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    Codebase Bug Fixer

    1

    Diagnose software bugs, trace execution paths, and generate minimal patches with targeted validation tests.

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    Codebase Bug Fixer

    Codebase Bug Fixer

    Example session with this skill installed

    I'm getting 'TypeError: Cannot read properties of undefined (reading 'map')' in my React app when the user filters results too quickly. Here is the component and the stack trace.

    • Read your context and instructions
    • Compiled the codebase bug fixer

    I have analyzed the stack trace and the filtering logic. The crash occurs because the results state is briefly set to null during the transition between rapid filter updates, but the render method assumes an array.

    Bug Analysis and Fix Plan

    Bug Summary

    • Symptom: Application crash (TypeError)
    • Expected: Component should show a loading state or empty list during filter transitions.
    • Actual: results.map is called on an undefined variable.
    • Root-cause confidence: Confirmed

    Execution Trace

    Filter Change Event → handleFilter (Async) → State Update (setResults(undefined)) → Component Re-render → results.map() → Crash

    Recommended Fix

    • File: src/components/SearchGrid.tsx

    Change: Add optional chaining and a fallback empty array to the mapping logic, and initialize state as an empty array.

    • Reason: Prevents the UI from attempting to iterate over non-iterable state during async updates.

    Patch

    // src/components/SearchGrid.tsx

// Before:
// const [results, setResults] = useState();
// {results.map(item => <Card key={item.id} data={item} />)}

// After:
const [results, setResults] = useState<Item[]>([]);

return (
  <div className="grid">
    {results?.map(item => (
      <Card key={item.id} data={item} />
    )) ?? <p>No results found.</p>}
  </div>
);

    Validation Plan

    TestExpected ResultPriority
    Rapid Filter TriggerUI remains stable; no TypeErrorCritical
    Null API ResponseDisplays "No results found"High
    Regression: Valid DataItems render correctly in gridHigh

    Next steps

    1. Apply the initialization change to useState([]) to ensure a consistent data type.
    2. Replace the .map call with the optional chaining implementation.
    3. Verify the fix by spamming the filter inputs in the dev environment.

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    About this skill

    The problem

    Debugging often involves hours of aimless console logging and chasing red herrings. Developers struggle to isolate root causes in complex execution paths or provide minimal fixes that don't break existing functionality.

    What it does

    • Analyzes stack traces and reproduction steps to map the execution flow from trigger to failure.
    • Identifies root causes like race conditions, state synchronization issues, and null handling gaps with evidence-based confidence levels.
    • Designs minimal, architecture-compliant patches that fix the bug without unnecessary refactoring.
    • Generates targeted validation plans including reproduction tests, edge cases, and regression checks.
    • Evaluates side effects on shared state, API consumers, and performance.

    Frameworks & tools

    Works across JavaScript/TypeScript, React/Next.js, Python, Java, C#, Go, PHP, Ruby, and SQL-backed applications.

    Why this beats prompting it yourself

    Generic prompts often suggest "best guess" fixes or rewrite entire modules. This skill enforces a strict REPRODUCE-LOCATE-TRACE workflow that demands evidence before proposing code changes, ensuring you get a surgical patch rather than a destructive hallucination.

    Use cases

    • Tracing an obscure 'undefined' error through a deeply nested React component tree.
    • Debugging race conditions in asynchronous Python or Go backend services.
    • Fixing incorrect state transitions in complex Vue or Angular forms.
    • Patching API contract mismatches between microservices without breaking backward compatibility.

    Requires specific code context or stack traces to verify findings; cannot debug environments or files that are not provided in the prompt context.

    How to use

    1. 1

      Connect your agent to the Agensi MCP

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    2. 2

      Sign in to Agensi

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    3. 3

      Ask for what you need

      Your agent loads this skill and uses it on your task. It always asks before any payment.

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    Listed1 month ago

    What's inside

    Frequently Asked Questions

    The Codebase Bug Fixer utilizes a structured REPRODUCE-LOCATE-TRACE workflow to isolate the root cause of a bug before proposing a solution, ensuring surgical patches rather than generic code rewrites. Unlike basic prompts, it specifically generates targeted validation tests to confirm the fix works and doesn't introduce regressions.

    This skill is compatible with any LLM-powered agent that has access to your file system or version control, including popular IDE extensions and CLI-based coding assistants. It works across major languages and frameworks like React, Python, Java, and Go.

    You will receive the specialized agent configuration, the structured debugging workflow logic, and documentation on how to integrate the skill into your existing development environment. It includes logic for stack trace analysis, execution path mapping, and patch generation.

    Setup is straightforward: once you import the skill into your preferred AI agent platform, you simply provide the bug report, stack trace, or reproduction steps to begin the diagnostic process. No complex environment configuration is required beyond giving the agent access to the relevant source files.

    Yes, the skill is designed to handle multi-file execution paths, such as tracing a state change from a React frontend through to an API endpoint or a SQL database query. It identifies side effects across shared states and API consumers to ensure the patch is safe for complex architectures.

    New in Testing & Debugging