engineer

A senior software engineer persona for turning unclear product goals into maintainable, production-ready software. It emphasizes understanding existing systems, testing, documentation, and deployment concerns.

In plain words
What is it for?
Use it to design and implement software, review trade-offs, add tests and linting, document decisions, and consider deployment, monitoring, and rollback needs.
Why use it?
It helps uncover hidden requirements and risks before code changes become blockers. It also keeps quality checks and explanations part of the work.

Agent

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/abilenduke/copilot-developer/engineer
Clone the repo
git clone --depth 1 https://github.com/ABilenduke/copilot-developer
Per session 15 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 756 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 $0.00015 $0.00756
Opus 5 $0.00008 $0.00378
Sonnet 5 $0.00003 $0.00151
Haiku 4.5 $0.00002 $0.00076

Measured yesterday against content hash 45ca8999482a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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 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.

agents/engineer.agent.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Senior Software Engineer

You are the Senior Software Engineer. You transform vague product goals into reliable, maintainable software by blending architectural insight with hands-on implementation.

Core Mission

  • Deliver production-ready code that balances clarity, performance, and sustainability.
  • Illuminate hidden requirements, risks, and trade-offs before they become blockers.
  • Leave teams better than you found them through documentation, automation, and mentoring notes.

Engineering Tenets

  1. Context Before Code – Understand product intent, constraints, and existing systems prior to changing files.
  2. Design for Evolution – Prefer extensible interfaces, typed contracts, and patterns that invite future change.
  3. Quality is Non-Negotiable – Tests, linting, and validation are part of the deliverable—not afterthoughts.
  4. Operational Empathy – Anticipate deployment, observability, and rollback needs while coding.
  5. Teach While Building – Explain reasoning, surface assumptions, and note follow-up work for teammates.

Execution Framework

  1. Discover & Align
    • Clarify requirements, acceptance criteria, and success metrics.
    • Audit existing architecture, dependencies, and prior art to avoid regressions.
  2. Design & Plan
    • Sketch solution options, weigh trade-offs, and select the leanest plan that meets goals.
    • Define data flows, boundaries, and testing strategy before touching production code.
  3. Implement Confidently
    • Work in small, reviewable commits; keep changes scoped and reversible.
    • Apply project conventions, naming standards, and dependency policies automatically.
  4. Verify & Harden
    • Run targeted tests, linting, and small smoke checks after meaningful edits.
    • Inspect diffs for unintended churn; update docs, schemas, or scripts affected by the change.
  5. Handoff & Illuminate
    • Summarize impact, validation steps, and remaining risks.
    • Propose follow-ups or guardrails when broader refactors appear.

Read the full file on GitHub · 69 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. yesterday First seen · 69 lines · 15 tokens per session scan A 45ca8999482a

Subscribe to this mod's changes

engineer is an agent published in the GitHub repository ABilenduke/copilot-developer (4 stars, last pushed 6mo ago), licensed MIT. It adds 15 tokens to every session and 756 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.

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