subgraph-extractor

subgraph-extractor is a skill for Claude Code, Codex from NyxFoundation/speca. It costs 25 tokens per session (1,845 once invoked), scanned A, original, MIT.

A formal-methods tool that turns one specification document into program graphs: diagrams of steps, actions, tests, and possible paths.

In plain words
What is it for?
Use it to extract graphs for functions, protocol stages, validation flows, and other functional units from a specification.
Why use it?
It provides a structured way to understand the behavior described in a specification instead of interpreting the document informally.

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/nyxfoundation/speca/subgraph-extractor
Any agent
npx skills add NyxFoundation/speca --skill subgraph-extractor
Clone the repo
git clone --depth 1 https://github.com/NyxFoundation/speca

Made for: Claude Code, Codex.

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 subgraph-extractor

README.md
[![agentmods](https://agentmods.dev/badge/skills/nyxfoundation/speca/subgraph-extractor.svg)](https://agentmods.dev/skills/nyxfoundation/speca/subgraph-extractor)
Your own site
<a href="https://agentmods.dev/skills/nyxfoundation/speca/subgraph-extractor"><img src="https://agentmods.dev/badge/skills/nyxfoundation/speca/subgraph-extractor.svg" alt="Measured on agentmods" height="20"></a>
Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,845 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 $0.00025 $0.01845
Opus 5 $0.00013 $0.00923
Sonnet 5 $0.00005 $0.00369
Haiku 4.5 $0.00003 $0.00185

Measured 4d ago against content hash c0f3d101975a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

subgraph-extractor 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 4d 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/subgraph-extractor/SKILL.md · 210 lines

How it starts

The opening of the file, as written. The whole thing — 210 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SKILL: Subgraph Extractor

Mindset

You are a Formal Methods Specialist trained in program graph extraction. Your task is to transform a single specification document into program graphs following the formal definition from Nielson & Nielson's "Formal Methods: An Appetizer" (Springer 2019).

A program graph PG = (Q, q▷, q◀, Act, E) consists of:

  • Q: a finite set of nodes (program points)
  • q▷, q◀ ∈ Q: initial and final nodes
  • Act: a set of actions (assignments, tests/guards)
  • E ⊆ Q × Act × Q: a finite set of edges

Scope

This skill processes one specification URL per invocation. A single specification typically yields multiple program graphs — one per functional unit (function, protocol phase, validation flow, etc.).

The calling worker is responsible for batching and aggregation.

Input

The caller provides:

  • url — the source URL of the specification (always provided)
  • output_dir — directory where .mmd files should be written
  • local_path (optional) — path to a pre-downloaded copy of the specification

Procedure

  1. Read Specification: If local_path is provided and the file exists, read from it. Otherwise, fetch the content from url using mcp__fetch__fetch.

  2. Identify Functional Units: Break down the document into logical units:

    • Function definitions
    • State transition descriptions
    • Protocol phases
    • Validation logic

    Each functional unit becomes one program graph.

  3. Extract Program Graph Components:

    For each functional unit, identify:

    Component What to Extract
    Nodes (Q) Program points: entry, exit, decision points, intermediate states
    Initial (q▷) The starting point of the function/process
    Final (q◀) The termination point(s)
    Actions (Act) Assignments (x = expr), function calls, tests/guards (x > 0)
    Edges (E) Transitions: (source_node, action, target_node)

Read the full file on GitHub · 210 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. 4d ago First seen · 210 lines · 25 tokens per session scan A c0f3d101975a

Subscribe to this mod's changes

subgraph-extractor is a skill published in the GitHub repository NyxFoundation/speca (454 stars, last pushed 23d ago), licensed MIT. It adds 25 tokens to every session and 1,845 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 2026-08-30.

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