openspec-plus-spec

A specification workflow for OpenSpec changes, where a specification describes what software must do before it is designed and implemented. It turns requirements into clear, testable Gherkin scenarios and checks their alignment with the proposal or design.

In plain words
What is it for?
Use it to create, continue, update, or review OpenSpec requirements and express expected behavior as Gherkin scenarios before implementation.
Why use it?
It exposes missing, ambiguous, or contradictory requirements before coding begins. The required review steps help prevent an incomplete specification from being written prematurely.

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/sudokar/openspec-plus/openspec-plus-spec
Any agent
npx skills add sudokar/openspec-plus --skill openspec-plus-spec
Clone the repo
git clone --depth 1 https://github.com/sudokar/openspec-plus

Made for: Claude Code, Codex.

Per session 88 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,758 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 $0.00088 $0.03758
Opus 5 $0.00044 $0.01879
Sonnet 5 $0.00018 $0.00752
Haiku 4.5 $0.00009 $0.00376

Measured 3d ago against content hash 8cf4ab6ed1c1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

openspec-plus-spec 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/openspec-plus-spec/SKILL.md · 351 lines

How it starts

The opening of the file, as written. The whole thing — 351 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OpenSpec Plus Spec

Mission

Strengthen specification quality. Requirements complete, testable, unambiguous, expressed as Gherkin scenarios for behavioral correctness, aligned with approved proposal and any existing design. Improves requirement quality before design (spec-first) or aligns requirements with existing design boundaries (design-first).


This skill is RIGID. NEVER write any spec file before completing Phase 1, presenting analysis to user, passing pre-write alignment gate, and (after writing) running self-review subagent. Running analysis internally and writing immediately is a skill violation — even if you checked every gate.

Red flags — STOP, you are about to violate this skill:

  • "I already checked all the gates"
  • "The requirements look complete from the proposal"
  • "The user wants this quickly, I'll just write it"
  • "I surfaced these gaps in my reasoning, that counts"
  • "I'll list all my ambiguities in a table and ask the user to fill them in"
  • "I'll ask all questions at once so the user can answer in one message"
  • "These ambiguities are related so I'll group them into one question"
  • "Free-form scenarios are clearer than Gherkin here"
  • "I should read the code to understand the context"
  • "The code I need to read is small, I'll just open it directly"
  • "I'll skim the spec myself, the reviewer subagent isn't needed"
  • "The fixes from the reviewer were minor, I should re-dispatch to confirm"

Inputs Available

OpenSpec allows either order after proposal:

  • proposal → spec → design (no design yet)
  • proposal → design → spec (design exists)

When this skill runs:

  • ALWAYS read approved proposal — authoritative source of intent
  • If design exists, ALWAYS read it — constrains acceptable spec language and bounded behavior
  • Spec MUST align with proposal AND any existing design

Workflow

Four phases. NEVER skip or merge.

Phase 0: Schema & Template Resolution
Phase 1: Interactive Analysis
Phase 2: Drift Check
Phase 3: Write & Self-Review

Read the full file on GitHub · 351 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. 3d ago First seen · 351 lines · 88 tokens per session scan A 8cf4ab6ed1c1

Subscribe to this mod's changes

openspec-plus-spec is a skill published in the GitHub repository sudokar/openspec-plus (154 stars, last pushed 3d ago), licensed MIT. It adds 88 tokens to every session and 3,758 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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