Slopwatch: LLM Anti-Cheat for .NET

When to Use This Skill

Use this skill constantly. Every time an LLM (including Claude) makes changes to:

• C# source files (.cs)
• Project files (.csproj)
• Props files (Directory.Build.props, Directory.Packages.props)
• Test files

Run slopwatch to validate the changes don't introduce "slop."

What is Slop?

"Slop" refers to shortcuts LLMs take that make tests pass or builds succeed without actually solving the underlying problem. These are reward hacking behaviors - the LLM optimizes for apparent success rather than real fixes.

Common Slop Patterns

Never accept these patterns. If an LLM introduces slop, reject the change and require a proper fix.

Installation

As a Local Tool (Recommended)

Add to .config/dotnet-tools.json:

{
  "version": 1,
  "isRoot": true,
  "tools": {
    "slopwatch.cmd": {
      "version": "0.3.3",
      "commands": ["slopwatch"],
      "rollForward": false
    }
  }
}

Then restore:

dotnet tool restore

As a Global Tool

dotnet tool install --global Slopwatch.Cmd

First-Time Setup: Establish a Baseline

Before using slopwatch on an existing project, create a baseline:

# Initialize baseline from existing code
slopwatch init

# This creates .slopwatch/baseline.json
git add .slopwatch/baseline.json
git commit -m "Add slopwatch baseline"

Why baseline? Legacy code may have existing issues. The baseline ensures slopwatch only catches new slop being introduced.

Usage

Basic Analysis

# Analyze current directory for slop
slopwatch analyze

# Analyze specific directory
slopwatch analyze -d ./src

# Strict mode -- fail on warnings too
slopwatch analyze --fail-on warning

# JSON output for tooling integration
slopwatch analyze --output json

# Show performance stats
slopwatch analyze --stats

Updating the Baseline (Rare)

Only update when slop is truly justified and documented:

slopwatch analyze --update-baseline

Valid reasons: third-party library forces a pattern, intentional rate-limiting delay (not test flakiness), generated code that cannot be modified. Always add a code comment explaining the justification.

Configuration

Create .slopwatch/slopwatch.json to customize:

{
  "minSeverity": "warning",
  "rules": {
    "SW001": { "enabled": true, "severity": "error" },
    "SW002": { "enabled": true, "severity": "warning" },
    "SW003": { "enabled": true, "severity": "error" },
    "SW004": { "enabled": true, "severity": "warning" },
    "SW005": { "enabled": true, "severity": "warning" },
    "SW006": { "enabled": true, "severity": "warning" }
  },
  "exclude": [
    "**/Generated/**",
    "**/obj/**",
    "**/bin/**"
  ]
}

Strict Mode (Recommended for LLM Sessions)

{
  "minSeverity": "warning",
  "rules": {
    "SW001": { "enabled": true, "severity": "error" },
    "SW002": { "enabled": true, "severity": "error" },
    "SW003": { "enabled": true, "severity": "error" },
    "SW004": { "enabled": true, "severity": "error" },
    "SW005": { "enabled": true, "severity": "error" },
    "SW006": { "enabled": true, "severity": "error" }
  }
}

Detection Rules

When Slopwatch Flags an Issue

❌ SW001 [Error]: Disabled test detected
   File: tests/MyApp.Tests/OrderTests.cs:45
   Pattern: [Fact(Skip="Test is flaky")]

1. Understand why the LLM took the shortcut
2. Request a proper fix - be specific about what's wrong
3. Verify the fix doesn't introduce different slop

Never disable tests to achieve a green build. Fix the underlying issue.

Claude Code Hook Integration

Add slopwatch as a hook to automatically validate every edit. Create or update .claude/settings.json:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit|MultiEdit",
        "hooks": [
          {
            "type": "command",
            "command": "slopwatch analyze -d . --hook",
            "timeout": 60000
          }
        ]
      }
    ]
  }
}

The --hook flag:

• Only analyzes git dirty files (fast, even on large repos)
• Outputs errors to stderr in readable format
• Blocks the edit on warnings/errors (exit code 2)
• Claude sees the error and can fix it immediately

CI/CD Integration

GitHub Actions

jobs:
  slopwatch:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup .NET
        uses: actions/setup-dotnet@v4
        with:
          dotnet-version: '8.0.x'

      - name: Install Slopwatch
        run: dotnet tool install --global Slopwatch.Cmd

      - name: Run Slopwatch
        run: slopwatch analyze -d . --fail-on warning

Azure Pipelines

- task: DotNetCoreCLI@2
  displayName: 'Install Slopwatch'
  inputs:
    command: 'custom'
    custom: 'tool'
    arguments: 'install --global Slopwatch.Cmd'

- script: slopwatch analyze -d . --fail-on warning
  displayName: 'Slopwatch Analysis'

The Philosophy: Zero Tolerance for New Slop

1. Baseline captures legacy - Existing issues are acknowledged but isolated
2. New slop is blocked - Any new shortcut fails the build/edit
3. Exceptions require justification - If you must update baseline, document why
4. LLMs are not special - The same rules apply to human and AI-generated code

Quick Reference

# First time setup
slopwatch init
git add .slopwatch/baseline.json

# After every LLM code change
slopwatch analyze

# Strict mode (recommended)
slopwatch analyze --fail-on warning

# With stats (performance debugging)
slopwatch analyze --stats

# Update baseline (rare, document why)
slopwatch analyze --update-baseline

# JSON output for tooling
slopwatch analyze --output json

# Hook mode (for Claude Code integration)
slopwatch analyze -d . --hook

When to Override (Almost Never)

The only valid reasons to update baseline or disable a rule:

Invalid reasons:

• "The test is flaky" → Fix the flakiness
• "The warning is annoying" → Fix the code
• "It works on my machine" → Fix the race condition
• "We'll fix it later" → Fix it now

Agent Gotchas

• Do not suppress slopwatch findings. If slopwatch flags an issue, fix the code.
• Run after every code change, not just at the end.
• Use --hook flag in Claude Code hooks, not bare analyze.
• Baseline is not a wastebasket. Adding items requires documented justification.
• Local tool preferred over global. Use .config/dotnet-tools.json.

References

• Slopwatch NuGet Package