Fix AI API & Tooling Errors

Step-by-step fixes for the errors developers actually hit with Claude, OpenAI, Cursor, and GitHub Copilot — what each error means, the most common causes in order, and exactly how to resolve it.

Anthropic API authentication_error (HTTP 401)
Claude API returning 401 with authentication_error? Here are the 6 most common causes — wrong env var,…
Claude API 401 Unauthorized (authentication_error)
Getting a 401 from the Anthropic Claude API? Here are the 5 causes in diagnostic order — bad key,…
Claude API "overloaded_error" (HTTP 529)
The Claude API 529 overloaded_error means Anthropic's API is temporarily overloaded. Here's what…
Claude Code "command not found"
Terminal returning 'claude: command not found' after installing Claude Code? Here are the 4 causes in…
Claude Code Permission Denied
Claude Code returning 'permission denied' or refusing to read/write files? Here are the 4 causes in…
Cursor Authentication Failed
Cursor showing 'Authentication failed' or logged out unexpectedly? Here are the 5 causes in diagnostic…
Cursor Rate Limit Exceeded
Cursor showing 'Rate limit exceeded' or 'Too many requests'? Here are the 4 causes in diagnostic order —…
GitHub Copilot Not Showing in VS Code
GitHub Copilot not appearing in VS Code? Inline suggestions gone or Copilot Chat missing? Here are 6…
OpenAI API 429 Error
A 429 error from the OpenAI API has two completely different causes: a rate limit (too fast) or…
OpenAI API 500 Internal Server Error
OpenAI API 500 errors are server-side and not your fault — but here's how to distinguish 500 from…
OpenAI API Timeout Errors — Connection vs. Read Timeout & Fixes (2026)
Fix OpenAI API timeout errors in Python. Covers connection timeouts vs. read timeouts, how to configure…
OpenAI context_length_exceeded (HTTP 400)
OpenAI 400 context_length_exceeded means your input tokens exceed the model's context window. Here's how…
OpenAI "Insufficient Quota" Error
OpenAI API returning 'You exceeded your current quota'? Here are 4 causes in diagnostic order — no…
OpenAI "Invalid API Key" (AuthenticationError / HTTP 401)
Getting AuthenticationError or HTTP 401 from the OpenAI API? Here are the 6 most common causes in…
OpenAI "Model Not Found" Error — 3 Causes & Exact Fixes (2026)
Fix the OpenAI model_not_found error. Three distinct causes: wrong model ID string, no access to that…
Anthropic API permission_error (HTTP 403)
Getting a 403 permission_error from the Anthropic API? Here are the 5 causes in diagnostic order — model tier access, beta feature headers,…
Claude Code "API key not configured"
Getting 'API key not configured' or authentication errors in Claude Code? Here are the 5 causes in diagnostic order — ANTHROPIC_API_KEY not set,…
LangChain Anthropic Authentication Error
Getting authentication errors with LangChain and Anthropic Claude? Here are the 5 causes in diagnostic order — wrong env var name, package mismatch,…
OpenAI API "No Such Organization" Error
Getting 'No such organization' from the OpenAI API? Here are the 5 causes in diagnostic order — wrong org ID, key not in org, org deactivated,…
Genspark "Context Length Exceeded"
Getting 'context length exceeded, please open a new session' in Genspark? Here's why it happens and the 4-step fix — when to start a new session,…