dfd

dfd is a skill for Claude Code, Codex from alunduil/alunduil-chezmoi. It costs 80 tokens per session (1,232 once invoked), scanned A, original, 0BSD.

Data-flow diagram guide for showing where information comes from, where it is stored, and how the system transforms it. A data-flow diagram focuses on data movement, not step-by-step timing or object structure, and uses Mermaid flowcharts.

In plain words
What is it for?
Use it to create or review diagrams containing outside parties, processes, data stores such as files or databases, and named data flows.
Why use it?
It gives security reviews and threat modeling a consistent picture of system boundaries and data movement. It also catches missing labels, incorrect connections, and inconsistencies between diagram levels.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to create or review diagrams containing outside parties, processes, data stores such as files or databases, and named data flows.

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Install with agentmods
npx agentmods add skills/alunduil/alunduil-chezmoi/dfd
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 alunduil/alunduil-chezmoi --skill dfd
Clone the repo
git clone --depth 1 https://github.com/alunduil/alunduil-chezmoi

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 dfd

README.md
[![agentmods](https://agentmods.dev/badge/skills/alunduil/alunduil-chezmoi/dfd/github.svg)](https://agentmods.dev/skills/alunduil/alunduil-chezmoi/dfd)
Your own site
<a href="https://agentmods.dev/skills/alunduil/alunduil-chezmoi/dfd"><img src="https://agentmods.dev/badge/skills/alunduil/alunduil-chezmoi/dfd/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 dfd

Your own site · 80×15
<a href="https://agentmods.dev/skills/alunduil/alunduil-chezmoi/dfd"><img src="https://agentmods.dev/badge/skills/alunduil/alunduil-chezmoi/dfd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,232 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 $0.00080 $0.01232
Opus 5 $0.00040 $0.00616
Sonnet 5 $0.00016 $0.00246
Haiku 4.5 $0.00008 $0.00123

Measured 12d ago against content hash 81c676580363, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

dfd 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 12d 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.

dot_claude/skills/dfd/SKILL.md · 130 lines

How it starts

The opening of the file, as written. The whole thing — 130 lines — stays where its author put it; the contents beside it link to each section on GitHub.

DFD

References:

A DFD shows where data moves and what transforms it. Sequencing belongs in a flowchart, object structure in UML; a DFD carries neither. Control signals are not data — leave them out.

Components

Four, and only four:

Component Is Gane–Sarson Yourdon/DeMarco Mermaid
External entity A source or sink outside the system boundary square rectangle E[Name]
Process Work that transforms input data into output data rounded rectangle circle P(1.0 Verb the thing)
Data store Data at rest — a file, table, queue, keyring open-ended rectangle two parallel lines S[(Name)]
Data flow Named data moving between the above labelled arrow labelled arrow A -->|data name| B

Name every element. Entities and stores take noun phrases, processes take verb phrases, flows take the name of the data itself (plaintext token), never the mechanism carrying it.

Levels

Each level decomposes one process from the level above.

  • Context — the whole system as a single process numbered 0, surrounded by every external entity it exchanges data with. No data stores; internal storage is inside the system.
  • Level 0 — process 0 opened up into its major processes, numbered 1.0, 2.0, 3.0. Data stores appear here first.
  • Level 1 onward — one process from the level above opened up, numbered beneath it. Decomposing 2.0 gives 2.1, 2.2; decomposing 2.1 gives 2.1.1.

Stop at the level that answers the question asked, or at a process whose decomposition would only restate it.

Pick logical or physical per diagram and hold it: a logical DFD names business activities, a physical one names the software, hosts, and files doing the work.

Read the full file on GitHub · 130 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. 12d ago First seen · 130 lines · 80 tokens per session scan A 81c676580363

Subscribe to this mod's changes

dfd is a skill published in the GitHub repository alunduil/alunduil-chezmoi (2 stars, last pushed today), licensed 0BSD. It adds 80 tokens to every session and 1,232 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 2026-08-31.

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