diff --git a/internal/utils/timeout.go b/internal/utils/timeout.go
index 423bc41..e15036c 100644
--- a/internal/utils/timeout.go
+++ b/internal/utils/timeout.go
@@ -45,7 +45,7 @@ func WithInactivityTimeout(parent context.Context, d time.Duration) (context.Con
 				timer.Reset(d)
 
 			case <-timer.C:
-				cancel(fmt.Errorf("no activity for %v", d))
+				cancel(fmt.Errorf("no activity for %v: %w", d, context.DeadlineExceeded))
 				return
 			}
 		}
diff --git a/internal/utils/timeout_test.go b/internal/utils/timeout_test.go
new file mode 100644
index 0000000..e49d80a
--- /dev/null
+++ b/internal/utils/timeout_test.go
@@ -0,0 +1,33 @@
+// Copyright 2026 The A2A Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package utils
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestWithInactivityTimeoutCauseIsDeadlineExceeded(t *testing.T) {
+	t.Parallel()
+
+	ctx, _ := WithInactivityTimeout(t.Context(), 10*time.Millisecond)
+	<-ctx.Done()
+
+	if err := UnpackCause(ctx, ctx.Err()); !errors.Is(err, context.DeadlineExceeded) {
+		t.Errorf("UnpackCause() = %v, want an error wrapping context.DeadlineExceeded", err)
+	}
+}