spec-design

spec-design is a skill for Claude Code from komluk/scaffolding. It costs 51 tokens per session (925 once invoked), scanned A, original, MIT.

A writing guide for OpenSpec design and task documents. OpenSpec is a system for planning software changes before implementation.

In plain words
What is it for?
Use it to document context, goals, requirements, technical decisions, risks, migration steps, open questions, and the tasks needed to build the feature.
Why use it?
It turns an approved proposal into a clear technical plan and an implementation checklist.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the scaffolding plugin — 35 skills, 9 commands, 13 agents shipped together

Good fit Use it to document context, goals, requirements, technical decisions, risks, migration steps…

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/komluk/scaffolding/spec-design
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.

Any agent
npx skills add komluk/scaffolding --skill spec-design
Clone the repo
git clone --depth 1 https://github.com/komluk/scaffolding

Made for: Claude Code.

Or install scaffolding, the plugin that ships this one along with the rest of its 35 skills, 9 commands, 13 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for spec-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/komluk/scaffolding/spec-design.svg)](https://agentmods.dev/skills/komluk/scaffolding/spec-design)
Your own site
<a href="https://agentmods.dev/skills/komluk/scaffolding/spec-design"><img src="https://agentmods.dev/badge/skills/komluk/scaffolding/spec-design.svg" alt="Measured on agentmods" height="20"></a>
Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 925 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00051 $0.00925
Opus 5 $0.00026 $0.00463
Sonnet 5 $0.00010 $0.00185
Haiku 4.5 $0.00005 $0.00093

Measured 7d ago against content hash ec1df5ce4940, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

spec-design 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 7d 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/spec-design/SKILL.md · 118 lines

How it starts

The opening of the file, as written. The whole thing — 118 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OpenSpec Design & Tasks Writing

Guide for creating design.md (WHAT + HOW) and tasks.md (implementation checklist).

Prerequisite

Read {specs_path}/proposal.md first. Reference its capabilities and impact sections.

Path Enforcement: The specs_path MUST be .scaffolding/conversations/{UUID}/specs/ where {UUID} is a valid UUID (format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx). NEVER use descriptive folder names.

design.md

Output Path

Write to: {specs_path}/design.md

Required Sections

Section Purpose Format
Context Background, current state, constraints Prose
Goals / Non-Goals Scope boundaries Bullet lists
Specifications Requirements + scenarios GIVEN/WHEN/THEN
Decisions Technical choices + rationale Decision: Why X over Y
Risks / Trade-offs Known limitations [Risk] -> Mitigation
Migration Plan Deploy + rollback steps Checklist (if applicable)
Open Questions Unresolved items Numbered list

Specification Format

### Requirement: user-session-timeout

The system SHALL terminate idle sessions after 30 minutes.

#### Scenario: session expires after inactivity

- **GIVEN** a user has an active session
- **WHEN** no activity occurs for 30 minutes
- **THEN** the session is invalidated and user is redirected to login

Rules:

  • Use SHALL/MUST for normative requirements (avoid should/may)
  • Every requirement MUST have at least one scenario
  • Each scenario is a potential test case
  • Map capabilities from proposal.md to requirement groups

Decision Format

## Decisions

### Use Redis for session storage
**Alternatives**: PostgreSQL, in-memory
**Rationale**: Sub-millisecond lookups, built-in TTL, already in stack

Scaffolding Constraints

Include in all designs:

  • Max 200 lines per Edit operation
  • Files must stay under 500 lines
  • Backend validation: pytest; Frontend: npm run validate
  • Map steps to specific workflow chain agents

Read the full file on GitHub · 118 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. 7d ago First seen · 118 lines · 51 tokens per session scan A ec1df5ce4940

Subscribe to this mod's changes

spec-design is a skill published in the GitHub repository komluk/scaffolding (15 stars, last pushed 1mo ago), licensed MIT. It adds 51 tokens to every session and 925 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 2026-08-30.

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