diff --git a/@packages/shared/Sources/MacSyncShared/Sync/TraceLog.swift b/@packages/shared/Sources/MacSyncShared/Sync/TraceLog.swift
index 41d8151..66193cb 100644
--- a/@packages/shared/Sources/MacSyncShared/Sync/TraceLog.swift
+++ b/@packages/shared/Sources/MacSyncShared/Sync/TraceLog.swift
@@ -9,6 +9,14 @@ import Foundation
 /// Intentionally minimal and dependency-free. Serialized on a private queue
 /// so concurrent callers don't interleave partial lines.
 public enum TraceLog {
+    /// Verbose send-queue file tracing. Disabled unless `debugSendQueue` is
+    /// set `true` in the app config (`config.json` → UserDefaults). The trace
+    /// calls are intentionally kept in the code (not deleted) so the send
+    /// pipeline can be re-diagnosed by flipping this flag — no rebuild needed.
+    public static var isEnabled: Bool {
+        UserDefaults.standard.bool(forKey: "debugSendQueue")
+    }
+
     private static let url: URL = FileManager.default
         .homeDirectoryForCurrentUser
         .appendingPathComponent("Library/Application Support/MacSync", isDirectory: true)
@@ -22,8 +30,9 @@ public enum TraceLog {
         return f
     }()
 
-    public static func write(_ message: String) {
-        let line = "\(formatter.string(from: Date())) \(message)\n"
+    public static func write(_ message: @autoclosure () -> String) {
+        guard isEnabled else { return }
+        let line = "\(formatter.string(from: Date())) \(message())\n"
         queue.async {
             guard let data = line.data(using: .utf8) else { return }
             let fm = FileManager.default