Claude Code Common Errors and Fixes

Common Claude Code Errors and How to Fix Them

Claude Code is a powerful agentic coding tool, but like any development tool, you will encounter errors. This guide covers the most common Claude Code errors with their causes and solutions, so you can get back to productive coding quickly.

1. "Could not connect to the API"

Cause: Claude Code cannot reach the API endpoint. This could be a network issue, incorrect base URL, or the API service being down.

Solutions:

• Check your internet connection
• Verify ANTHROPIC_BASE_URL is correctly set
• Test the endpoint with curl

# Test connectivity
curl -I https://claude4u.com/antigravity/v1/messages

# If using a relay, verify the URL
echo $ANTHROPIC_BASE_URL
# Expected: https://claude4u.com/antigravity

2. "Invalid API key"

Cause: The API key is missing, malformed, or does not match the endpoint you are using.

Solutions:

# Check if the key is set
echo $ANTHROPIC_API_KEY

# For relay services, ensure you use the relay key format
export ANTHROPIC_API_KEY="cr_your_relay_key_here"

# Make sure key and URL are consistent
export ANTHROPIC_BASE_URL="https://claude4u.com/antigravity"

# Reload your shell
source ~/.zshrc

3. "Model not available" or "Model not found"

Cause: The requested model name is incorrect or your account does not have access to it.

Solutions:

• Check for typos in the model name
• Use the full model identifier: claude-sonnet-4-20250514
• Verify your API key has access to the requested model tier
• If using a relay service, confirm the model is enabled for your key

# Specify model explicitly
claude --model claude-sonnet-4-20250514

4. "Rate limit exceeded" (429 Error)

Cause: You have sent too many requests in a short time period, or your account has hit its token usage limit.

Solutions:

• Wait a few minutes and try again
• Use /compact to reduce conversation context and token usage
• Switch to a more efficient model like Sonnet instead of Opus
• Use a relay service like claude4u.com that pools multiple accounts for higher effective limits

5. "Context window exceeded"

Cause: Your conversation plus the files Claude Code is reading exceeds the 200K token context window.

Solutions:

• Use /compact to summarize the conversation history
• Start a new conversation with /clear
• Be more selective about which files Claude reads
• Break large tasks into smaller, focused conversations

6. "Permission denied" When Editing Files

Cause: Claude Code does not have filesystem write permission to the target file or directory.

Solutions:

# Check file permissions
ls -la /path/to/file

# Fix ownership if needed
sudo chown $(whoami) /path/to/file

# Ensure you are in the correct project directory
pwd

7. "Git operation failed"

Cause: Claude Code tried to perform a git operation that failed due to uncommitted changes, merge conflicts, or missing git configuration.

Solutions:

# Check git status
git status

# If there are merge conflicts, resolve them
git diff --name-only --diff-filter=U

# Ensure git is configured
git config --global user.name "Your Name"
git config --global user.email "your@email.com"

8. "Command timed out"

Cause: A shell command executed by Claude Code took too long to complete.

Solutions:

• Check if the command is hanging (e.g., waiting for input)
• Ensure test suites have appropriate timeouts configured
• For long-running builds, consider running them outside Claude Code

9. "Failed to parse response" or Streaming Errors

Cause: The API response was corrupted or the connection was interrupted during streaming.

Solutions:

• Check your network stability
• If using a proxy or VPN, try a direct connection
• A relay service like claude4u.com can provide more stable streaming through optimized connection handling

10. "CLAUDE.md not found" or Instructions Not Loading

Cause: Claude Code cannot find your project instructions file.

Solutions:

• Ensure CLAUDE.md is in the project root directory
• Check the filename is exactly CLAUDE.md (case-sensitive)
• Verify you launched Claude Code from the project root

11. Node.js Version Incompatibility

Cause: Claude Code requires Node.js 18 or later.

# Check your Node.js version
node --version

# If below v18, update using nvm
nvm install 18
nvm use 18

# Or install directly
# macOS: brew install node
# Ubuntu: sudo apt install nodejs

General Troubleshooting Checklist

1. Verify environment variables: echo $ANTHROPIC_API_KEY and echo $ANTHROPIC_BASE_URL
2. Check Node.js version: node --version (must be 18+)
3. Update Claude Code: npm update -g @anthropic-ai/claude-code
4. Test API connectivity: curl $ANTHROPIC_BASE_URL/v1/messages
5. Check available disk space: df -h
6. Review recent Claude Code logs for detailed error information