diff --git a/src/macos_mcp/__main__.py b/src/macos_mcp/__main__.py
index 5926107..dd4a891 100644
--- a/src/macos_mcp/__main__.py
+++ b/src/macos_mcp/__main__.py
@@ -734,6 +734,9 @@ def _handle_sigint(signum, frame):
                 show_banner=False,
                 middleware=_http_middleware(auth_key=auth_key, ip_allowlist=parsed_allowlist, oauth_validator=oauth_validator),
                 uvicorn_config=uvicorn_config or None,
+                # No tools need per-client HTTP session state; avoid retaining
+                # abandoned SDK transports when clients reconnect without DELETE.
+                stateless_http=transport == "streamable-http",
             )
         case _:
             raise ValueError(f"Invalid transport: {transport}")
diff --git a/tests/test_server_transport.py b/tests/test_server_transport.py
new file mode 100644
index 0000000..14cc5ca
--- /dev/null
+++ b/tests/test_server_transport.py
@@ -0,0 +1,45 @@
+from click.testing import CliRunner
+
+import macos_mcp.__main__ as server
+
+
+def _run_serve(mocker, tmp_path, transport: str):
+    """Invoke the serve command with FastMCP execution mocked."""
+    config = tmp_path / "macos-mcp.toml"
+    config.write_text("")
+    mocker.patch.object(server, "validate_permissions")
+    run = mocker.patch.object(server.mcp, "run")
+
+    result = CliRunner().invoke(
+        server.main,
+        [
+            "serve",
+            "--transport",
+            transport,
+            "--host",
+            "127.0.0.1",
+            "--port",
+            "18199",
+            "--config",
+            str(config),
+        ],
+    )
+
+    assert result.exit_code == 0, result.output
+    return run.call_args.kwargs
+
+
+def test_streamable_http_runs_stateless(mocker, tmp_path):
+    """Streamable HTTP must use stateless sessions to bound retained resources."""
+    kwargs = _run_serve(mocker, tmp_path, "streamable-http")
+
+    assert kwargs["transport"] == "streamable-http"
+    assert kwargs["stateless_http"] is True
+
+
+def test_sse_keeps_stateful_transport_default(mocker, tmp_path):
+    """SSE must retain its existing stateful transport behavior."""
+    kwargs = _run_serve(mocker, tmp_path, "sse")
+
+    assert kwargs["transport"] == "sse"
+    assert kwargs["stateless_http"] is False