The handoff starts when all three parties are on the line

Diligence week. Three firms, yours, the acquirer's and the escrow agent's, each need an identical copy of the 40GB evidence archive, delivered at the same moment, with nobody's copy arriving early.

You send it once: tar czf - evidence | curl -T - .../api/v1/pipe/dd-2026?n=3. Your terminal prints [INFO] Waiting for 3 receiver(s) to connect... and nothing moves. Each firm runs its receiver with the same ?n=3. The transfer doesn't begin until all three receivers and the sender are connected; then the bytes stream once from your disk and fan out to three byte-identical copies, with no upload service holding a fourth in the middle. If a receiver drops mid-transfer, the sender's status log says so, and the log is your delivery receipt.

The release condition was a query parameter.