feat: What-If Scenario Simulator for predicting code change impacts

[haasonsaas]

Summary

This PR implements the What-If Scenario Simulator, a powerful new feature that predicts the impact of code changes before implementation. It uses AI-powered comparative analysis to identify risks, emergent behaviors, and system-wide impacts.

Features Implemented

1. Core Simulation Engine

• ✅ simulateChange method in DeepCodeReasonerV2
• ✅ Three-step comparative analysis:
  1. Baseline Analysis: Understand current code behavior
  2. Change Analysis: Apply proposed changes and compare
  3. Impact Assessment: Identify emergent behaviors and risks
• ✅ Risk assessment with recommendations: safe_to_implement, proceed_with_caution, or high_risk_do_not_implement

2. Integration with MCP Protocol

• ✅ Extended hypothesis_test tool to accept proposed_change parameter
• ✅ Support for git-style diffs
• ✅ Stress condition simulation (high concurrency, network latency, high error rate)
• ✅ Automatic routing to simulation engine when proposed_change is provided

3. Data Models

• ✅ SimulationResult with risk levels and findings
• ✅ SimulationFinding for individual risk assessments
• ✅ ProposedChange for representing code changes
• ✅ SimulationParameters for stress testing configuration

4. Documentation & Examples

• ✅ Comprehensive examples showing three real-world scenarios:
  • Retry logic changes (exponential → linear backoff)
  • Adding caching to database queries
  • Changing error handling patterns
• ✅ Detailed request/response format documentation

5. GitHub Action Integration (Template)

• ✅ Workflow that triggers on PR events
• ✅ Extracts diff and affected files
• ✅ Posts formatted results as PR comments
• ✅ Risk level indicators with emojis
• ✅ Updates existing comments on re-runs

Example Usage

{
  "name": "hypothesis_test",
  "arguments": {
    "hypothesis": "Changing retry from exponential to linear backoff",
    "code_scope": { "files": ["src/utils/RetryHandler.ts"] },
    "test_approach": "Analyze retry behavior under load",
    "proposed_change": {
      "description": "Replace exponential with linear backoff",
      "diff": "--- a/src/utils/RetryHandler.ts\n+++ b/...",
      "affected_files": ["src/utils/RetryHandler.ts"]
    },
    "simulation_parameters": {
      "stress_conditions": ["high_error_rate"]
    }
  }
}

Technical Implementation

The simulator uses the Conversational Gemini Service to maintain context between analysis steps, enabling deep comparative reasoning:

1. Analyzes current code state focusing on affected areas
2. Applies the proposed diff mentally and re-analyzes
3. Compares before/after states to identify:
   • Performance impacts
   • Breaking changes
   • Emergent behaviors (feedback loops, resource exhaustion)
   • Downstream effects on other services

Next Steps

• Integrate with actual MCP server runtime in GitHub Action
• Add more sophisticated diff parsing for better function extraction
• Implement caching for faster re-analysis of similar changes
• Add support for multiple file diffs
• Create VS Code extension for real-time analysis

Testing

The implementation includes proper error handling and validation:

• Input sanitization using existing security measures
• Graceful fallback on analysis errors
• TypeScript build passes with no errors

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This feature represents a significant advancement in proactive code quality assurance, allowing developers to "see the future" before making changes.

🤖 Generated with Claude Code

[github-actions]

⚠️ What-If Scenario Analysis

Recommendation: PROCEED WITH CAUTION

Justification: Analysis pending full implementation

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🤖 Generated by Deep Code Reasoning MCP What-If Simulator