Aegis is a method pack that guides coding agents to inspect a project's baseline, make bounded changes, and verify their work with fresh evidence. It is for people using coding-agent hosts who want fewer unverified changes and less unnecessary process. The catalogue add-ons implement this method through skills, instructions, commands, a hook, and a plugin.
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 skills add GanyuanRan/Aegis --skill systematic-debugginggit clone --depth 1 https://github.com/GanyuanRan/AegisWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/ganyuanran/aegis/systematic-debugging)<a href="https://agentmods.dev/skills/ganyuanran/aegis/systematic-debugging"><img src="https://agentmods.dev/badge/skills/ganyuanran/aegis/systematic-debugging/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/ganyuanran/aegis/systematic-debugging"><img src="https://agentmods.dev/badge/skills/ganyuanran/aegis/systematic-debugging.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00021 | $0.02457 |
| Opus 5.5 | $0.00008 | $0.00983 |
| Sonnet 5.5 | $0.00004 | $0.00491 |
| Haiku 4.5 | $0.00002 | $0.00246 |
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 7d 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 — 203 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Execute
Bug, failure, or unexpected behavior:
- Isolate — read error, reproduce, inspect the diff, and drill upward through diagnostic layers: L1 symptom → L2 logic → L3 system → L4 architecture → L5 cross-system contract → L6 platform → L7 spec gap. Layers are observation altitudes, not one causal chain; the causal shape at the stop altitude is classified explicitly before any root claim. Stop only when causal proof accounts for the recurrence generator or reaches a T-class boundary.
- Identify owner — compare working behavior, trace the bad value, locate the canonical owner, and treat duplicate owners as a finding.
- Decide before editing — Before fixing, run Patch-Shape Triage and Ripple Signal Triage when shared logic,
contracts, fallbacks, adapters, producer/consumer seams, or source-of-truth
boundaries are involved. Surface Change Necessity for any new source-code
path or non-trivial source edit. Run Minimality Check for a new branch,
fallback, adapter, owner, or compatibility path, and Pre-Edit Complexity
Check for an overloaded owner or complexity growth. After Change Necessity
selects
code-changeand before the first repair edit, own the TDD Route for the repair slice pertest-driven-development(offdefault;stricton behavior/bugfix/shared/contract/persistence/permission/migration risk). - Prove — test one hypothesis with the smallest reproduction or
verification. A failing test first is required only by a recorded
TDD Route: strict; withTDD Mode: off, do not require a failing test or RED/GREEN cycle. Three failed fixes means stop and question architecture. - Repair and close — fix minimally at the canonical owner, verify in proportion to risk, review architecture, and close both repair and retirement tracks. If any symptom remains, stop and diagnose it separately.
Done: confidence ≥ B, causal status matches recurrence evidence or an external terminal, tracks explicit, no H signal, and required D evidence passes.
What ships with it
8 files 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.
- 7d ago Changed · +3 lines fc5b0888c386
- 17d ago Changed · +4 lines d251d254da3f
- 1mo ago Changed · -47 lines 5d642fb60775
- 1mo ago Changed · +4 lines 6b923ab1f799
- 1mo ago Changed · +17 lines f54b9e1f185f
- 1mo ago First seen · 222 lines · 21 tokens per session scan A 3416b67da9c4
systematic-debugging is a skill published in the GitHub repository GanyuanRan/Aegis (1,358 stars, last pushed today), licensed MIT. It adds 21 tokens to every session and 2,457 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-08-30.
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