code-that-fits-in-your-head SKILL.md skillA
code-that-fits-in-your-head from codealive-ai/ai-driven-development is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add codealive-ai/ai-driven-development/code-that-fits-in-your-head@git:20260813.a1fd9f2Pins git:20260813.a1fd9f2 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- codealive-ai/ai-driven-development
- Path
skills/code-that-fits-in-your-head/SKILL.md- Versions recorded
- 3
- Latest version
- git:20260813.a1fd9f2, committed Aug 13, 2026
- First version recorded
- Jun 18, 2026
- Size
- 6,916 bytes
- Repository stars
- 163
- License
- MIT
Software-engineering heuristics based on Mark Seemann's Code That Fits in Your Head (2021), updated for agent-driven development. Use when writing or reviewing code, refactoring accidental complexity or a Big Ball of Mud, controlling technical or architectural debt in generated code, designing APIs and invariants, adding a feature through a walking skeleton and acceptance tests, debugging a defect with reproducible tests or bisection, threat-modelling endpoints and trust boundaries with…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Code That Fits in Your Head Engineering heuristics for sustainable software, based on Mark Seemann's 2021 book and clearly labelled agent-era amendments. Code examples are C#-first; every rule and the tooling tables are language-neutral. ## Philosophy (Why This Skill Exists) Software development is principally a **design activity**, not construction. An agent may produce most of the text, but people still review, operate, extend, and own the resulting system. These heuristics make software sustainable: understandable, resistant to architectural erosion, and cheap to change after thousands of decisions. Core mental model from Chapter 1: | Metaphor | What it gets right | What it misses | |----------|-------------------|-----------------| | **Building a house** | Plans, structure | Software endures; there's no construction phase (compiling is free); dependencies can start anywhere | | **Growing a garden** | Pruning, refactoring, tending | Code does not improve by itself; generated code still needs stewardship | | **Art / craft** | Skill, mastery, situational knowledge | Doesn't scale; leaves newcomers without guidance | …
Read the whole file at its exact version.
How to install
mdr add codealive-ai/ai-driven-development/code-that-fits-in-your-head@sha256:997c0361f3b8cb1fThe line at the top of this page pins the label git:20260813.a1fd9f2, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_bu55plhtralxv22u)
5 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 3 versions of this file, between Jun 18, 2026 and Aug 13, 2026, about one every 28 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260813.a1fd9f2 latest | 2026-08-13 | a1fd9f2 | 6,916 B | A | view · diff |
| git:20260728.6a369da | 2026-07-28 | 6a369da | 6,413 B | A | view · diff |
| git:20260618.02f44b4 | 2026-06-18 | 02f44b4 | 6,242 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (6916 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
codealive-ai/ai-driven-development · 163 stars · license MIT · pushed 2026-10-20 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_bu55plhtralxv22u GET https://markdownregistry.com/api/v1/resolve?ref=codealive-ai/ai-driven-development/code-that-fits-in-your-head GET https://markdownregistry.com/api/v1/blob/997c0361f3b8cb1feec06aea87239670b7cc48473c8f940571bcc61db78a091d
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.