implement

implement is a skill for Claude Code, Codex from vasuag09/harness-claude. It costs 52 tokens per session (972 once invoked), scanned A, original, MIT.

A test-driven implementation step for carrying out an approved plan. Test-driven development means writing a failing test first, adding the smallest code that makes it pass, and then improving the code.

In plain words
What is it for?
Use it after planning to implement work phase by phase, with tests, type checks, formatting checks, and other project checks.
Why use it?
It ties each change to an expected result and catches regressions while the feature is being built.

Skill for Claude CodeCodex

Part of the harness-claude plugin — 34 skills, 8 agents, 6 hooks, 3 MCP servers shipped together

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/vasuag09/harness-claude/implement
Any agent
npx skills add vasuag09/harness-claude --skill implement
Clone the repo
git clone --depth 1 https://github.com/vasuag09/harness-claude

Made for: Claude Code, Codex.

Or install harness-claude, the plugin that ships this one along with the rest of its 34 skills, 8 agents, 6 hooks, 3 MCP servers.

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 implement

README.md
[![agentmods](https://agentmods.dev/badge/skills/vasuag09/harness-claude/implement.svg)](https://agentmods.dev/skills/vasuag09/harness-claude/implement)
Your own site
<a href="https://agentmods.dev/skills/vasuag09/harness-claude/implement"><img src="https://agentmods.dev/badge/skills/vasuag09/harness-claude/implement.svg" alt="Measured on agentmods" height="20"></a>
Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 972 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 $0.00052 $0.00972
Opus 5 $0.00026 $0.00486
Sonnet 5 $0.00010 $0.00194
Haiku 4.5 $0.00005 $0.00097

Measured 4d ago against content hash 8563b2960ddc, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

implement 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 4d 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/implement/SKILL.md · 64 lines

How it starts

The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/implement — build it, test-first

Goal: turn the plan into working, tested, clean code — one phase at a time.

Do this

  1. Branch first (non-trivial work). Apply branch-at-first-write (rules/git.md): not a git repo → skip silently; already on a non-default branch → stay there; on the default branch (main/master/develop, or what git symbolic-ref refs/remotes/origin/HEAD resolves to) → create claude/feat-<slug> (slug from .claude/STATE.md) before the first file edit. Never commit or push — that stays gated behind the user's explicit ask.
  2. Take the plan's tasks in order — read .claude/planning/<slug>/PLAN.md if present (slug in .claude/STATE.md) so a fresh-context executor works from the file, not the conversation. For each task/phase:
    • Delegate to harness-claude:tdd-guide (or run TDD inline): write a failing test against an acceptance criterion (RED) → minimum code to pass (GREEN) → refactor.
    • Keep files modular and lean (<800 lines), immutable patterns, inputs validated.
    • Let the format/typecheck hooks run; fix what they flag immediately.
  3. Parallel-fan-out checkpoint — evaluate before editing, don't skip. Before you start editing a phase serially, count the files it will write. If it spans 3+ independent files with disjoint write-sets and no dependency between them (the plan may already flag this phase as a /harness-claude:orchestrate candidate), you must surface the fan-out option: name the file split and propose /harness-claude:orchestrate, then let the user choose before proceeding. Surfacing the offer is mandatory whenever the trigger fires — that is the only path by which parallel mode ever gets used; what stays opt-in is acting on it — never silently start a multi-agent run (it spawns workers and costs more tokens). If the trigger doesn't fire, note that in one line and edit serially.
  4. After each phase, confirm its exit check (test green, build clean) before moving on.
  5. If the build breaks and the fix is non-obvious, hand off to /harness-claude:build-fix.
  6. Stay inside the plan. If reality diverges from it, stop, update the plan, then resume — don't silently improvise scope.

Read the full file on GitHub · 64 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. 4d ago First seen · 64 lines · 52 tokens per session scan A 8563b2960ddc

Subscribe to this mod's changes

implement is a skill published in the GitHub repository vasuag09/harness-claude (2 stars, last pushed 1mo ago), licensed MIT. It adds 52 tokens to every session and 972 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.