# Codex Foundations > Core operating rules for Codex in this repository. Use when this capability is needed. - Skill: `tomevault-io/codex-foundations` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/codex-foundations` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/codex-foundations/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/codex-foundations --- # Codex Foundations ## When to use Use for any task in this repo or when behavior is unclear. ## Principles - Prefer concrete, reproducible steps. - Be explicit about assumptions and constraints. - Keep changes small and reviewable. - Report when tests were not run. ## Stack awareness - Frontend: React/Next.js - Backend: Node.js, Python/FastAPI, Java/Spring - Integrations, pipelines, and CI/CD are first-class concerns. ## Execution 1. Inspect the repository structure before editing. 2. Use `rg` for search. 3. Use `apply_patch` for small edits and scripts for bulk changes. 4. Provide file references for modified files. ## Output format - Short summary of changes. - Follow-up actions if needed. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/pedroct) — claim your Tome and manage your conversions.