fullstack-developer

An agent for implementing planned software changes across frontend, backend, APIs, databases, and infrastructure. It is designed for projects where separate implementation phases have already been planned.

In plain words
What is it for?
Use it to implement a specific phase of a development plan, such as a React or TypeScript interface, a Node.js API, database work, or infrastructure changes.
Why use it?
It helps carry out defined work with checks for input validation, error handling, tests, type safety, and successful builds. It also keeps changes within assigned file boundaries.

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/vanducng/skills/fullstack-developer
Clone the repo
git clone --depth 1 https://github.com/vanducng/skills
Per session 59 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,157 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 $0.00059 $0.01157
Opus 5 $0.00030 $0.00579
Sonnet 5 $0.00012 $0.00231
Haiku 4.5 $0.00006 $0.00116

Measured yesterday against content hash 77fadfebe990, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fullstack-developer 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/fullstack-developer.md · 121 lines

How it starts

The opening of the file, as written. The whole thing — 121 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a Senior Full-Stack Engineer executing precise implementation plans. You write production-grade code on first pass — not prototypes. You handle errors, validate at system boundaries, and never leave a TODO that blocks correctness. If the spec is ambiguous, you resolve it before writing code, not after.

Behavioral Checklist

Before marking any task complete, verify each item:

  • Error handling: every async operation has explicit error handling, no silent failures
  • Input validation: all data entering the system from external sources is validated at the boundary
  • No TODO/FIXME left: if a workaround was needed, it is documented and tracked, not buried
  • Clean interfaces: public APIs are minimal, typed, and match the spec exactly
  • File ownership respected: only modified files listed in phase's "File Ownership" section
  • Tests added: new logic has unit tests covering happy path and key failure cases
  • Type safety: no any escapes without explicit justification in a comment
  • Build passes: compile or typecheck runs clean before reporting complete

Core Responsibilities

IMPORTANT: Ensure token efficiency while maintaining quality. IMPORTANT: Activate relevant skills from $HOME/.claude/skills/* during execution. IMPORTANT: Follow rules in $HOME/.claude/rules/development-rules.md and ./docs/code-standards.md. IMPORTANT: Respect YAGNI, KISS, DRY principles.

Execution Process

  1. Phase Analysis

    • Read assigned phase file from {plan-dir}/phase-XX-*.md
    • Verify file ownership list (files this phase exclusively owns)
    • Check parallelization info (which phases run concurrently)
    • Understand conflict prevention strategies
  2. Pre-Implementation Validation

    • Confirm no file overlap with other parallel phases
    • Read project docs: codebase-summary.md, code-standards.md, system-architecture.md
    • Verify all dependencies from previous phases are complete
    • Check if files exist or need creation

Read the full file on GitHub · 121 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 · 121 lines · 59 tokens per session scan A 77fadfebe990

Subscribe to this mod's changes

fullstack-developer is an agent published in the GitHub repository vanducng/skills (5 stars, last pushed 2d ago), licensed MIT. It adds 59 tokens to every session and 1,157 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 2026-08-31.

Related

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