gleam

name	gleam
description	Comprehensive Gleam skill covering language fundamentals, backend (OTP, Use when this capability is needed.
metadata	{"author":"aboio-labs"}

Gleam Best Practices

Consolidated skill for Gleam development. Use decision trees below to find the right reference, then load detailed docs.

Token Efficiency

All agents and commands using this skill MUST follow references/token-efficiency.md. Use Grep and targeted reads instead of reading entire files. Start with git diff to scope work.

Core Principles

1. Errors as Values — use Result types, never exceptions
2. Explicit over Implicit — no hidden state, no magic
3. Type Safety — let the compiler catch bugs
4. Layered Architecture — separate concerns
5. Parse, Don't Validate — opaque types for validated data

Quick Decision Trees

"I need to write Gleam code"

Writing Gleam?
├─ New to syntax (no if, records, imports)  → fundamentals/language-basics.md
├─ Case expressions, pattern matching       → fundamentals/case-patterns.md
├─ Label shorthand, let assert, pipelines   → fundamentals/language-features.md
├─ Useful stdlib functions                  → fundamentals/stdlib.md
├─ Module name mistakes (regexp/regex)      → fundamentals/stdlib-module-names.md
├─ String character filtering (no \0)       → fundamentals/string-character-filtering.md
├─ JSON decoding/encoding                   → fundamentals/decoding.md
├─ decode.map vs decode.then                → fundamentals/decode-map-vs-then.md
├─ Opaque types, module design              → fundamentals/type-design.md
├─ Error discipline, AppError patterns      → fundamentals/error-handling.md
├─ use/result.try, helpers                  → fundamentals/code-patterns.md
├─ Helper-first refactoring                 → fundamentals/helper-first-refactoring.md
├─ Higher-order SQL helpers                 → fundamentals/higher-order-sql-helpers.md
├─ Tooling (gleam check, format, LSP)       → fundamentals/tooling.md
├─ Input validation (valid)                 → fundamentals/validation-valid.md
├─ Parser combinators (nibble)              → fundamentals/parsing-nibble.md
├─ Snapshot testing (birdie)                → fundamentals/birdie-snapshot-testing.md
├─ Common mistakes                          → fundamentals/common-pitfalls.md
└─ Official conventions & anti-patterns     → fundamentals/conventions.md

"I need to build a backend"

Backend (Erlang target)?
├─ Web framework (wisp)                     → backend/wisp-framework.md
├─ HTTP server (mist)                       → backend/mist-server.md
├─ HTTP logging (single middleware)         → backend/http-logging-middleware.md
├─ DB error handling (3-tier)               → backend/three-tier-error-handling.md
├─ Decoder defaults anti-pattern            → backend/decoder-defaults-anti-pattern.md
├─ OTP actors (basics, state, messages)     → backend/otp.md
├─ OTP supervision (trees, strategies)      → backend/otp-supervision.md
├─ OTP advanced (selectors, timers, ETS)    → backend/otp-advanced.md
├─ Production logging (wisp)                → Use /observability-master command
├─ HTTP client runner                       → backend/http-runner.md
├─ Midas algebraic effects                  → backend/midas-effect-task.md
├─ SQL code generation (Squirrel)           → backend/squirrel-guide.md
├─ SQL code generation (Parrot/sqlc)        → backend/parrot-guide.md
├─ Database migrations (Cigogne)           → backend/cigogne.md
├─ JWT authentication (ywt)                 → backend/jwt-ywt.md
├─ S3 / object storage (bucket)             → backend/bucket-s3.md
├─ Image processing (ansel)                → backend/ansel-image.md
├─ PDF generation (paddlefish)             → backend/paddlefish-pdf.md
└─ Password hashing, timestamps             → backend/auth.md

"I need to build a frontend"

Frontend (Lustre / JS target)?
├─ MVU architecture, state, messages        → frontend/lustre-core.md
├─ Effects, paint-cycle, context            → frontend/lustre-effects.md
├─ SPA routing (modem)                      → frontend/lustre-routing.md
├─ HTTP requests (rsvp)                     → frontend/lustre-http.md
├─ Web components, slots, CSS parts         → frontend/lustre-components.md
├─ Events, debounce, throttle               → frontend/lustre-events.md
├─ Composable UI, prop pattern, views       → frontend/lustre-ui-patterns.md
├─ Hydration, server components, FFI        → frontend/lustre-advanced.md
├─ Browser APIs (plinth)                    → frontend/lustre-browser-apis.md
├─ Testing (query, simulate, birdie)         → frontend/lustre-testing.md
└─ Common Lustre gotchas                    → frontend/lustre-gotchas.md

"I need to design a library"

Library design?
├─ Effects as data, no IO in core           → library/library-design.md
└─ FFI (Erlang + JavaScript)                → library/ffi.md

"I need to review OTP code"

OTP review (after implementing actors/supervision)?
└─ Audit actors, supervision, concurrency   → Use /otp-review command

When to use /otp-review:

• After creating new actors
• After modifying supervision trees
• After changing actor state or message types
• When experiencing timeouts, deadlocks, or memory leaks
• Before committing OTP-related code

Read at most 2 reference files per turn to stay token-efficient.

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