# Architecture

Thin index of structural truth. Module detail lives under `docs/architecture/`.
Agent operating digests live under `docs/agents/`. Product behavior contracts live
under `docs/product/`.

## Dependency Direction

```text
Host projects (RevitDevTool, AcadDevTool)
  -> shared platform (source/DevTools.*)
  -> host-only helpers only when API-bound (e.g. RevitDevTool.Core)
```

Default: features are sharable. Host API, threading, and host-specific rendering
stay in host projects. Visualization (DirectContext3D) is Revit-host only.
Process identity and generic host launch live in `DevTools.Hosting`; Revit/Acad
launch specs are `DevTools.Hosting.Revit` / `Hosting.Acad`; offline file parse
stays `FileMetadata.*`; add-in DI lives in `RevitDevTool/Composition` /
`AcadDevTool/Composition` ([0018](decisions/0018-host-identity-and-out-of-process-infrastructure.md)).

## Module Map

| Module | Architecture | Product contract | Agent digest |
|--------|--------------|------------------|--------------|
| Execution | [architecture/Execution](architecture/Execution/README.md) | [product/execution.md](product/execution.md) | [agents/execution-system.md](agents/execution-system.md) |
| MCP | [architecture/MCP](architecture/MCP/README.md) | [product/mcp.md](product/mcp.md) | [agents/mcp-pytest-bridge.md](agents/mcp-pytest-bridge.md) |
| PyTest bridge | [architecture/Execution/pytest-bridge.md](architecture/Execution/pytest-bridge.md) | [product/pytest-bridge.md](product/pytest-bridge.md) | [agents/mcp-pytest-bridge.md](agents/mcp-pytest-bridge.md) |
| Logging | [architecture/Logging](architecture/Logging/README.md) | [product/logging.md](product/logging.md) | — |
| Visualization | [architecture/Visualization](architecture/Visualization/README.md) | [product/visualization.md](product/visualization.md) | — |
| MTP host testing | [architecture/Testing](architecture/Testing/README.md) | [product/host-testing.md](product/host-testing.md), [tunit-host-testing.md](product/tunit-host-testing.md) | [agents/host-testing.md](agents/host-testing.md) |
| PythonDemo | [architecture/PythonDemo](architecture/PythonDemo/README.md) | — | — |

## Cross-Cutting

| Topic | Read |
|-------|------|
| Host boundaries | [agents/host-boundaries.md](agents/host-boundaries.md) |
| Build / TFM matrix | [agents/build-matrix.md](agents/build-matrix.md) |
| Verification | [agents/verification.md](agents/verification.md) |
| Test matrix | [agents/test-matrix.md](agents/test-matrix.md) |
| Lasting decisions | [decisions/](decisions/README.md) |

## Source Layout

- Shared: `source/DevTools.*` (Hosting, Hosting.Revit, Hosting.Acad, Execution, Execution.Abstractions, Ipc, Mcp.Catalog + Mcp.Revit/Acad, FileMetadata.Core/Revit/Acad, Logging, Presentation, Settings, Telemetry, UI, Utilities, Daemon, Testing.Abstractions/Transport/Host, NUnit.MTP/Runtime, TUnit.MTP/Runtime, TestAdapter, TestRunner)
- Revit host: `source/RevitDevTool/`; Revit-only helpers: `source/RevitDevTool.Core/`; in-host MCP tools: `source/DevTools.Mcp.Revit/`
- AutoCAD host: `source/AcadDevTool/`; in-host MCP tools: `source/DevTools.Mcp.Acad/`
- Samples: `samples/`; build: `build/`; scripts: `scripts/`