Windows sandbox causes MCP startup failures for local named-pipe tools

What happened?

Codex reports:

MCP startup incomplete (failed: cocoindex-code)

The failing MCP server is configured as:

[mcp_servers.cocoindex-code]
command = "ccc"
args = ["mcp"]

The underlying local tool is healthy outside the Codex sandbox:

ccc daemon status
Daemon version: 0.2.33
No projects loaded.

ccc doctor
[OK] Model Check (indexing)
Embedding dimension: 384
[OK] Model Check (query)
Embedding dimension: 384

Inside the Codex sandbox, diagnostics/startup can fail with Windows named-pipe and network-related errors. For example:

PermissionError: [WinError 5] Access is denied
... multiprocessing.connection.PipeListener / CreateNamedPipe ...

And model metadata checks can fail while requesting HuggingFace URLs with:

[WinError 10013] An attempt was made to access a socket in a way forbidden by its access permissions

The daemon environment also includes CODEX_SANDBOX_NETWORK_DISABLED, which appears to affect local MCP tools that perform lazy network/model checks during startup.

Expected behavior

Trusted local MCP servers that use Windows named pipes should start reliably, or Codex should provide a clearer allowlist/opt-out path for local MCP servers that need named pipes and local daemon IPC.

If network is intentionally blocked, MCP startup errors should clearly identify sandbox policy as the cause instead of surfacing as a generic MCP startup failure.

Actual behavior

Codex shows a generic MCP startup failure, even though the same local tool works outside the sandbox. This makes the local dev environment look broken and requires manual daemon restarts or rerunning diagnostics outside the sandbox.

Environment

• OS: Windows
• Shell: PowerShell
• Codex sandbox: workspace-write / Windows sandbox
• MCP server: cocoindex-code via ccc mcp
• cocoindex-code version: 0.2.33
• Local daemon transport: Windows named pipe

Why this matters

This creates noisy false failures for local development setups that rely on MCP servers backed by local daemons, named pipes, and already-installed model caches. The underlying tool is functional, but Codex startup reports it as failed.