HeaderGatePlugin is a per-route .NET plugin for the titanium CLI. It answers 403 when a request lacks one header and stamps another request header on the requests it lets through.

dotnet build -c Release

Copy bin/Release/net10.0/Titanium.Web.Proxy.Examples.RoutePlugin.dll next to your twp.yaml and add:

plugins:
  - name: header-gate
    assembly: ./Titanium.Web.Proxy.Examples.RoutePlugin.dll
    settings:
      requiredHeader: X-Api-Client
      stampHeader: X-Route-Plugin
    failMode: closed
    timeoutMs: 200

routes:
  - id: api
    clusterId: backend
    match: { path: /api, pathKind: Prefix }
    middleware: [header-gate]

Only /api runs the plugin. Every other route is unchanged.

• [ProxyPlugin(ProxyPluginContract.CurrentVersion)] declares the contract version the plugin was built for.
• The constructor takes the settings map.
• The project references Titanium.Web.Proxy.Abstractions and Titanium.Web.Proxy with Private=false and ExcludeAssets=runtime, so the host's own copies are the ones the plugin uses.

The full guide is in website/docs/plugins.md.