From eaed92952cc43315d195c0ab45d2996e48a98886 Mon Sep 17 00:00:00 2001
From: ciaranbor <81697641+ciaranbor@users.noreply.github.com>
Date: Thu, 26 Feb 2026 10:59:36 +0000
Subject: [PATCH] Use tmpdir for coordination file (#1624)

## Motivation

Coordination files for MLX distributed init were written to the current
working directory (./hosts_*.json)

## Changes

- Move coordination file creation to a tempfile.TemporaryDirectory(),
which auto-cleans on context manager exit
---
 src/exo/worker/engines/mlx/utils_mlx.py | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/src/exo/worker/engines/mlx/utils_mlx.py b/src/exo/worker/engines/mlx/utils_mlx.py
index 78f3be20..3199d6d9 100644
--- a/src/exo/worker/engines/mlx/utils_mlx.py
+++ b/src/exo/worker/engines/mlx/utils_mlx.py
@@ -2,6 +2,7 @@ import json
 import os
 import re
 import sys
+import tempfile
 import time
 from pathlib import Path
 from typing import Any, cast
@@ -98,14 +99,13 @@ def mlx_distributed_init(
     rank = bound_instance.bound_shard.device_rank
     logger.info(f"Starting initialization for rank {rank}")
 
-    coordination_file = None
-    try:
+    with tempfile.TemporaryDirectory() as tmpdir:
+        coordination_file = str(
+            Path(tmpdir) / f"hosts_{bound_instance.instance.instance_id}_{rank}.json"
+        )
         # TODO: singleton instances
         match bound_instance.instance:
             case MlxRingInstance(hosts_by_node=hosts_by_node, ephemeral_port=_):
-                coordination_file = (
-                    f"./hosts_{bound_instance.instance.instance_id}_{rank}.json"
-                )
                 hosts_for_node = hosts_by_node[bound_instance.bound_node_id]
                 hosts_json = HostList.from_hosts(hosts_for_node).model_dump_json()
 
@@ -128,9 +128,6 @@ def mlx_distributed_init(
                     jaccl_devices[i][i] is None for i in range(len(jaccl_devices))
                 )
                 # Use RDMA connectivity matrix
-                coordination_file = (
-                    f"./hosts_{bound_instance.instance.instance_id}_{rank}.json"
-                )
                 jaccl_devices_json = json.dumps(jaccl_devices)
 
                 with open(coordination_file, "w") as f:
@@ -150,10 +147,6 @@ def mlx_distributed_init(
         logger.info(f"Rank {rank} mlx distributed initialization complete")
 
         return group
-    finally:
-        with contextlib.suppress(FileNotFoundError):
-            if coordination_file:
-                os.remove(coordination_file)
 
 
 def initialize_mlx(