API Override

The API Override module applies Map Local-style rules to your MITM proxy traffic: when a proxied request matches one of your rules, Hexbuffer returns the configured fake response instead of forwarding the request upstream.

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How It Works

1. Add a Host: Right-click any request in Live Traffic and choose Send to API Override to add the request's host as an override target.
2. Define Rules: For each host, create routes specifying the method, path, status code, response body, and headers to return.
3. Live Override: As proxy traffic flows, matching requests are intercepted and answered locally—nothing reaches the real server.
4. Toggle Freely: Enable or disable individual domains and routes, or delete them, without restarting the proxy.

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Rule Configuration

Override rules use the same structure as the API Mock server, so anything you can mock locally you can also override on live traffic:

• Path Matching: Match paths with dynamic parameters in Express (:id) or OpenAPI ({id}) style.
• Request Matchers: Optionally restrict rules to requests with specific headers, query pairs, or body content.
• Templated Responses: Inject extracted path and query parameters into the response body with template variables (e.g., {{param.id}}).
• Chaos Engineering: Apply fixed or randomized latency and error-rate injection to overridden responses—useful for testing how your client behaves when a live API degrades.

Hexbuffer skips stale content-length and encoding headers when replacing responses, so the substituted body is delivered with correct framing automatically.

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Override Logging

Every overridden request is logged (method, path, status, latency, headers, body) with an override source marker and streamed into the Logs sub-tab (buffer of 200 entries), making it easy to confirm which requests were intercepted.

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Common Use Cases

• Frontend-Backend Decoupling: Point a live page's API calls at stubbed responses while the backend is under maintenance.
• Failure Simulation: Force specific endpoints to return 500 or 429 responses to exercise error handling.
• Response Shaping: Replace large production payloads with trimmed fixtures to speed up UI iteration.