---
title: 🔀 Dev Server Routing
description: code-server built-in proxy routes, framework caveats, and why pretty per-port subdomains are not configured here
source: verified deployment on the loca operator host, 2026-08-19
reviewed: 2026-08-19
---

# 🔀 Dev Server Routing

## Why No Pretty Subdomains

Pretty per-port subdomain proxying (`proxy-domain`) is intentionally not configured because:

- DNS is not the blocker — multi-label wildcards do resolve on this host; `3000.cdsr.loca.zone` and deeper names all answer with the host address
- TLS certificate issuance is the blocker — the `cdsr.loca.zone` lineage covers exactly two SANs: `cdsr.loca.zone` and `wiki.cdsr.loca.zone`
- A `*.cdsr.loca.zone` certificate would require DNS-01 validation with DNS-provider API credentials, which are not configured on this host
- HTTP-01 via webroot (the method used for every lineage here) cannot issue wildcard certificates at all
- Therefore per-port hostnames would serve a name mismatch to the browser; code-server's built-in `/proxy/<port>/` and `/absproxy/<port>/` routes remain the supported routes and need no new certificate

See upstream: [Accessing web services — Using a subdomain](https://coder.com/docs/code-server/guide#using-a-subdomain) about requiring a DNS entry per port and wildcard TLS support.

## Default Route: `/proxy/<port>/`

The default subpath proxy strips the `/proxy/<port>` prefix before forwarding to the dev server.

Worked example:

```bash
# In code-server integrated terminal (binds 127.0.0.1 only)
python3 -m http.server 52325 --bind 127.0.0.1
```

Then open:

```
https://cdsr.loca.zone/proxy/52325/
```

- Trailing slash matters, always use it
- Dev server must bind `127.0.0.1`, not `0.0.0.0`
- Port must not collide with code-server loopback port `52224`
- Ad-hoc dev-server ports must avoid every port in the AGENTS.md `port_convention` registry (52222 pwiz, 52223 reserved for pwiz, 52224 cdsr, 52226 code) and must be checked with `ss -ltn` before binding — an ad-hoc listener inside 51000-53000 can shadow a registered backend and block that service's restart

Upstream: [Using a subpath](https://coder.com/docs/code-server/guide#using-a-subpath)

## Path-Preserving Route: `/absproxy/<port>/`

Use `/absproxy/<port>/` when the framework needs the request path preserved and not stripped.

| Route | Path sent to dev server |
| --- | --- |
| `/proxy/3000/app/path` | `/app/path` |
| `/absproxy/3000/app/path` | `/absproxy/3000/app/path` |

Upstream: [Stripping `/proxy/<port>` from the request path](https://coder.com/docs/code-server/guide#stripping-proxyport-from-the-request-path)

## Framework Caveat Table

| Framework | Route | Required config |
| --- | --- | --- |
| React / create-react-app | `/absproxy/<port>/` | `PUBLIC_URL=/absproxy/<port>` and `WDS_SOCKET_PATH=$PUBLIC_URL/sockjs-node` |
| Vue (Vue CLI) | `/absproxy/<port>/` | `publicPath: "/absproxy/<port>"` and `devServer.sockPath: "sockjs-node"` |
| Angular | `/absproxy/<port>/` | `<base href="./">` in `src/index.html` and `--serve-path /absproxy/<port>` in `ng serve` |
| Svelte (SvelteKit) | `/absproxy/<port>/` | `kit.paths.base: "/absproxy/<port>"` in `svelte.config.js` |

Notes:

- React requirement source: [Proxying to create a React app](https://coder.com/docs/code-server/guide#proxying-to-create-a-react-app)
- Vue requirement source: [Proxying to a Vue app](https://coder.com/docs/code-server/guide#proxying-to-a-vue-app)
- Angular requirement source: [Proxying to an Angular app](https://coder.com/docs/code-server/guide#proxying-to-an-angular-app)
- Svelte requirement source: [Proxying to a Svelte app](https://coder.com/docs/code-server/guide#proxying-to-a-svelte-app)
- HMR note: websocket-driven HMR needs Nginx headers already configured in the app block (`proxy_read_timeout 86400`, `Upgrade $http_upgrade`, `Connection $connection_upgrade`)

## Troubleshooting Checklist

- Dev server binds to `0.0.0.0` only; set `--bind 127.0.0.1` or `--host 127.0.0.1`
- Missing trailing slash (`/proxy/52325` versus `/proxy/52325/`)
- Proxy port equals `52224`
- Assets load from `/` and not the proxied prefix, indicating a base path mismatch
- HMR fails to connect, confirm websocket forwarding and timeout headers in Nginx
- CORS/preflight issues on custom auth chains, see `--skip-auth-preflight` if auth is enabled

## Source URLs (read during this task)

- https://coder.com/docs/code-server/guide
- https://coder.com/docs/code-server/guide#using-a-subdomain
- https://coder.com/docs/code-server/guide#using-a-subpath
- https://coder.com/docs/code-server/guide#stripping-proxyport-from-the-request-path
- https://coder.com/docs/code-server/guide#proxying-to-create-a-react-app
- https://coder.com/docs/code-server/guide#proxying-to-a-vue-app
- https://coder.com/docs/code-server/guide#proxying-to-an-angular-app
- https://coder.com/docs/code-server/guide#proxying-to-a-svelte-app
- https://coder.com/docs/code-server/guide#preflight-requests