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+# Component Detection - AI Coding Agent Instructions
+
+## Project Overview
+Component Detection is a **package scanning tool** that detects open-source dependencies across 15+ ecosystems (npm, NuGet, Maven, Go, etc.) and outputs a **dependency graph**. It's designed for build-time scanning and can be used as a library or CLI tool.
+
+## Architecture
+
+### Core Concepts
+- **Detectors**: Ecosystem-specific parsers that discover and parse manifest files (e.g., `package.json`, `requirements.txt`)
+- **Component Recorders**: Immutable graph stores that track detected components and their relationships
+- **Typed Components**: Strongly-typed models for each ecosystem (e.g., `NpmComponent`, `PipComponent`) in `src/Microsoft.ComponentDetection.Contracts/TypedComponent/`
+
+### Project Structure
+```
+src/
+├── Microsoft.ComponentDetection/           # CLI entry point (Program.cs)
+├── Microsoft.ComponentDetection.Orchestrator/  # Command execution, DI setup, detector coordination
+├── Microsoft.ComponentDetection.Contracts/     # Interfaces (IComponentDetector, IComponentRecorder) and TypedComponent models
+├── Microsoft.ComponentDetection.Common/        # Shared utilities (file I/O, Docker, CLI invocation)
+└── Microsoft.ComponentDetection.Detectors/     # Per-ecosystem detector implementations (npm/, pip/, nuget/, etc.)
+```
+
+### Detector Lifecycle Stages
+All new detectors start as **IDefaultOffComponentDetector** (must be explicitly enabled via `DetectorArgs`). Maintainers promote through:
+1. **DefaultOff** → 2. **IExperimentalDetector** (enabled but output not captured) → 3. **Default** (fully integrated)
+
+### Dependency Injection
+All services auto-register via `ServiceCollectionExtensions.AddComponentDetection()` in Orchestrator. Detectors are discovered at runtime via `[Export]` attribute.
+
+## Creating a New Detector
+
+### Required Steps
+1. **Define Component Type** (if new ecosystem):
+   - Add enum to `DetectorClass` and `ComponentType` in Contracts
+   - Create `YourEcosystemComponent : TypedComponent` with required properties
+   - Use `ValidateRequiredInput()` for mandatory fields
+
+2. **Implement Detector**:
+   ```csharp
+   [Export]
+   public class YourDetector : FileComponentDetector, IDefaultOffComponentDetector
+   {
+       public override string Id => "YourEcosystem";
+       public override IEnumerable<string> Categories => [DetectorClass.YourCategory];
+       public override IEnumerable<ComponentType> SupportedComponentTypes => [ComponentType.YourType];
+       public override IEnumerable<string> SearchPatterns => ["manifest.lock"]; // Glob patterns
+
+       protected override Task OnFileFoundAsync(ProcessRequest request, IDictionary<string, string> detectorArgs)
+       {
+           var recorder = request.SingleFileComponentRecorder;
+           // Parse file, create components, call recorder.RegisterUsage()
+       }
+   }
+   ```
+
+3. **Register Components**:
+   ```csharp
+   var component = new DetectedComponent(new YourComponent("name", "1.0.0"));
+   recorder.RegisterUsage(
+       component,
+       isExplicitReferencedDependency: true,  // Direct dependency?
+       parentComponentId: parentId,           // For graph edges (can be null)
+       isDevelopmentDependency: false         // Build-only dependency?
+   );
+   ```
+
+### Detector Lifecycle Methods
+- `OnPrepareDetection()` - **Optional**: Pre-processing (e.g., filter files before parsing)
+- `OnFileFoundAsync()` - **Required**: Main parsing logic for matched files
+- `OnDetectionFinished()` - **Optional**: Cleanup (e.g., delete temp files)
+
+### Testing Pattern
+```csharp
+[TestClass]
+public class YourDetectorTests : BaseDetectorTest<YourDetector>
+{
+    [TestMethod]
+    public async Task TestBasicDetection()
+    {
+        var fileContent = "name: pkg\nversion: 1.0.0";
+        var (scanResult, componentRecorder) = await this.DetectorTestUtility
+            .WithFile("manifest.lock", fileContent, ["manifest.lock"])
+            .ExecuteDetectorAsync();
+
+        scanResult.ResultCode.Should().Be(ProcessingResultCode.Success);
+        var components = componentRecorder.GetDetectedComponents();
+        components.Should().HaveCount(1);
+    }
+}
+```
+
+Use minimal file content needed to exercise specific scenarios. Avoid testing multiple features in one test.
+
+### End-to-End Verification
+Add test resources to `test/Microsoft.ComponentDetection.VerificationTests/resources/[ecosystem]/` with real-world examples that fully exercise your detector. These run in CI to prevent regressions.
+
+## Development Workflows
+
+### Build & Run
+```bash
+# Build
+dotnet build
+
+# Run scan with new detector (replace YourDetectorId)
+dotnet run --project src/Microsoft.ComponentDetection/Microsoft.ComponentDetection.csproj scan \
+  --Verbosity Verbose \
+  --SourceDirectory /path/to/scan \
+  --DetectorArgs YourDetectorId=EnableIfDefaultOff
+```
+
+### Testing
+```bash
+# Run all tests
+dotnet test
+
+# Run specific test project
+dotnet test test/Microsoft.ComponentDetection.Detectors.Tests/
+```
+
+### Debug Mode
+Add `--Debug` flag to wait for debugger attachment on startup (prints PID).
+
+## Key Patterns
+
+### File Discovery
+Detectors specify `SearchPatterns` (glob patterns like `*.csproj` or `package-lock.json`). The orchestrator handles file traversal; detectors receive matched files via `ProcessRequest.ComponentStream`.
+
+### Graph Construction
+- Use `RegisterUsage()` to add nodes and edges
+- `isExplicitReferencedDependency: true` marks direct dependencies (like packages in `package.json`)
+- `parentComponentId` creates parent-child edges (omit for flat graphs)
+- Some ecosystems don't support graphs (e.g., Go modules) - register components without parents
+
+### Component Immutability
+`TypedComponent` classes must be immutable (no setters). Validation happens in constructors via `ValidateRequiredInput()`.
+
+### Directory Exclusion
+Detectors can filter directories in `OnPrepareDetection()`. Example: npm detector ignores `node_modules` if a root lockfile exists.
+
+## Common Pitfalls
+
+- **Don't** implement `IComponentDetector` directly unless doing one-shot scanning (like Linux detector). Use `FileComponentDetector` for manifest-based detection.
+- **Don't** guess parent relationships - only create edges if the manifest explicitly defines them.
+- **Don't** use setters on `TypedComponent` - pass required values to constructor.
+- **Always** test with `DetectorTestUtility` pattern, not manual `ComponentRecorder` setup.
+- **Remember** new detectors must implement `IDefaultOffComponentDetector` until promoted by maintainers.
+
+## References
+- Detector implementation examples: `src/Microsoft.ComponentDetection.Detectors/npm/`, `pip/`, `nuget/`
+- Creating detectors: `docs/creating-a-new-detector.md`
+- CLI arguments: `docs/detector-arguments.md`
+- Test utilities: `test/Microsoft.ComponentDetection.TestsUtilities/DetectorTestUtility.cs`