fix(preview-server): requiring peers to also have matching esbuild versions

[gabrielmfern]

Summary by cubic

Auto-set ESBUILD_BINARY_PATH to the matching platform/arch esbuild binary resolved alongside the esbuild JS the preview server uses. This prevents crashes from version mismatches in monorepos and works cross-platform.

• Bug Fixes
  • Resolve @esbuild/- next to the loaded esbuild JS and point ESBUILD_BINARY_PATH to its real binary (bin/esbuild or esbuild.exe).
  • Only runs when ESBUILD_BINARY_PATH is unset, preserving manual overrides.
  • Addresses OSS-400 (mismatching esbuild versions break the preview server).

^{Written for commit 5c73c27. Summary will update on new commits.}

[changeset-bot]

⚠️ No Changeset found

Latest commit: 5c73c27

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
react-email	Ready	Preview, Comment	Feb 25, 2026 7:27pm
react-email-demo	Ready	Preview, Comment	Feb 25, 2026 7:27pm

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/resend/react-email@2971

commit: 5c73c27

[cubic-dev-ai]

1 issue found across 1 file (changes from recent commits).

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="packages/react-email/src/utils/preview/start-dev-server.ts">

<violation number="1" location="packages/react-email/src/utils/preview/start-dev-server.ts:146">
P2: `esmResolve()` returns the module entry path (like `.../bin/esbuild`), so joining `subpath` again produces a non-existent path and prevents `ESBUILD_BINARY_PATH` from being set. Use the entry file’s directory before appending `subpath` so the binary can be found and the OSS-400 fix works.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}