docs/services/mcp-gateway.md

# MCP Gateway v2 — Operational

DinD MCP gateway on CT 104. Single OAuth-gated entry point fronting 24 MCP servers (mix of static, spawned, and Docker-catalog-bridged). Public via Zoraxy at `https://mcp.nuclide.systems` (→ `192.168.1.40:8080`).

## Architecture

- **Stack**: `ai/mcp-gateway/` — FastAPI app, container `mcp-gateway`.
- **Spawn model**: Docker-in-Docker. Each spawnable server runs as `mcp-<name>` on the `ai-internal` network with no host ports — servers talk over internal DNS.
- **Transport bridge**: generic streaming reverse proxy `https://mcp.nuclide.systems/<server>/<path>` → `http://<upstream>/<path>`. Transport-agnostic (streamable-HTTP `/mcp` and legacy SSE `/sse` + `/messages`). Registered last so specific routes win.
- **Auth**: Pocket ID. Two paths off the same OIDC app:
  - **MCP clients / API / proxy** — `Bearer` token, validated via OIDC userinfo (300 s TTL cache). `401` carries `WWW-Authenticate` + RFC 9728 `/.well-known/oauth-protected-resource` for discovery.
  - **Browser Web UI** — Authorization-Code flow with httpOnly session cookie. `/ui` and `/api/*` accept cookie or Bearer; `/{srv}/` stays Bearer-only.
- **Secrets**: per-server OAuth client secrets live in `ai/.env` (read via `os.environ`), never hardcoded.

## Server inventory (as of 2026-05-22)

26 servers configured in `mcp-gateway/config.json`. **Status: 26 healthy, 1 disabled (nextcloud re-enabled 2026-05-22).**

| Group | Server | Kind | Notes |
|---|---|---|---|
| **dev** | context7 | catalog | `mcp/context7` |
| | fetch | spawn | `mcp-server-fetch` via uvx |
| | git | catalog | `mcp/git` — Docker MCP Catalog; `mcp-git` bridge + DinD child |
| | gitlab | catalog | `mcp/gitlab` — `GITLAB_API_URL=https://gitlab.dlr.de/api/v4`; requires `--pass-environment` in bridge cmd |
| | kroki | static | `kroki-mcp:8000` (own stack) |
| | markitdown | catalog | `mcp/markitdown` |
| | sequential-thinking | catalog | `mcp/sequentialthinking` |
| | time | spawn | `mcp-server-time` |
| | docling | static | `docling-mcp:8000` |
| | coder | static | `coder-mcp:8000` |
| | shepard | static | `https://shepard.nuclide.systems/v2/mcp` |
| **research** | crawl4ai | spawn | `unclecode/crawl4ai` |
| | paper-search | catalog | `mcp/paper-search` — Docker MCP Catalog; replaces old `python:3.12-slim` inline approach |
| | searxng | spawn | `isokoliuk/mcp-searxng` |
| | wikipedia-mcp | catalog | |
| | youtube-transcript | catalog | `mcp/youtube-transcript` |
| **personal** | bluesky | static | `ariel-mcp:8000` |
| | gotify | spawn | |
| | home-assistant | static | `http://192.168.1.60:9583/private_...` (HA add-on) |
| | immich | spawn | |
| | memos | spawn | uses `MEMOS_TOKEN` from `.env` |
| | n8n | static | `https://n8n.nuclide.systems/mcp-server/http` |
| | nextcloud | spawn | `ghcr.io/cbcoutinho/nextcloud-mcp-server` — `single_user_basic` mode, `NEXTCLOUD_VERIFY_SSL=false`; app-password generated via `occ` for `fkrebs@nucli.de` 2026-05-22 |
| | unifi | spawn | |
| **image** | comfyui | static | `comfyui-mcp:8000` (own stack, see [comfyui.md](comfyui.md)) |
| **storage** | upload-artifact | static | `upload-artifact-mcp:8000` |

> **Catalog bridge env var passthrough**: `mcp-proxy`'s `stdio_client` uses a sanitized env (`get_default_environment()`), stripping custom vars. For catalog servers that need env vars (e.g. `gitlab`), the bridge command **must** include `--pass-environment` so Docker CLI can resolve `-e KEY` passthrough from the bridge container's env.

> **Nextcloud server count**: 27 total (26 enabled + nextcloud now re-enabled 2026-05-22). Gateway updated to persist `enabled` flag across restarts.

## Client registration

### Easy path — `/mcp-config` download

The gateway hands back a ready-to-use config blob for the signed-in user:

```
GET https://mcp.nuclide.systems/mcp-config?format=claude   # default
GET https://mcp.nuclide.systems/mcp-config?format=cursor
GET https://mcp.nuclide.systems/mcp-config?format=raw      # token + URLs
```

- Requires Pocket-ID session cookie or existing Bearer (303 → `/login` otherwise).
- Mints a fresh long-lived gateway token (`mcp_<urlsafe>`) bound to the user; persisted in `gateway_tokens.json` with `purpose=client-config:<format>` so it's distinguishable from OAuth-issued tokens and revocable.
- Returns JSON with `Content-Disposition: attachment`.

**Claude Code workflow:**
1. Sign in at `https://mcp.nuclide.systems`.
2. Click **Claude config** in the top nav → browser downloads `nuclide-mcp.claude.json`.
3. Merge the `mcpServers` block into `~/.claude/settings.json`. Restart Claude Code.

The downloaded file has one entry per enabled MCP server, with `type: http` + `url: https://mcp.nuclide.systems/<server>/mcp` + `Authorization: Bearer ...` header. No per-server config needed.

### Manual

**LobeChat** — Settings → Skills → Skill Store → Custom → Import JSON:

```json
{ "mcpServers": { "comfyui": { "type": "http",
  "url": "https://mcp.nuclide.systems/comfyui/mcp",
  "auth": { "type": "bearer", "accessToken": "<pocket-id token>" } } } }
```

(For ComfyUI specifically, LobeChat can also connect straight to `http://comfyui-mcp:8000/mcp` internally — see [comfyui.md](comfyui.md) — no token.)

**Claude.ai** — add `https://mcp.nuclide.systems/<server>/mcp` as a custom connector; auth is discovered via the protected-resource metadata.

### Token rotation

Each `/mcp-config` download mints a NEW token. Old tokens stay valid until removed from `gateway_tokens.json` (manual prune; future: admin UI button).

## Ops

```bash
cd /opt/stacks/ai/mcp-gateway && docker compose up -d --build
docker logs mcp-gateway
```

UI: `https://mcp.nuclide.systems/ui` (Pocket-ID-gated; `/login` to sign in).

Config: `mcp-gateway/config.json` (live config, persisted). Timestamped backups created on every edit (`config.json.bak.YYYYMMDD-HHMMSS`).

### Add or enable a server

1. Edit `mcp-gateway/config.json` — add an `mcpServers.<name>` entry (or set `enabled: true`).
2. Restart the gateway: `docker restart mcp-gateway`.
3. Spawn servers come up on demand via `POST /api/servers/<name>/start` (bearer); or `POST /api/servers/bulk/start` for all.

### Disable a server

Set `mcpServers.<name>.enabled = false` and add `disabled_reason`. Stop+rm the container (`docker stop mcp-<name> && docker rm mcp-<name>`); the gateway will not re-spawn it.

### UI check (Playwright)

Live UI is auth-gated, so the local check serves the template + mocks `/api/servers`:

```bash
uv run --with playwright -- python -m playwright install chromium   # once
uv run --with playwright -- python ai/mcp-gateway/ui_check.py        # -> /tmp/mcp_ui.png
```

## Verified end-to-end

- `/health` 200 (no auth); `/.well-known/oauth-protected-resource` JSON (no auth).
- `/mcp.json`, `/<server>/mcp` → 401 without token; correct `WWW-Authenticate`.
- Static upstreams (`bluesky`, `coder`, `comfyui`, `docling`, `kroki`, `upload-artifact`) — endpoints reachable from inside `ai-internal` (406/405 to plain GET, which is the correct MCP behavior).
- All spawn/catalog containers up (`docker ps mcp-*`): 16/17 (nextcloud disabled; git/gitlab/paper-search added 2026-05-22).