# Core Development

> Use when writing or reviewing code in any stack. It captures the cross-cutting engineering baseline shared by frontend and backend work. Covers TypeScript and JavaScript conventions, the unit-testing contract, git and gitflow, clean-code principles, and a security baseline. Referenced by frontend-development and backend-development.

- Skill: `xitssky/core-development` (Agent Skill, multi-file: 15 files)
- Install (CLI): `npx skillmds@latest add xitssky/core-development`
- Raw SKILL.md: https://api.skillmd.com/api/skills/xitssky/core-development/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: xItsSky (https://skillmd.com/u/xitssky)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/xitssky/core-development

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# Core Development

Standards that hold regardless of framework. The `frontend-development` and `backend-development` skills point here for anything that is not stack-specific. Read only the file that matches what you are doing.

## References

| When you are | Read |
|---|---|
| Writing typed code | `references/typescript.md` |
| Writing untyped JS | `references/javascript.md` |
| Writing or reviewing any unit test | `references/testing-philosophy.md` |
| Branching, committing, or opening a PR | `references/git-gitflow.md` |
| Structuring code or naming things | `references/clean-code.md` |
| Designing layers, boundaries, DI, or error handling | `references/architecture.md` |
| Writing doc comments or documenting a public API | `references/code-documentation.md` |
| Checking a framework version, EOL status, or a migration | `references/versioning-and-migration.md` |
| Working in an NX monorepo (`nx.json` present) | `references/nx.md` |
| Authoring a custom NX generator or executor | `references/nx-generators.md`, `references/nx-executors.md` |
| Writing a Dockerfile or image (`Dockerfile` present) | `references/docker.md` |
| Writing GitHub Actions CI workflows (`.github/workflows` present) | `references/github-actions.md` |
| Handling input, secrets, or trust boundaries | `references/security-baseline.md` |
| Adding or upgrading a dependency | `references/security-baseline.md` |

## The contract, in one line each

- Types are strict. `any` is a bug; reach for `unknown` when a type is genuinely open.
- Every feature and fix ships with meaningful unit tests. Coverage floor is 80%. See `testing-philosophy.md`.
- Work happens on a branch, never on `main` or `develop`. See `git-gitflow.md`.
- Untrusted input is validated before use. Secrets never reach the client or the repo.
- New dependencies are vetted before install. On known vulnerabilities, stop and get the user's approval. See `security-baseline.md`.