typescript-dev - SKILL.md Agent Skill

name: typescript-dev description: "TypeScript development. Use for TypeScript, Node.js, Express, Fastify, Zod, vitest, jest. Backend, CLI, libraries only — no frontend frameworks." user-invocable: true allowed-tools: Glob, Read, Grep, Bash, Task, Skill, Edit, Write, AskUserQuestion

TypeScript Development

Announce: "I'm using the typescript-dev skill. Following the 4-phase workflow."

MANDATORY: Read and Follow the Shared Workflow

You MUST read workflow.md NOW and follow ALL 4 phases defined there. The sections below provide TypeScript-specific inputs for each phase.

Read patterns.md during Phase 1.

If you lost workflow.md from context: Re-read ../../shared/workflow.md NOW before continuing.

TypeScript-Specific Configuration

Verification Commands (Phase 1 plan + Phase 3 verify)

WORKFLOW STATE Verification line: tsc --noEmit, <lint-commands>, vitest/jest (lint failure BLOCKS Phase 3 verify — see Lint Enforcement below).

Phase 3 Tier A commands:

tsc --noEmit — type checking
Lint — see Lint Enforcement below; failure blocks Phase 3
vitest or jest — tests
Coverage target: 70-80%

Phase 3 Tier B additional MCP verifications:

PostgreSQL MCP → Query DB state before/after

Lint Enforcement (Phase 3)

Lint failures BLOCK Phase 3 verification with the same severity as a failing test. Read references/lint-enforcement.md at the start of Phase 3 verification and follow it.

Detection is a union, not a priority ladder:

If package.json defines scripts.lint → run <PM> run lint (PM detected per references/package-manager.md). Done.
Else, run every detected standalone linter (biome / eslint / oxlint) — all must pass.
Else, record "Lint: skipped (no linter configured)" and do not block.

No --fix auto-remediation — agents fix lint errors intentionally.

Implementation Rules (Phase 3)

Schema structure — Zod CRUD variants per entity (CreateInput/UpdateInput/Output), domain-driven schemas.ts, types derived via z.infer, composition over deep extends chains
Minimize complexity — Map/Set lookups over array scans
Preserve compatibility — .transform() for renamed fields, .default() for new fields, preserve exported signatures, re-export moved symbols

Staff Review Configuration (Phase 4)

Patterns file path: Path to this skill's patterns.md

TypeScript-Specific Rules

Types are erased at runtime — external data needs Zod validation
Fix type errors during implementation, not after
No positive claim without running tsc --noEmit
Before emitting any install / run <script> / exec <bin> command, detect the project's package manager — read references/package-manager.md. Never default to npm.
Lint failures BLOCK Phase 3 verify — same severity as test failures. Skip is allowed only when no linter is configured (no scripts.lint, no biome/eslint/oxlint config). See references/lint-enforcement.md.

Quality Checklist (TypeScript-Specific)

Add these to the shared workflow's verification checklist:

Using TypeScript 5.x+ features where appropriate
strict: true enabled in tsconfig.json
No any types (or explicitly justified)
Proper type guards for runtime checks
Zod or similar for external data validation
ESM imports with proper extensions
tsc --noEmit passes (no type errors)
Lint passed (or explicitly skipped because no linter is configured)
Tests pass (vitest/jest)