---
title: "Source-first workflow"
description: "Michael Arnaldi says agents should inspect a library's current source instead of trusting stale model knowledge."
plain: "Michael Arnaldi says agents learn a fast-moving library best from its current source, not from old model knowledge."
diagram: |-
  current source
    │ agent reads
    ▼
  change
    │
    ▼
  diagnostics, tests, lint
    │ feedback
    ▼
  next change
group: concept
terms:
  - "source-first workflow"
  - "read the source"
sources:
  - url: https://youtu.be/Wmp2Tku2PrI?t=531
    title: "Vibe Engineering Effect Apps — Michael Arnaldi, Effectful - YouTube"
    publisher: "Michael Arnaldi"
    note: "Source-first demonstration; used for learning a fast-moving library from its repository."
    accessed: "2026-10-01"
  - url: https://youtu.be/Wmp2Tku2PrI?t=779
    title: "Vibe Engineering Effect Apps — Michael Arnaldi, Effectful - YouTube"
    publisher: "Michael Arnaldi"
    note: "Workshop explanation; used for the limits of stale model knowledge and large prompts."
    accessed: "2026-10-01"
---

# Source-first workflow

> For agents: start with the [agent guide](https://ratstack.sh/llms.txt). Every page is Markdown by default; add `Accept: text/html` for HTML.

New on /news: [Effect Office Hours 52 with Resonate HQ](/news).

Michael says coding agents learn a fast-moving library more reliably from its source repository. Stale model knowledge and large prompts are less reliable. [08:51](https://youtu.be/Wmp2Tku2PrI?t=531) [12:59](https://youtu.be/Wmp2Tku2PrI?t=779)

He describes compiler diagnostics, tests, lint checks, and saved patterns as feedback for the next move.

Diagnostics report problems found by the compiler. Lint checks reject code patterns that break project rules.
He says patterns should fit the project and model. [30:30](https://youtu.be/Wmp2Tku2PrI?t=1830) [58:08](https://youtu.be/Wmp2Tku2PrI?t=3488)

See [Vibe engineering Effect apps](/lore/ai-engineer-vibe-engineering-effect-apps-michael-arnaldi).

## Sources

1. [Vibe Engineering Effect Apps — Michael Arnaldi, Effectful - YouTube](https://youtu.be/Wmp2Tku2PrI?t=531)
   Michael Arnaldi. Source-first demonstration; used for learning a fast-moving library from its repository. Accessed 2026-10-01.

2. [Vibe Engineering Effect Apps — Michael Arnaldi, Effectful - YouTube](https://youtu.be/Wmp2Tku2PrI?t=779)
   Michael Arnaldi. Workshop explanation; used for the limits of stale model knowledge and large prompts. Accessed 2026-10-01.

## Linked from

- Agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms.txt)

- Change log → What changed in the files served here, newest first. → [Read page](https://ratstack.sh/log)

- Full agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms-full.txt)

- Rat Stack lore | rat-stack → Short, source-grounded notes on the ideas and decisions behind rat-stack. → [Read page](https://ratstack.sh/lore)

- security-audit → Security guidance and vulnerability review for codebases, APIs, services, CLI tools, libraries, and daemons. Use for security questions, focused reviews, vulnerability research, security audits, or pen tests. Run the complete workflow only for explicit codebase audit or pen-test requests, full/comprehensive/end-to-end reviews, or requested report artifacts. → [Read page](https://ratstack.sh/skills/security-audit)

- Source change history (log.md) → The generated change log as Markdown. → [Read page](https://ratstack.sh/log.md)