Assumption: Streaming observer

Accessible carriers are delivered once in their specified order. A passive supplier may hold undelivered carriers but performs no measurement, encoding, selection, or decoding.

The observer may pause delivery. It may not return an intermediate quantum register to the supplier, revisit consumed radiation, use an unpriced quantum buffer, share auxiliary entanglement, or export quantum output before the final return.

A delivered carrier is counted before any gate involving it. Receiving a new qubit while another remains live therefore costs two live slots, even if a gate immediately consumes one.

Every laboratory qubit is destructively measured or returned. Classical memory is unrestricted unless a bound is stated. The internal emission maps are fixed and are not controlled by the observer's measurement outcomes.