diff --git a/CHANGELOG.md b/CHANGELOG.md
index 557df1fa6c..fc19263c98 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - **GFQL Cypher conversion operand validation**: statically invalid conversion operands, such as lists, maps, and graph entities, are rejected at compile time before the engine sees them. Dynamic operands, null propagation, and list-comprehension lexical shadowing keep their existing behavior.
 
 - **GFQL remote Let/DAG compatibility**: `gfql_remote` no longer substitutes an empty `gfql_operations` array for a Let/DAG query, so unsupported older servers receive `gfql_query` and reject it explicitly instead of silently running an identity program.
+- **GFQL old/current server wire contract tests**: added hermetic HTTP-route tests for public, serialized, Cypher, and flat-chain queries against source-pinned old and current server request-key selection and response formats.
 - **GFQL temporal scalar filters**: an empty timestamp or duration string no longer silently becomes a `NaT` bound; it raises the same typed `GFQLSchemaError` E302 as an unparseable bound. Naive bounds are handled as `Timestamp` values before timezone localization, and optional `pytz` exception discovery is confined to aware-column localization.
 - **GFQL Cypher null-equality conjunctions**: comparisons such as `n.v = null` now preserve three-valued `UNKNOWN` when combined with `AND`, instead of being replaced as if no predicate existed. `NeverMatch` predicates now round-trip through GFQL JSON, and raw JSON `filter_dict` null matching is unchanged.
 - **GFQL Cypher grouped aggregates after scalar reentry**: when a multirow scalar `WITH` prefix feeds another `MATCH`, grouping now covers all joined suffix rows together. For example, `WITH s MATCH (b)-[]->(s) RETURN s.type, count(*)` returns one aggregate per group instead of one per carried prefix row (#2235).
diff --git a/graphistry/tests/compute/gfql/routes/test_old_current_server_wire_2248.py b/graphistry/tests/compute/gfql/routes/test_old_current_server_wire_2248.py
new file mode 100644
index 0000000000..a47db0f538
--- /dev/null
+++ b/graphistry/tests/compute/gfql/routes/test_old_current_server_wire_2248.py
@@ -0,0 +1,310 @@
+"""Cross-version GFQL route contract (#2248).
+
+The fixtures are source-mapped hermetic HTTP routes:
+
+- old server ``054e79c87d74a87dbd68c40d4d43a9a6e23f61c3``:
+  ``server/routes/gfql.py`` requires ``gfql_operations``.
+- current server ``72d2664c2e61859cb813cb94c6479e3bc0824291``:
+  ``server/routes/gfql.py`` accepts ``gfql_query`` or ``gfql_operations``.
+- both handlers delegate execution through
+  ``server/client/graph/processing_handler.py::process_gfql_query`` to ``g.gfql``.
+
+The public client sends real HTTP requests to local ThreadingHTTPServer routes.
+No credentials, datasets, deployment, or Hub endpoint is involved.
+"""
+from __future__ import annotations
+
+import io
+import json
+import threading
+import zipfile
+from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
+from typing import Any, Dict, List, Mapping, Optional, Tuple
+
+import pandas as pd
+import pytest
+
+import graphistry
+from graphistry.compute.ast import ASTEdge, ASTLet, ASTNode
+from graphistry.compute.chain import Chain
+from graphistry.compute.exceptions import (
+    GFQLRemoteError,
+    GFQLTypeError,
+    GFQLValidationError,
+)
+
+
+OLD_SERVER = "054e79c87d74a87dbd68c40d4d43a9a6e23f61c3"
+CURRENT_SERVER = "72d2664c2e61859cb813cb94c6479e3bc0824291"
+DATASET_ID = "0d3d9a5a-880f-45f1-8486-b7983f6f9228"
+
+
+NODES = pd.DataFrame(
+    {
+        "id": [1, 2, 3],
+        "kind": ["A", "B", "B"],
+    }
+)
+EDGES = pd.DataFrame(
+    {
+        "src": [1, 2],
+        "dst": [2, 3],
+    }
+)
+
+
+def public_let() -> ASTLet:
+    path = Chain(
+        [
+            ASTNode(filter_dict={"kind": "A"}, name="a"),
+            ASTEdge(name="r"),
+            ASTNode(filter_dict={"kind": "B"}, name="b"),
+        ]
+    )
+    return ASTLet({"path": path, "result": path})
+
+
+def cypher_let() -> str:
+    return (
+        "GRAPH path = GRAPH { MATCH (a {kind:'A'})-[r]->(b) } "
+        "USE path MATCH (x) RETURN x"
+    )
+
+
+def flat_chain() -> List[ASTNode]:
+    return [ASTNode(filter_dict={"kind": "A"})]
+
+
+def _records(frame: Optional[pd.DataFrame]) -> List[Dict[str, Any]]:
+    if frame is None:
+        return []
+    return frame.to_dict(orient="records")
+
+
+def _json_response(payload: Mapping[str, Any]) -> Tuple[int, bytes, str]:
+    return 200, json.dumps(payload).encode("utf-8"), "application/json"
+
+
+def _parquet_all_response(result: graphistry.Plottable) -> Tuple[int, bytes, str]:
+    buffer = io.BytesIO()
+    with zipfile.ZipFile(buffer, "w") as archive:
+        for name, frame in (("nodes", result._nodes), ("edges", result._edges)):
+            frame_buffer = io.BytesIO()
+            (frame if frame is not None else pd.DataFrame()).to_parquet(frame_buffer, index=False)
+            archive.writestr(f"{name}.parquet", frame_buffer.getvalue())
+    return 200, buffer.getvalue(), "application/zip"
+
+
+def _error_response(status: int, message: str) -> Tuple[int, bytes, str]:
+    return status, json.dumps({"success": False, "error_code": status, "message": message}).encode("utf-8"), "application/json"
+
+
+def _execute(
+    body: Mapping[str, Any],
+    graph: graphistry.Plottable,
+    *,
+    mode: str,
+) -> graphistry.Plottable:
+    if mode == "current":
+        operations = body.get("gfql_query") or body.get("gfql_operations")
+    else:
+        operations = body["gfql_operations"]
+    output = body.get("gfql_output")
+    return graph.gfql(operations, output=output, engine="pandas")
+
+
+class RouteServer:
+    def __init__(self, mode: str):
+        self.mode = mode
+        self.requests: List[Dict[str, Any]] = []
+        self.port = 0
+        self.server = ThreadingHTTPServer(("127.0.0.1", 0), self._handler)
+        self.port = self.server.server_address[1]
+        self.thread = threading.Thread(target=self.server.serve_forever, daemon=True)
+
+    def start(self) -> None:
+        self.thread.start()
+
+    def close(self) -> None:
+        self.server.shutdown()
+        self.server.server_close()
+        self.thread.join(timeout=2)
+
+    def _handler(self, *args: Any, **kwargs: Any) -> BaseHTTPRequestHandler:
+        return _RequestHandler(self, *args, **kwargs)
+
+
+class _RequestHandler(BaseHTTPRequestHandler):
+    def __init__(self, route_server: RouteServer, *args: Any, **kwargs: Any):
+        self.route_server = route_server
+        super().__init__(*args, **kwargs)
+
+    def log_message(self, format: str, *args: Any) -> None:
+        return
+
+    def do_POST(self) -> None:
+        assert self.command == "POST"
+        expected_path = f"/api/v2/etl/datasets/{DATASET_ID}/gfql/all"
+        assert self.path == expected_path
+
+        raw_length = self.headers.get("Content-Length", "0")
+        raw = self.rfile.read(int(raw_length))
+        body = json.loads(raw.decode("utf-8")) if raw else {}
+        self.route_server.requests.append({"path": self.path, "body": body})
+
+        if self.route_server.mode == "old":
+            route = _old_route(body)
+        else:
+            route = _current_route(body)
+        status, payload, content_type = route
+        self.send_response(status)
+        self.send_header("Content-Type", content_type)
+        self.send_header("Content-Length", str(len(payload)))
+        self.end_headers()
+        self.wfile.write(payload)
+
+
+def _old_route(body: Mapping[str, Any]) -> Tuple[int, bytes, str]:
+    # Source map: old gfql.py lines 303-323 only consult gfql_operations.
+    if "gfql_operations" not in body:
+        return _error_response(422, 'Missing required "gfql_operations" field in payload.')
+    result = _execute(body, _local_graph(), mode="old")
+    return _json_response({"nodes": _records(result._nodes), "edges": _records(result._edges)})
+
+
+def _current_route(body: Mapping[str, Any]) -> Tuple[int, bytes, str]:
+    # Source map: current gfql.py lines 303-322 consult gfql_query first.
+    if body.get("gfql_operations") is None and body.get("gfql_query") is None:
+        return _error_response(
+            422,
+            'Missing required "gfql_operations" or "gfql_query" field in payload.',
+        )
+    result = _execute(body, _local_graph(), mode="current")
+    if body.get("format") == "parquet":
+        return _parquet_all_response(result)
+    return _json_response({"nodes": _records(result._nodes), "edges": _records(result._edges)})
+
+
+def _local_graph() -> graphistry.Plottable:
+    return graphistry.edges(EDGES, "src", "dst").nodes(NODES, "id")
+
+
+@pytest.fixture(params=["old", "current"])
+def route_server(request: pytest.FixtureRequest) -> Any:
+    server = RouteServer(request.param)
+    server.start()
+    try:
+        yield server
+    finally:
+        server.close()
+
+
+def _bound_graph(server: RouteServer) -> graphistry.Plottable:
+    graph = graphistry.edges(EDGES, "src", "dst").nodes(NODES, "id")
+    graph._dataset_id = DATASET_ID
+    graph.session.protocol = "http"
+    graph.session.hostname = f"127.0.0.1:{server.port}"
+    return graph
+
+
+def _remote(
+    graph: graphistry.Plottable,
+    query: Any,
+    *,
+    output: Optional[str] = None,
+    data_format: str = "json",
+) -> graphistry.Plottable:
+    return graph.gfql_remote(
+        query,
+        api_token="wire-test-token",
+        output=output,
+        output_type="all",
+        format=data_format,
+        engine="pandas",
+    )
+
+
+@pytest.mark.parametrize("data_format", ["json", "parquet"])
+def test_current_server_accepts_all_query_shapes(route_server: RouteServer, data_format: str) -> None:
+    if route_server.mode != "current":
+        pytest.skip("current-server half of paired fixture")
+
+    graph = _bound_graph(route_server)
+
+    let_result = _remote(graph, public_let(), output="path", data_format=data_format)
+    assert sorted(let_result._nodes["id"].tolist()) == [1, 2]
+    assert list(zip(let_result._edges["src"], let_result._edges["dst"])) == [(1, 2)]
+
+    serialized_result = _remote(
+        graph,
+        public_let().to_json(),
+        output="path",
+        data_format=data_format,
+    )
+    assert sorted(serialized_result._nodes["id"].tolist()) == [1, 2]
+    assert list(zip(serialized_result._edges["src"], serialized_result._edges["dst"])) == [(1, 2)]
+
+    cypher_result = _remote(graph, cypher_let(), data_format=data_format)
+    assert sorted(cypher_result._nodes["id"].tolist()) == [1, 2]
+    assert len(cypher_result._edges) == 0
+
+    flat_result = _remote(graph, flat_chain(), data_format=data_format)
+    assert flat_result._nodes["id"].tolist() == [1]
+    assert len(flat_result._edges) == 0
+
+    assert len(route_server.requests) == 4
+    request_bodies = [request["body"] for request in route_server.requests]
+    assert request_bodies[0]["gfql_query"]["type"] == "Let"
+    assert "gfql_operations" not in request_bodies[0]
+    assert request_bodies[1]["gfql_query"]["type"] == "Let"
+    assert request_bodies[2]["gfql_query"]["type"] == "Let"
+    assert request_bodies[3]["gfql_query"]["type"] == "Chain"
+    assert request_bodies[3]["gfql_operations"]
+
+
+@pytest.mark.parametrize("query,output", [
+    pytest.param(public_let, "path", id="public-client-let"),
+    pytest.param(lambda: public_let().to_json(), "path", id="serialized-let"),
+    pytest.param(cypher_let, None, id="compiled-cypher-let"),
+])
+def test_old_server_rejects_let(route_server: RouteServer, query: Any, output: Optional[str]) -> None:
+    if route_server.mode != "old":
+        pytest.skip("old-server half of paired fixture")
+
+    with pytest.raises(GFQLRemoteError) as error:
+        _remote(_bound_graph(route_server), query(), output=output)
+
+    assert "gfql_operations" in str(error.value)
+    assert error.value.context["status_code"] == 422
+    assert "HTTP 422" in str(error.value)
+    assert not isinstance(error.value, ConnectionError)
+    assert len(route_server.requests) == 1
+    assert "gfql_operations" not in route_server.requests[0]["body"]
+
+
+def test_old_server_accepts_nonempty_flat_chain(route_server: RouteServer) -> None:
+    if route_server.mode != "old":
+        pytest.skip("old-server half of paired fixture")
+
+    result = _remote(_bound_graph(route_server), flat_chain())
+    assert result._nodes["id"].tolist() == [1]
+    assert len(result._edges) == 0
+    assert route_server.requests[0]["body"]["gfql_operations"]
+
+
+def test_public_client_rejects_invalid_query_type_without_request(route_server: RouteServer) -> None:
+    graph = _bound_graph(route_server)
+
+    with pytest.raises(GFQLValidationError) as missing:
+        _remote(graph, {})
+
+    assert missing.value.code == "missing-required-field"
+    assert missing.value.context["field"] == "type"
+
+    with pytest.raises(GFQLTypeError) as invalid:
+        _remote(graph, {"type": "bogus"})
+
+    assert invalid.value.code == "invalid-query-type"
+    assert invalid.value.context["field"] == "type"
+    assert invalid.value.context["value"] == "bogus"
+    assert not route_server.requests