Migrate from bunchee to tsdown

README.md

@@ -132,7 +132,8 @@ This monorepo is designed around a **bundler-first approach** that prioritizes:
 
 Instead of relying on TypeScript project references, this monorepo uses:
 
-1. **Bundlers (bunchee)** to compile shared packages into optimized dist files
+1. **Bundlers (tsdown)** to compile shared packages into optimized dist files
+   (with `.d.ts` and source maps)
 2. **Turborepo** to orchestrate build dependencies and ensure proper ordering
 3. **TypeScript** purely for type checking against built artifacts
 
@@ -160,7 +161,7 @@ Instead of relying on TypeScript project references, this monorepo uses:
 The build process follows this sequence:
 
 1. **Shared packages build first** (`@repo/common`, `@repo/core`)
-   - Create optimized dist files with type declarations
+   - Create optimized dist files with `.d.ts` and `.d.ts.map`
    - Enable bundler optimizations (tree-shaking, minification, etc.)
 
 2. **Consumer packages check types** (`@repo/web`, `@repo/api`, `@repo/fns`)
@@ -171,9 +172,46 @@ The build process follows this sequence:
    - Ensures proper dependency ordering
    - Caches build artifacts for faster subsequent runs
 
+#### tsdown configuration
+
+Each buildable package contains a `tsdown.config.ts` that defines entries and
+output behavior. Examples:
+
+```ts
+// packages/common/tsdown.config.ts
+import { defineConfig } from "tsdown";
+
+export default defineConfig({
+  entry: "src/index.ts",
+  outDir: "dist",
+  target: "es2022",
+  sourcemap: true,
+  dts: true,
+});
+```
+
+```ts
+// packages/core/tsdown.config.ts
+import { defineConfig } from "tsdown";
+
+export default defineConfig({
+  entry: {
+    "db-refs": "src/db-refs.ts",
+    firebase: "src/firebase.ts",
+    "utils/index": "src/utils/index.ts",
+  },
+  outDir: "dist",
+  target: "es2022",
+  sourcemap: true,
+  dts: true,
+  platform: "node",
+});
+```
+
 **Key commands:**
 
-- `pnpm build` - Builds all packages with proper dependency ordering
+- `pnpm build` - Builds all packages with proper dependency ordering using
+  tsdown configs
 - `pnpm check-types` - Runs type checking after ensuring dependencies are built
 - `pnpm watch` - Continuously rebuilds packages as they change
 
@@ -192,7 +230,7 @@ sooner.
 ### Packages
 
 - [common](./packages/common) Code that is shared across both front-end and
-  back-end environments simultaneously. Built with bunchee for optimal output.
+  back-end environments simultaneously. Built with tsdown for optimal output.
 - [core](./packages/core) Code that is only shared between server environments,
   like cloud functions, containing mostly "core" business logic. Depends on
   common.

apps/web/package.json

@@ -35,9 +35,9 @@
     "@types/react": "^19.1.11",
     "@types/react-dom": "^19.0.3",
     "del-cli": "^6.0.0",
-
     "madge": "^8.0.0",
     "postcss": "^8.5.1",
-    "tailwindcss": "^4.1.12"
+    "tailwindcss": "^4.1.12",
+    "tsdown": "^0.14.2"
   }
 }

package.json

@@ -39,7 +39,7 @@
     "dev": "turbo dev",
     "deploy": "firebase deploy",
     "watch": "turbo watch build --filter=@repo/core --filter=@repo/fns --filter=@repo/api",
-    "test": "turbo test -- --watch false",
+    "test": "turbo test",
     "emulate": "firebase emulators:start --project demo-mono-ts",
     "format": "biome check --write",
     "db:get-indexes": "firebase firestore:indexes > firestore.indexes.json"

packages/common/package.json

@@ -17,7 +17,7 @@
     "check-biome": "biome check",
     "check-circular": "madge --circular --extensions ts ./src --ts-config ./tsconfig.json",
     "test": "vitest",
-    "build": "bunchee --sourcemap --target es2022",
+    "build": "tsdown",
     "clean": "del-cli dist tsconfig.tsbuildinfo",
     "coverage": "vitest run --coverage"
   },
@@ -28,9 +28,9 @@
   },
   "devDependencies": {
     "@codecompose/typescript-config": "^1.2.0",
-    "bunchee": "^6.6.0",
     "del-cli": "^6.0.0",
     "madge": "^8.0.0",
+    "tsdown": "^0.14.2",
     "typescript": "^5.9.2",
     "vitest": "^3.0.4"
   }

packages/common/tsdown.config.ts

@@ -0,0 +1,9 @@
+import { defineConfig } from "tsdown";
+
+export default defineConfig({
+  entry: "src/index.ts",
+  outDir: "dist",
+  target: "es2022",
+  sourcemap: true,
+  dts: true,
+});

packages/core/package.json

@@ -11,7 +11,7 @@
     "check-biome": "biome check",
     "check-circular": "madge --circular --extensions ts ./src --ts-config ./tsconfig.json",
     "test": "vitest",
-    "build": "bunchee --sourcemap --runtime node --target es2022",
+    "build": "tsdown",
     "clean": "del-cli dist tsconfig.tsbuildinfo",
     "coverage": "vitest run --coverage "
   },
@@ -26,9 +26,9 @@
   "devDependencies": {
     "@codecompose/typescript-config": "^1.2.0",
     "@types/node": "^24.3.0",
-    "bunchee": "^6.6.0",
     "del-cli": "^6.0.0",
     "madge": "^8.0.0",
+    "tsdown": "^0.14.2",
     "typescript": "^5.9.2",
     "vitest": "^3.0.4"
   },

packages/core/src/db-refs.ts

@@ -4,7 +4,7 @@ import type { CollectionReference } from "firebase-admin/firestore";
  * Here we are using a path alias ~/ to be able to reference the src directory
  * from anywhere. This is configured out-of-the box via
  * codecompose/typescript-config. This is the responsibility of the bundler
- * (Bunchee), because the Typescript compiler does not do this for us. Not all
+ * (tsdown), because the Typescript compiler does not do this for us. Not all
  * bundlers have this feature.
  */
 import { db } from "~/firebase";

packages/core/tsdown.config.ts

@@ -0,0 +1,14 @@
+import { defineConfig } from "tsdown";
+
+export default defineConfig({
+  entry: {
+    "db-refs": "src/db-refs.ts",
+    firebase: "src/firebase.ts",
+    "utils/index": "src/utils/index.ts",
+  },
+  outDir: "dist",
+  target: "es2022",
+  sourcemap: true,
+  dts: true,
+  platform: "node",
+});