Thin waist: one registry per job¶

This page explains how the runtime turns a name in a manifest into code. Read it before you add a plugin type or a lookup table. Other terms are in the glossary.

A plugin is a unit of behaviour that a manifest selects by name. The runtime is the Python package that executes agents (mas-runtime).

The problem¶

A manifest names behaviour, such as governance: hitl. Something must turn that name into code. If two tables map the same names, they drift apart.

The thin waist is the small, fixed set of lookup tables that every layer uses. Each name resolves in exactly one place.

spec:
  governance: hitl      # resolved by PluginRegistry.resolve_by_type("governance", "hitl")

PluginRegistry¶

PluginRegistry (mas.runtime.registry) maps a name to an implementation. It reads the manifest spec.* keys. Plugin types include design_pattern, governance, llm_provider, and skill_impl.

Every plugin type loads through PluginRegistry.resolve_by_type.
Skills use skill_impl rows in library.yaml.
SkillPluginRegistry (library-skills) is a facade over resolve_by_type("skill_impl", ...). It is not a second table.

Boundary slots are the plugin types that the kernel envelope calls at fixed points. See Contracts. They form a closed set. register_type(..., layer="boundary") raises UnknownBoundarySlotError for a type outside that set.

Library types are not envelope slots. Examples: related_state, execute_sandbox, circuit_breaker, skill_*, and lab steps.

Component catalog¶

The embedder is the program that hosts the runtime. It chooses the infra: runtime, placement, and framework. These resolve from component-registry.yaml.

Framework adapters and placement backends start empty and fill from the catalog.
Unknown ids fail in validate_component_id and get_framework_adapter.
Docker and Kubernetes placement stay status: planned until an availability plugin is declared.

Control and snapshots¶

Pause, navigate, spec revision, and snapshot storage are ControlContract and SnapshotTree APIs. They are not plugin-type enums. See Snapshots vs checkpoints.

The JSON-lines control wire is a library control_protocol plugin.
A2A (Agent2Agent, the protocol for remote agents) session attach is agent_expose. The A2A contextId is the session id.
A user turn on that session is ControlContract.send_message (A2A message/send).
AgentCommContract sends outbound to a peer after delegation. It is not inbound user input.

Why one registry per job¶

A third table that maps the same names would duplicate the first two. One registry per job keeps a name from resolving two ways.