debugging

A set of rules for investigating bugs, failed tests, and unexpected behavior by reproducing the problem, finding its cause, making a small fix, and checking the result.

In plain words
What is it for?
Use it to define expected and actual behavior, diagnose the failing code path, add or run a confirming test, and record useful lessons in repository memory.
Why use it?
It prevents guess-and-check changes that hide symptoms while leaving the underlying problem unresolved.

Cursor rule for Cursor

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 rules/kingemma7/cursor-os/debugging
Clone the repo
git clone --depth 1 https://github.com/KingEmma7/cursor-os

Made for: Cursor.

Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 195 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 $0.00017 $0.00195
Opus 5 $0.00009 $0.00097
Sonnet 5 $0.00003 $0.00039
Haiku 4.5 $0.00002 $0.00019

Measured yesterday against content hash 48415f3ddd4d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

debugging 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.

template/.cursor/rules/debugging.mdc · 14 lines

What it actually says

Opt-in debugging discipline: find the root cause before changing code. For a structured walkthrough, use the debugging-loop skill.

  • Reproduce first. Establish the exact steps and the expected-vs-actual behavior before forming a fix.
  • Diagnose before editing. Read the failing path and form a hypothesis; don't guess-and-check by mutating code.
  • Change the cause, not the symptom. Avoid masking errors with broad try/catch, retries, or silencing logs.
  • Make the smallest fix that addresses the root cause. Keep unrelated cleanup out of the bugfix.
  • Prove it. Add or run a test (or a concrete manual check) that fails before the fix and passes after.
  • If the bug revealed a gap in project memory, note it in docs/repo-memory.md so it doesn't recur.
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 · 14 lines · 17 tokens per session scan A 48415f3ddd4d

Subscribe to this mod's changes

debugging is a cursor rule published in the GitHub repository KingEmma7/cursor-os (2 stars, last pushed 20d ago), licensed MIT. It adds 17 tokens to every session and 195 once invoked, about $0.0001 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.