QFabric is a programmable quantum network emulation platform built on the FABRIC testbed, for studying quantum network protocols as distributed systems. Fiber attenuation is emulated in a P4/BMv2 data plane as probabilistic drop of custom EtherType 0x7101 photon frames (per photon of a pulse, so decoy-state sources ride the same path), and the classical channel is raw 0x7102 frames through the same switch. BB84, decoy-state BB84, E91/BBM92, n-node entanglement swapping and a distributed gate (teleportation, non-local CNOT) run as separate processes on separate FABRIC VMs on top of an unmodified SeQUeNCe 1.0, with full key distillation: Cascade, key verification, Toeplitz privacy amplification, finite-key bounds, decoy (GLLP) accounting and an authenticated classical channel. A central time authority gives every run a shared logical clock and a delivery certificate. The quantum states are statistical models (a Werner register), not photonics, and delays are modeled, not measured. Cross-validation runs the measured result, a QFabric simulation, SeQUeNCe and NetSquid on the same slice and checks agreement. Notebooks drive everything on a slice: fabric/ (set up, run, sweep, analyse), sequence/ (the distributed runtime, E91) and concepts/ (eavesdropper, reconciliation, repeaters, security depth, distributed computing). See README.md, docs/ASSUMPTIONS.md, docs/SPEC.md, docs/ROADMAP.md.