 	if strings.Contains(strings.ToLower(privateSpec.Select), "m.content as content") || strings.Contains(strings.ToLower(groupSpec.Select), "m.content as content") {
 		t.Fatal("message list query must not expose full message content")
 	}
+	if !strings.Contains(privateSpec.Select, "CAST(m.`from` AS CHAR) AS from_user_id") || !strings.Contains(privateSpec.Select, "CAST(rs.userid AS CHAR) AS to_user_id") {
+		t.Fatal("private message query must expose 64-bit user IDs as strings")
+	}
+	if !strings.Contains(groupSpec.Select, "CAST(m.from_user AS CHAR) AS from_user_id") {
+		t.Fatal("group message query must expose 64-bit user IDs as strings")
+	}
 }
 
 func TestGroupMessageQuerySupportsOperationalFilters(t *testing.T) {
diff --git a/server/internal_admin_query_resources.go b/server/internal_admin_query_resources.go
index 1cb9070..65d724b 100644
--- a/server/internal_admin_query_resources.go
+++ b/server/internal_admin_query_resources.go
@@ -305,9 +305,9 @@ func privateMessagesInternalQuerySpec() *internalQuerySpec {
 	contentExcerpt := `LEFT(COALESCE(NULLIF(JSON_UNQUOTE(JSON_EXTRACT(m.content,'$.txt')),''),CASE JSON_TYPE(m.content) WHEN 'STRING' THEN JSON_UNQUOTE(m.content) ELSE CONCAT('[',` + contentType + `,']') END,''),500)`
 	status := `CASE WHEN aa.action='delete' THEN 'deleted' WHEN aa.action='hide' THEN 'hidden' WHEN m.recalled_at IS NOT NULL THEN 'recalled' WHEN m.deletedat IS NOT NULL THEN 'deleted' ELSE 'normal' END`
 	return &internalQuerySpec{
-		Select: `SELECT m.topic,m.seqid AS seq_id,m.` + "`from`" + ` AS from_user_id,
+		Select: `SELECT m.topic,m.seqid AS seq_id,CAST(m.` + "`from`" + ` AS CHAR) AS from_user_id,
 			COALESCE(su.username,'') AS sender_username,COALESCE(sp.nickname,'') AS sender_nickname,
-			rs.userid AS to_user_id,COALESCE(ru.username,'') AS receiver_username,COALESCE(rp.nickname,'') AS receiver_nickname,
+			CAST(rs.userid AS CHAR) AS to_user_id,COALESCE(ru.username,'') AS receiver_username,COALESCE(rp.nickname,'') AS receiver_nickname,
 			` + contentType + ` AS content_type,` + contentExcerpt + ` AS content_excerpt,
 			` + status + ` AS status,m.createdat AS created_at,m.updatedat AS updated_at`,
 		From: `FROM (SELECT * FROM im_messages WHERE topic LIKE 'p2p%') AS m
@@ -327,7 +327,7 @@ func groupMessagesInternalQuerySpec() *internalQuerySpec {
 	contentType := `CASE m.msg_type WHEN 'call' THEN 'system' WHEN 'system_notice' THEN 'system' WHEN 'contact_card' THEN 'card' WHEN 'forward_bundle' THEN 'card' WHEN 'link' THEN 'text' ELSE m.msg_type END`
 	contentExcerpt := `LEFT(COALESCE(NULLIF(JSON_UNQUOTE(JSON_EXTRACT(m.content,'$.txt')),''),CASE JSON_TYPE(m.content) WHEN 'STRING' THEN JSON_UNQUOTE(m.content) ELSE CONCAT('[',` + contentType + `,']') END,''),500)`
 	return &internalQuerySpec{
-		Select: `SELECT m.topic,m.seqid AS seq_id,m.from_user AS from_user_id,
+		Select: `SELECT m.topic,m.seqid AS seq_id,CAST(m.from_user AS CHAR) AS from_user_id,
 			COALESCE(u.username,'') AS sender_username,COALESCE(p.nickname,'') AS sender_nickname,
 			COALESCE(gs.name,'') AS group_name,m.topic AS group_no,` + contentType + ` AS content_type,
 			` + contentExcerpt + ` AS content_excerpt,