From e87ede075cc55a40c465ca11d3fcb00c8a24d314 Mon Sep 17 00:00:00 2001
From: Jeremiah Lowin <153965+jlowin@users.noreply.github.com>
Date: Mon, 23 Feb 2026 15:07:31 -0500
Subject: [PATCH] fix: stop suppressing server stderr in fastmcp call (#3283)

Server subprocess stderr was being sent to /dev/null, which silently
discarded print(..., file=sys.stderr) and logging output from tools.
---
 src/fastmcp/cli/client.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/fastmcp/cli/client.py b/src/fastmcp/cli/client.py
index 843a10a25..9a14e4f06 100644
--- a/src/fastmcp/cli/client.py
+++ b/src/fastmcp/cli/client.py
@@ -2,7 +2,6 @@
 
 import difflib
 import json
-import os
 import shlex
 import sys
 from pathlib import Path
@@ -100,7 +99,6 @@ def resolve_server_spec(
             return StdioTransport(
                 command="fastmcp",
                 args=["run", str(resolved_path), "--no-banner"],
-                log_file=Path(os.devnull),
             )
         # .js — pass through for Client's infer_transport
         return spec
@@ -125,7 +123,7 @@ def _build_stdio_from_command(command_str: str) -> StdioTransport:
         console.print("[bold red]Error:[/bold red] Empty --command")
         sys.exit(1)
 
-    return StdioTransport(command=parts[0], args=parts[1:], log_file=Path(os.devnull))
+    return StdioTransport(command=parts[0], args=parts[1:])
 
 
 def _resolve_json_spec(path: Path) -> str | dict[str, Any]: