fix(packages): add server-only bundles (#1349)

build/scripts/check-workspace.mjs

@@ -11,6 +11,7 @@
  * 4. Package metadata — non-private packages have required fields
  * 5. Release-please config — every versioned package is registered
  * 6. Define imports — no bare side-effect imports from relative paths
+ * 7. Server bundles — browser/default export conditions match tsdown config
  */
 import { existsSync, readdirSync, readFileSync } from 'node:fs';
 import { dirname, join, resolve } from 'node:path';
@@ -298,6 +299,74 @@ function checkDefineImports() {
   return { ok: warnings.length === 0, warnings };
 }
 
+// ── Check 7: Server bundles ──────────────────────────────────────────────────
+
+/**
+ * Packages with `browser` export conditions must have a matching server build
+ * in tsdown (build mode 'server', `__BROWSER__` define, `platform: 'node'`).
+ *
+ * For each export entry with a `browser` condition:
+ * - The sibling `default` path must point to `dist/server/`
+ * - The tsdown config must declare a `'server'` build mode
+ * - The tsdown config must define `__BROWSER__`
+ */
+function checkServerBundles() {
+  const warnings = [];
+
+  for (const dir of getPackageDirs()) {
+    const pkg = readPackageJson(dir);
+    if (pkg.private) continue;
+
+    const exports = pkg.exports;
+    if (!exports) continue;
+
+    // Collect export keys that have a `browser` condition.
+    const browserExports = [];
+
+    for (const [key, value] of Object.entries(exports)) {
+      if (typeof value !== 'object' || value === null) continue;
+      if ('browser' in value) {
+        browserExports.push(key);
+
+        // The `default` sibling must resolve to dist/server/.
+        const serverPath = value.default;
+        if (typeof serverPath === 'string' && !serverPath.includes('dist/server/')) {
+          warnings.push(
+            `${pkg.name}: export "${key}" has \`browser\` condition but \`default\` path "${serverPath}" does not point to dist/server/`
+          );
+        }
+      }
+    }
+
+    if (browserExports.length === 0) continue;
+
+    // Validate tsdown config has server build mode and __BROWSER__ define.
+    const tsdownPath = join(PACKAGES_DIR, dir, 'tsdown.config.ts');
+    if (!existsSync(tsdownPath)) {
+      warnings.push(`${pkg.name}: has \`browser\` exports but no tsdown.config.ts`);
+      continue;
+    }
+
+    const tsdownText = readText(tsdownPath);
+
+    if (!/'server'/.test(tsdownText)) {
+      warnings.push(`${pkg.name}: has \`browser\` exports but tsdown.config.ts is missing 'server' build mode`);
+    }
+
+    if (!/__BROWSER__/.test(tsdownText)) {
+      warnings.push(`${pkg.name}: has \`browser\` exports but tsdown.config.ts does not define __BROWSER__`);
+    }
+
+    if (!/platform.*['"]node['"]/.test(tsdownText)) {
+      warnings.push(
+        `${pkg.name}: has \`browser\` exports but tsdown.config.ts does not set platform to 'node' for server builds`
+      );
+    }
+  }
+
+  return { ok: warnings.length === 0, warnings };
+}
+
 // ── Main ────────────────────────────────────────────────────────────────────
 
 const checks = [
@@ -307,6 +376,7 @@ const checks = [
   { name: 'Package metadata', fn: checkPackageMetadata },
   { name: 'Release-please config', fn: checkReleasePleaseConfig },
   { name: 'Define imports', fn: checkDefineImports },
+  { name: 'Server bundles', fn: checkServerBundles },
 ];
 
 let failed = 0;