Translation API

Self-hosted translation backend. It runs LibreTranslate behind an auth-proxy, so only signed-in, authorized plugin users can reach it — LibreTranslate itself is never exposed to the public internet.

Stack

• LibreTranslate — the translation engine
• Redis — backing store for the auth-proxy
• auth-proxy — the only service that is publicly reachable; everything goes through it

Requirements

• Docker and Docker Compose
• A reverse proxy on the host (e.g. Caddy) to terminate TLS for your domain and forward to the auth-proxy's port
• A Discord application: https://discord.com/developers/applications

Discord application setup

1. Create an application at the link above.
2. Under OAuth2, add a redirect URL matching whatever you set DISCORD_REDIRECT_URI to (e.g. https://translate.example.com/auth/callback).
3. Copy the Client ID and Client Secret into your .env.

Configuration

Copy the example env file and fill it in:

cp .env.example .env

Variable	Description
PUBLIC_BASE_URL	The public URL the auth-proxy is served at (behind your reverse proxy).
DISCORD_CLIENT_ID	From your Discord application.
DISCORD_CLIENT_SECRET	From your Discord application.
DISCORD_GUILD_ID	The ID of the Discord server users must belong to.
DISCORD_REDIRECT_URI	Must exactly match the redirect URL registered on the Discord application.
SESSION_JWT_SECRET	Random secret used to sign session tokens. Generate with openssl rand -base64 48.

PORT, REDIS_URL, and LIBRETRANSLATE_URL are also in .env.example with sensible defaults; Docker Compose overrides them for the containers automatically, so you generally only need to touch them for local, non-Docker development. Additional tuning knobs (timeouts, rate limits, etc.) live in src/config.ts and all have working defaults.

Running

docker compose up -d --build

This starts libretranslate, redis, and auth-proxy. Only auth-proxy publishes a port to the host (127.0.0.1:47281 by default) — point your host's reverse proxy at that port for your public domain.

Local development (without Docker)

bun install
bun run dev

Requires a Redis instance and a LibreTranslate instance reachable at whatever you set REDIS_URL / LIBRETRANSLATE_URL to in .env.

API

GET /auth/login

Redirects the user to Discord's OAuth consent screen.

GET /auth/callback

Discord redirects here after the user consents. On success, responds with:

{ "accessToken": "...", "refreshToken": "...", "expiresIn": 900 }

Use accessToken as a bearer token when calling /translate. Hold on to refreshToken so the plugin can get a new session without sending the user through Discord's consent screen again.

If the account doesn't meet the access requirements, the callback responds with an error instead of tokens.

POST /auth/refresh

{ "refreshToken": "..." }

Returns a new accessToken / refreshToken pair. Each refresh token can only be used once.

POST /translate

Requires Authorization: Bearer <accessToken>.

{ "q": "text to translate", "source": "auto", "target": "en" }

Returns whatever LibreTranslate's /translate endpoint returns.