Mobile and games
Expo and React Native rules file
React Native agents often emit div and className. This file requires View, Text, and Pressable, installs SDK modules with expo install, and tells the agent not to hand-edit generated ios and android folders.
Change this stack in the generator
The files
Same rules, wrapped for each tool. Use the file your editor lists. Legacy files are there for older builds.
CursorUse this.cursor/rules/project.mdc
---description: "Project rules for TypeScript, Expo / React Native, Jest, npm. Generated by RulePaste."alwaysApply: true--- # Project rules Stack: TypeScript, Expo / React Native, Jest, npm. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - JavaScript package manager is npm. The lockfile to commit is package-lock.json. Do not add a second lockfile.- Install: `npm install`.- Dev server: `npm run dev` when that script exists.- Lint: `npm run lint` when that script exists. Typecheck with the project's typecheck script or `tsc --noEmit` if the repo uses it.- Build: `npm run build` when you changed a build path.- Tests: `npm test`. One file: `npx jest path/to/file.test.ts`.- Add Expo SDK packages with `npx expo install <pkg>` so the version matches the SDK.- Run the narrowest command that checks the change. Do not loop install, build, or the full test suite. ## TypeScript - Leave `strict` on. Do not weaken `tsconfig` to make a build pass.- No new `any`, and no `// @ts-ignore`. Use `unknown` and narrow. `@ts-expect-error` needs a reason on that line.- Match the file's style for `type` versus `interface`. Prefer a string union over a new `enum` unless the file already uses enums.- Use `import type` for type-only imports. Await promises. Do not leave a promise floating.- Do not use a non-null assertion on a value that came from outside the function. Narrow it instead. ## Expo and React Native - Use `View`, `Text`, `Pressable`, and `ScrollView` from `react-native`. Do not use `div`, `span`, or CSS files.- Use the navigation the repo already has: Expo Router or React Navigation. Do not add both.- Style with `StyleSheet.create` unless NativeWind or another styling library is already installed. Do not add one.- Add Expo SDK modules with `npx expo install` so the version matches the SDK.- If `ios/` and `android/` are generated or gitignored, change `app.json` or config plugins instead of hand-editing native projects.- Do not import Node built-ins into components. They do not exist on device. ## Jest - Match the existing test location and suffix. Do not add Vitest beside Jest.- Await async assertions. Do not use `done` callbacks in new tests.- Do not leak mock state between tests. Do not snapshot large trees, ids, or dates. ## npm - npm is the package manager. The lockfile is `package-lock.json`. Do not commit `pnpm-lock.yaml`, `yarn.lock`, or `bun.lock`.- Add packages with `npm install <pkg>`. Run scripts with `npm run <script>` and `npm test`. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Create `.cursor/rules/` in the project root if it does not exist.
- Save this file as `.cursor/rules/project.mdc`. The `.mdc` extension and the frontmatter are required. A plain `.md` file in that folder is ignored.
- Commit it. Open a new Cursor chat. Check Settings, Rules, and confirm the rule is listed as Always Apply.
- Keep a single rule under a few hundred lines. Split later files by topic and set `alwaysApply: false` plus `globs` when a rule is only for some files.
Cursor (legacy)Legacy.cursorrules
# Project rules Stack: TypeScript, Expo / React Native, Jest, npm. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - JavaScript package manager is npm. The lockfile to commit is package-lock.json. Do not add a second lockfile.- Install: `npm install`.- Dev server: `npm run dev` when that script exists.- Lint: `npm run lint` when that script exists. Typecheck with the project's typecheck script or `tsc --noEmit` if the repo uses it.- Build: `npm run build` when you changed a build path.- Tests: `npm test`. One file: `npx jest path/to/file.test.ts`.- Add Expo SDK packages with `npx expo install <pkg>` so the version matches the SDK.- Run the narrowest command that checks the change. Do not loop install, build, or the full test suite. ## TypeScript - Leave `strict` on. Do not weaken `tsconfig` to make a build pass.- No new `any`, and no `// @ts-ignore`. Use `unknown` and narrow. `@ts-expect-error` needs a reason on that line.- Match the file's style for `type` versus `interface`. Prefer a string union over a new `enum` unless the file already uses enums.- Use `import type` for type-only imports. Await promises. Do not leave a promise floating.- Do not use a non-null assertion on a value that came from outside the function. Narrow it instead. ## Expo and React Native - Use `View`, `Text`, `Pressable`, and `ScrollView` from `react-native`. Do not use `div`, `span`, or CSS files.- Use the navigation the repo already has: Expo Router or React Navigation. Do not add both.- Style with `StyleSheet.create` unless NativeWind or another styling library is already installed. Do not add one.- Add Expo SDK modules with `npx expo install` so the version matches the SDK.- If `ios/` and `android/` are generated or gitignored, change `app.json` or config plugins instead of hand-editing native projects.- Do not import Node built-ins into components. They do not exist on device. ## Jest - Match the existing test location and suffix. Do not add Vitest beside Jest.- Await async assertions. Do not use `done` callbacks in new tests.- Do not leak mock state between tests. Do not snapshot large trees, ids, or dates. ## npm - npm is the package manager. The lockfile is `package-lock.json`. Do not commit `pnpm-lock.yaml`, `yarn.lock`, or `bun.lock`.- Add packages with `npm install <pkg>`. Run scripts with `npm run <script>` and `npm test`. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `.cursorrules` in the project root only if you are on an older Cursor build that still lists this file.
- Current Cursor uses `.cursor/rules/*.mdc`. If you keep both, they will drift unless you regenerate them together.
Claude CodeUse thisCLAUDE.md
# Project rules Stack: TypeScript, Expo / React Native, Jest, npm. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - JavaScript package manager is npm. The lockfile to commit is package-lock.json. Do not add a second lockfile.- Install: `npm install`.- Dev server: `npm run dev` when that script exists.- Lint: `npm run lint` when that script exists. Typecheck with the project's typecheck script or `tsc --noEmit` if the repo uses it.- Build: `npm run build` when you changed a build path.- Tests: `npm test`. One file: `npx jest path/to/file.test.ts`.- Add Expo SDK packages with `npx expo install <pkg>` so the version matches the SDK.- Run the narrowest command that checks the change. Do not loop install, build, or the full test suite. ## TypeScript - Leave `strict` on. Do not weaken `tsconfig` to make a build pass.- No new `any`, and no `// @ts-ignore`. Use `unknown` and narrow. `@ts-expect-error` needs a reason on that line.- Match the file's style for `type` versus `interface`. Prefer a string union over a new `enum` unless the file already uses enums.- Use `import type` for type-only imports. Await promises. Do not leave a promise floating.- Do not use a non-null assertion on a value that came from outside the function. Narrow it instead. ## Expo and React Native - Use `View`, `Text`, `Pressable`, and `ScrollView` from `react-native`. Do not use `div`, `span`, or CSS files.- Use the navigation the repo already has: Expo Router or React Navigation. Do not add both.- Style with `StyleSheet.create` unless NativeWind or another styling library is already installed. Do not add one.- Add Expo SDK modules with `npx expo install` so the version matches the SDK.- If `ios/` and `android/` are generated or gitignored, change `app.json` or config plugins instead of hand-editing native projects.- Do not import Node built-ins into components. They do not exist on device. ## Jest - Match the existing test location and suffix. Do not add Vitest beside Jest.- Await async assertions. Do not use `done` callbacks in new tests.- Do not leak mock state between tests. Do not snapshot large trees, ids, or dates. ## npm - npm is the package manager. The lockfile is `package-lock.json`. Do not commit `pnpm-lock.yaml`, `yarn.lock`, or `bun.lock`.- Add packages with `npm install <pkg>`. Run scripts with `npm run <script>` and `npm test`. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `CLAUDE.md` in the project root. `.claude/CLAUDE.md` also works if you want the root left clear.
- Commit it. Start a new Claude Code session. The file loads at session start, not in the middle of an old one.
- When the file gets long, move a topic into `.claude/rules/<topic>.md`. Add a `paths` list only if that topic should load for certain files.
Windsurf / DevinUse this.devin/rules/project.md
---trigger: always_ondescription: "Project rules for TypeScript, Expo / React Native, Jest, npm. Generated by RulePaste."--- # Project rules Stack: TypeScript, Expo / React Native, Jest, npm. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - JavaScript package manager is npm. The lockfile to commit is package-lock.json. Do not add a second lockfile.- Install: `npm install`.- Dev server: `npm run dev` when that script exists.- Lint: `npm run lint` when that script exists. Typecheck with the project's typecheck script or `tsc --noEmit` if the repo uses it.- Build: `npm run build` when you changed a build path.- Tests: `npm test`. One file: `npx jest path/to/file.test.ts`.- Add Expo SDK packages with `npx expo install <pkg>` so the version matches the SDK.- Run the narrowest command that checks the change. Do not loop install, build, or the full test suite. ## TypeScript - Leave `strict` on. Do not weaken `tsconfig` to make a build pass.- No new `any`, and no `// @ts-ignore`. Use `unknown` and narrow. `@ts-expect-error` needs a reason on that line.- Match the file's style for `type` versus `interface`. Prefer a string union over a new `enum` unless the file already uses enums.- Use `import type` for type-only imports. Await promises. Do not leave a promise floating.- Do not use a non-null assertion on a value that came from outside the function. Narrow it instead. ## Expo and React Native - Use `View`, `Text`, `Pressable`, and `ScrollView` from `react-native`. Do not use `div`, `span`, or CSS files.- Use the navigation the repo already has: Expo Router or React Navigation. Do not add both.- Style with `StyleSheet.create` unless NativeWind or another styling library is already installed. Do not add one.- Add Expo SDK modules with `npx expo install` so the version matches the SDK.- If `ios/` and `android/` are generated or gitignored, change `app.json` or config plugins instead of hand-editing native projects.- Do not import Node built-ins into components. They do not exist on device. ## Jest - Match the existing test location and suffix. Do not add Vitest beside Jest.- Await async assertions. Do not use `done` callbacks in new tests.- Do not leak mock state between tests. Do not snapshot large trees, ids, or dates. ## npm - npm is the package manager. The lockfile is `package-lock.json`. Do not commit `pnpm-lock.yaml`, `yarn.lock`, or `bun.lock`.- Add packages with `npm install <pkg>`. Run scripts with `npm run <script>` and `npm test`. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Create `.devin/rules/` and save this file as `.devin/rules/project.md`. Devin Desktop (formerly Windsurf) prefers this path. `.windsurf/rules/` still works as a fallback.
- `trigger: always_on` loads it in every chat. Keep the file under 12,000 characters or it can be truncated with no error.
- Commit it and start a new chat. If you also keep `.windsurfrules`, make sure the two files do not disagree.
Windsurf (legacy)Legacy.windsurfrules
# Project rules Stack: TypeScript, Expo / React Native, Jest, npm. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - JavaScript package manager is npm. The lockfile to commit is package-lock.json. Do not add a second lockfile.- Install: `npm install`.- Dev server: `npm run dev` when that script exists.- Lint: `npm run lint` when that script exists. Typecheck with the project's typecheck script or `tsc --noEmit` if the repo uses it.- Build: `npm run build` when you changed a build path.- Tests: `npm test`. One file: `npx jest path/to/file.test.ts`.- Add Expo SDK packages with `npx expo install <pkg>` so the version matches the SDK.- Run the narrowest command that checks the change. Do not loop install, build, or the full test suite. ## TypeScript - Leave `strict` on. Do not weaken `tsconfig` to make a build pass.- No new `any`, and no `// @ts-ignore`. Use `unknown` and narrow. `@ts-expect-error` needs a reason on that line.- Match the file's style for `type` versus `interface`. Prefer a string union over a new `enum` unless the file already uses enums.- Use `import type` for type-only imports. Await promises. Do not leave a promise floating.- Do not use a non-null assertion on a value that came from outside the function. Narrow it instead. ## Expo and React Native - Use `View`, `Text`, `Pressable`, and `ScrollView` from `react-native`. Do not use `div`, `span`, or CSS files.- Use the navigation the repo already has: Expo Router or React Navigation. Do not add both.- Style with `StyleSheet.create` unless NativeWind or another styling library is already installed. Do not add one.- Add Expo SDK modules with `npx expo install` so the version matches the SDK.- If `ios/` and `android/` are generated or gitignored, change `app.json` or config plugins instead of hand-editing native projects.- Do not import Node built-ins into components. They do not exist on device. ## Jest - Match the existing test location and suffix. Do not add Vitest beside Jest.- Await async assertions. Do not use `done` callbacks in new tests.- Do not leak mock state between tests. Do not snapshot large trees, ids, or dates. ## npm - npm is the package manager. The lockfile is `package-lock.json`. Do not commit `pnpm-lock.yaml`, `yarn.lock`, or `bun.lock`.- Add packages with `npm install <pkg>`. Run scripts with `npm run <script>` and `npm test`. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `.windsurfrules` in the project root if your build still asks for that filename.
- This file is always on and cannot be scoped. Prefer `.devin/rules/project.md` on current builds.
GitHub CopilotUse this.github/copilot-instructions.md
# Project rules Stack: TypeScript, Expo / React Native, Jest, npm. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - JavaScript package manager is npm. The lockfile to commit is package-lock.json. Do not add a second lockfile.- Install: `npm install`.- Dev server: `npm run dev` when that script exists.- Lint: `npm run lint` when that script exists. Typecheck with the project's typecheck script or `tsc --noEmit` if the repo uses it.- Build: `npm run build` when you changed a build path.- Tests: `npm test`. One file: `npx jest path/to/file.test.ts`.- Add Expo SDK packages with `npx expo install <pkg>` so the version matches the SDK.- Run the narrowest command that checks the change. Do not loop install, build, or the full test suite. ## TypeScript - Leave `strict` on. Do not weaken `tsconfig` to make a build pass.- No new `any`, and no `// @ts-ignore`. Use `unknown` and narrow. `@ts-expect-error` needs a reason on that line.- Match the file's style for `type` versus `interface`. Prefer a string union over a new `enum` unless the file already uses enums.- Use `import type` for type-only imports. Await promises. Do not leave a promise floating.- Do not use a non-null assertion on a value that came from outside the function. Narrow it instead. ## Expo and React Native - Use `View`, `Text`, `Pressable`, and `ScrollView` from `react-native`. Do not use `div`, `span`, or CSS files.- Use the navigation the repo already has: Expo Router or React Navigation. Do not add both.- Style with `StyleSheet.create` unless NativeWind or another styling library is already installed. Do not add one.- Add Expo SDK modules with `npx expo install` so the version matches the SDK.- If `ios/` and `android/` are generated or gitignored, change `app.json` or config plugins instead of hand-editing native projects.- Do not import Node built-ins into components. They do not exist on device. ## Jest - Match the existing test location and suffix. Do not add Vitest beside Jest.- Await async assertions. Do not use `done` callbacks in new tests.- Do not leak mock state between tests. Do not snapshot large trees, ids, or dates. ## npm - npm is the package manager. The lockfile is `package-lock.json`. Do not commit `pnpm-lock.yaml`, `yarn.lock`, or `bun.lock`.- Add packages with `npm install <pkg>`. Run scripts with `npm run <script>` and `npm test`. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Create `.github/` if needed and save this file as `.github/copilot-instructions.md`.
- Commit it. Copilot picks up repository instructions for Chat and, on supported plans, code review and the cloud agent.
- For rules that should only affect some files, add `.github/instructions/<name>.instructions.md` with `applyTo` frontmatter instead of growing this file.
Codex + AGENTS.mdAGENTS.md
# Project rules Stack: TypeScript, Expo / React Native, Jest, npm. Follow these rules on every task. If a rule disagrees with existing code, match the code and mention the difference. If a rule disagrees with a direct user instruction, follow the user. ## Working agreement - Read the files you will change before editing them. Do not invent the project layout from memory.- Change only what the task needs. No drive-by refactors, renames, or formatting of untouched lines.- Match the patterns already in the repo over a generic style guide.- Do not add dependencies, config files, or abstractions the task did not ask for.- Do not commit secrets, and do not paste `.env` values, tokens, or private keys into code or chat.- If a requirement is ambiguous, choose the smallest reading, state that assumption, and continue. ## Commands - JavaScript package manager is npm. The lockfile to commit is package-lock.json. Do not add a second lockfile.- Install: `npm install`.- Dev server: `npm run dev` when that script exists.- Lint: `npm run lint` when that script exists. Typecheck with the project's typecheck script or `tsc --noEmit` if the repo uses it.- Build: `npm run build` when you changed a build path.- Tests: `npm test`. One file: `npx jest path/to/file.test.ts`.- Add Expo SDK packages with `npx expo install <pkg>` so the version matches the SDK.- Run the narrowest command that checks the change. Do not loop install, build, or the full test suite. ## TypeScript - Leave `strict` on. Do not weaken `tsconfig` to make a build pass.- No new `any`, and no `// @ts-ignore`. Use `unknown` and narrow. `@ts-expect-error` needs a reason on that line.- Match the file's style for `type` versus `interface`. Prefer a string union over a new `enum` unless the file already uses enums.- Use `import type` for type-only imports. Await promises. Do not leave a promise floating.- Do not use a non-null assertion on a value that came from outside the function. Narrow it instead. ## Expo and React Native - Use `View`, `Text`, `Pressable`, and `ScrollView` from `react-native`. Do not use `div`, `span`, or CSS files.- Use the navigation the repo already has: Expo Router or React Navigation. Do not add both.- Style with `StyleSheet.create` unless NativeWind or another styling library is already installed. Do not add one.- Add Expo SDK modules with `npx expo install` so the version matches the SDK.- If `ios/` and `android/` are generated or gitignored, change `app.json` or config plugins instead of hand-editing native projects.- Do not import Node built-ins into components. They do not exist on device. ## Jest - Match the existing test location and suffix. Do not add Vitest beside Jest.- Await async assertions. Do not use `done` callbacks in new tests.- Do not leak mock state between tests. Do not snapshot large trees, ids, or dates. ## npm - npm is the package manager. The lockfile is `package-lock.json`. Do not commit `pnpm-lock.yaml`, `yarn.lock`, or `bun.lock`.- Add packages with `npm install <pkg>`. Run scripts with `npm run <script>` and `npm test`. ## Testing expectations - When you fix a bug, add a test that fails before the fix and passes after, in the repo's current test style.- When you change behavior a caller can observe, update or add a test for that behavior.- Do not test private helpers, framework internals, or third-party libraries. ## Code style - Keep strict type and lint settings on. Do not weaken them to get a green build.- No new `any`, and no empty catch blocks. Prefer `unknown` and narrowing. Handle every fallible call.- Give exported functions an explicit type when the inferred type is not obvious.- Follow the repo formatter. Do not hand-format files the formatter owns.- Do not add comments that restate the code.- Comment only a constraint, invariant, or tradeoff the code itself cannot show.- No file-header banners and no changelog comments. ## Safety - Never commit `.env`, keystores, or credential files. When a new variable is required, add an empty placeholder to the example env file.- Do not disable authentication, authorization, or TLS checks to make a test pass.- Do not force-push, `reset --hard`, drop a database, or delete a directory tree unless the user asked for that exact action.- Do not edit vendored or generated output (`node_modules`, `dist`, `.next`, `vendor`, `Library`, `.godot`). Change the source and regenerate. ## Done when - The change does what was asked and nothing extra.- New or changed behavior is covered at the level in Testing expectations.- The commands in this file that apply to the touched files have been run, or you say which command you could not run.- The diff has no unrelated files, lockfile churn, or secrets. Install
- Save as `AGENTS.md` in the project root. Codex, Cursor, Copilot CLI, Devin, and many other agents look for this name.
- The file is plain Markdown. Do not add frontmatter.
- In a monorepo, add a nested AGENTS.md next to a service that needs different commands. Do not leave an empty `AGENTS.override.md` beside it. Codex treats that empty file as the instructions for the folder.
- Commit it and start a new agent session.
What each section does
Working agreement
The habits that keep an agent from rewriting the repo while it solves a small task.
Commands
The install, dev, test, and lint commands for this stack, so the agent runs the project's tools instead of guessing.
TypeScript
Keeps the compiler strict and tells the agent how to type new code.
Expo and React Native
Keeps the agent from writing HTML and from upgrading native folders that Expo generates.
Jest
Stays on Jest and avoids a second runner.
npm
Locks the repo to npm so a second lockfile does not appear.
Testing expectations
How much test coverage this project wants from the agent, separate from which test runner is installed.
Code style
How strict the types, lint, and comments should be. This is the knob most people actually want to change.
Safety
Hard stops: secrets, destructive git commands, and generated folders.
Done when
The checklist the agent should satisfy before it calls the task finished.
Questions
Does this support Expo Router and React Navigation?
It tells the agent to keep whichever one the repo already uses, and not to install the other.
Why npm instead of pnpm?
Expo's docs and many templates still default to npm. Change the package manager in the generator if your repo uses pnpm or bun.
Related stacks
Newsletter
Stack notes, occasionally
A short email when a tool changes its rules filename or a new stack page ships. No product drip. If this form is not connected yet, your address is not stored.