DXT doesn't preserve binary executable permissions during packaging

[ishaq-fynd]

Summary

When creating a DXT package with dxt pack, the binary files lose their executable permissions, causing EACCES errors when Claude tries to run the MCP server.

Steps to Reproduce

1. Create a Go binary: go build -o server/some_binary main.go
2. Set executable permissions: chmod +x server/some_binary
3. Create DXT package: dxt pack
4. Install the DXT in Claude
5. Try to use the MCP server

Expected Behavior

The binary should retain executable permissions and run without errors.

Actual Behavior

Claude fails to spawn the binary with EACCES error, requiring manual chmod +x on the extracted binary.

Error Log

2025-06-27T14:32:13.870Z [some-mcp-server] [error] spawn /Users/username/Library/Application Support/Claude/Claude Extensions/local.dxt.example.some-mcp-server/server/some_binary EACCES {
  metadata: {
    context: 'connection',
    stack: 'Error: spawn /Users/username/Library/Application Support/Claude/Claude Extensions/local.dxt.example.some-mcp-server/server/some_binary EACCES\n' +
      '    at ChildProcess._handle.onexit (node:internal/child_process:285:19)\n' +
      '    at onErrorNT (node:internal/child_process:483:16)\n' +
      '    at process.processTicksAndRejections (node:internal/process/task_queues:90:21)'
  }
}

Environment

• OS: macOS
• DXT CLI Version: 0.1.0
• Node.js Version: v22.15.1
• Claude Version: Claude 0.11.3 (58ae3f) 2025-06-26T02:57:32.000Z

Manifest Configuration

{
  "server": {
    "type": "binary",
    "entry_point": "server/some_binary",
    "args": ["--transport", "stdio"],
    "env": {
        "HOME": "${HOME}"
      }
  }
}

Workaround

After DXT installation, manually run:

chmod +x "/Users/username/Library/Application Support/Claude/Claude Extensions/local.dxt.*/server/some_binary"

Proposed Solution

The DXT packaging process should:

1. Preserve file permissions when creating the ZIP archive
2. Or automatically set executable permissions for files specified in entry_point
3. Or provide a permissions field in manifest.json to specify required permissions

Related

This affects any DXT package using compiled binaries (Go, Rust, C++, etc.) and likely impacts other users creating binary-based MCP servers.

[danielmackay]

I've run into this issue also. I was able to workaround by manually adding executable permissions as suggested above.

Need a proper solution to this as manually having to run commands defeats the purpose of making MCPs easy to install.

[bryan-anthropic]

Permission preservation has been addressed on the mcpb CLI side: pack (#14) now captures Unix file permissions in ZIP external attributes, and unpack (#43) restores them via chmodSync. These fixes are included in the current release.

If executable permissions are still lost when installing via Claude Desktop, that would be related to Claude Desktop's own unpacking behavior, which uses separate code. See #13 for related discussion.

Closing as resolved on the mcpb CLI side.