Merge branch 'fix/mcp_subprocess_stdin' into 'master'

fix(tools): detach MCP tool subprocess stdin from JSON-RPC pipe

Closes IDFGH-18123

See merge request espressif/esp-idf!51872
This commit is contained in:
Roland Dobai
2026-08-24 13:43:23 +02:00

View File

@@ -153,6 +153,9 @@ def action_extensions(base_actions: dict, project_path: str) -> dict:
mcp = _MCPServer('ESP-IDF')
# === TOOLS (Actions) ===
# Tool handlers spawn idf.py with stdin=subprocess.DEVNULL. The MCP server's
# stdin is the long-lived JSON-RPC transport pipe; a child that inherits it
# can hang instead of exiting.
@mcp.tool(description=f'Build the ESP-IDF project (runs `idf.py build`). {bound_hint}')
def build_project(project_dir: str | None = None) -> str:
"""Build the ESP-IDF project.
@@ -176,7 +179,7 @@ def action_extensions(base_actions: dict, project_path: str) -> dict:
'build',
]
print(f'INFO: Building project with command: {" ".join(cmd)} in path: {effective_dir}', file=sys.stderr)
result = subprocess.run(cmd, capture_output=True, text=True)
result = subprocess.run(cmd, capture_output=True, text=True, stdin=subprocess.DEVNULL)
if result.returncode == 0:
print('INFO: Build successful', file=sys.stderr)
return 'Successfully built project'
@@ -217,7 +220,7 @@ def action_extensions(base_actions: dict, project_path: str) -> dict:
target,
]
print(f'INFO: Setting target with command: {" ".join(cmd)} in path: {effective_dir}', file=sys.stderr)
result = subprocess.run(cmd, capture_output=True, text=True)
result = subprocess.run(cmd, capture_output=True, text=True, stdin=subprocess.DEVNULL)
if result.returncode == 0:
print(f'INFO: Target set to: {target}', file=sys.stderr)
return f'Target set to: {target}'
@@ -259,7 +262,7 @@ def action_extensions(base_actions: dict, project_path: str) -> dict:
effective_dir,
] + flash_args
print(f'INFO: Flashing project with command: {" ".join(cmd)} in path: {effective_dir}', file=sys.stderr)
result = subprocess.run(cmd, capture_output=True, text=True)
result = subprocess.run(cmd, capture_output=True, text=True, stdin=subprocess.DEVNULL)
if result.returncode == 0:
print('INFO: Flash successful', file=sys.stderr)
@@ -300,7 +303,7 @@ def action_extensions(base_actions: dict, project_path: str) -> dict:
name,
]
print(f'INFO: Creating project "{name}" in {parent_dir}', file=sys.stderr)
result = subprocess.run(cmd, capture_output=True, text=True)
result = subprocess.run(cmd, capture_output=True, text=True, stdin=subprocess.DEVNULL)
if result.returncode == 0:
project_path_new = os.path.join(parent_dir, name)
print(f'INFO: Project "{name}" created at {project_path_new}', file=sys.stderr)
@@ -336,7 +339,7 @@ def action_extensions(base_actions: dict, project_path: str) -> dict:
'clean',
]
print(f'INFO: Cleaning project with command: {" ".join(cmd)} in path: {effective_dir}', file=sys.stderr)
result = subprocess.run(cmd, capture_output=True, text=True)
result = subprocess.run(cmd, capture_output=True, text=True, stdin=subprocess.DEVNULL)
if result.returncode == 0:
print('INFO: Project cleaned successfully', file=sys.stderr)
return 'Project cleaned successfully'
@@ -434,15 +437,16 @@ def action_extensions(base_actions: dict, project_path: str) -> dict:
except Exception as e:
return f'Error getting devices: {str(e)}'
# Start the MCP server
print('MCP Server running on stdio...')
# Start the MCP server. Diagnostics should go to stderr — stdout is reserved
# for the JSON-RPC transport and any non-JSON bytes can confuse MCP clients.
print('MCP Server running on stdio...', file=sys.stderr)
try:
mcp.run()
except KeyboardInterrupt:
print('\nMCP Server stopped.')
print('\nMCP Server stopped.', file=sys.stderr)
except Exception as e:
print(f'MCP Server error: {e}')
print(f'MCP Server error: {e}', file=sys.stderr)
# Return the action extension
return {