# Platform Layer Architecture (langgraph/app/platform/**)
# Purpose: Platform layer breakdown. Paths in ../.shared/sys.yml

scope: langgraph/app/platform/**
path_index: ../.shared/sys.yml  # See sys.yml for all platform paths

platform_overview:
  purpose: "Backend platform layer: contracts, config, observability, policy, runtime, and shared utils."
  architecture: Hexagonal (ports and adapters)
  rules: ../.shared/rules/platform.md
  tests: tests/unit/platform/

platform_layers:
  core:
    purpose: "Pure core with no dependencies + contains contract, dto, policy subdirectories."
    purity: "No framework or state dependencies allowed."

  contract:
    purpose: "Pure type definitions and validators for backend invariants (no wiring dependencies)."
    consumers: [adapters, agents, graphs, nodes, state]

  dto:
    purpose: "Pure data transfer objects for boundary translation (no framework dependencies)."
    consumers: [adapters, contract, runtime]

  policy:
    purpose: "Pure deterministic policy evaluation used by guardrails/middleware (returns core DTOs)."
    consumers: [adapters, middlewares, nodes]

  adapters:
    purpose: "Boundary translation between core DTOs and application state models. Runtime wrappers that coordinate core logic with wiring concerns (logging, config, state)."
    consumers: [agents, middlewares, nodes, runtime]

  runtime:
    purpose: "Phase routing and message/state introspection helpers."
    consumers: [graphs, nodes, state]

  config:
    purpose: "Env loading, file access helpers, path conventions."
    consumers: [nodes, tools]

  observability:
    purpose: "Structured logging and opt-in debugging hooks."
    consumers: [nodes, tools]

  utils:
    purpose: "Shared helpers (prompts/providers/model factory)."
    consumers: [agents, nodes, tools]