docs: add ChatGPT Plus/Pro provider setup guide

docs/providers/index.json

@@ -6,6 +6,12 @@
       "extension": true,
       "cloud": true
     },
+    {
+      "id": "providers/openai-chatgpt-plus-pro",
+      "title": "ChatGPT Plus/Pro",
+      "extension": true,
+      "cloud": false
+    },
     {
       "id": "providers/claude-code",
       "title": "Claude Code",

docs/providers/openai-chatgpt-plus-pro.md

@@ -0,0 +1,53 @@
+---
+sidebar_label: ChatGPT Plus/Pro
+title: ChatGPT Plus/Pro
+description: Use OpenAI models in Roo Code with your ChatGPT Plus/Pro subscription (OAuth sign-in, no API key).
+keywords:
+  - OpenAI Codex
+  - ChatGPT Plus
+  - ChatGPT Pro
+  - Roo Code
+  - OAuth
+  - no api key
+  - subscription
+---
+
+<div style={{ position: 'relative', paddingBottom: '56.25%', height: 0, overflow: 'hidden' }}>
+  <iframe
+    src="https://www.youtube.com/embed/c1IXRMl5i0g"
+    title="OpenAI – ChatGPT Plus/Pro provider setup"
+    style={{
+      position: 'absolute',
+      top: 0,
+      left: 0,
+      width: '100%',
+      height: '100%',
+    }}
+    frameBorder="0"
+    allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
+    allowFullScreen
+  ></iframe>
+</div>
+
+---
+
+## Quickstart: Connect your subscription to Roo Code
+
+1. Open Roo Code settings (click the gear icon <Codicon name="gear" /> in the Roo Code panel).
+2. In **API Provider**, select **OpenAI – ChatGPT Plus/Pro**.
+3. Click **Sign in to OpenAI Codex**.
+4. Finish the sign-in flow in your browser.
+5. Back in Roo Code settings, pick a model from the dropdown.
+6. Save.
+
+
+## Tips and Notes
+
+- **Subscription Required:** You need an active ChatGPT Plus or Pro subscription. This provider won't work with free ChatGPT accounts. See [OpenAI's ChatGPT plans](https://openai.com/chatgpt/pricing) for more info.
+- **No API Costs:** Usage through this provider counts against your ChatGPT subscription, not separately billed API usage.
+- **Sign Out:** To disconnect, use the "Sign Out" button in the provider settings.
+
+## What you can't do (and why)
+
+- **You can't use arbitrary OpenAI API models.** This provider only exposes the models listed in Roo's Codex model catalog.
+- **You can't export/migrate your sign-in state with settings export.** OAuth tokens are stored in VS Code SecretStorage, which isn't included in Roo's settings export.

docs/providers/openai.md

@@ -17,6 +17,10 @@ keywords:
 
 Roo Code supports accessing models directly through the official OpenAI API, including the latest GPT-5 family with advanced features like reasoning effort control and verbosity settings.
 
+:::info Want to use a ChatGPT Plus/Pro subscription instead?
+Use the **OpenAI – ChatGPT Plus/Pro** provider to sign in via OAuth (no API key): [OpenAI – ChatGPT Plus/Pro](/providers/openai-chatgpt-plus-pro).
+:::
+
 **Website:** [https://openai.com/](https://openai.com/)
 
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