feat(auth): enhance middleware to support Bearer token auth

* Added support for extracting Bearer tokens from Authorization header.
* Updated middleware to prefer explicit header over Bearer token.
* Improved test coverage for authentication scenarios.

internal/auth/keyring_test.go

@@ -57,6 +57,58 @@ func TestMiddlewareAllowsHeaderAuthAndSetsContext(t *testing.T) {
 	}
 }
 
+func TestMiddlewareAllowsBearerAuthAndSetsContext(t *testing.T) {
+	keyring, err := NewKeyring([]config.APIKey{{ID: "client-a", Value: "secret"}})
+	if err != nil {
+		t.Fatalf("NewKeyring() error = %v", err)
+	}
+
+	handler := Middleware(config.AuthConfig{HeaderName: "x-brain-key"}, keyring, testLogger())(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		keyID, ok := KeyIDFromContext(r.Context())
+		if !ok || keyID != "client-a" {
+			t.Fatalf("KeyIDFromContext() = (%q, %v), want (client-a, true)", keyID, ok)
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/mcp", nil)
+	req.Header.Set("Authorization", "Bearer secret")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
+	}
+}
+
+func TestMiddlewarePrefersExplicitHeaderOverBearerAuth(t *testing.T) {
+	keyring, err := NewKeyring([]config.APIKey{
+		{ID: "client-a", Value: "secret"},
+		{ID: "client-b", Value: "other-secret"},
+	})
+	if err != nil {
+		t.Fatalf("NewKeyring() error = %v", err)
+	}
+
+	handler := Middleware(config.AuthConfig{HeaderName: "x-brain-key"}, keyring, testLogger())(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		keyID, ok := KeyIDFromContext(r.Context())
+		if !ok || keyID != "client-a" {
+			t.Fatalf("KeyIDFromContext() = (%q, %v), want (client-a, true)", keyID, ok)
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/mcp", nil)
+	req.Header.Set("x-brain-key", "secret")
+	req.Header.Set("Authorization", "Bearer other-secret")
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
+	}
+}
+
 func TestMiddlewareAllowsQueryParamWhenEnabled(t *testing.T) {
 	keyring, err := NewKeyring([]config.APIKey{{ID: "client-a", Value: "secret"}})
 	if err != nil {

internal/auth/middleware.go

@@ -21,7 +21,7 @@ func Middleware(cfg config.AuthConfig, keyring *Keyring, log *slog.Logger) func(
 
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			token := strings.TrimSpace(r.Header.Get(headerName))
+			token := extractToken(r, headerName)
 			if token == "" && cfg.AllowQueryParam {
 				token = strings.TrimSpace(r.URL.Query().Get(cfg.QueryParam))
 			}
@@ -43,6 +43,21 @@ func Middleware(cfg config.AuthConfig, keyring *Keyring, log *slog.Logger) func(
 	}
 }
 
+func extractToken(r *http.Request, headerName string) string {
+	token := strings.TrimSpace(r.Header.Get(headerName))
+	if token != "" {
+		return token
+	}
+
+	authHeader := strings.TrimSpace(r.Header.Get("Authorization"))
+	scheme, credentials, ok := strings.Cut(authHeader, " ")
+	if !ok || !strings.EqualFold(scheme, "Bearer") {
+		return ""
+	}
+
+	return strings.TrimSpace(credentials)
+}
+
 func KeyIDFromContext(ctx context.Context) (string, bool) {
 	value, ok := ctx.Value(keyIDContextKey).(string)
 	return value, ok