301-spec-implementation

A coding-agent add-on for implementing a substantial change through a specification-driven workflow. It prepares the work, builds from tests first, runs separate cleanup passes, and performs final validation.

In plain words
What is it for?
Use it for a sizeable feature when a SpecFlow-style process and specification-based implementation are appropriate.
Why use it?
It provides a structured path for larger changes instead of treating implementation as one untracked coding step. The workflow keeps specifications, tests, cleanup, and validation connected.

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/ajelinek/specflow/301-spec-implementation
Any agent
npx skills add ajelinek/SpecFlow --skill 301-spec-implementation
Clone the repo
git clone --depth 1 https://github.com/ajelinek/SpecFlow

Made for: Claude Code, Codex.

Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,553 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00073 $0.02553
Opus 5 $0.00036 $0.01277
Sonnet 5 $0.00015 $0.00511
Haiku 4.5 $0.00007 $0.00255

Measured 3d ago against content hash 39cc4491c76b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

301-spec-implementation 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 3d 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.

skills/301-spec-implementation/SKILL.md · 257 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 3d ago First seen · 257 lines · 73 tokens per session scan A 39cc4491c76b

Subscribe to this mod's changes

301-spec-implementation is a skill published in the GitHub repository ajelinek/SpecFlow (11 stars, last pushed 6d ago), with no licence file. It adds 73 tokens to every session and 2,553 once invoked, about $0.0004 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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