Server-filesystem Child Process Exits With Code=1 When Launched By Mcp-superassistant-proxy
Description
The mcp-superassistant-proxy (version 0.0.6) fails to connect to @modelcontextprotocol/server-filesystem when it's configured as an stdio server. The child process for @modelcontextprotocol/server-filesystem exits with code=1 shortly after the proxy sends the initialize JSON-RPC message, leading to a connection timeout.
This issue occurs despite the following:
@modelcontextprotocol/server-filesystemruns without immediately crashing when executed directly vianpxin the terminal.- A custom minimal Node.js stdio MCP server (see details below) connects and communicates successfully with
mcp-superassistant-proxy, indicating the proxy's basic stdio child process management is functional. @modelcontextprotocol/server-filesystemreportedly works correctly with other MCP clients (e.g., Claude Desktop), suggesting an incompatibility or issue specific to its interaction withmcp-superassistant-proxy.
Environment
mcp-superassistant-proxyVersion:0.0.6- Server Package:
@modelcontextprotocol/server-filesystem(latest version vianpx -y) - Operating System: Windows 11
- Node.js Version:
v23.10.0
Configuration (mcptestconfig.json)
{
"mcpServers": {
"filesystem": {
"command": "npx",
"args": [
"-y",
"@modelcontextprotocol/server-filesystem",
"C:/Users/theuser/Documents/Projects/show_start_menu_Copy"
]
}
}
}
(Note: The issue also occurred when using simple local paths like C:/mcptemp/dir1)
Observed Behavior (Proxy Log Output)
When running npx @srbhptl39/mcp-superassistant-proxy@latest --config "path/to/mcptestconfig.json":
[mcp-superassistant-proxy] Loading configuration from: C:\Users\theuser\Documents\u\mcptools\mcptestconfig.json
[mcp-superassistant-proxy] Resolved config path to: C:\Users\theuser\Documents\u\mcptools\mcptestconfig.json
[mcp-superassistant-proxy] Starting proxy server...
[mcp-superassistant-proxy] - port: 3006
[mcp-superassistant-proxy] - baseUrl: http://localhost:3006
[mcp-superassistant-proxy] - ssePath: /sse
[mcp-superassistant-proxy] - messagePath: /message
[mcp-superassistant-proxy] - heartbeat interval: 30000ms
[mcp-superassistant-proxy] - Connected servers: filesystem
{"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{},"clientInfo":{"name":"mcp-superassistant-proxy","version":"0.0.6"}},"jsonrpc":"2.0","id":0}
[mcp-superassistant-proxy] Child process "filesystem" exited: code=1, signal=null
{"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":0reason":"McpError: MCP error -32001: Request timed out"}}
[mcp-superassistant-proxy] Failed to connect to servers: filesystem
[mcp-superassistant-proxy] - Failed to connect to stdio server "filesystem": MCP error -32001: Request timed out
[mcp-superassistant-proxy] No MCP servers could be connected. The proxy will start but will not be functional.
[mcp-superassistant-proxy] Connected to 0 of 1 servers
[mcp-superassistant-proxy] Proxy server listening on port 3006
...
Expected Behavior
The mcp-superassistant-proxy should successfully connect to the @modelcontextprotocol/server-filesystem and log Connected to 1 of 1 servers without the child process exiting prematurely.
Troubleshooting Steps Performed
Direct Execution of Filesystem Server
Running npx -y @modelcontextprotocol/server-filesystem "PATH1" "PATH2" directly in the terminal starts the server, and it outputs:
Secure MCP Filesystem Server running on stdio
Allowed directories: [ ... ]
It does not crash immediately, indicating the server package itself can start.
Simplified Paths
The issue persists even when the paths provided in mcptestconfig.json are changed to simple local directories (e.g., C:/mcptemp/dir1).
Custom Minimal Stdio MCP Server Test
A minimal Node.js script (test-stdio.js, see content below) acting as a compliant MCP server was configured in mcptestconfig.json:
- Configuration:
// mcptestconfig.json using test-stdio.js "mcpServers" } }
This minimal server **connects successfully** to `mcp-superassistant-proxy`:
* **Log Output:**
```log
[mcp-superassistant-proxy] ...
{"method":"initialize","params":{"protocolVersion":"2025-03-26", ...},"jsonrpc":"2.0","id":0}
{"method":"notifications/initialized","jsonrpc":"2.0"}
[mcp-superassistant-proxy] Connected to 1 of 1 servers
[mcp-superassistant-proxy] Proxy server listening on port 3006
...
* **Content of `test-stdio.js` (v3) used for successful test:**
```javascript
// test-stdio.js (Corrected Version 3) process.stderr.write("Minimal test-stdio.js server (v3) started.\n");
const initializeResponse = jsonrpc, capabilities: {} } };
process.stderr.write("Minimal test-stdio.js (v3) preparing to send initialize response.\n"); process.stdout.write(JSON.stringify(initializeResponse) + '\n'); process.stderr.write("Minimal test-stdio.js (v3) sent initialize response.\n");
let incomingData = '';
process.stdin.on('data', (chunk) =>
incomingData += chunk;
let newlineIndex;
while ((newlineIndex = incomingData.indexOf('\n')) !== -1) {
const messageString = incomingData.substring(0, newlineIndex);
incomingData = incomingData.substring(newlineIndex + 1);
if (messageString) {
process.stderr.write(`test-stdio.js (v3) received raw\n); try { const message = JSON.parse(messageString); process.stderr.write(test-stdio.js (v3) received parsed method: $message.method}, id\n); if (message.id !== undefined && message.id !== null) { const genericResponse = { jsonrpc: "2.0", id: message.id, result: { status: "received", method: message.method || "notification" } }; process.stdout.write(JSON.stringify(genericResponse) + '\n'); process.stderr.write(test-stdio.js (v3) sent generic response for id $message.id}.\n); } } catch (e) { process.stderr.write(test-stdio.js (v3) error parsing JSON on data: ${messageString}\n`);
}
}
}
});
process.stdin.on('end', () => { process.stderr.write("Minimal test-stdio.js (v3) stdin ended. Exiting.\n"); process.exit(0); });
This confirms that the proxy's basic stdio child process management and MCP handshake mechanism are functional with a compliant server.
### Works with Other MCP Clients
The `@modelcontextprotocol/server-filesystem` works correctly with other MCP client applications (e.g., Claude Desktop).
## Conclusion/Hypothesis
The `code=1` exit of `@modelcontextprotocol/server-filesystem` appears to be specific to its interaction with `mcp-superassistant-proxy`. It's likely crashing after receiving the `initialize` message from the proxy, possibly due to:
* An issue within `@modelcontextprotocol/server-filesystem` when processing the `initialize` parameters sent by this specific proxy (e.g., the `clientInfo` or empty `capabilities` object).
* A subtle difference in how `mcp-superassistant-proxy` manages stdio or the child process environment on Windows that affects `@modelcontextprotocol/server-filesystem` negatively, but not simpler scripts.
Given that a minimal compliant MCP server works with the proxy, and `@modelcontextprotocol/server-filesystem` works with other clients, the incompatibility seems to lie in the specific handshake or environment setup between these two particular pieces of software.
## Steps to Reproduce
1. **Install Node.js on Windows 11.**
2. **Create the `mcptestconfig.json` file as specified above.** (Using example paths `C:/Users/theuser/Documents/Projects/show_start_menu_Copy` and `C:/Users/theuser/Documents/Projects/VoiceAssistant - Copy` or any other accessible directories).
3. **Run<br/>
# server-filesystem child process exits with code=1 when launched by mcp-superassistant-proxy
## Q&A
### Q: What is the issue with `mcp-superassistant-proxy` and `@modelcontextprotocol/server-filesystem`?
A: The `mcp-superassistant-proxy` (version 0.0.6) fails to connect to `@modelcontextprotocol/server-filesystem` when it's configured as an stdio server. The child process for `@modelcontextprotocol/server-filesystem` exits with `code=1` shortly after the proxy sends the `initialize` JSON-RPC message, leading to a connection timeout.
### Q: What are the symptoms of this issue?
A: The proxy logs show the following error:
```log
[mcp-superassistant-proxy] Child process "filesystem" exited: code=1, signal=null
{"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":0,"reason":"McpError: MCP error -32001: Request timed out"}}
[mcp-superassistant-proxy] Failed to connect to servers: filesystem
[mcp-superassistant-proxy] - Failed to connect to stdio server "filesystem": MCP error -32001: Request timed out
Q: What troubleshooting steps have been performed?
A: The following troubleshooting steps have been performed:
- Direct Execution of Filesystem Server: Running
npx -y @modelcontextprotocol/server-filesystem "PATH1" "PATH2"directly in the terminal starts the server, and it outputs:
Secure MCP Filesystem Server running on stdio Allowed directories: [ ... ]
It does not crash immediately, indicating the server package itself can start.
2. **Simplified Paths:** The issue persists even when the paths provided in `mcptestconfig.json` are changed to simple local directories (e.g., `C:/mcptemp/dir1`).
3. **Custom Minimal Stdio MCP Server Test:** A minimal Node.js script (`test-stdio.js`, see content below) acting as a compliant MCP server was configured in `mcptestconfig.json`:
* **Configuration:**
```json
// mcptestconfig.json using test-stdio.js
{
"mcpServers": {
"filesystem": {
"command": "node",
"args": ["C:/path/to/your/test-stdio.js"]
}
}
}
This minimal server **connects successfully** to `mcp-superassistant-proxy`:
* **Log Output:**
```log
[mcp-superassistant-proxy] ... "method","jsonrpc":"2.0","id":0} "method" [mcp-superassistant-proxy] Connected to 1 of 1 servers [mcp-superassistant-proxy] Proxy server listening on port 3006 ...
* **Content of `test-stdio.js` (v3) used for successful test:**
```javascript
// test-stdio.js (Corrected Version 3)
process.stderr.write("Minimal test-stdio.js server (v3) started.\n");
const initializeResponse = {
jsonrpc: "2.0",
id: 0,
result: {
protocolVersion: "2025-03-26",
serverInfo: {
name: "test-stdio-server",
version: "1.0.0"
},
capabilities: {}
}
};
process.stderr.write("Minimal test-stdio.js (v3) preparing to send initialize response.\n");
process.stdout.write(JSON.stringify(initializeResponse) + '\n');
process.stderr.write("Minimal test-stdio.js (v3) sent initialize response.\n");
let incomingData = '';
process.stdin.on('data', (chunk) => {
incomingData += chunk;
let newlineIndex;
while ((newlineIndex = incomingData.indexOf('\n')) !== -1) {
const messageString = incomingData.substring(0, newlineIndex);
incomingData = incomingData.substring(newlineIndex + 1);
if (messageString) {
process.stderr.write(`test-stdio.js (v3) received raw: ${messageString}\n`);
try {
const message = JSON.parse(messageString);
process.stderr.write(`test-stdio.js (v3) received parsed method: ${message.method}, id: ${message.id}\n`);
if (message.id !== undefined && message.id !== null) {
const genericResponse = {
jsonrpc: "2.0",
id: message.id,
result: { status: "received", method: message.method || "notification" }
};
process.stdout.write(JSON.stringify(genericResponse) + '\n');
process.stderr.write(`test-stdio.js (v3) sent generic response for id ${message.id}.\n`);
}
} catch (e) {
process.stderr.write(`test-stdio.js (v3) error parsing JSON: ${e.message} on data: ${messageString}\n`);
}
}
}
});
process.stdin.on('end', () => {
process.stderr.write("Minimal test-stdio.js (v3) stdin ended. Exiting.\n");
process.exit(0);
});
This confirms that the proxy's basic stdio child process management and MCP handshake mechanism are functional with a compliant server.
Q: What is the expected behavior?
A: The mcp-superassistant-proxy should successfully connect to the @modelcontextprotocol/server-filesystem and log Connected to 1 of 1 servers without the child process exiting prematurely.
Q: What are the possible causes of this issue?
A: The possible causes of this issue are:
- An issue within
@modelcontextprotocol/server-filesystemwhen processing theinitializeparameters sent by this specific proxy (e.g., theclientInfoor emptycapabilitiesobject). - A subtle difference in how
mcp-superassistant-proxymanages stdio or the child process environment on Windows that affects@modelcontextprotocol/server-filesystemnegatively, but not simpler scripts.
Q: How can this issue be reproduced?
A: To reproduce this issue, follow these steps:
- Install Node.js on Windows 11.
- Create the
mcptestconfig.jsonfile as specified above. (Using example pathsC:/Users/theuser/Documents/Projects/show_start_menu_CopyandC:/Users/theuser/Documents/Projects/VoiceAssistant - Copyor any other accessible directories). - Run
npx @srbhptl39/mcp-superassistant-proxy@latest --config "path/to/mcptestconfig.json".