feat: display browser runtime errors in the terminal

[chenjiahan]

Summary

When building web applications with coding agents, we need to provide the LLM with enough context. One current limitation is that the agent cannot observe runtime errors occurring in the browser.

This PR addresses that by forwarding browser runtime errors to the socket server via WebSocket and logging them in the terminal, enabling the agent to access richer context for analysis and decision-making.

TODO

• Capture unhandledrejection events
• Display error stacks
• Add an option to disable this behavior
• Add test cases
• Update documentation

Related links

• https://x.com/RobKnight__/status/1937724464395092137

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR adds browser runtime error forwarding functionality, enabling runtime errors that occur in the browser to be displayed in the terminal through WebSocket communication. This provides better debugging context for coding agents by making browser-side errors visible on the server side.

• Adds WebSocket message handling for runtime errors on the server side
• Implements browser error event listening and forwarding to the server
• Refactors WebSocket helper functions for better code organization

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
packages/core/src/server/socketServer.ts	Adds runtime error message type and server-side handling to log browser errors
packages/core/src/client/hmr.ts	Implements browser error capture and WebSocket forwarding with connection state management

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