0006 — Sans-I/O protocol core with a simulated network

Date: 2026-08-08. Status: accepted.

All code must be testable offline, including every error condition met in the wild. Therefore the protocol engine (yoke.core) performs no I/O and never reads a clock: inputs are decoded frames and explicit timestamps; outputs are effect lists (frames to send, driver commands, events, state to persist). The asyncio shell (yoke.net) and the drivers are thin, separately tested adapters.

tests/simnet.py schedules many cores over a virtual network with seeded, scriptable loss, duplication, reordering, delay, and partitions. Every failure-model row in ARCHITECTURE.md has a deterministic reproduction there. New field incidents must land as a simnet scenario before their fix merges — the simulation is the regression record.