v3.9.0: add multi-account rotation docs to README

README.md

@@ -535,6 +535,53 @@ The launcher generates model catalog JSON with dual field naming to satisfy both
 
 ---
 
+## Multi-Account Rotation
+
+Codex Launcher supports **multiple accounts per provider** with automatic rotation
+when one account is rate-limited.
+
+### Codebuff (Multiple Accounts)
+
+Register additional free accounts at [codebuff.com](https://www.codebuff.com), then
+add them to `~/.config/manicode/credentials.json`:
+
+```json
+{
+  "default": { "authToken": "token-primary", "email": "you+1@gmail.com" },
+  "accounts": [
+    { "authToken": "token-secondary", "email": "you+2@gmail.com" },
+    { "authToken": "token-tertiary", "email": "you+3@gmail.com" }
+  ]
+}
+```
+
+Each account gets 5 free requests/day. With 3 accounts = **15 requests/day**.
+
+### Google OAuth (Multiple Projects)
+
+Add additional Google Cloud token files:
+
+```
+~/.cache/codex-proxy/google-antigravity-oauth-token.json     # primary
+~/.cache/codex-proxy/google-antigravity-oauth-token-1.json   # extra project 1
+~/.cache/codex-proxy/google-antigravity-oauth-token-2.json   # extra project 2
+```
+
+### API Keys (Comma-Separated)
+
+For any OpenAI-compatible provider:
+```json
+{ "api_key": "sk-key1,sk-key2,sk-key3" }
+```
+
+### Account Status Endpoint
+
+```bash
+curl http://127.0.0.1:PORT/v1/accounts
+```
+
+---
+
 ## Provider Presets
 
 | Preset | Backend | Base URL |