api-proxy: inject X-Initiator: agent default on all Copilot-bound requests to prevent billing inflation

containers/api-proxy/server.js

@@ -320,6 +320,15 @@
     headers['x-request-id'] = requestId;
     Object.assign(headers, injectHeaders);
 
+    // Default X-Initiator to "agent" for billing purposes on Copilot-bound requests.
+    // In agentic workflows, the vast majority of requests are agent-initiated.
+    // If the client already set it (e.g. standard Copilot CLI), respect that value.
+    // Check is on targetHost rather than provider name so that OpenCode requests
+    // routed to the Copilot backend also receive the header.
+    if (targetHost.endsWith('githubcopilot.com') && !headers['x-initiator']) {
+      headers['x-initiator'] = 'agent';
+    }
+
     if (body.length !== inboundBytes) {
       headers['content-length'] = String(body.length);
       delete headers['transfer-encoding'];

containers/api-proxy/server.test.js

@@ -15,7 +15,7 @@ const { deriveCopilotApiTarget, deriveGitHubApiTarget, deriveGitHubApiBasePath,
 const { resolveOpenCodeRoute } = require('./providers/opencode');
 
 // Core proxy functions that remain in server.js
-const { proxyWebSocket, httpProbe, validateApiKeys, keyValidationResults, resetKeyValidationState, fetchJson, extractModelIds, fetchStartupModels, reflectEndpoints, healthResponse, cachedModels, resetModelCacheState, makeModelBodyTransform, MODEL_ALIASES, buildModelsJson, writeModelsJson, createProviderServer } = require('./server');
+const { proxyRequest, proxyWebSocket, httpProbe, validateApiKeys, keyValidationResults, resetKeyValidationState, fetchJson, extractModelIds, fetchStartupModels, reflectEndpoints, healthResponse, cachedModels, resetModelCacheState, makeModelBodyTransform, MODEL_ALIASES, buildModelsJson, writeModelsJson, createProviderServer } = require('./server');
 
 describe('normalizeApiTarget', () => {
   it('should strip https:// prefix', () => {
@@ -2773,3 +2773,109 @@ describe('provider adapter alwaysBind', () => {
     expect(body.error).toMatch(/no candidate provider credentials/);
   });
 });
+
+// ── proxyRequest X-Initiator billing header injection ─────────────────────────
+//
+// When forwarding to the Copilot API, the proxy must inject "X-Initiator: agent"
+// when the header is absent so that autonomous turns are billed correctly instead
+// of defaulting to the (more expensive) "user" rate.
+//
+describe('proxyRequest X-Initiator injection', () => {
+  /** Minimal mock for http.IncomingMessage backed by EventEmitter. */
+  function makeReq(headers = {}) {
+    const req = new EventEmitter();
+    req.url = '/v1/chat/completions';
+    req.method = 'POST';
+    req.headers = { 'content-type': 'application/json', ...headers };
+    return req;
+  }
+
+  /** Minimal mock for http.ServerResponse. */
+  function makeRes() {
+    return {
+      headersSent: false,
+      setHeader: jest.fn(),
+      writeHead: jest.fn(),
+      end: jest.fn(),
+    };
+  }
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  /**
+   * Mock https.request to capture the outgoing options (including headers)
+   * without making a real network connection.
+   */
+  function mockHttpsRequest() {
+    let capturedOptions;
+    jest.spyOn(https, 'request').mockImplementation((options) => {
+      capturedOptions = options;
+      const proxyReq = new EventEmitter();
+      proxyReq.end = jest.fn();
+      proxyReq.write = jest.fn();
+      proxyReq.destroy = jest.fn();
+      return proxyReq;
+    });
+    return { getCaptured: () => capturedOptions };
+  }
+
+  it('injects x-initiator: agent when absent on direct copilot requests', () => {
+    const { getCaptured } = mockHttpsRequest();
+    const req = makeReq();
+    proxyRequest(req, makeRes(), 'api.githubcopilot.com', { 'Authorization': 'Bearer token' }, 'copilot');
+    req.emit('end');
+    expect(getCaptured().headers['x-initiator']).toBe('agent');
+  });
+
+  it('injects x-initiator: agent when absent on enterprise githubcopilot.com target', () => {
+    const { getCaptured } = mockHttpsRequest();
+    const req = makeReq();
+    proxyRequest(req, makeRes(), 'api.enterprise.githubcopilot.com', { 'Authorization': 'Bearer token' }, 'copilot');
+    req.emit('end');
+    expect(getCaptured().headers['x-initiator']).toBe('agent');
+  });
+
+  it('injects x-initiator: agent when OpenCode routes to Copilot backend', () => {
+    // OpenCode delegates to Copilot; provider name is "opencode" but target host is Copilot.
+    const { getCaptured } = mockHttpsRequest();
+    const req = makeReq();
+    proxyRequest(req, makeRes(), 'api.githubcopilot.com', { 'Authorization': 'Bearer token' }, 'opencode');
+    req.emit('end');
+    expect(getCaptured().headers['x-initiator']).toBe('agent');
+  });
+
+  it('preserves a client-supplied x-initiator value on copilot requests', () => {
+    const { getCaptured } = mockHttpsRequest();
+    const req = makeReq({ 'x-initiator': 'user' });
+    proxyRequest(req, makeRes(), 'api.githubcopilot.com', { 'Authorization': 'Bearer token' }, 'copilot');
+    req.emit('end');
+    expect(getCaptured().headers['x-initiator']).toBe('user');
+  });
+
+  it('preserves a client-supplied x-initiator value on OpenCode→Copilot requests', () => {
+    const { getCaptured } = mockHttpsRequest();
+    const req = makeReq({ 'x-initiator': 'user' });
+    proxyRequest(req, makeRes(), 'api.githubcopilot.com', { 'Authorization': 'Bearer token' }, 'opencode');
+    req.emit('end');
+    expect(getCaptured().headers['x-initiator']).toBe('user');
+  });
+
+  it('does not inject x-initiator for non-copilot provider targets', () => {
+    const { getCaptured } = mockHttpsRequest();
+    const req = makeReq();
+    proxyRequest(req, makeRes(), 'api.anthropic.com', { 'x-api-key': 'sk-ant-test' }, 'anthropic');
+    req.emit('end');
+    expect(getCaptured().headers['x-initiator']).toBeUndefined();
+  });
+
+  it('does not inject x-initiator when OpenCode routes to non-Copilot backend', () => {
+    // OpenCode routing to OpenAI — no Copilot billing header should be injected.
+    const { getCaptured } = mockHttpsRequest();
+    const req = makeReq();
+    proxyRequest(req, makeRes(), 'api.openai.com', { 'Authorization': 'Bearer sk-test' }, 'opencode');
+    req.emit('end');
+    expect(getCaptured().headers['x-initiator']).toBeUndefined();
+  });
+});