# Performance Audit Report

**Branch**: fix/tech-debt-v0.3.2
**Base**: main
**Date**: 2025-12-08 20:47
**Files Analyzed**: 7
**Lines Changed**: +177 / -83

---

## Executive Summary

This branch contains **positive performance changes** with **no blocking issues introduced**. The changes include:

1. **Performance improvement**: Replaced `getQueueStats()` with `getQueueSize()` to avoid unnecessary array copying
2. **Type safety improvements**: Added explicit row types (`DependencyRow`, `TaskRow`) replacing `Record<string, any>`
3. **Configurability**: Made `MAX_DEPENDENCY_CHAIN_DEPTH` configurable
4. **Documentation fix**: Corrected complexity claim for `getMaxDepth()` from O(1) to O(V+E)

---

## Analysis of Changes by Commit

### Commit: `ae29b02` - perf: replace getQueueStats() with getQueueSize()

**Category**: Performance Improvement (YOUR CHANGE)

**File**: `/workspace/delegate/src/services/handlers/queue-handler.ts:346-354`

**Before** (in main):
```typescript
getQueueStats(): { size: number; tasks: readonly any[] } {
  const allResult = this.queue.getAll();
  return {
    size: this.queue.size(),
    tasks: allResult.ok ? allResult.value : []
  };
}
```

**After** (this branch):
```typescript
getQueueSize(): number {
  return this.queue.size();
}
```

**Assessment**: POSITIVE CHANGE
- Eliminates unnecessary `getAll()` call that copies entire task array
- Returns only the count, not the full task list
- Expected improvement: O(n) to O(1) for queue size queries
- Memory: Eliminates temporary array allocation

**Risk**: LOW - API signature changed from `getQueueStats()` to `getQueueSize()`. Must ensure no callers depend on the `tasks` property.

---

### Commit: `ee9d13b` - refactor(types): add explicit row types for repository database access

**Category**: Type Safety Improvement (YOUR CHANGE)

**Files**:
- `/workspace/delegate/src/implementations/dependency-repository.ts:15-27`
- `/workspace/delegate/src/implementations/task-repository.ts:13-43`

**Assessment**: POSITIVE CHANGE (Performance Neutral)
- Added `DependencyRow` and `TaskRow` interfaces
- Replaced `Record<string, any>` with explicit types
- No runtime performance impact (types are erased at compile time)
- Improves code maintainability and catches type errors at compile time

---

### Commit: `52d366c` - refactor: make MAX_DEPENDENCY_CHAIN_DEPTH configurable

**Category**: Configuration Improvement (YOUR CHANGE)

**File**: `/workspace/delegate/src/services/handlers/dependency-handler.ts:24-32, 37, 49, 76, 101, 112, 181`

**Assessment**: POSITIVE CHANGE (Performance Neutral)
- Made depth limit configurable via `DependencyHandlerOptions`
- Default remains 100 (same as before)
- Allows testing with lower limits without code changes
- No runtime performance impact

---

### Commit: `724b055` - docs: fix incorrect getMaxDepth complexity claim in invariants

**Category**: Documentation Fix (YOUR CHANGE)

**File**: `/workspace/delegate/docs/architecture/HANDLER-DECOMPOSITION-INVARIANTS.md`

**Change**: Corrected documentation from:
```
Depth check uses `this.graph.getMaxDepth()` - cached O(1) after first call
```
To:
```
Depth check uses `this.graph.getMaxDepth()` - O(V+E) with internal memoization for diamond patterns
```

**Assessment**: This is a documentation accuracy fix. The actual `getMaxDepth()` implementation uses per-call memoization (not cross-call caching), so complexity is O(V+E) per call, not O(1).

---

### Commit: `413489c` - feat(db): add CHECK constraint on resolution column

**Category**: Database Schema Change (YOUR CHANGE)

**File**: `/workspace/delegate/src/implementations/database.ts:273-318`

**Migration approach**:
1. Create new table with CHECK constraint
2. Copy all existing data
3. Drop old table
4. Rename new table
5. Recreate all indexes

**Assessment**: SAFE MIGRATION
- Uses proper SQLite table migration pattern
- Data is preserved during migration
- Indexes are properly recreated
- CHECK constraint provides defense-in-depth validation

**Performance Impact**:
- One-time migration cost (only runs once per database)
- Slight INSERT overhead for constraint checking (negligible)

---

## Pre-existing Performance Observations

### Informational: `getMaxDepth()` is O(V+E) per call

**File**: `/workspace/delegate/src/core/dependency-graph.ts:634-677`

**Observation**: The `getMaxDepth()` method uses internal memoization within a single call (for diamond-shaped graphs), but does NOT cache results across calls.

**Current behavior**:
```typescript
getMaxDepth(taskId: TaskId): number {
  const memo = new Map<string, number>();  // Fresh map per call
  // ... DFS with memoization
}
```

**Impact**: Each call to `validateSingleDependency()` during `handleTaskDelegated()` calls `getMaxDepth()`, resulting in O(D * (V+E)) complexity where D = number of dependencies being added.

**Recommendation** (not blocking, future optimization):
- Consider adding persistent cross-call caching similar to `dependenciesCache`/`dependentsCache`
- Cache should be invalidated on graph mutations (addEdge, removeEdge, removeTask)

**Why not blocking**: The dependency graph is typically small in production workflows (< 100 nodes), and the depth check runs during task creation (not a hot path). The documentation was corrected in this branch.

---

### Informational: Sequential dependency validation followed by sequential event emission

**File**: `/workspace/delegate/src/services/handlers/dependency-handler.ts:323-327, 358`

**Current flow**:
```typescript
// Step 2: Validate all dependencies in parallel
const validationResults = await Promise.all(
  task.dependsOn.map(depId => this.validateSingleDependency(task.id, depId))
);

// ... later ...

// Step 6: Emit success events (sequential)
await this.emitDependencyAddedEvents(addResult.value);  // Loops with await
```

**Observation**: Validation is parallelized (good), but `emitDependencyAddedEvents()` emits events sequentially with `await` in a loop.

**Impact**: For N dependencies, event emission is O(N) sequential operations.

**Why not blocking**: Events are typically processed synchronously by the EventBus (in-memory), so the sequential `await` has minimal real impact. True parallel emission (`Promise.all`) could cause event ordering issues.

---

### Informational: `resolveDependencies()` has N+1 pattern for unblock checks

**File**: `/workspace/delegate/src/services/handlers/dependency-handler.ts:481-528`

**Pattern**:
```typescript
for (const dep of dependents) {
  // ... emit event ...
  
  // N+1: One isBlocked() query per dependent
  const isBlockedResult = await this.dependencyRepo.isBlocked(dep.taskId);
  
  if (!isBlockedResult.value) {
    // Another query per unblocked task
    const taskResult = await this.taskRepo.findById(dep.taskId);
    // ...
  }
}
```

**Impact**: For N dependents, this results in N `isBlocked()` queries + up to N `findById()` queries.

**Why not blocking**: The batch resolution optimization (`resolveDependenciesBatch`) already reduces the UPDATE queries to 1. The remaining queries are necessary to check individual task blocking state, which requires fresh data. A batch `areBlocked()` method could optimize this in a future iteration.

---

## Summary

**Your Changes:**
- No CRITICAL issues
- No HIGH issues
- No MEDIUM issues
- No LOW issues
- 1 POSITIVE performance improvement (`getQueueSize()`)

**Code You Touched:**
- No performance issues introduced

**Pre-existing:**
- 3 INFORMATIONAL observations (not introduced by this branch)

**Performance Score**: 9/10

The branch actively improves performance by eliminating unnecessary array copying in queue stats.

---

## Merge Recommendation

**APPROVED** - No performance issues in your changes. The branch contains one explicit performance improvement (`getQueueStats()` -> `getQueueSize()`) and several type safety/documentation fixes.

---

## Change Summary Table

| File | Change Type | Performance Impact |
|------|-------------|-------------------|
| `queue-handler.ts` | `getQueueStats()` -> `getQueueSize()` | +POSITIVE (O(n) -> O(1)) |
| `dependency-repository.ts` | Add `DependencyRow` type | Neutral |
| `task-repository.ts` | Add `TaskRow` type | Neutral |
| `dependency-handler.ts` | Configurable max depth | Neutral |
| `database.ts` | Add CHECK constraint migration | Neutral (one-time) |
| `HANDLER-DECOMPOSITION-INVARIANTS.md` | Fix complexity documentation | N/A |
| `TASK_ARCHITECTURE.md` | Update line references | N/A |

---

## Checklist

- [x] No N+1 queries introduced
- [x] No O(n^2) algorithms introduced
- [x] No memory leaks introduced
- [x] No unnecessary I/O in hot paths
- [x] No missing resource cleanup
- [x] No blocking I/O in async contexts
- [x] Database queries use indexes appropriately

---

*Report generated by Claude Code performance audit*
