config: a parallel size has one spelling; a patched scope declares its own (#36621)

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

test/registered/unit/server_args/test_resolution_declarations.py

@@ -433,19 +433,11 @@ class TestResolutionDeclarations(CustomTestCase):
         mapping = namespace_of(ServerArgs)
         self.assertGreater(len(mapping), 400, "the namespace mapping collapsed")
 
-        # The five sizes keep a live property shadowing the bare name; the
-        # comparison below reaches them anyway, through `get_parallel().config`.
-        self.assertGreaterEqual(
-            _live_topology_leaves()
-            & {
-                "tp_size",
-                "pp_size",
-                "moe_dp_size",
-                "attn_cp_size",
-                "dcp_size",
-            },
-            {"tp_size", "pp_size", "moe_dp_size", "attn_cp_size", "dcp_size"},
-            "a parallel size stopped being served from the live topology",
+        self.assertEqual(
+            set(),
+            _live_topology_leaves() & set(mapping),
+            "a parallel leaf gained a live member of the same name, so the "
+            "comparison below reads the group rather than the published leaf",
         )
 
         compared = 0
@@ -461,10 +453,6 @@ class TestResolutionDeclarations(CustomTestCase):
                     unreachable.append(f"no get_{groups[0]}() for {path}.{field}")
                     continue
                 node = accessor()
-                if groups[0] == "parallel":
-                    # Bare names there are the live topology; the published
-                    # leaves are one hop down, so the reader takes that hop.
-                    node = node.config
                 try:
                     for group in groups[1:]:
                         node = getattr(node, group)

test/registered/unit/server_args/test_resolution_reads_the_declarations.py

@@ -420,7 +420,7 @@ def reads_a_leaf_through_the_alias(runner):
 
 
 def hands_the_accessor_to_a_helper():
-    return compute_world_size(get_server_args())
+    return attention_backends_of(get_server_args())
 
 
 def reads_the_view(runner):
@@ -580,7 +580,7 @@ class TestResolutionReadsTheDeclarations(CustomTestCase):
         """
         helpers = _config_reading_helpers()
         decided = _declared_fields()
-        for name in ("m3_fp8_attn_gemm_enabled", "compute_world_size"):
+        for name in ("m3_fp8_attn_gemm_enabled", "attention_backends_of"):
             self.assertIn(name, helpers, f"the helper derivation lost {name}")
         for field in ("speculative_num_draft_tokens", "attention_backend"):
             self.assertIn(field, decided, f"the declared set lost {field}")
@@ -598,8 +598,8 @@ class TestResolutionReadsTheDeclarations(CustomTestCase):
                 "sa_local.attention_backend",
                 "self._server_args.attention_backend",
                 "engine_args.attention_backend",
-                "compute_world_size(get_server_args())"
-                " reads " + ", ".join(helpers["compute_world_size"]),
+                "attention_backends_of(get_server_args())"
+                " reads " + ", ".join(helpers["attention_backends_of"]),
             },
             "the scan lost a spelling, or started flagging a legal one:\n  "
             + "\n  ".join(sorted(flagged)),