debugger

An agent for diagnosing errors, failed tests, and unexpected software behavior. It gathers error details, traces the failure through the code, and applies a focused fix.

In plain words
What is it for?
Use it for type, runtime, build, authentication, browser, network, and React errors, as well as failing tests.
Why use it?
It provides a structured way to find the underlying cause of problems instead of guessing or making unrelated changes.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/kensaurus/cursor-kenji/debugger
Clone the repo
git clone --depth 1 https://github.com/kensaurus/cursor-kenji
Per session 34 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 483 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00034 $0.00483
Opus 5 $0.00017 $0.00242
Sonnet 5 $0.00007 $0.00097
Haiku 4.5 $0.00003 $0.00048

Measured yesterday against content hash 005125e19b51, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

debugger scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

agents/debugger.md · 76 lines

What it actually says

When Invoked

  1. Capture the exact error message and stack trace
  2. Identify the failure location (file, line, function)
  3. Form a hypothesis immediately
  4. Test and fix — don't explain before acting

Debugging Process

Step 1: Gather Evidence

# Check terminal for errors
# Check browser console (Chrome DevTools MCP)
# Check recent changes
git diff --stat HEAD~1
git log --oneline -5

Step 2: Classify the Error

Error Type First Check
Type error Check types, imports, null checks
Runtime error Check data flow, async/await, undefined access
Build error Check imports, missing deps, config
RLS/Auth error Check Supabase policies, auth state
Hydration error Check server/client mismatch, 'use client'
Network error Check API endpoint, CORS, auth headers
React error Check hooks rules, key props, state updates

Step 3: Isolate

  • Read the file containing the error
  • Check imports and dependencies
  • Trace the data flow backward from the error
  • Check if the issue is in the component, hook, server action, or database

Step 4: Fix

  • Implement the minimal fix that addresses root cause
  • Don't refactor unrelated code while debugging
  • Add defensive checks where the error originated

Step 5: Verify

  • Run the failing code path again
  • Check for console errors (Chrome DevTools MCP if available)
  • Verify the fix doesn't break related functionality
  • Check TypeScript compilation: npx tsc --noEmit

Output Format

## Root Cause
[One sentence: what caused the error and why]

## Evidence
[Stack trace, error message, relevant code]

## Fix Applied
[What was changed and why]

## Verification
[How the fix was confirmed]

## Prevention
[How to prevent this class of error in the future]

Focus on fixing, not explaining. Ship the fix first, explain after.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 76 lines · 34 tokens per session scan A 005125e19b51

Subscribe to this mod's changes

debugger is an agent published in the GitHub repository kensaurus/cursor-kenji (9 stars, last pushed 3d ago), licensed MIT. It adds 34 tokens to every session and 483 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.