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.
npx agentmods add skills/rileyhilliard/agentrc/systematic-debuggingnpx skills add rileyhilliard/agentrc --skill systematic-debugginggit clone --depth 1 https://github.com/rileyhilliard/agentrcWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00037 | $0.00647 |
| Opus 5 | $0.00018 | $0.00324 |
| Sonnet 5 | $0.00007 | $0.00129 |
| Haiku 4.5 | $0.00004 | $0.00065 |
Grade A, and why
systematic-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 2d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Systematic Debugging
Core principle: Find root cause before attempting fixes. Symptom fixes are failure.
The Four Phases
Complete each phase before proceeding to the next.
Debugging Progress:
- [ ] Phase 1: Root Cause Investigation
- [ ] Phase 2: Pattern Analysis
- [ ] Phase 3: Hypothesis Testing
- [ ] Phase 4: Implementation
Phase 1: Root Cause Investigation
Before attempting ANY fix:
- Read error messages carefully - Stack traces often contain the solution
- Reproduce consistently - If not reproducible, gather more data
- Check recent changes - Git diff, new dependencies, config changes
- Trace data flow backward - Find where invalid data originates
For multi-component systems: Add diagnostic logging at each component boundary before proposing fixes. See references/debugging-techniques.md for instrumentation patterns.
For log-heavy investigations: Use Skill(ce:reading-logs) for efficient analysis.
Phase 2: Pattern Analysis
- Find working examples of similar code in the codebase
- Compare working vs broken - list every difference
- Read reference implementations completely, not just skimming
Phase 3: Hypothesis Testing
- Form single hypothesis: "X is the root cause because Y"
- Make the SMALLEST possible change to test it
- Verify before continuing - if wrong, form NEW hypothesis
Phase 4: Implementation
- Create failing test case first
- Implement single fix at root cause
- Apply defense-in-depth - Validate at multiple layers
- Verify fix and run tests
If 3+ fixes have failed: Stop fixing symptoms. Question the architecture.
Red Flags
Stop and return to Phase 1 if you catch yourself:
- Proposing fixes without completing investigation
- "Just try changing X and see if it works"
- Adding multiple changes at once
- "It's probably X, let me fix that" (without evidence)
- Each fix reveals new problems in different places
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 95 lines · 37 tokens per session scan A a45e169e075a
systematic-debugging is a skill published in the GitHub repository rileyhilliard/agentrc (3 stars, last pushed 6mo ago), licensed MIT. It adds 37 tokens to every session and 647 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.
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