---
title: mcp-bridge
sdk: docker
app_port: 7860
---

# mcp-bridge

Authenticated MCP-over-SSE bridge for Hugging Face Spaces, with OAuth support for ChatGPT remote MCP clients.

Public endpoints are intentionally quiet:

```json
{"ok": true}
```

MCP endpoint:

```txt
https://patdev-mcp-bridge.hf.space/sse
```

## Required Space secrets / variables

Secret:

```txt
MCP_API_KEY=<your-long-random-access-key>
```

Recommended variable:

```txt
PUBLIC_BASE_URL=https://patdev-mcp-bridge.hf.space
```

Optional secret to invalidate OAuth tokens independently from `MCP_API_KEY`:

```txt
MCP_OAUTH_SIGNING_KEY=<another-long-random-secret>
```

## ChatGPT remote MCP

Use this URL in ChatGPT:

```txt
https://patdev-mcp-bridge.hf.space/sse
```

If ChatGPT can use Dynamic Client Registration, it should discover OAuth automatically. During the OAuth authorization page, enter your `MCP_API_KEY` once.

If ChatGPT says DCR/CIMD is unavailable, use manual OAuth:

```txt
OAuth client ID: chatgpt
OAuth client secret: leave empty
Token endpoint auth method: none
Scopes: mcp
```

No callback URL needs to be pasted by default. The bridge accepts ChatGPT callback URLs matching:

```txt
https://chatgpt.com/connector/oauth/*
```

Sync with:

```powershell
python .\scripts\sync_hf.py --space-id patdev/mcp-bridge --api-key "YOUR_LONG_RANDOM_KEY" --restart
```

Using the PowerShell wrapper:

```powershell
powershell -ExecutionPolicy Bypass -File .\scripts\sync_hf.ps1 -ApiKey "YOUR_LONG_RANDOM_KEY" -Restart
```

For stricter security, you may still force an exact redirect allowlist by setting:

```powershell
python .\scripts\sync_hf.py --space-id patdev/mcp-bridge --api-key "YOUR_LONG_RANDOM_KEY" --chatgpt-callback-url "EXACT_CHATGPT_CALLBACK_URL" --restart
```

## OAuth endpoints included

```txt
/.well-known/oauth-protected-resource
/.well-known/oauth-authorization-server
/oauth/register
/oauth/authorize
/oauth/token
/oauth/revoke
/oauth/jwks
```

## Manual auth still works

For non-ChatGPT clients, these still work:

```txt
Authorization: Bearer <MCP_API_KEY>
```

or:

```txt
x-api-key: <MCP_API_KEY>
```

## Generate a key

```powershell
python -c "import secrets; print(secrets.token_urlsafe(48))"
```

## Notes

- `/` and `/health` reveal only `{"ok": true}`.
- OAuth client registrations and pending authorization codes are in memory.
- Manual ChatGPT OAuth accepts `https://chatgpt.com/connector/oauth/*` unless `OAUTH_ALLOWED_REDIRECT_URIS` is set.
- OAuth access/refresh tokens are stateless signed tokens.
- Rotate `MCP_OAUTH_SIGNING_KEY` or `MCP_API_KEY` to invalidate all OAuth tokens.
- `mcp_connect` expects an HTTP(S) MCP URL such as `https://example.com/sse` or `http://127.0.0.1:4000/mcp`; bare remote hosts are normalized to `https://...`, while `localhost`/`127.0.0.1` targets are normalized to `http://...`.
- `mcp_connect` now accepts optional `bearer_token` and `x_api_key` arguments for protected upstream MCP servers and verifies the remote endpoint by default during connect.
- If you do not want to pass remote credentials on each call, set `REMOTE_MCP_BEARER_TOKEN` or `REMOTE_MCP_X_API_KEY` in the bridge environment and they will be applied automatically when explicit auth headers are absent.
- FastMCP tool results are serialized as text-first when a tool returns mixed text plus image content, so the bridge emits image-only outputs whenever the upstream result includes images. This preserves screenshot rendering in hosts that otherwise hide the image behind the leading text item.
- For Windows-MCP specifically, `Snapshot` only includes an actual screenshot when called with `use_vision=true`; plain `Snapshot` calls can legitimately return text-only desktop state.
- Bridge sessions created by `mcp_connect` are in memory and reset when the Space restarts or sleeps.