From f36c29376c0500c3eaf576a93b51099c90015e6d Mon Sep 17 00:00:00 2001
From: David Koski <dkoski@apple.com>
Date: Fri, 27 Mar 2026 15:45:19 -0700
Subject: [PATCH] hold evalLock during mlx_save_safetensors etc

- fix #378
- save functions call eval internally and must be run under evalLock
---
 Source/MLX/IO.swift | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/Source/MLX/IO.swift b/Source/MLX/IO.swift
index acdb590d..519096dc 100644
--- a/Source/MLX/IO.swift
+++ b/Source/MLX/IO.swift
@@ -36,7 +36,9 @@ public func save(array: MLXArray, url: URL, stream: StreamOrDevice = .default) t
     switch url.pathExtension {
     case "npy":
         _ = try withError {
-            mlx_save(path.cString(using: .utf8), array.ctx)
+            _ = evalLock.withLock {
+                mlx_save(path.cString(using: .utf8), array.ctx)
+            }
         }
 
     default:
@@ -72,7 +74,9 @@ public func save(
     switch url.pathExtension {
     case "safetensors":
         _ = try withError {
-            mlx_save_safetensors(path.cString(using: .utf8), mlx_arrays, mlx_metadata)
+            _ = evalLock.withLock {
+                mlx_save_safetensors(path.cString(using: .utf8), mlx_arrays, mlx_metadata)
+            }
         }
 
     default:
@@ -283,7 +287,11 @@ public func saveToData(
     let writer = new_mlx_io_writer_dataIO()
     defer { mlx_io_writer_free(writer) }
 
-    mlx_save_safetensors_writer(writer, mlx_arrays, mlx_metadata)
+    _ = evalLock.withLock {
+        _ = evalLock.withLock {
+            mlx_save_safetensors_writer(writer, mlx_arrays, mlx_metadata)
+        }
+    }
 
     return getData(writer)
 }