implement

A workflow that carries out a written project specification, meaning a document that defines what should be built, in a fresh coding session.

In plain words
What is it for?
It is for loading a project specification, implementing its requested changes, running validation checks, and fixing problems as they appear.
Why use it?
It separates planning from implementation and checks the work after each change, so mistakes are found before they accumulate.

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

Made for: Claude Code, Codex.

Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,532 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 $0.00038 $0.03532
Opus 5 $0.00019 $0.01766
Sonnet 5 $0.00008 $0.00706
Haiku 4.5 $0.00004 $0.00353

Measured yesterday against content hash d6c03cca19fd, 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.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/peer-sweep.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

templates/claude/skills/implement/SKILL.md · 247 lines

How it starts

The opening of the file, as written. The whole thing — 247 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/implement — SPEC-Driven Executor

The "do" verb of the loop. A prior session used /project to think and write a lean SPEC; this session executes it. Validation loops catch mistakes early: run checks after every change, fix issues immediately, never accumulate broken state.

Start in a fresh context

A session that wrote the plan is invested in it. It defends the choices it made while thinking instead of building cleanly to what the SPEC actually says. A fresh session has no such attachment — it reads the contract and implements it honestly.

So before you run /implement: open a new tab (or clear the context), then reload the SPEC from disk. Nothing enforces this. It is a discipline you follow because it is the whole point of separating the think and do verbs. Skip it and you lose that benefit.

load — read the SPEC

The argument is either a project name/slug or a SPEC-file path.

  1. If the argument resolves to an existing file path, use it directly.
  2. Otherwise treat it as a project slug — find projects/*/{date}_<slug>/ (any date prefix).
  3. Inside the matched folder, find *.spec.md:
Match shape Behavior
0 SPEC files HALT: "no SPEC in <project> — run /project <project> to write one first."
1 SPEC file Use it.
Multiple SPEC files Pick the most-recent with no sibling *-report.md (not yet implemented). Still ambiguous → AskUserQuestion listing them.
No project matches the slug HALT: "no project matches <name>" + list nearest slugs.

Then read the SPEC. It follows the lean 4-section template (.claude/templates/spec-lean.md):

  • § 1 — Ask — the verbatim ask. This is what you check the finished work against; it informs Verify Assumptions and the mechanism-match line.
  • § 2 — Behavior — the behavior contract, including boundary cases (0/1/empty/max/error per @rule:boundary-inputs).
  • § 3 — Files — files to create/change, patterns to mirror, downstream consumers to update in the same pass (nothing deferred, per @rule:no-deferral).
  • § 4 — Done — the exact commands to run and the output that means success, including the end-to-end check.

Read the full file on GitHub · 247 lines

Files

What ships with it

1 file 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. yesterday First seen · 247 lines · 38 tokens per session scan A d6c03cca19fd

Subscribe to this mod's changes

implement is a skill published in the GitHub repository Ashkaan/contextium (32 stars, last pushed 4d ago), licensed MIT. It adds 38 tokens to every session and 3,532 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 2026-08-30.