implement

A coding workflow for completing one work item, adding tests, updating project records, and sending the result to a separate review pass.

In plain words
What is it for?
Use it to build or fix one feature, prove changed behaviour with tests, update progress and decision records, and prepare the work for review.
Why use it?
It keeps implementation tied to the agreed requirements and leaves a clear record of what was done. Separate review helps catch mistakes the original coder may miss.

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

Made for: Claude Code, Codex.

Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 644 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 $0.00060 $0.00644
Opus 5 $0.00030 $0.00322
Sonnet 5 $0.00012 $0.00129
Haiku 4.5 $0.00006 $0.00064

Measured yesterday against content hash dc00c7014747, 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 · 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

Delegate this to mstack:implementer rather than doing it in the main session. The gain is review separation: a pass that wrote the code cannot review it, and "it was faster to do it myself" trades away the only structural check in the workflow.

Where the contract lives

On the spec path, work from .mstack/specs/<slug>/ and execute tasks.md in order, ticking each box as you finish. Not from the issue, and not from the acceptance array: the spec is what was reviewed.

On the direct path, the item's acceptance array is the contract. Do not widen it. If the work turns out to need something outside it, that is a finding, not a licence.

While you work

Keep .mstack/progress/current.md updated as you go, not at the end. Its last section answers one question: if this session stops right now, what should the next one do first.

mstack decide --phase implement --decision "..." --why "..." --evidence "..." --result "..."

One row is one decision. If it does not fit on one line, the decision is not crisp yet.

Tests

Every behaviour change gets a test that fails without the change. Check that: revert the change locally and watch it go red. A test that passes either way is not coverage, it is decoration.

Never weaken an existing test to get green. If a test is genuinely wrong, fix it deliberately, in its own commit, with the reason recorded. That is a different act from making a failure go away, and the commit history should show which one happened.

Prefer no new test over a bad one. A bad test is one that mostly exercises mocks, encodes current implementation details, depends on timing or global state, or would be deleted the moment it had proved its point.

The report

.mstack/progress/impl_<slug>.md:

  • What changed, in a paragraph.
  • Files, the real list.
  • Commands, fenced, with the actual output pasted. Not a summary of it.
  • R to test: each requirement, the test that covers it, and the file:line where that test lives. On the direct path, map acceptance bullets instead.

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. yesterday First seen · 64 lines · 60 tokens per session scan A dc00c7014747

Subscribe to this mod's changes

implement is a skill published in the GitHub repository romerma/mstack (1 stars, last pushed 8d ago), licensed MIT. It adds 60 tokens to every session and 644 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.

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