sdd-constitution

sdd-constitution is a skill for Claude Code from rubenzarroca/sdd-plugin. It costs 68 tokens per session (2,259 once invoked), scanned A, original, MIT.

A project rulebook containing non-negotiable principles for architecture, testing, security, dependencies, and coding standards.

In plain words
What is it for?
Use it to create or update a project's technical guardrails and standards.
Why use it?
It gives later feature plans and implementations clear technical boundaries to follow. The rules are intended to be checkable rather than general preferences.

Skill for Claude Code

Written for Claude Code: argument-hint in frontmatter. Also seen: mentions CLAUDE.md.

Part of the sdd plugin — 12 skills shipped together

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/rubenzarroca/sdd-plugin/sdd-constitution
Any agent
npx skills add rubenzarroca/sdd-plugin --skill sdd-constitution
Clone the repo
git clone --depth 1 https://github.com/rubenzarroca/sdd-plugin

Made for: Claude Code.

Or install sdd, the plugin that ships this one along with the rest of its 12 skills.

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 sdd-constitution

README.md
[![agentmods](https://agentmods.dev/badge/skills/rubenzarroca/sdd-plugin/sdd-constitution.svg)](https://agentmods.dev/skills/rubenzarroca/sdd-plugin/sdd-constitution)
Your own site
<a href="https://agentmods.dev/skills/rubenzarroca/sdd-plugin/sdd-constitution"><img src="https://agentmods.dev/badge/skills/rubenzarroca/sdd-plugin/sdd-constitution.svg" alt="Measured on agentmods" height="20"></a>
Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,259 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 5.1 $0.00068 $0.02259
Opus 5 $0.00034 $0.01130
Sonnet 5 $0.00014 $0.00452
Haiku 4.5 $0.00007 $0.00226

Measured 6d ago against content hash 07a635564efc, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

sdd-constitution 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 6d 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/sdd-constitution/SKILL.md · 190 lines

How it starts

The opening of the file, as written. The whole thing — 190 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/sdd:constitution — Define or edit project principles

You are managing the project's constitution — the set of verifiable, non-negotiable principles that govern all implementation. Follow the instructions below based on whether constitution.md already exists in the project root.

First, check if constitution.md exists in the project root. Then branch:

  • If it does NOT exist → Create mode
  • If it exists → Edit mode

If $ARGUMENTS contains a specific category name (e.g., "testing", "architecture", "security", "dependencies", "code standards"), jump directly to that category instead of going through all categories sequentially.

Coaching Layer

The constitution is the highest-authority document in the project — every spec, plan, and validation checks against it. Weak principles cascade into every downstream step.

Create mode: Use the same scaffolding triggers as sdd-init's coaching layer — detect vague answers, non-verifiable principles, and deferred decisions. Propose concrete options grounded in the detected stack. Read .sdd/state.json field completed_features: on the first feature (0), explain what makes a principle verifiable with examples from the user's own project. On subsequent sessions, skip the explanation.

Edit mode scaffolding:

What Claude detects What Claude does
Overly broad new rule ("no external dependencies") Flag the impact: "This would prevent using any npm package, including ones you already use. Did you mean 'no new dependencies without approval'?"
Overly specific rule ("always use lodash.debounce") Suggest abstraction: "This locks you to one library. Would 'all debounce logic must go through a shared utility' work better? You can swap the implementation later."
Rule contradicts existing principle Surface the conflict: "This conflicts with [existing rule]. Which one takes priority? We should resolve this so validate doesn't flag false violations."
Rule duplicates a tool's enforcement Note the redundancy: "Your ESLint config already enforces this — adding it here means two places to maintain. Keep it in one place, or add it here as documentation?"

Read the full file on GitHub · 190 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. 6d ago First seen · 190 lines · 68 tokens per session scan A 07a635564efc

Subscribe to this mod's changes

sdd-constitution is a skill published in the GitHub repository rubenzarroca/sdd-plugin (6 stars, last pushed 6mo ago), licensed MIT. It adds 68 tokens to every session and 2,259 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 2026-08-31.