> ## Documentation Index > Fetch the complete documentation index at: https://mintlify.com/sanbuphy/claude-code-source-code/llms.txt > Use this file to discover all available pages before exploring further. # Installation > Install Claude Code via the pre-built CLI or build from source using esbuild. There are three ways to get Claude Code running. Choose based on what you need. The npm package already contains a compiled `cli.js`. This is the fastest path and requires no build tooling beyond Node.js. ## Prerequisites ```bash theme={null} node --version # >= 18 ``` ## Run directly ```bash theme={null} cd /path/to/claude-code-source-code node cli.js --version # → 2.1.88 (Claude Code) ``` ## Install globally ```bash theme={null} npm install -g . claude --version # → 2.1.88 (Claude Code) ``` For automation and scripting, prefer `node cli.js` directly. Global install is convenient for interactive use. A best-effort source build using esbuild gets approximately 95% complete. Some internal modules are unavailable (see warning below). ## Prerequisites ```bash theme={null} node --version # >= 18 npm --version # >= 9 ``` ## Steps ```bash theme={null} cd claude-code-source-code/ # 1. Install the build dependency npm install --save-dev esbuild # 2. Run the build script node scripts/build.mjs # 3. Run the output node dist/cli.js --version ``` The source build is **incomplete by design**. 108 modules referenced by `feature()`-gated branches are not included in the published npm package — they exist only in Anthropic's internal monorepo and were dead-code-eliminated at compile time. They cannot be recovered from `cli.js`, `sdk-tools.d.ts`, or any published artifact. The esbuild build creates stubs for these modules automatically, but some functionality will be absent at runtime. ## What the build script does | Phase | Action | | ----------------- | ------------------------------------------------------------- | | **1. Copy** | `src/` → `build-src/` (original source is untouched) | | **2. Transform** | `feature('X')` → `false` to enable dead code elimination | | **2b. Transform** | `MACRO.VERSION` → `'2.1.88'` (compile-time version injection) | | **2c. Transform** | `import from 'bun:bundle'` → stub import | | **3. Entry** | Create a wrapper that injects `MACRO` globals | | **4. Bundle** | esbuild with iterative stub creation for missing modules | ## Known issues The source uses **Bun compile-time intrinsics** that esbuild cannot fully replicate: 1. **`feature('FLAG')` from `bun:bundle`** — Bun resolves this at compile time to `true`/`false` and eliminates dead branches. The build script replaces these with `false`, but esbuild still attempts to resolve `require()` calls inside those branches. 2. **`MACRO.X`** — Bun's `--define` replaces these at compile time. The build script uses string replacement, which works for most cases but can miss edge cases in complex expressions. 3. **108 missing modules** — Feature-gated internal modules (daemon, bridge assistant, context collapse, etc.) that don't exist in the published source. Normally dead-code-eliminated by Bun, but esbuild can't eliminate them because the `require()` calls remain syntactically present. 4. **`bun:ffi`** — Used for native proxy support. Stubbed out in the build. 5. **`import type` from generated files** — Some generated type files are not in the published source. ## Diagnosing remaining issues ```bash theme={null} # Check what's still missing after a build attempt npx esbuild build-src/entry.ts --bundle --platform=node \ --packages=external --external:'bun:*' \ --log-level=error --log-limit=0 --outfile=/dev/null 2>&1 | \ grep "Could not resolve" | sort -u ``` For each unresolved module, create a stub file in `build-src/src/` that exports empty functions, then re-run `node scripts/build.mjs`. A full rebuild requires Bun for its compile-time intrinsics (`feature()`, `MACRO`, `bun:bundle`). The internal build configuration is not included in the published package — you would need access to Anthropic's internal monorepo. This option is documented here for completeness and for Anthropic engineers. ## Install Bun ```bash theme={null} curl -fsSL https://bun.sh/install | bash ``` ## The real build command (reference only) ```bash theme={null} # bun build src/entrypoints/cli.tsx \ # --define:feature='(flag) => flag === "SOME_FLAG"' \ # --define:MACRO.VERSION='"2.1.88"' \ # --target=bun \ # --outfile=dist/cli.js ``` The internal build configuration, feature flag definitions, and the 108 internal modules are not included in this repository. Running the command above without Anthropic's internal monorepo will fail. ## Why Bun is required Bun's `feature()` is a **compile-time intrinsic**: * Returns `true` in Anthropic's internal build → code is kept in the bundle * Returns `false` in the published build → code is dead-code-eliminated * The 108 missing modules simply do not exist anywhere in the published artifact ``` Anthropic Internal Monorepo Published npm Package ────────────────────────── ───────────────────── feature('DAEMON') → true ──build──→ feature('DAEMON') → false ↓ ↓ daemon/main.js ← INCLUDED ──bundle─→ daemon/main.js ← DELETED (DCE) tools/REPLTool ← INCLUDED ──bundle─→ tools/REPLTool ← DELETED (DCE) ``` ## Project structure ``` claude-code-source-code/ ├── src/ # Original TypeScript source (1,884 files, 512K LOC) ├── stubs/ # Build stubs for Bun compile-time intrinsics │ ├── bun-bundle.ts # feature() stub → always returns false │ ├── macros.ts # MACRO version constants │ └── global.d.ts # Global type declarations ├── scripts/ │ └── build.mjs # Build script (esbuild-based) ├── node_modules/ # 192 npm dependencies ├── vendor/ # Native module source stubs ├── build-src/ # Created by build script (transformed copy) ├── dist/ # Build output (created by build script) └── cli.js # Pre-built CLI bundle (~12 MB) ```