docs: add ChatGPT Plus/Pro provider setup guide

docs/providers/index.json

@@ -126,6 +126,12 @@
       "extension": true,
       "cloud": true
     },
+    {
+      "id": "providers/openai-chatgpt-plus-pro",
+      "title": "OpenAI – ChatGPT Plus/Pro",
+      "extension": true,
+      "cloud": false
+    },
     {
       "id": "providers/openai-compatible",
       "title": "OpenAI Compatible",

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

@@ -0,0 +1,76 @@
+---
+sidebar_label: OpenAI – ChatGPT Plus/Pro
+title: OpenAI – ChatGPT Plus/Pro
+description: Use Codex models in Roo Code with a ChatGPT Plus/Pro subscription (OAuth sign-in, no API key).
+keywords:
+  - OpenAI Codex
+  - ChatGPT Plus
+  - ChatGPT Pro
+  - Roo Code
+  - OAuth
+  - no api key
+  - subscription
+---
+
+<iframe
+  width="600"
+  height="338"
+  src="https://www.youtube.com/embed/t0sIT8nGvrk"
+  title="OpenAI – ChatGPT Plus/Pro provider setup"
+  frameborder="0"
+  allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
+  allowfullscreen
+></iframe>
+
+Why this video matters: it shows the exact sign-in flow and where to click in the Roo Code settings panel.
+
+Use Codex models in Roo Code **without an OpenAI API key**. Just sign in with the ChatGPT account you already pay for.
+
+---
+
+If you want the official OpenAI API (API keys, usage-based billing, broader model availability), use the regular OpenAI provider instead: [Using OpenAI With Roo Code](/providers/openai).
+
+## Quickstart: sign in and run a task
+
+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. Start a task.
+
+## 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.
+- **You can't sign in if Roo can't bind `localhost:1455`.** The OAuth callback uses a local server; if your machine (or security software) blocks it, the flow can't complete.
+
+## Troubleshooting
+
+#### Not authenticated with OpenAI Codex (or Roo asks you to sign in)
+
+- **Symptom:** Roo fails immediately and tells you to sign in.
+- **Cause:** You haven't completed OAuth sign-in, or your stored refresh token was revoked and Roo cleared it.
+- **Fix:** In the provider settings panel, click **Sign in to OpenAI Codex** again.
+- **Prevention:** Don't delete VS Code extension secrets unless you expect to re-auth.
+
+#### Port 1455 is already in use during sign-in
+
+- **Symptom:** Sign-in fails right away and mentions port `1455`.
+- **Cause:** Another process is listening on that port.
+- **Fix:** Stop the process using `1455`, then retry sign-in.
+- **Prevention:** Avoid running other local OAuth callback servers on the same port.
+
+#### 403 Forbidden or Model not available
+
+- **Symptom:** Requests fail with access denied.
+- **Cause:** Your ChatGPT subscription or organization doesn't have access to that model.
+- **Fix:** Pick a different model, or verify your account/org subscription.
+- **Prevention:** Treat the model list in the provider settings as the source of truth.
+
+#### Cost shows as $0
+
+- **Symptom:** Roo shows usage but cost is zero.
+- **Cause:** This provider is subscription-covered, so Roo intentionally reports cost as $0.
+- **Fix:** Nothing to fix.
+- **Prevention:** Don't treat $0 as “no tokens consumed”; it's “not billed per token in Roo”.

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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