Specification · section 2

Architecture

Host · any agent harness Claude Code, Codex, OpenClaw, Hermes, Claude Science, Open Science, your own SDK agent MHP client MHP client one per device JSON-RPC · stdio / HTTP JSON-RPC · stdio / HTTP MHP server · driver thermocycler-01, serial link gates, jobs, descriptor MHP server · adapter arm-01, wraps a SiLA 2 feature same gates, same descriptor instrument instrument
One server per device. The host is any agent harness; it sees no difference between a native driver and an adapter over another control layer.
RoleResponsibility
HostAny agent harness: Claude Code, Codex, OpenClaw, Hermes, Claude Science, Open Science, a MADSci workcell manager, or your own program on any SDK. It owns the conversation with the model, decides what to do, holds one client per device, and presents human confirmation prompts. Most hosts reach MHP through the mhp-mcp bridge (§10.1) rather than speaking MHP directly.
ClientOne connection to one server. Sends requests, receives responses and notifications, tracks the lease.
Server (driver)Owns exactly one device. Serves the descriptor, enforces the safety envelope, translates primitives into vendor commands, runs jobs.
DeviceThe physical thing. A single instrument, or a coordinated cell exposed as one logical device.
DirectoryA server whose role is finding devices rather than being one. Indexes cards, answers searches, holds no device connections (§3.2).