v3.9.0: update CHANGELOG.md

CHANGELOG.md

@@ -1,5 +1,50 @@
 # Changelog
 
+## v3.9.0 (2026-05-24)
+
+**Multi-Account Rotation — Never Hit a Dead End Again**
+
+### What's New
+The proxy now supports **multiple accounts per provider**. When one account hits its
+rate limit (429/426), the proxy automatically rotates to the next available account.
+This means 3 codebuff accounts = 15 free requests/day instead of 5.
+
+### Codebuff Multi-Account
+Add extra accounts to `~/.config/manicode/credentials.json`:
+```json
+{
+  "default": { "authToken": "...", "email": "primary@example.com" },
+  "accounts": [
+    { "authToken": "...", "email": "secondary@example.com" },
+    { "authToken": "...", "email": "tertiary@example.com" }
+  ]
+}
+```
+
+### Google OAuth Multi-Account
+Add extra Google Cloud token files alongside the primary:
+- `~/.cache/codex-proxy/google-antigravity-oauth-token.json` (primary)
+- `~/.cache/codex-proxy/google-antigravity-oauth-token-1.json` (extra 1)
+- `~/.cache/codex-proxy/google-antigravity-oauth-token-2.json` (extra 2)
+
+### API Key Rotation
+For any OpenAI-compatible provider, use comma-separated API keys in config:
+```json
+{ "api_key": "sk-key1,sk-key2,sk-key3" }
+```
+Keys rotate automatically on 429 errors.
+
+### New Endpoints
+- `GET /v1/accounts` — shows account pool status (active, rate-limited, time until reset)
+
+### Other Fixes
+- Added `x-codebuff-model` and `x-codebuff-instance-id` headers to codebuff requests
+- Improved instance ID extraction (supports both `instanceId` and `data.instance_id`)
+- Fixes `codebuff_update_required` (HTTP 426) error when session endpoint succeeds
+
+---
+
+
 ## v3.8.4 (2026-05-24)
 
 **Critical Fix — Codebuff DeepSeek V4 Tool-Call Sessions Now Work**