Transfer Lanes

Ultra separates policy and share state from byte movement, then chooses the fastest safe lane for the file size, device profile, and transfer intent.

Control Plane, Many Data Lanes

Every lane creates normal Ultra shares with the same policy, grant, delete-token, expiration, and lifecycle semantics. The data lane changes how bytes move.

Control plane:
  Share, Policy, Grant, Manifest, Auth, Telemetry, Lifecycle

Data lanes:
  Live Pipe
  Hybrid Live
  Turbo Multipart
  TUS Compatibility
  Import from URL

Routing Rule

Class	Default lane	Behavior
0 to 1 GiB	`live_pipe`	Instant share link, receiver can open immediately, hot-buffered live stream when both sides are present.
1 to 10 GiB	`hybrid_live`	Live UX with durable backing. Desktop can stream when safe; mobile avoids unsafe fallback paths.
10 to 100 GiB	`turbo_multipart`	Async-friendly, resumable multipart upload with normal Ultra share policy after completion.
iOS large encrypted receive	`safe_mobile_receive`	No multi-GB JavaScript Blob assembly. The receiver gets a predictable blocked or ready state.

Live Pipe

Live Pipe is for small human-to-human sessions where both sides are likely present. PipeDO keeps a bounded hot buffer so connected receivers can read fresh chunks directly while R2 remains the replay and durability layer.

Hybrid Live

Hybrid Live keeps the live product feel for 1 to 10 GiB transfers: the link exists immediately, the receiver can watch sender progress, hot-buffered chunks can stream directly to an attached receiver, and R2 durability is scheduled asynchronously for replay or resume.

Turbo Multipart

Turbo is Ultra's native high-throughput lane for larger files. It maps directly to R2 multipart upload and avoids putting Durable Objects in the hot byte path.

POST /api/upload/multipart/init
POST /api/upload/multipart/part
POST /api/upload/multipart/complete
POST /api/upload/multipart/abort
GET  /api/upload/multipart/status

TUS Compatibility

TUS is a compatibility adapter over multipart manifests for clients that already speak resumable TUS. Ultra-native multipart remains the fastest first-party lane.

OPTIONS /api/tus
POST    /api/tus
HEAD    /api/tus/{id}
PATCH   /api/tus/{id}
DELETE  /api/tus/{id}

Import From URL

Import-from-URL is for bytes that already live at an HTTP(S) URL. Ultra revalidates redirects, blocks private and internal targets, enforces byte and timeout caps, then stores the result as a normal file share.

Folder/Bulk

Folder state lives in FolderDO, files use the folder multipart lane, and ready files can be downloaded through GET /api/folder/{folderId}/zip as a Worker-streamed ZIP archive.

Opt-in folder E2EE keeps the key in the URL fragment, encrypts upload chunks in the browser, and decrypts individual file downloads in the browser. Encrypted folders do not use server-side plaintext ZIP because the Worker never receives the key; the ZIP endpoint returns 409 before consuming a folder share use.

Mobile Safety

Large mobile receive paths must be explicit and memory-safe. Ultra blocks unsafe iOS fallback behavior instead of silently assembling multi-GB decrypted chunks in JavaScript memory.