spec-evolution

spec-evolution is a skill for Claude Code from tranhieutt/software_development_department. It costs 27 tokens per session (1,452 once invoked), scanned A, original, MIT.

A workflow for resolving conflicts between an approved software specification and what the code or environment actually supports. It requires the mismatch to be addressed before implementation continues.

In plain words
What is it for?
Use it when tests, existing code, dependencies, or user requests reveal that a specification needs controlled changes.
Why use it?
It prevents developers from silently changing requirements or code when the two no longer agree.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: agent in frontmatter.

Good fit Use it when tests, existing code, dependencies, or user requests reveal that a specification needs controlled changes.

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Install with agentmods
npx agentmods add skills/tranhieutt/software_development_department/spec-evolution
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 tranhieutt/software_development_department --skill spec-evolution
Clone the repo
git clone --depth 1 https://github.com/tranhieutt/software_development_department

Made for: Claude Code.

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-evolution

README.md
[![agentmods](https://agentmods.dev/badge/skills/tranhieutt/software_development_department/spec-evolution/github.svg)](https://agentmods.dev/skills/tranhieutt/software_development_department/spec-evolution)
Your own site
<a href="https://agentmods.dev/skills/tranhieutt/software_development_department/spec-evolution"><img src="https://agentmods.dev/badge/skills/tranhieutt/software_development_department/spec-evolution/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for spec-evolution

Your own site · 80×15
<a href="https://agentmods.dev/skills/tranhieutt/software_development_department/spec-evolution"><img src="https://agentmods.dev/badge/skills/tranhieutt/software_development_department/spec-evolution.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,452 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 $0.00027 $0.01452
Opus 5 $0.00014 $0.00726
Sonnet 5 $0.00005 $0.00290
Haiku 4.5 $0.00003 $0.00145

Measured 8d ago against content hash cfe600ecc246, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

spec-evolution 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 8d 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.

.claude/skills/spec-evolution/SKILL.md · 185 lines

How it starts

The opening of the file, as written. The whole thing — 185 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Spec Evolution

Purpose

spec-evolution keeps specs alive as the source of truth. When implementation reality teaches that an approved spec is incomplete, wrong, obsolete, or conflicting, this workflow resolves the mismatch deliberately before more code is written.

This is not a shortcut around spec-driven-development. It is the controlled path for changing a spec after evidence shows the current spec no longer matches the project.

Core Rule

Do not silently change code to fit reality or silently change the spec to fit code.
Resolve the mismatch explicitly, then continue.

If the mismatch affects behavior, architecture, data, security, release policy, or user-visible workflow, user approval is required before implementation continues.

When To Use

Use this workflow when:

  • Tests or implementation reveal the approved spec is impossible or unsafe.
  • Code review finds behavior that is useful but not specified.
  • Existing code contradicts a new spec.
  • A user asks to change requirements after a spec or plan was approved.
  • A dependency, API, data model, or platform constraint invalidates the spec.
  • A bug fix discovers the desired behavior differs from documented behavior.

Do not use it for:

  • Initial spec creation. Use spec-driven-development.
  • Pure typo fixes in a spec with no behavior meaning.
  • Implementation bugs where the spec is clear and correct. Use test-driven-development or diagnose.

Workflow

1. Freeze Execution

Stop implementation, planning, review approval, or release progression until the mismatch is classified.

State:

Spec evolution gate: execution paused because <spec> and <evidence> disagree.

2. Gather Evidence

Read the minimum required context:

  • The approved spec or source-of-truth section
  • The code, test, review finding, user request, or runtime evidence that contradicts it
  • Any ADR, PRD, API contract, or README section that constrains the decision
  • For existing-domain evolution, SHOULD query recent related ledger entries via /trace-history to avoid repeating or reversing prior decisions without evidence

Read the full file on GitHub · 185 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. 8d ago First seen · 185 lines · 27 tokens per session scan A cfe600ecc246

Subscribe to this mod's changes

spec-evolution is a skill published in the GitHub repository tranhieutt/software_development_department (72 stars, last pushed 4mo ago), licensed MIT. It adds 27 tokens to every session and 1,452 once invoked, about $0.0001 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 2026-09-03.