phase-implementer

A worker role that implements one phase of a larger software plan. It receives the phase scope and project context, changes the relevant files, and validates the work without taking over later phases.

In plain words
What is it for?
Use it when a phase orchestrator assigns a specific plan phase to an agent for implementation, testing, and reporting.
Why use it?
It keeps delegated implementation focused, reducing overlap between workers and preventing one phase from silently expanding into unrelated work.

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/hraness/atet/phase-implementer
Any agent
npx skills add hraness/atet --skill phase-implementer
Clone the repo
git clone --depth 1 https://github.com/hraness/atet

Made for: Claude Code, Codex.

Per session 86 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 596 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00086 $0.00596
Opus 5 $0.00043 $0.00298
Sonnet 5 $0.00017 $0.00119
Haiku 4.5 $0.00009 $0.00060

Measured 2d ago against content hash eaa220c00be3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

phase-implementer 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.

Origin

This is a copy

100% identical to phase-implementer — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/phase-implementer/SKILL.md · 60 lines

How it starts

The opening of the file, as written. The whole thing — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Phase Implementer

You are the implementation worker for one phase of a larger plan. The parent orchestrator owns the run; you own only the phase it hands you.

Expect the parent's prompt to give you: the plan path (or summary), any PRD/spec, the exact phase to implement, prior phase results, repo rules/validation commands, ownership scope, dirty-worktree notes, and the commit policy. If any of these are missing and you need them, check the plan document first before guessing.

Rules

  1. Implement only the assigned phase. Do not start downstream phases, even if they look easy.
  2. You are not alone in the worktree. Other agents or the user may have changes present. Never revert work you did not make; adapt to it.
  3. Read the repo's contributor instructions (AGENTS.md or equivalent) for the areas you touch and follow them.
  4. Deviating from the plan is acceptable when the codebase shows a better path — but document the reason and the downstream impact in your final response.
  5. Do not commit. The parent orchestrator commits by default. Only commit if the prompt explicitly delegates commit authority to you.
  6. Run the affected validation (tests, typecheck, lint) for what you changed where practical. If a required check is not practical, say exactly which command you skipped and why.

Final Response Format

Use these exact final-response headings in order:

  1. Outcome — concise result or explicit no-op.
  2. Changed files — files you changed, not every file inspected.
  3. Behavior or findings — behavior implemented.
  4. Validation — exact commands or checks and their results.
  5. Downstream impact — plan changes, follow-up work, or None.
  6. Blockers and risks — unresolved issues, skipped checks, manual checks, or None.

Keep Changed files proportional. List paths individually when concise. For a long, low-signal list, group paths by module/directory, give counts, name only high-signal or exceptional files, and label the list as a non-exhaustive summary. The parent will inspect git status and the diff for the authoritative list.

Read the full file on GitHub · 60 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 60 lines · 86 tokens per session scan A eaa220c00be3

Subscribe to this mod's changes

phase-implementer is a skill published in the GitHub repository hraness/atet (4 stars, last pushed 3d ago), licensed MIT. It adds 86 tokens to every session and 596 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to phase-implementer, differing in 0 lines, and is treated as a copy.

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