Specter

OpenAPI-first VS Code extension: read your openapi.yaml → start a local mock server → see breaking changes — without leaving the IDE.

Features

🟢 Mock Server

Start a local HTTP server on localhost:4010 directly from your OpenAPI spec. No configuration needed — just open a spec file and click the status bar.

curl localhost:4010/pets
# → [{"id": 1, "name": "Rex"}, {"id": 2, "name": "Whiskers"}]

🔍 Try It Panel

Browse and test all endpoints directly inside VS Code. Click an endpoint → hit Send → see the response. No Postman, no browser, no context switching.

⚡ Breaking Change Diff

Every time you save your spec, Specter compares it against the last Git commit and flags breaking changes in the Problems panel:

• Removed endpoints
• Removed or newly required parameters
• Changed response status codes
• Removed or type-changed response fields

Usage

1. Open any OpenAPI .yaml or .json file
2. Click Mock :4010 in the status bar to start the mock server
3. Open Specter: Open Try It from Command Palette (Cmd+Shift+P / Ctrl+Shift+P)
4. Edit and save your spec — breaking changes appear instantly in the Problems panel (Cmd+Shift+M)

Configuration

Requirements

• VS Code 1.85+
• Node.js 18+ (bundled with VS Code)
• Git (for diff functionality)

No external tools, no Docker, no CLI setup.

How it works

Specter reads examples defined in your OpenAPI spec and serves them as HTTP responses. The diff runs against git HEAD — so it catches breaking changes before you push.

License

MIT