# Container Layout Discovery Contract

## Module
Scanner

## Status
VERIFIED

## Description
Standardized contract for discovering and mapping container filesystem layouts, enabling analyzers to locate language-specific artifacts across different container image structures.

## Implementation Details
- **Root File System Abstraction**:
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/FileSystem/IRootFileSystem.cs` - Interface for abstract root filesystem access
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/FileSystem/DirectoryRootFileSystem.cs` - Directory-backed root filesystem implementation
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/FileSystem/LayeredRootFileSystem.cs` - Layered (OCI) root filesystem implementation
- **OCI Image Context**:
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/Oci/OciImageConfig.cs` - OCI image config model for container layout discovery
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/EntryTraceImageContextFactory.cs` - Creates image context for entrypoint analysis
- **Entry Trace Analyzer**:
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/IEntryTraceAnalyzer.cs` - Interface for entry trace analysis
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/EntryTraceAnalyzer.cs` - Main analyzer discovering container layout and locating language-specific artifacts
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/EntryTraceContext.cs` - Context model with discovered layout info
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/EntryTraceTypes.cs` - Type definitions for discovered artifacts
- **Entrypoint Specification**:
  - `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/EntrypointSpecification.cs` - Specifies expected entrypoints per container layout
- **DI**: `src/Scanner/__Libraries/StellaOps.Scanner.EntryTrace/ServiceCollectionExtensions.cs`

## E2E Test Plan
- [ ] Scan a container image and verify the `EntryTraceAnalyzer` discovers the filesystem layout (root paths, language directories)
- [ ] Verify `LayeredRootFileSystem` correctly merges multiple OCI layers into a unified filesystem view
- [ ] Verify language-specific artifacts are located across different base images (Alpine, Debian, Ubuntu, distroless)
- [ ] Verify the OCI image config is parsed to determine CMD/ENTRYPOINT for entrypoint analysis
- [ ] Verify the layout discovery works for multi-stage build images with non-standard directory structures

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## Verification

| Check | Result |
|-------|--------|
| Tier 0 - Source files exist | PASS |
| Tier 1 - Build + code review | PASS |
| Tier 2 - Integration tests | PASS |
| Verified | 2026-02-13T18:10:00Z |