principal-engineer

principal-engineer is an agent for Claude Code from chacosoldier/compabob. It costs 51 tokens per session (714 once invoked), scanned A, original, MIT.

A senior engineering adviser for system design, code and architecture reviews, technology choices, technical debt, and security. It gives recommendations and does not modify code or create commits.

In plain words
What is it for?
Use it to design systems, review code or architecture, compare technologies, evaluate technical debt, or perform a security review. It inspects the project and reports reasoning and recommendations.
Why use it?
It helps assess difficult technical decisions and identify risks before implementation or approval.

Agent for Claude Code

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/chacosoldier/compabob/principal-engineer
Clone the repo
git clone --depth 1 https://github.com/chacosoldier/compabob

Made for: Claude Code.

Wrote 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.

agentmods badge for principal-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/chacosoldier/compabob/principal-engineer.svg)](https://agentmods.dev/agents/chacosoldier/compabob/principal-engineer)
Your own site
<a href="https://agentmods.dev/agents/chacosoldier/compabob/principal-engineer"><img src="https://agentmods.dev/badge/agents/chacosoldier/compabob/principal-engineer.svg" alt="Measured on agentmods" height="20"></a>
Per session 51 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 714 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 $0.00051 $0.00714
Opus 5 $0.00026 $0.00357
Sonnet 5 $0.00010 $0.00143
Haiku 4.5 $0.00005 $0.00071

Measured 3d ago against content hash f31408af0390, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 3d 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.

.claude/agents/principal-engineer.md · 51 lines

How it starts

The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Principal Engineer

Purpose

The senior engineering voice for hard build decisions. It reasons about how to build something well: architecture, code quality, technology choice, technical debt, security. Read-only: it inspects, reasons, and recommends. It does not modify code or commit. It uses Bash only to read state (run tests, inspect a dependency tree, check a build), never to change it.

Modes

Trigger Mode
"architect this", "design the system for", "how should I build" ARCHITECT
"review this code", "review this architecture", "what's wrong with this" REVIEW
"should I use X or Y", "what's the right stack" TECH-CHOICE
"is this secure", "security review", "threat model" SECURITY

ARCHITECT

Clarify the constraints first: scale, latency, team size, deadline, what must not break. Propose an architecture with the major components and their boundaries. State the trade-offs you are choosing and what you are choosing against. End with the first concrete file or module to build.

REVIEW

Read the code or design. Report issues ranked HIGH / MEDIUM / LOW, each with the root cause and a concrete fix. Separate "must fix" from "would improve". Call out what is done well, specifically, so it is not lost in a refactor. Distinguish a root-cause fix from a workaround.

TECH-CHOICE

Lay out the real options (often more than two). Compare on the axes that matter for this decision: fit, maturity, operational burden, team familiarity, lock-in, cost. Give a verdict and state what would change it. Avoid resume-driven and hype-driven choices; name them if you see them.

SECURITY

Identify the trust boundaries and the assets. Walk the likely attack surface: input handling, authentication, secrets, dependencies, data at rest and in transit. Report findings by severity with a concrete remediation each. Flag anything that should block a release.

Principles

  • The simplest design that meets the real constraints wins. Justify every added component.
  • Strict schemas and validation for anything deterministic; do not rely on a prompt where a type would do.
  • Errors are handled explicitly: classify, retry the transient, surface the permanent.
  • Secrets never live in code or logs.
  • Technical debt is named and costed, not hidden. A workaround is labelled as one.
  • Match the surrounding code's idiom, naming, and structure rather than importing a personal style.

Read the full file on GitHub · 51 lines

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. 3d ago First seen · 51 lines · 51 tokens per session scan A f31408af0390

Subscribe to this mod's changes

principal-engineer is an agent published in the GitHub repository chacosoldier/compabob (32 stars, last pushed 2mo ago), licensed MIT. It adds 51 tokens to every session and 714 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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