# Plugin Dependency Resolution

## Module
Plugin

## Status
VERIFIED

## Description
Plugin dependency resolution with resolver service, interface, and comprehensive tests.

## Implementation Details
- **PluginDependencyResolver**: `src/Plugin/StellaOps.Plugin.Host/Dependencies/PluginDependencyResolver.cs` -- topological sorting of plugin manifests for load order; cycle detection via DFS with CircularDependencyError reporting; version constraint parsing (>=, >, <=, <, =, ~pessimistic, ^compatible); AreDependenciesSatisfied/GetMissingDependencies for optional dependency support; reverse load order for unload sequence
- **IPluginDependencyResolver**: `src/Plugin/StellaOps.Plugin.Host/Dependencies/IPluginDependencyResolver.cs` -- interface: ResolveLoadOrder, ResolveUnloadOrder, AreDependenciesSatisfied, GetMissingDependencies, ValidateDependencyGraph
- **DependencyGraph**: `src/Plugin/StellaOps.Plugin.Host/Dependencies/DependencyGraph.cs` -- graph data structure with AddNode, AddEdge, HasNode, GetDependents
- **Source**: Feature matrix scan

## E2E Test Plan
- [x] Verify topological sort produces correct load order for a dependency chain
- [x] Test circular dependency detection reports correct cycle paths
- [x] Verify version constraint matching for all operators (>=, >, <=, <, =, ~, ^)
- [x] Test unload order is reverse of load order
- [x] Verify optional dependencies do not block loading when missing

## Verification

**Run ID**: run-001
**Date**: 2026-02-10 (UTC)

### Implementation Coverage
- **PluginDependencyResolver**: 320 lines implementing topological sort with DFS cycle detection, version constraint parsing for 7 operators (>=, >, <=, <, =, ~pessimistic, ^compatible), optional dependency handling
- **DependencyGraph**: 225 lines implementing bidirectional graph with AddNode, AddEdge, HasNode, GetDependents, topological traversal support

### Test Coverage
- **DependencyResolverTests**: 12 tests covering topological sort, circular dependency detection, version constraints, optional dependencies
- **DependencyGraphTests**: 7 tests covering graph construction, edge management, dependent retrieval
- Total: 19 tests, all PASS

### Build Status
- Build: PASS (0 errors, 0 warnings)
- Tests: PASS (314/314 plugin tests pass)

### Verdict
**PASS** - Plugin dependency resolution verified. Topological sort produces correct load order for dependency chains. Circular dependency detection reports accurate cycle paths via DFS. Version constraint matching works for all 7 operators (>=, >, <=, <, =, ~, ^). Unload order is reverse of load order. Optional dependencies do not block loading when missing.