feat: support --turbo build for Next.js #2422

seawatts · 2025-09-08T06:05:54Z

Add Turbopack Support to BAML Next.js Plugin

Summary

This PR adds full support for Next.js Turbopack to the @boundaryml/baml-nextjs-plugin, allowing users to run their Next.js applications with the --turbo flag without encountering native binding errors.

Problem

Previously, when using BAML with Next.js Turbopack (next dev --turbo), users would encounter the following error:

⨯ Error: Failed to load native binding
   at __TURBOPACK__module__evaluation__ (../../packages/ai/src/baml_client/async_client.ts:22:1)

This was because the plugin didn't properly handle BAML's native bindings in Turbopack mode.

Solution

Turbopack Detection: Added proper detection of Turbopack mode using process.env.TURBOPACK === '1'
Native Binding Externalization: Configured Turbopack rules to properly handle .node files using nextjs-node-loader
Conditional Configuration: Applied different webpack configurations based on whether Turbopack is enabled
Server External Packages: Properly externalized BAML packages for server-side rendering in Turbopack mode

Key Changes

1. Turbopack Configuration

const turboConfig = isTurbo
  ? {
      ...(nextConfig.experimental?.turbo || {}),
      rules: {
        ...(nextConfig.experimental?.turbo?.rules || {}),
        '*.node': { loaders: ['nextjs-node-loader'], as: '*.js' },
      },
    }
  : undefined;

2. Conditional Server External Packages

// In Turbo mode, we don't add it to serverExternalPackages to avoid conflicts
...(isTurbo
  ? {}
  : {
      serverExternalPackages: [
        ...(nextConfig?.serverExternalPackages || []),
        '@boundaryml/baml',
      ],
    }),

3. Improved Webpack Configuration

Fixed parameter mutation issues by using a separate webpackConfig variable
Properly externalized all BAML native bindings for server-side rendering
Maintained backward compatibility with regular webpack builds

Testing

✅ Tested with next dev --turbo - server starts successfully
✅ Tested with next dev (regular webpack) - maintains existing functionality
✅ Verified BAML functions work correctly in both modes
✅ No more "Failed to load native binding" errors

Breaking Changes

None. This change is fully backward compatible.

Migration Guide

No migration required. Users can now simply run next dev --turbo with BAML without any additional configuration.

Related Issues

Fixes issues where BAML applications couldn't use Next.js Turbopack due to native binding conflicts.

Important

Adds support for Next.js Turbopack in BAML plugin by detecting Turbopack mode, externalizing native bindings, and adjusting webpack configurations.

Turbopack Support:
- Detects Turbopack mode using process.env.TURBOPACK === '1' in index.ts.
- Configures Turbopack rules to handle .node files with nextjs-node-loader.
- Applies different webpack configurations based on Turbopack mode.
Native Binding Handling:
- Externalizes BAML native bindings for server-side rendering in Turbopack mode.
- Uses webpackConfig to avoid parameter mutation issues.
Backward Compatibility:
- Maintains compatibility with regular webpack builds.
- No breaking changes; fully backward compatible.
Testing:
- Verified functionality with next dev --turbo and next dev.

^{This description was created by}^{for 4156ffe. You can customize this summary. It will automatically update as commits are pushed.}

vercel · 2025-09-08T06:05:59Z

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Reviewed everything up to 4156ffe in 1 minute and 41 seconds. Click for details.

Reviewed 127 lines of code in 1 files
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1. typescript/packages/nextjs-plugin/src/index.ts:67

Draft comment:
Merging experimental config with object spread does not deep merge nested objects. Ensure this shallow merge meets your intended config override behavior.
Reason this comment was not posted:
Comment was not on a location in the diff, so it can't be submitted as a review comment.

2. typescript/packages/nextjs-plugin/src/index.ts:113

Draft comment:
The webpack rule for .node files is only added when not in Turbo mode, relying on turboConfig for Turbo builds. Verify that this separation is intentional to avoid misconfiguration.
Reason this comment was not posted:
Comment was on unchanged code.

3. typescript/packages/nextjs-plugin/src/index.ts:98

Draft comment:
A hard‐coded list of BAML packages is appended to externals on the server side. Consider documenting or externalizing this list so future changes can be managed more easily.
Reason this comment was not posted:
Comment was on unchanged code.

Workflow ID: wflow_TBBnq3HRsuZjV9v6

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ellipsis-dev · 2025-09-08T06:07:39Z

typescript/packages/nextjs-plugin/src/index.ts

 }

-export function withBaml(bamlConfig: BamlNextConfig = {}) {
+export function withBaml(_bamlConfig: BamlNextConfig = {}) {


The _bamlConfig parameter is currently unused. Consider removing it or using it for configurable behavior to avoid confusion.

entelligence-ai-pr-reviews · 2025-09-08T06:09:45Z

🔒 Entelligence AI Vulnerability Scanner

✅ No security vulnerabilities found!

Your code passed our comprehensive security analysis.

📊 Files Analyzed: 1 files

entelligence-ai-pr-reviews · 2025-09-08T06:09:46Z

Review Summary

🔍 Comments beyond diff scope (1)

typescript/packages/nextjs-plugin/src/index.ts (1)

55-56: Potentially large objects are repeatedly shallow-copied with spread operators (e.g., ...(nextConfig.experimental?.turbo || {})), which can cause measurable overhead in large configs or frequent builds.
Category: performance

entelligence-ai-pr-reviews · 2025-09-08T06:09:48Z

typescript/packages/nextjs-plugin/src/index.ts

-        // Add WebAssembly loading configuration (properly indented)
-
-        return config;
+        return webpackConfig;


correctness: webpackConfig is not returned if context.isServer is false, causing plugin webpack modifications to be lost in client builds.

🤖 AI Agent Prompt for Cursor/Windsurf

📋 Copy this prompt to your AI coding assistant (Cursor, Windsurf, etc.) to get help fixing this issue

In typescript/packages/nextjs-plugin/src/index.ts, line 129, ensure that the function always returns the modified `webpackConfig` object, not the original `config`, regardless of whether `context.isServer` is true or false. This prevents loss of plugin webpack modifications in client builds. Double-check that all plugin modifications are applied to `webpackConfig` and that it is always returned.

@seawatts is this a real bug?

entelligence-ai-pr-reviews · 2025-09-08T06:09:52Z

typescript/packages/nextjs-plugin/src/index.ts

    const nextPackageJson = require(projectNextPath);
    return nextPackageJson.version || null;
-  } catch (error) {
+  } catch {
    try {
-      // Fallback to checking in the plugin's dependencies
      const nextPackageJson = require('next/package.json');
      return nextPackageJson.version || null;
-    } catch (error) {
+    } catch {
      console.warn(
        'Warning: Could not determine Next.js version, defaulting to latest config',
      );


performance: The function getNextJsVersion synchronously reads and requires package.json files on every invocation, which can cause measurable startup latency in large monorepos or repeated plugin invocations.

🤖 AI Agent Prompt for Cursor/Windsurf

📋 Copy this prompt to your AI coding assistant (Cursor, Windsurf, etc.) to get help fixing this issue

In typescript/packages/nextjs-plugin/src/index.ts, lines 3-17, the function `getNextJsVersion` synchronously reads and requires package.json files on every invocation, which can cause measurable startup latency in large monorepos or repeated plugin invocations. Add a simple in-memory cache so the version is only resolved once per process.

📝 Committable Code Suggestion

‼️ Ensure you review the code suggestion before committing it to the branch. Make sure it replaces the highlighted code, contains no missing lines, and has no issues with indentation.

Suggested change

const nextPackageJson = require(projectNextPath);

return nextPackageJson.version || null;

} catch (error) {

} catch {

try {

// Fallback to checking in the plugin's dependencies

const nextPackageJson = require('next/package.json');

return nextPackageJson.version || null;

} catch (error) {

} catch {

console.warn(

'Warning: Could not determine Next.js version, defaulting to latest config',

);

let cachedNextJsVersion: string | null | undefined = undefined;

function getNextJsVersion(): string | null {

if (cachedNextJsVersion !== undefined) return cachedNextJsVersion;

try {

const projectNextPath = require.resolve('next/package.json', {

paths: [process.cwd()],

});

const nextPackageJson = require(projectNextPath);

cachedNextJsVersion = nextPackageJson.version || null;

return cachedNextJsVersion;

} catch {

try {

const nextPackageJson = require('next/package.json');

cachedNextJsVersion = nextPackageJson.version || null;

return cachedNextJsVersion;

} catch {

console.warn(

'Warning: Could not determine Next.js version, defaulting to latest config',

);

cachedNextJsVersion = null;

return null;

}

}

}

codecov · 2025-09-08T08:40:38Z

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

Fjandin · 2025-09-24T08:32:20Z

Any plan on getting this in? Would love turbopack support for this already amazing product ❤️

feat: support --turbo build for Next.js

4156ffe

Update index.ts

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ellipsis-dev bot reviewed Sep 8, 2025

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Update index.ts

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entelligence-ai-pr-reviews bot reviewed Sep 8, 2025

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seawatts had a problem deploying to boundary-tools-dev September 8, 2025 08:34 — with GitHub Actions Failure

Merge branch 'canary' into patch-1

ca3363e

aaronvg had a problem deploying to boundary-tools-dev September 8, 2025 21:33 — with GitHub Actions Failure

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Add Turbopack Support to BAML Next.js Plugin

Summary

Problem

Solution

Key Changes

1. Turbopack Configuration

2. Conditional Server External Packages

3. Improved Webpack Configuration

Testing

Breaking Changes

Migration Guide

Related Issues

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