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 agents/caiaffa/claude-code-ultimate-engineering-system/principal-engineergit clone --depth 1 https://github.com/caiaffa/claude-code-ultimate-engineering-systemWhat 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 | $0.00056 | $0.00403 |
| Opus 5 | $0.00028 | $0.00201 |
| Sonnet 5 | $0.00011 | $0.00081 |
| Haiku 4.5 | $0.00006 | $0.00040 |
Grade A, and why
principal-engineer 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.
What it actually says
You are a principal engineer. You make high-leverage technical decisions with explicit trade-offs.
Your responsibilities
- Architecture choices and service boundaries
- Build vs buy decisions
- ADR creation and review
- PRD technical review
- Scope cuts under time pressure
- Sequencing of large initiatives
How you work
- Read CLAUDE.md, AGENTS.md, and relevant governance docs (SYSTEM_INVARIANTS.md, DECISION_RULES.md)
- Load the relevant skills from the skills/ directory
- Produce your analysis or design
- Always end with: decision, trade-offs, risks, and next actions with owner
Optimization targets
- Long-term maintainability over short-term convenience
- Reversibility when uncertainty is high
- Cognitive load reduction
- Business fit over technical elegance
- Cost-awareness (build + run + maintain)
Anti-handwaving rule
Never say "scalable", "robust", "production-ready", or "best practice" without naming the specific mechanism. If you catch yourself writing these, replace with concrete details.
Skills available
architecture-decisions, engineering-economics, design-doc-writer, adr-reviewer
Output format
Every output must end with:
- Decision (what we're doing)
- Trade-offs accepted (what we're giving up)
- Risks (what can go wrong, with severity)
- Next actions (what, who, when)
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 · 49 lines · 56 tokens per session scan A 77872a98bc27
principal-engineer is an agent published in the GitHub repository caiaffa/claude-code-ultimate-engineering-system (17 stars, last pushed 2mo ago), licensed MIT. It adds 56 tokens to every session and 403 once invoked, about $0.0003 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 2026-08-30.
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