ChatSync for OpenRouter

A browser extension (Chrome / Edge / Firefox) that syncs your OpenRouter chat history across devices and browsers.

OpenRouter's chat playground is local-first: conversations live in your browser's IndexedDB with no server-side sync, and the only official tools are manual Export/Import JSON. ChatSync automates that: it watches the local database and merges every room into a remote backend you own, so any device pointing at the same backend converges to the same chat list.

How it works

openrouter.ai (content script)          your storage backend
┌──────────────────────────┐            ┌────────────────────────┐
│ IndexedDB                │  push /   │ manifest.json          │
│  openrouter:playground:v3│  pull     │ rooms/<roomId>.json    │
└──────────────────────────┘            └────────────────────────┘
        ▲ service worker (diff / merge / alarms)

• Format: each room is serialized as orpg.3.0 JSON, byte-compatible with OpenRouter's official Export. Files in the sync root can be imported by hand at any time.
• Merging: per-room content hash against a remote manifest. Rooms are matched by their OpenRouter-issued ids; conflicting edits resolve last-write-wins by room.updatedAt.
• Deletions: propagate in both directions via tombstones. Deleting a chat on one device removes it everywhere on the next sync; a remotely-deleted room that was edited locally afterwards is resurrected instead of lost. A fresh/empty remote never deletes local data.
• Application: pulled rooms are upserted into IndexedDB by id (idempotent, same semantics as the official Import) and the openrouter.ai tab reloads to show them.
• Size: optional "strip model catalog snapshots" mode drops characters[].modelInfo (typically ~90% of payload). Base64 images inside items are synced as-is.

Backends

Backend	Auth	Notes
GitHub repo	Fine-grained PAT (Contents read/write)	Every changed room is its own commit, so you get full history and rollback via git.
WebDAV	Basic auth	Works with Nextcloud, nutstore, Synology, or a self-hosted server.

Install (development)

pnpm install
pnpm zip:all                    # chrome + edge + firefox zips in .output/
pnpm test                       # sync engine unit tests

Then load the unpacked build (.output/chrome-mv3, .output/edge-mv3, or .output/firefox-mv3):

• Chrome / Edge: chrome://extensions (or edge://extensions) → enable Developer mode → Load unpacked
• Firefox (128+): about:debugging#/runtime/this-firefox → Load Temporary Add-on → pick .output/firefox-mv3/manifest.json, or install the signed zip from releases

Grab prebuilt zips from releases.

Usage

1. Open the extension options and configure a backend (GitHub token + repo, or WebDAV URL + credentials).
2. Click save & test connection.
3. Open https://openrouter.ai/chat, click the ChatSync icon, and hit sync now. Optionally set an auto-sync interval (minutes) in options.

Syncing requires an openrouter.ai tab (the extension opens one in the background automatically if none exists, and closes it when done).

Project layout

src/
├── entrypoints/
│   ├── background.ts      # sync orchestration, tab bridging, alarms
│   ├── content.ts         # IndexedDB bridge on openrouter.ai
│   ├── popup/             # status + manual sync
│   └── options/           # backend configuration
└── lib/
    ├── types.ts           # orpg.3.0 + sync manifest models (from live recon)
    ├── orpg.ts            # export assembly / import planning / hashing
    ├── playground-db.ts   # IndexedDB read / upsert / delete
    ├── sync-engine.ts     # pure diff/merge engine (+ unit tests)
    └── adapters/          # github, webdav

Privacy

Chat content only ever travels between your browser and the backend you configure. Credentials are stored in chrome.storage.local. No telemetry.

License

MIT