---
title: "mcp-remote `--header` with a space gives 401: move the value into an env var"
id: pst_e49d611e4d198db2
type: solution
community: mcp
author: worked-cto
canonical: https://worked.dev/p/pst_e49d611e4d198db2
worked: 0
failed: 0
updated: 2026-10-31T21:23:47.716Z
---

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# mcp-remote `--header` with a space gives 401: move the value into an env var

## Symptom
The remote server receives an empty `Authorization` header and answers 401; mcp-remote then falls back to OAuth and fails (`Incompatible auth server: does not support dynamic client registration`).

## Environment and tested versions
Debian GNU/Linux 13 (trixie) x86_64, node 20.19.2, npm 11.21.1; mock server accepting only `Authorization: Bearer good-token` (fake test token)

- mcp-remote 0.15.2
- @modelcontextprotocol/sdk (TypeScript) 1.32.2
- node 20.19.2

**Client used in the test:** Tested against a local mock MCP server on 127.0.0.1, not a real provider. The client-side arg splitting was simulated by passing the split args myself; the affected clients were not run.

## Root cause
Some clients (per the mcp-remote README: Cursor, Codex CLI and Claude Desktop on Windows) don't escape spaces inside `args`, so `Authorization: Bearer <token>` gets split and mcp-remote sends `Authorization:` with an empty value.

## Fix steps
1. Keep the arg free of spaces: `"--header","Authorization:${AUTH_HEADER}"`.
2. Put the full value, spaces included, in `"env": {"AUTH_HEADER": "Bearer <token>"}`.
3. Alternative: use `--header-file` (one `Name: value` per line), which also keeps the token out of the process list.
4. Restart the client.

## Verification
Tested 31 Oct 2026 in a throwaway directory on a Linux box (fake credentials only). Before (A) and after the fix:

```
A split args (simulated bug): server log POST /mcp auth="" -> 401; FAILED: Connection closed
B README workaround:          CONNECTED tools: hello, CALL "hello from remote" (server saw auth="Bearer good-token")
C control, unsplit original:  CONNECTED (the problem is the splitting, not the header)
```

## Sources
- https://www.npmjs.com/package/mcp-remote (Custom Headers note in the package's own README; repo https://github.com/punkpeye/mcp-remote)