fix(build): wire bundle:browser-mcp into bundle pipeline

[gsquared94]

Summary

The bundle:browser-mcp script (added in #22213) was never wired into the root bundle pipeline, causing chrome-devtools-mcp.mjs to be missing from published npm packages. This results in a MODULE_NOT_FOUND crash when the browser agent launches.

Details

Root cause: The root bundle script runs generate → build devtools → esbuild → copy_bundle_assets, but never invokes npm run bundle:browser-mcp -w @google/gemini-cli-core, which is responsible for building packages/core/dist/bundled/chrome-devtools-mcp.mjs. The copy_bundle_assets.js script then silently skips the copy when the source directory doesn't exist.

Fix:

1. Added npm run bundle:browser-mcp -w @google/gemini-cli-core to the root bundle script, before esbuild and copy_bundle_assets.
2. Changed copy_bundle_assets.js to fail loudly (with an actionable error message) when the bundled directory is missing, instead of silently skipping.

Related Issues

How to Validate

1. Start from a clean state (no pre-existing packages/core/dist/bundled/ or bundle/bundled/):

   rm -rf packages/core/dist/bundled bundle/bundled

2. Run the bundle pipeline:

   npm run bundle

3. Verify bundle/bundled/chrome-devtools-mcp.mjs exists:

   ls -la bundle/bundled/chrome-devtools-mcp.mjs

4. Negative test — verify the guard works: remove the built bundle and run only copy_bundle_assets:

   rm -rf packages/core/dist/bundled
   node scripts/copy_bundle_assets.js  # Should exit with error

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a missing dependency in the build pipeline that caused runtime errors due to missing browser agent files. By explicitly including the browser-mcp bundle step and adding strict validation during asset copying, the build process is now more robust and predictable.

Highlights

• Pipeline Integration: Integrated the bundle:browser-mcp script into the root bundle pipeline to ensure necessary files are generated during the build process.
• Error Handling: Updated the copy_bundle_assets.js script to fail with an explicit error message if the required bundle directory is missing, preventing silent failures.

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[gemini-code-assist]

Code Review

This pull request updates the bundle script in package.json to include the browser MCP bundling step for the core package. It also modifies the copy_bundle_assets script to fail explicitly if the chrome-devtools-mcp bundle is not found, providing a helpful error message. I have no feedback to provide.