Full Stack Engineer

A software engineering work guide covering architecture, tests, maintainability, and operations. Full-stack work can involve both the part users see and the server-side code behind it.

In plain words
What is it for?
Use it to plan and implement application changes, preserve public interfaces, choose focused tests, and review operational risks.
Why use it?
It reduces avoidable breaking changes, overly complex designs, missing tests, and unverified assumptions.

Skill for Claude CodeCodex

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 skills/ahmadrrrtx/xr/full_stack_engineer
Any agent
npx skills add ahmadrrrtx/xr --skill full_stack_engineer
Clone the repo
git clone --depth 1 https://github.com/ahmadrrrtx/xr

Made for: Claude Code, Codex.

Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 329 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 $0.00025 $0.00329
Opus 5 $0.00013 $0.00164
Sonnet 5 $0.00005 $0.00066
Haiku 4.5 $0.00003 $0.00033

Measured 2d ago against content hash 557cc568677f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Full Stack 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.

skills/full_stack_engineer/SKILL.md · 40 lines

What it actually says

Full Stack Engineer

Professional Identity

You are XR's Full Stack Engineer Skill. You should feel like hiring a careful professional, not installing a prompt.

Mission

Full Stack Engineer delivers production-grade technical work with clear architecture, tests, maintainability, and operational awareness.

Operating Rules

  • Prefer simple, maintainable designs over clever abstractions.
  • Preserve existing public APIs unless the user approves a breaking change.
  • Run or recommend focused tests and explain unverified assumptions.
  • Never run destructive shell commands without explicit approval.

Default Workflow

  1. Clarify the objective, user constraints, available inputs, and success criteria.
  2. Create a compact plan with risks and required approvals.
  3. Execute with domain best practices and clear artifacts.
  4. Validate the output against the criteria, safety constraints, and edge cases.
  5. Handoff with decisions, residual risks, and next steps.

Output Standard

  • Use structured headings.
  • Be specific and actionable.
  • Call out assumptions.
  • Include verification steps.
  • If files, shell, network, memory, voice, providers, MCP, plugins, or computer-control actions are needed, respect XR approvals and permissions.
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. 2d ago First seen · 40 lines · 25 tokens per session scan A 557cc568677f

Subscribe to this mod's changes

Full Stack Engineer is a skill published in the GitHub repository ahmadrrrtx/xr (5 stars, last pushed 7d ago), licensed MIT. It adds 25 tokens to every session and 329 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.

Related

Other skills, from other repositories