---
title: "How to fix errors in Claude Code, Codex, and browser JavaScript"
description: "How to fix errors in Claude Code, Codex, and browser JavaScript, from runs we did ourselves. Each guide keeps the commands, versions, and output we saw."
canonical: "https://logbrew.co/en/guides"
last_updated: "2026-11-10"
---

# How to fix errors in Claude Code, Codex, and browser JavaScript

How to fix errors in Claude Code, Codex, and browser JavaScript, from runs we did ourselves. Each guide keeps the commands, versions, and output we saw.

By [Furkan Erday](https://github.com/furkanerday). Furkan Erday is the founder of LogBrew. He builds LogBrew with Claude Code and Codex every day.

Canonical: https://logbrew.co/en/guides

## Guides for AI coding agents

Setup steps and fixes for Claude Code and Codex. We ran each one on the versions the guide names.

- [Add an MCP server to Claude Code and Codex](https://logbrew.co/en/guides/mcp-server-claude-code-codex): Run `claude mcp add --transport http` in Claude Code or `codex mcp add --url` in Codex, then sign in. We tested both with the LogBrew MCP server.
  Tested on November 10, 2026 with Claude Code 2.1.319 and Codex CLI 0.167.0
- [Use AGENTS.md in Claude Code and Codex](https://logbrew.co/en/guides/agents-md): Codex reads `AGENTS.md` by default. Claude Code 2.1.277 or later reads it when your project has no `CLAUDE.md`. To keep both, put `@AGENTS.md` in your `CLAUDE.md`.
  Tested on November 10, 2026 with Claude Code 2.1.319 and Codex CLI 0.167.0
- [Fix the Claude overloaded error 529 and rate limit error 429](https://logbrew.co/en/guides/claude-overloaded-rate-limit-error): A 529 `overloaded_error` means the Claude API is busy for everyone. A 429 `rate_limit_error` means your organization hit a limit. Retry both with backoff.
  Tested on November 10, 2026 with Claude Code 2.1.319 and @anthropic-ai/sdk 1.7.0

## JavaScript error fixes

Each error reproduced in a real browser with the LogBrew browser SDK, then fixed, with what LogBrew recorded from that run.

- [Fix the script error that hides its message, file, and line](https://logbrew.co/en/errors/script-error): `Script error.` with line 0 and no stack means the browser hid an error from a script on another origin. Add `crossorigin` and a CORS header to get the message back.
  Tested on November 10, 2026 with Chromium 152, @logbrew/browser 0.1.21, and @logbrew/sdk 0.1.44
- [Fix the Failed to fetch error and tell its 3 causes apart](https://logbrew.co/en/errors/failed-to-fetch): `TypeError: Failed to fetch` means the request got no HTTP response. A missing CORS header, a server that is down, and a host that does not exist all give this same message.
  Tested on November 10, 2026 with Chromium 152, @logbrew/browser 0.1.21, and @logbrew/sdk 0.1.44