Merge pull request #329 from diegosouzapw/fix/issue-318-readme-oauth-en

docs: add English Remote OAuth guide to README (#318)

README.md

@@ -1508,11 +1508,102 @@ opencode
 - OmniRoute v1.0.6+ includes fallback validation via chat completions
 - Ensure base URL includes `/v1` suffix
 
-### 🔐 OAuth em Servidor Remoto (Remote OAuth Setup)
+### 🔐 OAuth on a Remote Server
 
+<a name="oauth-on-a-remote-server"></a>
 <a name="oauth-em-servidor-remoto"></a>
 
-> **⚠️ IMPORTANTE para usuários com OmniRoute em VPS/Docker/servidor remoto**
+> **⚠️ Important for users running OmniRoute on a VPS, Docker, or any remote server**
+
+#### Why does Antigravity / Gemini CLI OAuth fail on remote servers?
+
+The **Antigravity** and **Gemini CLI** providers use **Google OAuth 2.0**. Google requires the `redirect_uri` in the OAuth flow to exactly match one of the pre-registered URIs in the app's Google Cloud Console.
+
+The OAuth credentials bundled in OmniRoute are registered **for `localhost` only**. When you access OmniRoute on a remote server (e.g. `https://omniroute.myserver.com`), Google rejects the authentication with:
+
+```
+Error 400: redirect_uri_mismatch
+```
+
+#### Solution: Configure your own OAuth credentials
+
+You need to create an **OAuth 2.0 Client ID** in Google Cloud Console with your server's URI.
+
+#### Step-by-step
+
+**1. Open Google Cloud Console**
+
+Go to: [https://console.cloud.google.com/apis/credentials](https://console.cloud.google.com/apis/credentials)
+
+**2. Create a new OAuth 2.0 Client ID**
+
+- Click **"+ Create Credentials"** → **"OAuth client ID"**
+- Application type: **"Web application"**
+- Name: anything you like (e.g. `OmniRoute Remote`)
+
+**3. Add Authorized Redirect URIs**
+
+In the **"Authorized redirect URIs"** field, add:
+
+```
+https://your-server.com/callback
+```
+
+> Replace `your-server.com` with your server's domain or IP (include the port if needed, e.g. `http://45.33.32.156:20128/callback`).
+
+**4. Save and copy the credentials**
+
+After creating, Google will show the **Client ID** and **Client Secret**.
+
+**5. Set environment variables**
+
+In your `.env` (or Docker environment variables):
+
+```bash
+# For Antigravity:
+ANTIGRAVITY_OAUTH_CLIENT_ID=your-client-id.apps.googleusercontent.com
+ANTIGRAVITY_OAUTH_CLIENT_SECRET=GOCSPX-your-secret
+
+# For Gemini CLI:
+GEMINI_OAUTH_CLIENT_ID=your-client-id.apps.googleusercontent.com
+GEMINI_OAUTH_CLIENT_SECRET=GOCSPX-your-secret
+GEMINI_CLI_OAUTH_CLIENT_SECRET=GOCSPX-your-secret
+```
+
+**6. Restart OmniRoute**
+
+```bash
+# npm:
+npm run dev
+
+# Docker:
+docker restart omniroute
+```
+
+**7. Try connecting again**
+
+Dashboard → Providers → Antigravity (or Gemini CLI) → OAuth
+
+Google will now redirect correctly to `https://your-server.com/callback`.
+
+---
+
+#### Temporary workaround (without custom credentials)
+
+If you don't want to set up your own credentials right now, you can still use the **manual URL flow**:
+
+1. OmniRoute opens the Google authorization URL
+2. After authorizing, Google tries to redirect to `localhost` (which fails on the remote server)
+3. **Copy the full URL** from your browser's address bar (even if the page doesn't load)
+4. Paste that URL into the field shown in the OmniRoute connection modal
+5. Click **"Connect"**
+
+> This works because the authorization code in the URL is valid regardless of whether the redirect page loaded.
+
+---
+
+<details>
+<summary><b>🇧🇷 Versão em Português</b></summary>
 
 #### Por que o OAuth do Antigravity / Gemini CLI falha em servidores remotos?