feat(scripts): enable hybrid builds using tsup

Author: benjamincburns

libs/langchain-scripts/README.md

@@ -7,3 +7,54 @@ This package contains the LangChain.js shared scripts for our packages.
 ```bash npm2yarn
 npm install @langchain/scripts
 ```
+
+## Usage
+
+### Build Script
+
+The build script supports both traditional TypeScript compilation and modern tsup-based builds.
+
+```bash
+npx lc_build
+```
+
+#### Traditional TypeScript Build
+
+By default, the build script uses TypeScript's compiler (tsc) to build both ESM and CJS versions of your package.
+
+#### tsup-based Build
+
+The build script can also use [tsup](https://github.com/egoist/tsup) (a zero-config TypeScript bundler powered by esbuild) which offers significant performance improvements (10-100x faster builds).
+
+To migrate your package to use tsup:
+
+```bash
+npx lc_build --migrate-build
+```
+
+This command performs several migration steps:
+1. Creates a `tsup.config.ts` file with sensible defaults for LangChain packages
+2. Updates TypeScript to the latest version in your package.json
+3. Ensures your package.json has a `type-check` script
+4. Backs up the tsconfig.cjs.json file (which is no longer needed with tsup)
+5. Provides guidance on updating build scripts if needed
+
+After migration, simply run the build script normally:
+
+```bash
+npx lc_build
+```
+
+The script will automatically detect the presence of a tsup configuration file and use it for building.
+
+### Notebooks Type-Checking
+
+```bash
+npx notebook_validate
+```
+
+### Serialized Field Extraction 
+
+```bash
+npx extract_serializable_fields
+```

libs/langchain-scripts/package.json

@@ -22,7 +22,7 @@
   "scripts": {
     "build": "yarn clean && yarn turbo:command build:internal --filter=@langchain/scripts",
     "build:internal": "tsc --project ./tsconfig.build.json && yarn move:artifacts && yarn build:generated",
-    "move:artifacts": "rimraf dist && mkdir -p dist && mv dist_build/* dist/",
+    "move:artifacts": "rimraf dist && mkdir -p dist && cp -r dist_build/* dist/ && mkdir -p dist/build && cp src/build/tsup.config.template.ts dist/build/",
     "build:generated": "node bin/build.js --create-entrypoints --pre --tree-shaking",
     "build:turbo": "yarn turbo:command build --filter=@langchain/scripts",
     "lint:eslint": "NODE_OPTIONS=--max-old-space-size=4096 eslint --cache --ext .ts,.js src/",
@@ -52,6 +52,7 @@
     "rimraf": "^5.0.1",
     "rollup": "^4.5.2",
     "ts-morph": "^21.0.1",
+    "tsup": "^8.4.0",
     "typescript": "^5.4.5"
   },
   "devDependencies": {