# Gleam

> Use when Gleam, gleam.toml, BEAM, Erlang interop, TDD, or type-driven Gleam code are involved.

- Skill: `anntnzrb/gleam` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add anntnzrb/gleam`
- Raw SKILL.md: https://api.skillmd.com/api/skills/anntnzrb/gleam/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: AGPL-3.0-or-later
- Author: anntnzrb (https://skillmd.com/u/anntnzrb)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/anntnzrb/gleam

---


# Gleam Development

Idiomatic Gleam with **type-driven design** and **TDD**.

## Workflow

```
1. MODEL    → Define domain types first (make illegal states unrepresentable)
2. RED      → Write failing test
3. GREEN    → Minimal implementation
4. REFACTOR → Clean up, use pipelines
5. RUN      → gleam test && gleam run
```

## Research

Use `context7 docs` first, then `gh` as fallback.

## Engineering checks

- Decode external data at the boundary into domain types; model distinct concepts separately when mixing them is a bug
- Represent expected failures with explicit `Result` error types and exhaustively handle variants; do not use `panic` as normal control flow
- Keep effects at module boundaries and resource lifetimes explicit; keep domain logic pure where practical
- Test observable success and error behavior with deterministic values, not private function structure
- Add a type, helper, dependency, or abstraction only for a concrete caller or failure mode

## Required follow-up reads

|Need|Read|When|
|---|---|---|
|Research routing and code patterns|`references/guide.md`|API research or implementation guidance|

## CLI

```bash
gleam check                    # Fast type feedback (use often)
gleam test                     # Run tests
gleam run                      # Execute main
gleam format                   # Format all
gleam add pkg --dev            # Dev dependency
```