What is indexion-sdd?

A spec-driven development workflow that turns RFCs, which are technical proposals, into requirements and checks whether the implementation matches them. It also detects drift between the written specification and the code.

Use it to draft requirements from an RFC, compare a specification with its implementation, and run validation checks before merging.

It helps catch cases where code changes but the requirements are not updated, or where an implementation does not fully follow the specification.

indexion-sdd — Skill for Claude Code and Codex by trkbt10

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo

git clone --depth 1 https://github.com/trkbt10/indexion-skills

agentmods

npx agentmods add skills/trkbt10/indexion-skills/indexion-sdd

Made for: Claude Code, Codex.

Or install indexion-skills, the plugin that ships this one along with the rest of its 10 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/trkbt10/indexion-skills/indexion-sdd/github.svg)](https://agentmods.dev/skills/trkbt10/indexion-skills/indexion-sdd)

Your own site

<a href="https://agentmods.dev/skills/trkbt10/indexion-skills/indexion-sdd"><img src="https://agentmods.dev/badge/skills/trkbt10/indexion-skills/indexion-sdd/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/trkbt10/indexion-skills/indexion-sdd"><img src="https://agentmods.dev/badge/skills/trkbt10/indexion-skills/indexion-sdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 8,305 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. Third-party audits

Socket pass 8 May 2026
Snyk warn 8 May 2026

How audits are shown

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.

Model	Per session	Once invoked
Fable 5.1	$0.00053	$0.08305
Opus 5	$0.00026	$0.04152
Sonnet 5	$0.00011	$0.01661
Haiku 4.5	$0.00005	$0.00830

Measured 11d ago against content hash 569ac31da1ed, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

indexion-sdd 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 11d 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/indexion-sdd/SKILL.md · 854 lines

How it starts

The opening of the file, as written. The whole thing — 854 lines — stays where its author put it; the contents beside it link to each section on GitHub.

indexion SDD (Spec-Driven Development)

Bridge indexion's quantitative spec alignment tools with SDD agent workflows (cc-sdd, codex, etc.).

Provides: RFC/document → SDD draft, spec↔impl drift detection, and a validation loop that feeds indexion's quantitative results into agent-driven qualitative review.

When to Use

User wants to implement an RFC or specification as a library/package
User asks to verify spec-to-implementation conformance
User wants to set up a SDD project with cc-sdd + codex + indexion
User says "run the SDD loop" or "validate against the spec"
After codex spec-impl completes, to check for drift before merging

Important

Set cc-sdd --lang to match the implementation language, not the spec language. If code is in English, use --lang en. Mismatched languages break spec align diff vocabulary matching.

Process: RFC → Implementation → Validation

Step 0: Project Setup

# Create project directory
mkdir my-rfc-impl && cd my-rfc-impl

# Install cc-sdd for your agent — set lang to match the code language
npx cc-sdd@latest --codex-skills --lang en --yes   # codex (skills mode)
npx cc-sdd@latest --claude-skills --lang en --yes   # claude (skills mode)

# Initialize project (language-specific)
# e.g., cargo init, npm init, moon new, etc.

# Initialize git
git init && git add -A && git commit -m "init"

Verify indexion is available before proceeding. The drift gate (Step 2.5) and validation loop (Step 3) depend on it:

indexion --version                       # must be installed
indexion kgf edges <any-source-file>     # must detect language and show edges

If indexion is not installed, install it first. If the KGF for your spec format is not recognized, update indexion to a version that includes it. See Step 2.7 for the fallback when this cannot be resolved.

Step 1: Specification → SDD Draft (indexion)

Fetch the specification document (RFC, ISO standard, etc.) and prepare it:

Read the full file on GitHub · 854 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.

11d ago First seen · 854 lines · 53 tokens per session scan A 569ac31da1ed

Subscribe to this mod's changes

indexion-sdd is a skill published in the GitHub repository trkbt10/indexion-skills (2 stars, last pushed 18d ago), licensed Apache-2.0. It adds 53 tokens to every session and 8,305 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.

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indexion-sdd