feat: extract, log, and strip aibridgeproxy request ID header in aibridged (#23731)

## Problem

`aibridgeproxyd` sends `X-AI-Bridge-Request-Id` on every MITM request to
`aibridged` for cross-service log correlation, but aibridged never reads
it. The header is silently forwarded to upstream LLM providers.

## Changes

* Renamed the header to `X-Coder-AI-Governance-Request-Id` to match the
existing `X-Coder-AI-Governance-*` convention.
* `aibridged` now extracts the header, logs it and strips it before
forwarding upstream.
* Added `TestServeHTTP_StripInternalHeaders` to verify no `X-Coder-*`
headers leak to upstream

coderd/aibridge/aibridge.go

@@ -16,6 +16,10 @@ import (
 // that use per-user LLM credentials but cannot set custom headers.
 const HeaderCoderToken = "X-Coder-AI-Governance-Token" //nolint:gosec // This is a header name, not a credential.
 
+// HeaderCoderRequestID is a header set by aibridgeproxyd on each
+// request forwarded to aibridged for cross-service log correlation.
+const HeaderCoderRequestID = "X-Coder-AI-Governance-Request-Id"
+
 // IsBYOK reports whether the request is using BYOK mode, determined
 // by the presence of the X-Coder-AI-Governance-Token header.
 func IsBYOK(header http.Header) bool {

enterprise/aibridged/aibridged_test.go

@@ -574,3 +574,65 @@ func TestRouting(t *testing.T) {
 		})
 	}
 }
+
+// TestServeHTTP_StripInternalHeaders verifies that internal X-Coder-*
+// headers are never forwarded to upstream LLM providers.
+func TestServeHTTP_StripInternalHeaders(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name   string
+		header string
+		value  string
+	}{
+		{
+			name:   "X-Coder-AI-Governance-Token",
+			header: agplaibridge.HeaderCoderToken,
+			value:  "coder-token",
+		},
+		{
+			name:   "X-Coder-AI-Governance-Request-Id",
+			header: agplaibridge.HeaderCoderRequestID,
+			value:  uuid.NewString(),
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			mockH := &mockHandler{}
+
+			srv, client, pool := newTestServer(t)
+			conn := &mockDRPCConn{}
+			client.EXPECT().DRPCConn().AnyTimes().Return(conn)
+			client.EXPECT().IsAuthorized(gomock.Any(), gomock.Any()).AnyTimes().Return(&proto.IsAuthorizedResponse{OwnerId: uuid.NewString()}, nil)
+			pool.EXPECT().Acquire(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).AnyTimes().Return(mockH, nil)
+
+			httpSrv := httptest.NewServer(srv)
+			t.Cleanup(httpSrv.Close)
+
+			ctx := testutil.Context(t, testutil.WaitShort)
+			req, err := http.NewRequestWithContext(ctx, http.MethodPost, httpSrv.URL+"/anthropic/v1/messages", nil)
+			require.NoError(t, err)
+
+			// Always set a valid auth token so the request reaches
+			// the upstream handler.
+			req.Header.Set("Authorization", "Bearer coder-token")
+			req.Header.Set(tc.header, tc.value)
+
+			resp, err := http.DefaultClient.Do(req)
+			require.NoError(t, err)
+			defer resp.Body.Close()
+
+			require.Equal(t, http.StatusOK, resp.StatusCode)
+			require.NotNil(t, mockH.headersReceived)
+
+			// Assert no X-Coder-* headers were forwarded upstream.
+			for name := range mockH.headersReceived {
+				require.NotContains(t, name, "X-Coder-",
+					"internal header %q must not be forwarded to upstream providers", name)
+			}
+		})
+	}
+}

enterprise/aibridged/http.go

@@ -37,6 +37,16 @@ func (s *Server) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 
 	logger := s.logger.With(slog.F("path", r.URL.Path))
 
+	// Extract and strip proxy request ID for cross-service log
+	// correlation. Absent for direct requests not routed through
+	// aibridgeproxyd.
+	if proxyReqID := r.Header.Get(agplaibridge.HeaderCoderRequestID); proxyReqID != "" {
+		// Inject into context so downstream loggers include it.
+		ctx = slog.With(ctx, slog.F("aibridgeproxy_id", proxyReqID))
+		logger = logger.With(slog.F("aibridgeproxy_id", proxyReqID))
+	}
+	r.Header.Del(agplaibridge.HeaderCoderRequestID)
+
 	byok := agplaibridge.IsBYOK(r.Header)
 	authMode := "centralized"
 	if byok {

enterprise/aibridgeproxyd/aibridgeproxyd.go

@@ -39,9 +39,6 @@ const (
 )
 
 const (
-	// HeaderAIBridgeRequestID is the header used to correlate requests
-	// between aibridgeproxyd and aibridged.
-	HeaderAIBridgeRequestID = "X-AI-Bridge-Request-Id"
 	// ProxyAuthRealm is the realm used in Proxy-Authenticate challenges.
 	// The realm helps clients identify which credentials to use.
 	ProxyAuthRealm = `"Coder AI Bridge Proxy"`
@@ -981,9 +978,8 @@ func (s *Server) handleRequest(req *http.Request, ctx *goproxy.ProxyCtx) (*http.
 
 	injectBYOKHeaderIfNeeded(req.Header, reqCtx.CoderToken)
 
-	// Set custom header for cross-service log correlation.
-	// This allows correlating aibridgeproxyd logs with aibridged logs.
-	req.Header.Set(HeaderAIBridgeRequestID, reqCtx.RequestID.String())
+	// Set request ID header to correlate requests between aibridgeproxyd and aibridged.
+	req.Header.Set(agplaibridge.HeaderCoderRequestID, reqCtx.RequestID.String())
 
 	logger.Info(s.ctx, "routing MITM request to aibridged",
 		slog.F("aibridged_url", aiBridgeParsedURL.String()),

enterprise/aibridgeproxyd/aibridgeproxyd_test.go

@@ -1377,7 +1377,7 @@ func TestProxy_MITM(t *testing.T) {
 				receivedPath = r.URL.Path
 				receivedAuthz = r.Header.Get("Authorization")
 				receivedBYOK = r.Header.Get(agplaibridge.HeaderCoderToken)
-				receivedRequestID = r.Header.Get(aibridgeproxyd.HeaderAIBridgeRequestID)
+				receivedRequestID = r.Header.Get(agplaibridge.HeaderCoderRequestID)
 				w.WriteHeader(http.StatusOK)
 				_, _ = w.Write([]byte("hello from aibridged"))
 			}))