impl

A development workflow for completing one planned implementation phase from a project specification. It also requires an independent review against the specification before the phase is considered finished.

In plain words
What is it for?
Use it to build a named milestone or phase from project specs, then find and fix valid issues before delivery. It is not intended for isolated bug fixes or early prototypes.
Why use it?
It helps prevent partially completed phases, unfinished code, and work that drifts away from the agreed plan.

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/tyrchen/rust-lib-template/impl
Any agent
npx skills add tyrchen/rust-lib-template --skill impl
Clone the repo
git clone --depth 1 https://github.com/tyrchen/rust-lib-template

Made for: Claude Code, Codex.

Per session 148 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,343 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 $0.00148 $0.03343
Opus 5 $0.00074 $0.01672
Sonnet 5 $0.00030 $0.00669
Haiku 4.5 $0.00015 $0.00334

Measured 2d ago against content hash 2ab3732fb4d4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

impl 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.

.agents/skills/impl/SKILL.md · 187 lines

How it starts

The opening of the file, as written. The whole thing — 187 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Impl

Land one phase from ./specs/91-impl-plan.md to a publishable bar — no TODOs, no half-finished modules, no quality-gate bypasses — then run a thorough independent review against the spec and fix every valid finding before claiming done. The phase is the unit of completion; partial phases create drift the spec set is meant to prevent.

When this fires

  • "build phase N entirely" / "implement phase N" / "land M"
  • "based on @specs/91-impl-plan.md and other specs in ./specs, follow @AGENTS.md, think ultra hard, build phase X"
  • "previous phases are done — continue with the next one"
  • "ship the spec; one phase at a time"
  • The user names a milestone (M0/M1/M2/M3) or a Phase-N task and asks Codex to write the code

What this skill is not

  • Not for one-off bug fixes or feature requests outside a planned phase. Use direct edits.
  • Not for greenfield design work. If ./specs/ is empty or the relevant phase is not specified, hand off to the spec skill first.
  • Not for prototyping. The quality bar here is "publishable"; throwaway code lives somewhere else.

Diagram expectation

When an implementation phase changes architecture, data flow, processing flow, lifecycle/state transitions, or build/dependency order, update the corresponding spec or research diagrams in the same phase. Use fenced ASCII-style diagrams (```text) with nested boxes or grouped lanes for non-trivial systems, matching the spec/research skill standard. Prefer terminal-safe box-drawing characters (┌─┐│└┘, , ) when they make ownership and runtime boundaries clearer. For request/protocol flows, use vertical lifelines with numbered steps so the ordering is reviewable. Do not leave diagrams as stale prose-adjacent decorations; they must show the real components, channels, storage, external systems, state transitions, and failure/shutdown paths that changed.

Workflow

1. Bind the scope

Resolve which phase to build, exactly:

  • Read ./specs/91-impl-plan.md and find the requested phase. If the user named a milestone (M0/M1), translate it via the roadmap (90-roadmap.md) — milestones and phases pair 1:1 but are numbered differently.
  • Read every spec section the phase tasks cite. The impl plan's task table has a "Spec" column for a reason.
  • Read ./docs/research/ memos referenced by those specs. Their decisions bind the implementation.
  • Read project AGENTS.md (and global ~/.codex/AGENTS.md). Engineering norms (error handling, async, type design, security, logging) apply unconditionally.
  • Read ./vendors/ references the spec or research cites — for prior art and exact API shapes.

Read the full file on GitHub · 187 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. 2d ago First seen · 187 lines · 148 tokens per session scan A 2ab3732fb4d4

Subscribe to this mod's changes

impl is a skill published in the GitHub repository tyrchen/rust-lib-template (50 stars, last pushed 3mo ago), licensed MIT. It adds 148 tokens to every session and 3,343 once invoked, about $0.0007 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.

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