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+# Copilot Instructions for Electron
+
+## Build System
+
+Electron uses `@electron/build-tools` (`e` CLI). Install with `npm i -g @electron/build-tools`.
+
+```bash
+e sync              # Fetch sources and apply patches
+e build             # Build Electron (GN + Ninja)
+e build -k 999      # Build, continuing through errors
+e start             # Run built Electron
+e start --version   # Verify Electron launches
+e test              # Run full test suite
+e debug             # Run in debugger (lldb on macOS, gdb on Linux)
+```
+
+### Linting
+
+```bash
+npm run lint              # Run all linters (JS, C++, Python, GN, docs)
+npm run lint:js           # JavaScript/TypeScript only
+npm run lint:clang-format # C++ formatting only
+npm run lint:cpp          # C++ linting only
+npm run lint:docs         # Documentation only
+```
+
+### Running a Single Test
+
+```bash
+npm run test -- -g "pattern"   # Run tests matching a regex pattern
+# Example: npm run test -- -g "ipc"
+```
+
+### Running a Single Node.js Test
+
+```bash
+node script/node-spec-runner.js parallel/test-crypto-keygen
+```
+
+## Architecture
+
+Electron embeds Chromium (rendering) and Node.js (backend) to enable desktop apps with web technologies. The parent directory (`../`) is the Chromium source tree.
+
+### Process Model
+
+Electron has two primary process types, mirroring Chromium:
+
+- **Main process** (`shell/browser/` + `lib/browser/`): Controls app lifecycle, creates windows, system APIs
+- **Renderer process** (`shell/renderer/` + `lib/renderer/`): Runs web content in BrowserWindows
+
+### Native ↔ JavaScript Bridge
+
+Each API is implemented as a C++/JS pair:
+
+- C++ side: `shell/browser/api/electron_api_{name}.cc/.h` — uses `gin::Wrappable` and `ObjectTemplateBuilder`
+- JS side: `lib/browser/api/{name}.ts` — exports the module, registered in `lib/browser/api/module-list.ts`
+- Binding: `NODE_LINKED_BINDING_CONTEXT_AWARE(electron_browser_{name}, Initialize)` in C++ and registered in `shell/common/node_bindings.cc`
+- Type declaration: `typings/internal-ambient.d.ts` maps `process._linkedBinding('electron_browser_{name}')`
+
+### Patches System
+
+Electron patches upstream dependencies (Chromium, Node.js, V8, etc.) rather than forking them. Patches live in `patches/` organized by target, with `patches/config.json` mapping directories to repos.
+
+```text
+patches/{target}/*.patch  →  [e sync]   →  target repo commits
+                          ←  [e patches] ←
+```
+
+Key rules:
+
+- Fix existing patches rather than creating new ones
+- Preserve original authorship in TODO comments — never change `TODO(name)` assignees
+- Each patch commit message must explain why the patch exists
+- After modifying patches, run `e patches {target}` to export
+
+When working on the `roller/chromium/main` branch for Chromium upgrades, use `e sync --3` for 3-way merge conflict resolution.
+
+## Conventions
+
+### File Naming
+
+- JS/TS files: kebab-case (`file-name.ts`)
+- C++ files: snake_case with `electron_api_` prefix (`electron_api_safe_storage.cc`)
+- Test files: `api-{module-name}-spec.ts` in `spec/`
+- Source file lists are maintained in `filenames.gni` (with platform-specific sections)
+
+### JavaScript/TypeScript
+
+- Semicolons required (`"semi": ["error", "always"]`)
+- `const` and `let` only (no `var`)
+- Arrow functions preferred
+- Import order enforced: `@electron/internal` → `@electron` → `electron` → external → builtin → relative
+- API naming: `PascalCase` for classes (`BrowserWindow`), `camelCase` for module APIs (`globalShortcut`)
+- Prefer getters/setters over jQuery-style `.text([text])` patterns
+
+### C++
+
+- Follows Chromium coding style, enforced by `clang-format` and `clang-tidy`
+- Uses Chromium abstractions (`base::`, `content::`, etc.)
+- Header guards: `#ifndef ELECTRON_SHELL_BROWSER_API_ELECTRON_API_{NAME}_H_`
+- Platform-specific files: `_mac.mm`, `_win.cc`, `_linux.cc`
+
+### Testing
+
+- Framework: Mocha + Chai + Sinon
+- Test helpers in `spec/lib/` (e.g., `spec-helpers.ts`, `window-helpers.ts`)
+- Use `defer()` from spec-helpers for cleanup, `closeAllWindows()` for window teardown
+- Tests import from `electron/main` or `electron/renderer`
+
+### Documentation
+
+- API docs in `docs/api/` as Markdown, parsed by `@electron/docs-parser` to generate `electron.d.ts`
+- API history tracked via YAML blocks in HTML comments within doc files
+- Docs must pass `npm run lint:docs`
+
+### Build Configuration
+
+- `BUILD.gn`: Main GN build config
+- `buildflags/buildflags.gni`: Feature flags (PDF viewer, extensions, spellchecker)
+- `build/args/`: Build argument profiles (`testing.gn`, `release.gn`, `all.gn`)
+- `DEPS`: Dependency versions and checkout paths
+- `chromium_src/`: Chromium source file overrides (compiled instead of originals)