implement

A development workflow that writes tests first, then implements code until those tests pass.

In plain words
What is it for?
Use it to add behavior or close test-coverage gaps through repeated test-and-fix rounds, subject to defined limits.
Why use it?
It prevents implementation from starting before the requested behavior and success conditions are clear.

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

Made for: Claude Code, Codex.

Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 500 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 $0.00032 $0.00500
Opus 5 $0.00016 $0.00250
Sonnet 5 $0.00006 $0.00100
Haiku 4.5 $0.00003 $0.00050

Measured yesterday against content hash a655117084f7, 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 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.

skills/implement/SKILL.md · 21 lines

What it actually says

Your working contract is the 4 rules; their digest is injected at session start - read ${CLAUDE_PLUGIN_ROOT}/core/RULES.md in full only if that digest is not in your context. Read the implement stage from ${CLAUDE_PLUGIN_ROOT}/core/lifecycle.yaml (already in context if the flow runner loaded it - do not re-read) - agents, artifacts, gates, and the red-green loop definition (including max_rounds) are authoritative; do not hardcode them.

  1. Workspace: bash ${CLAUDE_PLUGIN_ROOT}/bin/workspace.sh resolve --repo . (later stage: never mints; on ambiguity or no-active-task, surface the script's message and stop).
  2. Criteria gate (tier B): bash ${CLAUDE_PLUGIN_ROOT}/bin/check-criteria.sh --workspace <ws> --repo . - refuse to start while it fails (Goal-Driven Execution). It writes its receipt.
  3. Red-green loop, at most max_rounds rounds:
    • Dispatch the test-engineer: red-first for behavior; cover-first at gaps named by the last gate report (a green-on-arrival test at a gap completes the round - skip the implementer turn).
    • bash ${CLAUDE_PLUGIN_ROOT}/bin/workspace.sh record-test-hashes --repo . after every test-engineer turn.
    • Dispatch the implementer to go green; it may not edit tests.
    • bash ${CLAUDE_PLUGIN_ROOT}/bin/workspace.sh verify-test-hashes --repo . before accepting the round - a violation fails the round and is recorded for the review lead.
    • bash ${CLAUDE_PLUGIN_ROOT}/bin/coverage/gate.sh --repo . --base <workspace base-ref> --workspace <ws> - its report feeds the next round.
    • Exit when the gate passes; on the cap, exit incomplete and record the disagreement in the workspace - never escape via an exemption marker.
  4. Producer duties on completion (KTD10): write boundary.md and diff-summary.md to the workspace.

Pass workspace paths, not prose recaps (R8). Orchestrate only (R9).

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 · 21 lines · 32 tokens per session scan A a655117084f7

Subscribe to this mod's changes

implement is a skill published in the GitHub repository foliveira/harmonia (2 stars, last pushed 17d ago), licensed MIT. It adds 32 tokens to every session and 500 once invoked, about $0.0002 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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