fix(next): resolve bare specifiers in copied step files for lazy discovery

.changeset/lazy-discovery-bare-specifiers.md

@@ -0,0 +1,10 @@
+---
+"@workflow/next": patch
+"@workflow/builders": patch
+---
+
+Fix lazy discovery bare specifier resolution in copied step files
+
+- Use `enhanced-resolve` with ESM conditions to resolve bare specifiers from the original source file's location
+- Only rewrite specifiers that can't resolve from the app directory (transitive SDK deps)
+- Add `enhanced-resolve` to pnpm catalog and use `catalog:` in both packages

packages/builders/package.json

@@ -46,7 +46,7 @@
     "@workflow/swc-plugin": "workspace:*",
     "builtin-modules": "5.0.0",
     "chalk": "5.6.2",
-    "enhanced-resolve": "5.19.0",
+    "enhanced-resolve": "catalog:",
     "esbuild": "catalog:",
     "find-up": "7.0.0",
     "json5": "2.2.3",

packages/next/package.json

@@ -37,6 +37,7 @@
     "@workflow/builders": "workspace:*",
     "@workflow/core": "workspace:*",
     "@workflow/swc-plugin": "workspace:*",
+    "enhanced-resolve": "catalog:",
     "semver": "catalog:",
     "watchpack": "2.5.1"
   },

packages/next/src/builder-deferred.ts

@@ -19,6 +19,7 @@ import {
   relative,
   resolve,
 } from 'node:path';
+import enhancedResolveOrig from 'enhanced-resolve';
 import {
   createSocketServer,
   type SocketIO,
@@ -63,6 +64,45 @@ export async function getNextBuilderDeferred() {
     'import("@workflow/builders")'
   )) as typeof import('@workflow/builders');
 
+  // Shared resolve options matching the configuration used by the SWC
+  // esbuild plugin (swc-esbuild-plugin.ts) for consistent resolution
+  // semantics across the toolchain.
+  const NODE_RESOLVE_OPTIONS = {
+    dependencyType: 'commonjs' as const,
+    modules: ['node_modules'],
+    exportsFields: ['exports'],
+    importsFields: ['imports'],
+    conditionNames: ['node', 'require'],
+    descriptionFiles: ['package.json'],
+    extensions: [
+      '.ts',
+      '.tsx',
+      '.mts',
+      '.cts',
+      '.cjs',
+      '.mjs',
+      '.js',
+      '.jsx',
+      '.json',
+      '.node',
+    ],
+    enforceExtensions: false,
+    symlinks: true,
+    mainFields: ['main'],
+    mainFiles: ['index'],
+    roots: [],
+    fullySpecified: false,
+    preferRelative: false,
+    preferAbsolute: false,
+    restrictions: [],
+  };
+
+  const NODE_ESM_RESOLVE_OPTIONS = {
+    ...NODE_RESOLVE_OPTIONS,
+    dependencyType: 'esm' as const,
+    conditionNames: ['node', 'import'],
+  };
+
   class NextDeferredBuilder extends BaseBuilderClass {
     private socketIO?: SocketIO;
     private readonly discoveredWorkflowFiles = new Set<string>();
@@ -74,6 +114,14 @@ export async function getNextBuilderDeferred() {
     private cacheWriteTimer: NodeJS.Timeout | null = null;
     private deferredRebuildTimer: NodeJS.Timeout | null = null;
     private lastDeferredBuildSignature: string | null = null;
+    // Lazily initialized resolvers for bare specifier rewriting.
+    // Cached to avoid re-creating on every import rewrite.
+    private esmSyncResolver?: ReturnType<
+      typeof enhancedResolveOrig.create.sync
+    >;
+    private cjsSyncResolver?: ReturnType<
+      typeof enhancedResolveOrig.create.sync
+    >;
 
     async build() {
       const outputDir = await this.findAppDirectory();
@@ -1267,6 +1315,33 @@ export async function getNextBuilderDeferred() {
       copiedStepFileBySourcePath: Map<string, string>
     ): string {
       if (!specifier.startsWith('.')) {
+        // Bare specifiers (e.g. '@workflow/serde') that are transitive
+        // dependencies of SDK packages can't be resolved by the bundler
+        // from the copied file's location (__workflow_step_files__/ inside
+        // the app dir) because the app doesn't directly depend on them.
+        //
+        // Only rewrite when the specifier can't be resolved from the app
+        // directory. If the package is a direct dependency of the app,
+        // the bare specifier will resolve normally and should be left as-is.
+        const appResolvable = this.resolveBareCopiedStepSpecifier(
+          specifier,
+          copiedFilePath
+        );
+        if (!appResolvable) {
+          const resolved = this.resolveBareCopiedStepSpecifier(
+            specifier,
+            sourceFilePath
+          );
+          if (!resolved) return specifier;
+          let rewrittenPath = relative(
+            dirname(copiedFilePath),
+            resolved
+          ).replace(/\\/g, '/');
+          if (!rewrittenPath.startsWith('.')) {
+            rewrittenPath = `./${rewrittenPath}`;
+          }
+          return rewrittenPath;
+        }
         return specifier;
       }
 
@@ -1300,6 +1375,41 @@ export async function getNextBuilderDeferred() {
       return `${rewrittenPath}${suffix}`;
     }
 
+    /**
+     * Resolves a bare specifier (e.g. '@workflow/serde', 'workflow') to an
+     * absolute file path using ESM-compatible resolution semantics via
+     * `enhanced-resolve`. Tries ESM conditions first (`node`, `import`),
+     * falling back to CJS resolution if ESM fails.
+     */
+    private resolveBareCopiedStepSpecifier(
+      specifier: string,
+      sourceFilePath: string
+    ): string | undefined {
+      if (!this.esmSyncResolver) {
+        this.esmSyncResolver = enhancedResolveOrig.create.sync(
+          NODE_ESM_RESOLVE_OPTIONS
+        );
+      }
+      if (!this.cjsSyncResolver) {
+        this.cjsSyncResolver =
+          enhancedResolveOrig.create.sync(NODE_RESOLVE_OPTIONS);
+      }
+      const context = dirname(sourceFilePath);
+      try {
+        const resolved = this.esmSyncResolver(context, specifier);
+        if (resolved) return resolved;
+      } catch {
+        // ESM resolution failed, try CJS
+      }
+      try {
+        const resolved = this.cjsSyncResolver(context, specifier);
+        if (resolved) return resolved;
+      } catch {
+        // CJS resolution also failed
+      }
+      return undefined;
+    }
+
     private resolveCopiedStepImportTargetPath(targetPath: string): string {
       if (existsSync(targetPath)) {
         return targetPath;

pnpm-workspace.yaml

@@ -14,6 +14,7 @@ catalog:
   "@vercel/queue": 0.1.4
   "@vitest/coverage-v8": ^4.0.18
   ai: 6.0.116
+  enhanced-resolve: 5.19.0
   esbuild: ^0.27.3
   nitro: 3.0.1-alpha.1
   semver: 7.7.4