Vibe engineering Effect apps

Effect is a TypeScript library for describing work with typed results, failures, and required services.

Michael says an agent should learn a fast-moving library from its source repository. Stale model knowledge and giant prompts are less reliable. 08:51 12:59

He describes repository feedback from compiler diagnostics, tests, lint checks, saved patterns, and short-lived contexts.

Diagnostics report compiler problems. Lint checks reject code patterns that break project rules. He recommends choosing patterns for the project and model. 30:30 38:15 58:08

Sources

  1. Vibe Engineering Effect Apps — Michael Arnaldi, Effectful - YouTube. Michael Arnaldi. Recording; used for source, tests, and diagnostics as agent feedback. Accessed 2026-10-01.

Last changed 2026-10-07 in e73c9d9. Source on GitHub. Change log.

Linked from

  1. Agent guide. An Effect stack so pure (aspirational) Kit Langton will blush.

    Vibe engineering Effect apps — Michael Arnaldi shows how source, tests, and diagnostics can guide agents working with Effect.

  2. Change log. What changed in the files served here, newest first.

    Vibe engineering Effect apps — edited: feat(learn): teach the next twenty cards with plain lines, diagrams and snippets

  3. Full agent guide. An Effect stack so pure (aspirational) Kit Langton will blush.
  4. Rat Stack lore | rat-stack. Short, source-grounded notes on the ideas and decisions behind rat-stack.

    Vibe engineering Effect apps — Michael Arnaldi shows how source, tests, and diagnostics can guide agents working with Effect.

  5. Source change history (log.md). The generated change log as Markdown.

    Vibe engineering Effect apps — edited: feat(learn): teach the next twenty cards with plain lines, diagrams and snippets

  6. Source-first workflow. Michael Arnaldi says agents should inspect a library's current source instead of trusting stale model knowledge.

    See Vibe engineering Effect apps.¶