fix(wpt): model Fetch status fixture responses

Serve fetch/api/resources/status.py with upstream status, reason, method
header and byte-preserving query content across supported request methods.
Keep duplicate parameter precedence and explicit empty values intact.

Validate fixture parameters and 32 HTTP status/method combinations. The
focused CLI comparison gains 16 UTF-8 subtests with the same engine binary;
null response bodies and BOM handling remain separate engine defects.

moli-benchmark/moli_benchmark/wpt_cross/server.py

@@ -1064,6 +1064,17 @@ def _response_content_type_and_extra_headers(
     return merged_content_type, merged_extra_headers
 
 
+def _fetch_status_response(query: str) -> tuple[int, str, str, bytes]:
+    """Model fetch/api/resources/status.py without decoding its byte payload."""
+    params = parse_qs(query, keep_blank_values=True, encoding="latin-1")
+    return (
+        int(params.get("code", ["200"])[0]),
+        params.get("text", ["OMG"])[0],
+        params.get("type", [""])[0],
+        params.get("content", [""])[0].encode("latin-1"),
+    )
+
+
 def _wasm_webapi_status_code(query: str) -> int | None:
     """Return the status for WPT's wasm/webapi/status.py fixture.
 
@@ -2072,6 +2083,9 @@ def _make_handler(
                     emit_body=emit_body,
                 )
                 return
+            if path == "/fetch/api/resources/status.py":
+                self._serve_fetch_status(parsed.query, emit_body=emit_body)
+                return
             if path == "/fetch/api/resources/inspect-headers.py":
                 self._send_bytes(
                     "text/plain",
@@ -2731,6 +2745,21 @@ def _make_handler(
                 except (BrokenPipeError, ConnectionResetError):
                     return
 
+        def _serve_fetch_status(self, query: str, *, emit_body: bool) -> None:
+            try:
+                status, text, content_type, body = _fetch_status_response(query)
+            except ValueError:
+                self.send_error(500)
+                return
+            self._send_bytes(
+                content_type,
+                body,
+                emit_body=emit_body,
+                status_code=status,
+                status_text=text,
+                extra_headers=[("X-Request-Method", self.command)],
+            )
+
         def _send_bytes(
             self,
             content_type: str,

moli-benchmark/tests/test_wpt_cross.py

@@ -126,6 +126,7 @@ from moli_benchmark.wpt_cross.server import (
     _host_header_hostname,
     _headers_include,
     _inspect_headers_response_headers,
+    _fetch_status_response,
     _normalize_harness_case_key,
     _nosniff_javascript_response,
     _needs_wpt_template_substitution,
@@ -4343,6 +4344,54 @@ test(() => {}, "ok");
                                 response.read(), b"FAIL" if method == "GET" else b""
                             )
 
+    def test_fixture_server_parses_fetch_status_parameters_as_bytes(self) -> None:
+        self.assertEqual(_fetch_status_response(""), (200, "OMG", "", b""))
+        self.assertEqual(
+            _fetch_status_response(
+                "code=201&code=404&text=&text=ignored&type=text%2Fplain"
+                "&content=%FF%FE%00%2B+end&content=ignored"
+            ),
+            (201, "", "text/plain", b"\xff\xfe\x00+ end"),
+        )
+
+    def test_fixture_server_models_fetch_status_for_supported_methods(self) -> None:
+        with tempfile.TemporaryDirectory() as root:
+            root_path = Path(root)
+            (root_path / "resources").mkdir()
+            (root_path / "resources" / "testharness.js").write_text(
+                "// testharness", encoding="utf-8"
+            )
+            with WptFixtureServer(root_path) as server:
+                for method in ["GET", "HEAD", "POST", "OPTIONS", "PUT", "PATCH", "DELETE", "YO"]:
+                    for status in [200, 204, 205, 304]:
+                        with self.subTest(method=method, status=status):
+                            connection = HTTPConnection("127.0.0.1", server.port, timeout=2)
+                            try:
+                                connection.request(
+                                    method,
+                                    "/fetch/api/resources/status.py"
+                                    f"?code={status}&text=Custom%20%FF"
+                                    "&type=text%2Fplain%3Bcharset%3DUTF-16"
+                                    "&content=%FF%FE%00%2B+end",
+                                    body=b"ignored" if method not in {"GET", "HEAD"} else None,
+                                )
+                                response = connection.getresponse()
+                                self.assertEqual(response.status, status)
+                                self.assertEqual(response.reason, "Custom \xff")
+                                self.assertEqual(response.headers["X-Request-Method"], method)
+                                self.assertEqual(
+                                    response.headers["Content-Type"],
+                                    "text/plain;charset=UTF-16",
+                                )
+                                self.assertEqual(response.headers["Content-Length"], "8")
+                                self.assertEqual(
+                                    response.read(),
+                                    b"" if method == "HEAD" or status in {204, 304}
+                                    else b"\xff\xfe\x00+ end",
+                                )
+                            finally:
+                                connection.close()
+
     def test_fixture_server_models_fetch_inspect_headers_handler(self) -> None:
         self.assertEqual(
             _inspect_headers_response_headers(