## The bug
Pasting `https://<workspace>.twenty.com/mcp` into an MCP client (Claude
connector, etc.) fails discovery. Curl shows why:
```bash
$ curl -si https://twentyfortwenty.twenty.com/.well-known/oauth-protected-resource
HTTP/2 200
...
{
\"resource\": \"http://{workspace}.twenty.com/mcp\",
\"authorization_servers\": [\"http://twentyfortwenty.twenty.com\"],
...
}
```
The response advertises `http://` even though the request came in on
`https://`. RFC 9728 / RFC 8707 require the client to validate that the
advertised `resource` matches the URL it connected to, so strict MCP
clients reject the mismatch and OAuth never starts.
## Why request.protocol returns \"http\"
Per [Express docs](https://expressjs.com/en/guide/behind-proxies.html),
`request.protocol` returns the socket-level protocol unless
`app.set('trust proxy', ...)` is configured. In our deployment:
```
client -- https --> Cloudflare -- https --> ingress-nginx -- http --> NestJS pod
```
TLS is terminated at the edge. The upstream TCP connection into the pod
is plain HTTP, and nginx sets `X-Forwarded-Proto: https` for the pod to
read. Without a `trust proxy` setting, Express ignores
`X-Forwarded-Proto` and `request.protocol === 'http'`.
`main.ts` currently has no `app.set('trust proxy', ...)` call anywhere.
## Why this only surfaced now
`grep -rn request.protocol` finds three pre-existing call sites —
`RestApiMetadataService`, `OpenApiService`, `RouteTriggerService`. All
three wrap it in `getServerUrl({ serverUrlEnv: SERVER_URL,
serverUrlFallback: \`${request.protocol}://${request.get('host')}\` })`,
which returns `SERVER_URL` whenever it's non-empty. In production
`SERVER_URL` is always set (e.g. \`api.twenty.com\`), so the
\`request.protocol\` branch is effectively dead code there.
#19755 introduced the first call site that uses `request.protocol`
unconditionally — the OAuth discovery controller has to echo the request
host, because the whole point is supporting multiple paste-able origins
(workspace subdomains, custom domains, etc.). That's why this is the
first \"wrong protocol\" bug anyone has seen in our app.
## The fix
One line in `main.ts`:
```ts
app.set('trust proxy', twentyConfigService.get('TRUST_PROXY'));
```
Backed by a new `TRUST_PROXY` env var with a default. `request.protocol`
then honors `X-Forwarded-Proto`, `request.ip` honors `X-Forwarded-For`,
etc. OAuth discovery URLs come out on the right scheme, and any future
`request.protocol` callers Just Work.
## Why this needs to be configurable (not hardcoded)
Twenty is open-source and deployed in at least three distinct
topologies:
1. **Kubernetes with ingress** (us, enterprise self-hosters) — TLS
terminated upstream, needs `trust proxy` **on**.
2. **Self-host behind a user-supplied reverse proxy** (Caddy, Traefik,
nginx — our [recommended
setup](https://twenty.com/developers/section/self-hosting)) — same as
above, needs `trust proxy` **on**.
3. **Self-host with NestJS exposed directly to the internet** — no
upstream proxy, needs `trust proxy` **off** (otherwise any curl with
`X-Forwarded-For: 1.2.3.4` spoofs `request.ip`, poisoning rate-limiters
and audit logs).
There is no single static value that's correct for all three. Express
makes this a setting for exactly this reason — we follow suit.
## Why the default is `'loopback, linklocal, uniquelocal'`
Shorthand for loopback (127/8, ::1), link-local (169.254/16, fe80::/10),
and unique-local (10/8, 172.16/12, 192.168/16, fc00::/7). In practical
terms: **trust peers coming from private networks; don't trust the
public internet**.
This default is correct for shapes 1 and 2 (cloud, proxied self-host)
because the ingress/proxy peer is always a private-network IP in every
sane deployment.
For shape 3 (directly exposed), the default is still safe because public
clients have public IPs, which are not in any of those ranges — so
`X-Forwarded-For` from an attacker on the internet is ignored. The only
way to be bitten is the exotic case where a public client reaches NestJS
through a private-network hop that isn't a proxy (e.g. a NAT appliance
that forwards to the pod on a private IP and blindly appends headers).
Narrow attack surface, and an operator running that kind of setup is
expected to configure `TRUST_PROXY=false` explicitly.
\"Safer than the naïve `true`, more useful than `false`\" — this matches
what Rails, Django, and many other frameworks recommend for
Kubernetes-style deployments.
## Why an env var instead of hardcoded
- Rejecting hardcoded `true`: would expose shape-3 self-hosters to IP
spoofing without a way to opt out.
- Rejecting hardcoded `false`: would leave cloud + shape-2 self-hosters
broken, same bug as today.
- Accepting string-typed env (not boolean): Express's `trust proxy`
accepts booleans, hop counts (`1`, `2`), IP ranges (`'10.0.0.0/8'`), and
named CIDRs (`'loopback'`). A boolean would hide that flexibility;
operators occasionally need the richer values. The string maps 1:1 onto
what Express accepts.
## Deployment matrix
| Deployment | Default works? | Override needed? |
|---|---|---|
| Cloud (us, K8s + nginx ingress + Cloudflare) | ✓ | — |
| Self-host behind reverse proxy (recommended) | ✓ | — |
| Self-host exposed directly on public IP | ✓ (public IPs not in private
ranges) | Optional: `TRUST_PROXY=false` for strictness |
| Local dev (direct, no proxy) | ✓ (no `X-Forwarded-*` headers arrive) |
— |
| Exotic: multi-hop through non-sanitizing private-network middlebox |
Risky | `TRUST_PROXY=false` |
## Related
- Blocks MCP connector OAuth on `<ws>.twenty.com` / custom domains.
After deploy: `curl -s
https://<ws>.twenty.com/.well-known/oauth-protected-resource | jq
.resource` should return `https://...` (not `http://...`).
- Fixes latent issue in `RestApiMetadataService`, `OpenApiService`,
`RouteTriggerService` fallback paths (pre-existing but dead in
production because `SERVER_URL` is always set — no behavior change
there).
## Test plan
- [x] `tsc --noEmit` clean
- [ ] After deploy: `curl -s
https://twentyfortwenty.twenty.com/.well-known/oauth-protected-resource`
returns `https://` URLs
- [ ] After deploy: MCP connector in Claude successfully completes OAuth
against `https://<ws>.twenty.com/mcp`
- [ ] No change in `request.ip` logging behavior on cloud (nginx-ingress
peer is already private-network, was already being trusted implicitly by
every framework layer that wasn't `request.protocol`)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Félix Malfait
b292a93376