Processes and boundaries

Process / crate	Job	Deliberately does not
services/control-plane	REST, identity, publish, compile, gRPC client	Live tag loop
services/runtime-core	Snapshot, poll, alarm, command, spool	Engineering PostgreSQL
services/historian-writer	ready/ → provider	Tag account
crates/domain-model	Canonical model, validation	HTTP, SQL
crates/compiler	Revision → snapshot	Driver I/O
crates/runtime-model	Snapshot schema, seal, load	Resource storage
crates/tag-runtime	Scale, totalizer, expression	File/DB
crates/alarm-engine	Alarm state machine	Clock/storage
crates/policy	Tenant + role	OIDC/LDAP
crates/driver-sdk	Driver trait + C header	Loading foreign code
drivers/*	Protocol clients	Engineering model
apps/studio-web	Browser client	Its own semantic model
crates/server-config	vion.toml schema	Engineering PG
packages/hmi-engine	Screen JSON → SVG	Does not paint values via React state

Schema versions

Namespace	Constant
Engineering	ENGINEERING_SCHEMA_VERSION
Snapshot	SNAPSHOT_SCHEMA_VERSION
Compiler	COMPILER_VERSION
Historian SPI	HISTORIAN_SPI_VERSION
Driver SDK	DRIVER_SDK_VERSION

ADR directory: docs/architecture/adr/ in the repo.