Bridge API

Updated July 2026

The bridge relay is the local HTTP service inside DousenDesktop (default 127.0.0.1:8766) that fans events out between DCCs. This page documents its full API so a studio tool — a batch exporter, a custom DCC, a watch-folder script — can participate in the pipeline exactly like the built-in addons do.

Authentication

Every request needs a bearer token:

HTTPAuthorization: Bearer <token>

DousenDesktop mints a fresh token at each start and writes it, readable only by the current user, to:

• Windows: %APPDATA%\Dousen\DousenDesktop\bridge.token
• Linux: ~/.local/share/Dousen/DousenDesktop/bridge.token
• macOS: ~/Library/Application Support/Dousen/DousenDesktop/bridge.token

Tools launched by DousenDesktop can instead read the DOUSEN_BRIDGE_TOKEN environment variable, which takes precedence. Read the token file fresh on every request — the token rotates when DousenDesktop restarts, and re-reading it means your tool survives that without a relaunch.

The relay also rejects, regardless of token: any request carrying an Origin header (403 — this blocks browsers outright) and any request whose Host is not a loopback address (403). A missing or wrong token gets 401.

Endpoints

The event envelope

GET /bridge/events returns:

JSON{
  "events": [
    {
      "timestamp_sec": 1751450000,
      "event_type": "mesh.export",
      "source_app": "maya",
      "target_app": "",
      "file_path": "D:/work/props/sword.fbx",
      "metadata_json": "{\"suggested_name\":\"S_Sword\", ...}",
      "task_id": "DOU-142",
      "changelist_id": "31"
    }
  ],
  "timestamp": 1751450001
}

An empty target_app means "everyone"; a set one means only that app should act on it. metadata_json is a JSON string — decode it a second time to get the metadata object.

Event types

Poll semantics

• The built-in addons poll every 0.5 seconds; anything up to a few seconds is fine for a background tool.
• Timestamps are whole seconds. To avoid dropping two events from the same second, poll with since one second behind your high-water mark and de-duplicate what you've already handled.
• The relay keeps the most recent 200 events; there is no replay beyond that.
• Registrations expire after 30 seconds without a heartbeat — re-register every 10 seconds to stay on the connected list (and the tray badge).
• Suppress your own events: skip anything whose source_app is your id.

Registering a studio tool

The Python package that ships with DousenDesktop does all of the above for you. From any Python 3 environment with <install>/python on the path:

PYTHONfrom dousen.bridge import BridgeClient

bridge = BridgeClient()                       # port 8766, token auto-read
bridge.register("batchtool", "Batch Exporter")

def on_event(event):
    print(event.event_type, event.file_path, event.metadata)

# poll in a background thread; auto-reconnects with backoff
bridge.subscribe_async("batchtool", "mesh.*", on_event)

bridge.publish(
    event_type="mesh.export",
    source_app="batchtool",
    file_path="D:/work/props/sword.fbx",
    metadata={"suggested_name": "S_Sword", "source_file": "D:/work/props/sword.ma"},
    task_id="DOU-142",
)

Event-type filters accept an exact name (mesh.export), a prefix (mesh.*), or empty for everything. Once registered and heartbeating, your tool appears in /bridge/dccs, on the desktop's connected-apps badge, and in Unreal's "Open in DCC" menu.