Chaos Rig

About

Building an MCP client requires thorough testing of OAuth flows, token refresh, tool discovery, error handling, and session lifecycle. Production servers don't offer the controlled failure scenarios needed for robust client development. Chaos Rig provides a local MCP server where developers can precisely control various failure modes, including authentication errors, disappearing tools, flaky responses, and token expiry, all managed through an intuitive web UI. It also offers live request logging to observe client interactions and server responses.

Key Features

• 8 GitHub stars
• Simulate authentication failures (401s, 500s), token expiry, and refresh token rejections
• Control tool availability and schema versions to trigger `tools/changed` events
• Inject random latency and configure tool call failure rates
• Live request log for inbound JSON-RPC calls and outbound SSE responses
• Interactive OAuth 2.1 consent page for testing various authorization flows

Use Cases

• Testing client handling of OAuth 2.1 consent and PKCE code exchange scenarios
• Validating client resilience to token rejection, expiry, and refresh failures mid-session
• Debugging client behavior when tools disappear or their schemas change
• Assessing client error handling for flaky or slow tool responses