Backport: ci(bundle-size): initial version

[vercel-ai-sdk]

This is an automated backport of #9411 to the release-v5.0 branch.

[vercel]

The error message suggests updating a GitHub Actions variable BUNDLE_SIZE_LIMIT_KB, but the script uses a hardcoded limit and doesn't read from any environment variable, making this guidance ineffective and misleading.

View Details

📝 Patch Details

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1b3e5e73c..8b415be31 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -132,6 +132,8 @@ jobs:
         run: pnpm run build:packages
 
       - name: Check bundle size
+        env:
+          BUNDLE_SIZE_LIMIT_KB: ${{ vars.BUNDLE_SIZE_LIMIT_KB }}
         run: cd packages/ai && pnpm run check-bundle-size
 
       - name: Upload bundle size metafiles
diff --git a/packages/ai/scripts/check-bundle-size.ts b/packages/ai/scripts/check-bundle-size.ts
index ff8cf4ad0..610c3713e 100644
--- a/packages/ai/scripts/check-bundle-size.ts
+++ b/packages/ai/scripts/check-bundle-size.ts
@@ -3,7 +3,9 @@ import { writeFileSync, statSync } from 'fs';
 import { join } from 'path';
 
 // Bundle size limits in bytes
-const LIMIT = 510 * 1024;
+const LIMIT = process.env.BUNDLE_SIZE_LIMIT_KB
+  ? parseInt(process.env.BUNDLE_SIZE_LIMIT_KB, 10) * 1024
+  : 510 * 1024;
 
 interface BundleResult {
   size: number;

Analysis

Bundle size check error message references non-functional GitHub Actions variable

What fails: The check-bundle-size.ts script error message at line 109 instructs users to update BUNDLE_SIZE_LIMIT_KB at https://github.com/vercel/ai/settings/variables/actions/BUNDLE_SIZE_LIMIT_KB, but the script hardcodes the limit at line 6 (const LIMIT = 510 * 1024;) and never reads from environment variables.

How to reproduce:

# The script uses hardcoded value:
cd packages/ai
grep "const LIMIT" scripts/check-bundle-size.ts
# Output: const LIMIT = 510 * 1024;

# The script doesn't use process.env:
grep "process.env" scripts/check-bundle-size.ts
# Output: (none)

# CI workflow doesn't pass the variable:
grep -A5 "Check bundle size" .github/workflows/ci.yml
# Shows no env vars passed to the script

Result: When a bundle size check fails, users follow the error message guidance to update the GitHub Actions variable, but the script continues failing because it never reads that variable. This wastes developer time troubleshooting why their configuration change has no effect.

Expected: The script should read from process.env.BUNDLE_SIZE_LIMIT_KB and the CI workflow should pass to the script, making the error message's guidance functional.

Fix: Modified the script to read from environment variable with fallback to hardcoded default, and updated the CI workflow to pass the GitHub Actions variable per GitHub Actions variables documentation.