Check the topology identities where the layout is written, and build at the published widths (#40340)

test/manual/ep/test_flashinfer_dispatcher.py

@@ -14,7 +14,7 @@ from sglang.srt.layers.moe.token_dispatcher.flashinfer import FlashinferDispatch
 from sglang.srt.layers.moe.utils import initialize_moe_config
 from sglang.srt.runtime_context import get_context, publish
 from sglang.srt.server_args import ServerArgs, set_global_server_args_for_scheduler
-from sglang.test.test_utils import CustomTestCase
+from sglang.test.test_utils import CustomTestCase, publish_build_topology
 
 
 class TestFlashinferDispatcher(CustomTestCase):
@@ -44,9 +44,8 @@ class TestFlashinferDispatcher(CustomTestCase):
         publish(server_args, role="scheduler")
         initialize_moe_config()
 
-        initialize_model_parallel(
-            tensor_model_parallel_size=world_size, expert_model_parallel_size=world_size
-        )
+        publish_build_topology(tp_size=world_size, ep_size=world_size, world_rank=rank)
+        initialize_model_parallel()
 
     @classmethod
     def tearDownClass(cls):

test/manual/test_custom_allreduce.py

@@ -18,7 +18,7 @@ from sglang.srt.distributed.parallel_state import (
     initialize_model_parallel,
 )
 from sglang.srt.server_args import ServerArgs, set_global_server_args_for_scheduler
-from sglang.test.test_utils import CustomTestCase
+from sglang.test.test_utils import CustomTestCase, publish_build_topology
 
 
 def get_open_port() -> int:
@@ -98,7 +98,8 @@ class TestCustomAllReduce(CustomTestCase):
             distributed_init_method=distributed_init_method,
             local_rank=rank,
         )
-        initialize_model_parallel(tensor_model_parallel_size=world_size)
+        publish_build_topology(tp_size=world_size, world_rank=rank)
+        initialize_model_parallel()
         group = get_tensor_model_parallel_group().device_group
 
         # Set global server args to avoid "Global server args is not set yet!" error
@@ -161,7 +162,8 @@ class TestCustomAllReduce(CustomTestCase):
             distributed_init_method=distributed_init_method,
             local_rank=rank,
         )
-        initialize_model_parallel(tensor_model_parallel_size=world_size)
+        publish_build_topology(tp_size=world_size, world_rank=rank)
+        initialize_model_parallel()
         group = get_tensor_model_parallel_group().device_group
 
         # Set global server args to avoid "Global server args is not set yet!" error

test/manual/test_quick_allreduce.py

@@ -23,7 +23,7 @@ from sglang.srt.distributed.parallel_state import (
     graph_capture,
     initialize_model_parallel,
 )
-from sglang.test.test_utils import CustomTestCase
+from sglang.test.test_utils import CustomTestCase, publish_build_topology
 
 torch.manual_seed(42)
 random.seed(44)  # keep the deterministic seed
@@ -117,7 +117,8 @@ class TestQuickAllReduce(CustomTestCase):
             distributed_init_method=distributed_init_method,
             local_rank=rank,
         )
-        initialize_model_parallel(tensor_model_parallel_size=world_size)
+        publish_build_topology(tp_size=world_size, world_rank=rank)
+        initialize_model_parallel()
         group = get_tensor_model_parallel_group().device_group
 
         # A small all_reduce for warmup.
@@ -186,7 +187,8 @@ class TestQuickAllReduce(CustomTestCase):
             distributed_init_method=distributed_init_method,
             local_rank=rank,
         )
-        initialize_model_parallel(tensor_model_parallel_size=world_size)
+        publish_build_topology(tp_size=world_size, world_rank=rank)
+        initialize_model_parallel()
         group = get_tensor_model_parallel_group().device_group
 
         for sz in self.TEST_SIZES:

test/manual/test_weight_loader_v2_equiv.py

@@ -24,6 +24,7 @@ import unittest
 import torch
 
 from sglang.srt.environ import envs
+from sglang.test.test_utils import publish_build_topology
 
 MODEL = "Qwen/Qwen2-0.5B"
 
@@ -43,7 +44,8 @@ def _init_model_parallel() -> None:
             local_rank=0,
             distributed_init_method="tcp://127.0.0.1:29634",
         )
-        initialize_model_parallel(tensor_model_parallel_size=1)
+        publish_build_topology(tp_size=1)
+        initialize_model_parallel()
         monkey_patch_vllm_parallel_state()
     except AssertionError:
         pass

test/registered/cpu/test_rank_consensus_checker.py

@@ -23,7 +23,11 @@ from sglang.srt.utils.rank_consensus_checker import (
     shutdown,
 )
 from sglang.test.ci.ci_register import register_cpu_ci
-from sglang.test.test_utils import CustomTestCase, find_available_port
+from sglang.test.test_utils import (
+    CustomTestCase,
+    find_available_port,
+    publish_build_topology,
+)
 
 register_cpu_ci(est_time=193, suite="stage-a-test-cpu-intel")
 
@@ -80,11 +84,8 @@ def run_distributed_test(
                 backend="gloo",
             )
 
-            initialize_model_parallel(
-                tensor_model_parallel_size=tp_size,
-                pipeline_model_parallel_size=pp_size,
-                backend="gloo",
-            )
+            publish_build_topology(tp_size=tp_size, pp_size=pp_size, world_rank=rank)
+            initialize_model_parallel(backend="gloo")
 
             fn()
         except Exception as e:

test/registered/e2e/pp/test_pp_spec_embed_scan.py

@@ -10,7 +10,11 @@ import torch
 from transformers import MistralConfig, PretrainedConfig
 
 from sglang.test.ci.ci_register import register_cuda_ci
-from sglang.test.test_utils import DEFAULT_SMALL_MODEL_NAME_FOR_TEST, CustomTestCase
+from sglang.test.test_utils import (
+    DEFAULT_SMALL_MODEL_NAME_FOR_TEST,
+    CustomTestCase,
+    publish_build_topology,
+)
 
 register_cuda_ci(est_time=60, stage="base-b", runner_config="1-gpu-small")
 
@@ -77,7 +81,8 @@ class TestDraftEmbedScan(CustomTestCase):
         init_distributed_environment(
             world_size=1, rank=0, local_rank=0, distributed_init_method="env://"
         )
-        initialize_model_parallel(tensor_model_parallel_size=1)
+        publish_build_topology(tp_size=1)
+        initialize_model_parallel()
         torch.set_default_dtype(torch.bfloat16)
         torch.cuda.set_device(0)
 

test/registered/eplb/test_lplb_distributed.py

@@ -38,6 +38,7 @@ from sglang.srt.distributed.parallel_state import (
     initialize_model_parallel,
 )
 from sglang.test.ci.ci_register import register_cuda_ci
+from sglang.test.test_utils import publish_build_topology
 
 register_cuda_ci(est_time=18, stage="base-b", runner_config="2-gpu-large")
 
@@ -238,10 +239,10 @@ def _worker_main(local_rank: int, world_size: int):
     init_distributed_environment(
         world_size=world_size, rank=local_rank, local_rank=local_rank
     )
-    initialize_model_parallel(
-        tensor_model_parallel_size=world_size,
-        expert_model_parallel_size=world_size,
+    publish_build_topology(
+        tp_size=world_size, ep_size=world_size, world_rank=local_rank
     )
+    initialize_model_parallel()
 
     from sglang.srt.eplb.lplb_solver import clear_global_lplb_solvers
 

test/registered/kernels/ops/communication/test_deterministic_reduce_scatter.py

@@ -14,6 +14,7 @@ from sglang.srt.distributed import parallel_state as ps
 from sglang.srt.environ import envs
 from sglang.test.ci.ci_register import register_cuda_ci
 from sglang.test.kernels.utils import multigpu_pytest_main
+from sglang.test.test_utils import publish_build_topology
 
 register_cuda_ci(est_time=45, stage="base-b-kernel-unit", runner_config="4-gpu-b200")
 
@@ -37,7 +38,8 @@ def group():
         local_rank=local_rank,
         distributed_init_method="env://",
     )
-    ps.initialize_model_parallel(tensor_model_parallel_size=world_size)
+    publish_build_topology(tp_size=world_size, world_rank=rank)
+    ps.initialize_model_parallel()
     yield ps.get_tp_group()
     ps.destroy_model_parallel()
     ps.destroy_distributed_environment()

test/registered/kernels/ops/moe/test_fused_swiglu_epilogue.py

@@ -19,6 +19,7 @@ import pytest
 import torch
 
 from sglang.test.ci.ci_register import register_cuda_ci
+from sglang.test.test_utils import publish_build_topology
 
 register_cuda_ci(est_time=12, stage="base-b-kernel-unit", runner_config="1-gpu-large")
 
@@ -52,12 +53,8 @@ def _runtime_scaffolding():
     if not torch.distributed.is_initialized():
         init_distributed_environment(world_size=1, rank=0, local_rank=0, backend="gloo")
     if not model_parallel_is_initialized():
-        initialize_model_parallel(
-            tensor_model_parallel_size=1,
-            expert_model_parallel_size=1,
-            pipeline_model_parallel_size=1,
-            backend="gloo",
-        )
+        publish_build_topology(tp_size=1, ep_size=1, pp_size=1)
+        initialize_model_parallel(backend="gloo")
 
 
 def _interleave_w13_rows(w13: torch.Tensor) -> torch.Tensor:

test/registered/layers/mamba/test_mamba2_mixer.py

@@ -17,6 +17,7 @@ from sglang.srt.distributed.parallel_state import (
 from sglang.srt.runtime_context import get_parallel
 from sglang.srt.utils import get_device, get_device_count
 from sglang.test.ci.ci_register import register_cuda_ci, register_xpu_ci
+from sglang.test.test_utils import publish_build_topology
 
 register_cuda_ci(est_time=30, stage="base-b", runner_config="2-gpu-large")
 register_xpu_ci(est_time=60, suite="nightly-xpu-2-gpu", nightly=True)
@@ -105,7 +106,8 @@ def mixer2_gated_norm_tensor_parallel(
         local_rank=local_rank,
         backend=get_default_distributed_backend(device.type),
     )
-    initialize_model_parallel(tensor_model_parallel_size=world_size)
+    publish_build_topology(tp_size=world_size, world_rank=local_rank)
+    initialize_model_parallel()
 
     # create random weights an inputs
     weight = torch.rand((hidden_size,), dtype=dtype, device=device)

test/registered/ops/test_aiter_allreduce_fusion_amd.py

@@ -14,7 +14,7 @@ import torch
 from sglang.srt.layers import communicator as comm
 from sglang.srt.layers.communicator import LayerCommunicator, ScatterMode
 from sglang.test.ci.ci_register import register_amd_ci
-from sglang.test.test_utils import CustomTestCase
+from sglang.test.test_utils import CustomTestCase, publish_build_topology
 
 register_amd_ci(est_time=240, suite="stage-c-test-large-8-gpu-amd")
 
@@ -64,7 +64,8 @@ def _run_residual_accuracy_check():
         distributed_init_method="env://",
         backend="nccl",
     )
-    initialize_model_parallel(tensor_model_parallel_size=world_size)
+    publish_build_topology(tp_size=world_size, world_rank=rank)
+    initialize_model_parallel()
 
     dtype = torch.bfloat16
     eps = 1e-6

test/registered/unit/distributed/test_parallel_state.py

@@ -44,6 +44,7 @@ import pytest
 import torch
 
 from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.test_utils import publish_build_topology
 
 register_cpu_ci(est_time=11, suite="base-a-test-cpu")
 
@@ -232,11 +233,8 @@ def test_parallel_group_construction_tp8_attn_cp2():
             mock_world_group.return_value = mock_world
 
             # Call the actual function
-            parallel_state.initialize_model_parallel(
-                tensor_model_parallel_size=8,
-                pipeline_model_parallel_size=1,
-                attention_context_model_parallel_size=2,
-            )
+            publish_build_topology(tp_size=8, pp_size=1, attn_cp_size=2)
+            parallel_state.initialize_model_parallel()
 
             # Verify TP groups
             tp_groups = created_groups.get("tp", [])
@@ -330,12 +328,8 @@ def test_parallel_group_construction_tp8_moe_ep4_cp2():
             mock_world_group.return_value = mock_world
 
             # Call the actual function
-            parallel_state.initialize_model_parallel(
-                tensor_model_parallel_size=8,
-                expert_model_parallel_size=4,
-                pipeline_model_parallel_size=1,
-                moe_data_model_parallel_size=2,
-            )
+            publish_build_topology(tp_size=8, ep_size=4, pp_size=1, moe_dp_size=2)
+            parallel_state.initialize_model_parallel()
 
             # Verify TP groups
             tp_groups = created_groups.get("tp", [])

test/registered/unit/layers/attention/test_vision_strided_qkv.py

@@ -16,6 +16,7 @@ from sglang.srt.distributed.parallel_state import (
 from sglang.srt.layers.attention import vision
 from sglang.srt.runtime_context import get_context, get_parallel
 from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.test_utils import publish_build_topology
 
 register_cpu_ci(est_time=12, suite="base-a-test-cpu")
 
@@ -52,7 +53,8 @@ def gloo_world():
         distributed_init_method=f"tcp://127.0.0.1:{port}",
         backend="gloo",
     )
-    initialize_model_parallel(tensor_model_parallel_size=1, backend="gloo")
+    publish_build_topology(tp_size=1)
+    initialize_model_parallel(backend="gloo")
     yield
     destroy_model_parallel()
     destroy_distributed_environment()

test/registered/unit/mem_cache/test_dsa_layer_split_broadcast.py

@@ -20,7 +20,7 @@ import torch
 import torch.multiprocessing as mp
 
 from sglang.test.ci.ci_register import register_cuda_ci
-from sglang.test.test_utils import CustomTestCase
+from sglang.test.test_utils import CustomTestCase, publish_build_topology
 
 register_cuda_ci(est_time=28, stage="base-c", runner_config="4-gpu-b200")
 
@@ -54,10 +54,8 @@ def _run(rank: int, world: int, port: int):
         distributed_init_method=f"tcp://127.0.0.1:{port}",
         backend="nccl",
     )
-    initialize_model_parallel(
-        tensor_model_parallel_size=world,
-        attention_context_model_parallel_size=world,
-    )
+    publish_build_topology(tp_size=world, attn_cp_size=world, world_rank=rank)
+    initialize_model_parallel()
 
     from sglang.srt.mem_cache.dsa_cache_layer_split import (
         LayerSplitDSATokenToKVPool,

test/registered/unit/mem_cache/test_page_interleave_shard.py

@@ -84,7 +84,7 @@ from sglang.srt.runtime_context import get_parallel, publish
 from sglang.srt.server_args import ServerArgs
 from sglang.srt.utils import ceil_div
 from sglang.test.ci.ci_register import register_cpu_ci
-from sglang.test.test_utils import CustomTestCase
+from sglang.test.test_utils import CustomTestCase, publish_build_topology
 
 register_cpu_ci(est_time=30, suite="base-a-test-cpu")
 
@@ -1215,10 +1215,8 @@ def _dist_init(rank, world, port, attn_cp_size):
         ServerArgs(model_path="dummy", tp_size=world, attn_cp_size=attn_cp_size),
         role="scheduler",
     )
-    initialize_model_parallel(
-        tensor_model_parallel_size=world,
-        attention_context_model_parallel_size=attn_cp_size,
-    )
+    publish_build_topology(tp_size=world, attn_cp_size=attn_cp_size, world_rank=rank)
+    initialize_model_parallel()
 
 
 def _gather_make_spec(shard_rank, max_prefix_groups=16, chunk_groups=4):

test/registered/unit/model_loader/test_presharded_loader.py

@@ -844,7 +844,9 @@ class TestShardConfig(unittest.TestCase):
         override.install()
         self.addCleanup(override.restore)
         with (
-            get_parallel().override(tp_size=8, pp_size=1, moe_dp_size=2, moe_ep_size=4),
+            get_parallel().override(
+                tp_size=8, pp_size=1, moe_dp_size=2, moe_ep_size=4, moe_tp_size=1
+            ),
             mock.patch(
                 "sglang.srt.layers.dp_attention.get_moe_cp_size",
                 return_value=2,

test/registered/unit/models/test_glm5_next_bfg_fusion.py

@@ -83,8 +83,19 @@ class TestGlm5NextBfgFusion(unittest.TestCase):
             for attn_tp, rank in ((1, 0), (2, 0), (2, 1)):
                 with (
                     self.subTest(route=expected_route, attn_tp=attn_tp, rank=rank),
+                    # A width is a whole topology: the attention triple has
+                    # to factor `tp_size`, and this process has to sit where
+                    # the triple puts it.
                     get_parallel().override(
-                        tp_size=4, tp_rank=3, attn_tp_size=attn_tp, attn_tp_rank=rank
+                        tp_size=4,
+                        tp_rank=rank,
+                        attn_tp_size=attn_tp,
+                        attn_tp_rank=rank,
+                        attn_dp_size=4 // attn_tp,
+                        attn_dp_rank=0,
+                        attn_cp_size=1,
+                        attn_cp_rank=0,
+                        moe_tp_size=4,
                     ),
                 ):
                     quant = MockFp8Config(ignored)

test/registered/unit/models/test_shared_experts_fusion_gates.py

@@ -61,7 +61,15 @@ class _FusionGateCase(CustomTestCase):
     def _reason(self, model_class, hf_config, quant_config=None, moe_ep_size=1):
         # The gates consult the live EP size; without a group installed the
         # canonical getter asserts, so every case states a topology.
-        with get_parallel().override(moe_ep_size=moe_ep_size):
+        with get_parallel().override(
+            tp_size=moe_ep_size,
+            attn_tp_size=moe_ep_size,
+            attn_dp_size=1,
+            attn_cp_size=1,
+            moe_ep_size=moe_ep_size,
+            moe_dp_size=1,
+            moe_tp_size=1,
+        ):
             return model_class.shared_experts_fusion_disable_reason(
                 hf_config, quant_config
             )

test/registered/unit/test_runtime_context.py

@@ -41,6 +41,7 @@ from sglang.srt.runtime_context import (
     RuntimeContext,
     SpawnRanks,
     _FlagGroupBase,
+    _validate_parallel,
     assert_published,
     derive_parallel_widths,
     get_context,
@@ -59,6 +60,56 @@ from sglang.srt.server_args import ServerArgs
 from sglang.test.test_utils import CustomTestCase
 
 _SRT = _pathlib.Path(next(iter(_sglang.__path__))).resolve() / "srt"
+_PACKAGE = _pathlib.Path(next(iter(_sglang.__path__))).resolve()
+
+
+def _sources():
+    """Every Python file this checkout ships, package and siblings alike.
+
+    The package alone is the wrong subject set for anything about entries or
+    public names: `benchmark/`, `examples/` and the top-level `test/` call the
+    same doors and are not covered by any suite that would notice them break.
+    An installed package has no siblings, and then this is the package alone."""
+    roots = [_PACKAGE]
+    checkout = _PACKAGE.parents[1]
+    roots += [
+        checkout / name
+        for name in ("benchmark", "examples", "scripts", "test")
+        if (checkout / name).is_dir()
+    ]
+    for root in roots:
+        for path in root.rglob("*.py"):
+            yield path
+
+
+def _scope_entries_that_say_nothing(paths):
+    """Draft-scope entries that do not state `owns_attention`, as `path:line`.
+
+    The scope either narrows the draft's attention and expert identity or
+    leaves the target's in place, and only the worker knows which -- so the
+    keyword has no default. Omitting it is a `TypeError`, but only on the path
+    that runs, and those paths want a GPU and a draft model.
+    """
+    import ast
+
+    missing = []
+    for path in paths:
+        try:
+            tree = ast.parse(path.read_text(encoding="utf-8"))
+        except (SyntaxError, UnicodeDecodeError):
+            continue
+        for node in ast.walk(tree):
+            if not isinstance(node, ast.Call):
+                continue
+            func = node.func
+            name = getattr(func, "attr", None) or getattr(func, "id", None)
+            if name not in ("draft_tp_context", "patch_tensor_parallel_group"):
+                continue
+            if not any(kw.arg == "owns_attention" for kw in node.keywords):
+                missing.append(f"{path}:{node.lineno}")
+    return missing
+
+
 _PS = "sglang.srt.distributed.parallel_state"
 _DP = "sglang.srt.layers.dp_attention"
 
@@ -347,9 +398,8 @@ class TestStampedRanks(_IsolatedOverrides):
     """`attn_dp_rank` comes from the stamp, and says so when there is none.
 
     It is the one rank no group answers with: `initialize_dp_attention`
-    computes it from this process's `tp_rank`, and an elastic scale-up
-    replaces it with a rank in the expanded WORLD. Falling back to anything
-    would be inventing a placement for this process.
+    computes it from this process's `tp_rank`. Falling back to anything would
+    be inventing a placement for this process.
     """
 
     def setUp(self):
@@ -407,21 +457,71 @@ class TestStampedRanks(_IsolatedOverrides):
             )
         self.assertIs(mode, DpPaddingMode.SUM_LEN)
 
-    def test_a_scale_up_stamps_the_width_and_the_rank_together(self):
-        """The two describe one topology; a reader that saw only one moved
-        would place this process in a group it is not in."""
+    def test_the_gather_slot_follows_the_list_that_was_gathered(self):
+        """The DP sync gathers over the attention-DP replicas, or over the
+        expanded WORLD once a scale-up has moved the gather there. The index
+        into that list is a property of the gather, so it is read beside the
+        flag that says which one happened rather than kept on the topology."""
+        from sglang.srt.layers.dp_attention import dp_gather_slot
+
+        self.addCleanup(reset_context)
+        dp_flags = get_flags().dp
+        saved = (
+            dp_flags.use_world_group_for_gather,
+            dp_flags.joiner_skip_all_gather,
+        )
+
+        def restore():
+            (
+                dp_flags.use_world_group_for_gather,
+                dp_flags.joiner_skip_all_gather,
+            ) = saved
+
+        self.addCleanup(restore)
+        publish(
+            ServerArgs(
+                model_path="dummy", tp_size=8, dp_size=8, enable_dp_attention=True
+            ),
+            role="test",
+            ranks=SpawnRanks(world_rank=3),
+        )
+        parallel = get_parallel()
+        dp_flags.use_world_group_for_gather = False
+        self.assertEqual(dp_gather_slot(), parallel.attn_dp_rank)
+
+        # After a scale-up the gather spans the expanded WORLD, and the joining
+        # cohort is numbered from its offset.
+        dp_flags.use_world_group_for_gather = True
+        dp_flags.joiner_skip_all_gather = False
+        parallel.override_permanently(ep_join_rank_offset=8)
+        self.assertEqual(dp_gather_slot(), 8 + parallel.tp_rank)
+        # and the topology it was read off is untouched
+        self.assertEqual(parallel.attn_dp_size, 8)
+        self.assertEqual(parallel.tp_size, 8)
+
+    def test_a_scale_up_writes_no_width(self):
+        """The identities stay unconditional because nothing overrides them:
+        the scale-up only points the gather at the expanded WORLD."""
         from sglang.srt.layers.dp_attention import update_dp_attention_post_scale
 
-        # It also flips a process-wide gather flag; put it back, or every
-        # later test in this process runs as if a scale-up had happened.
         dp_flags = get_flags().dp
         saved_gather = dp_flags.use_world_group_for_gather
         self.addCleanup(setattr, dp_flags, "use_world_group_for_gather", saved_gather)
-
+        self.addCleanup(reset_context)
+        publish(
+            ServerArgs(
+                model_path="dummy", tp_size=8, dp_size=8, enable_dp_attention=True
+            ),
+            role="test",
+            ranks=SpawnRanks(world_rank=3),
+        )
         parallel = get_parallel()
+        before = (parallel.attn_dp_size, parallel.attn_dp_rank, parallel.tp_size)
         update_dp_attention_post_scale(new_dp_size=16, new_dp_rank=11)
-        self.assertEqual(parallel.attn_dp_size, 16)
-        self.assertEqual(parallel.attn_dp_rank, 11)
+        self.assertTrue(dp_flags.use_world_group_for_gather)
+        self.assertEqual(
+            (parallel.attn_dp_size, parallel.attn_dp_rank, parallel.tp_size), before
+        )
 
 
 class TestEveryDeclaredParallelNameIsStatable(_IsolatedOverrides):
@@ -1898,14 +1998,26 @@ class TestDerivedWidths(_IsolatedOverrides):
 
     def test_a_topology_is_stated_by_naming_the_width(self):
         """Overriding a leaf does not move the quotient -- the quotient is not
-        recomputed on read. Naming it is how a test states one."""
+        recomputed on read. Naming it is how a caller states one, and naming
+        only some of them is refused: the caller owns the arithmetic, the
+        context only checks it."""
         reset_context()
         self.addCleanup(reset_context)
         publish(ServerArgs(model_path="dummy", tp_size=8), role="test")
         self.assertEqual(get_parallel().attn_tp_size, 8)
-        with get_parallel().override(tp_size=2):
-            self.assertEqual(get_parallel().attn_tp_size, 8)
-        with get_parallel().override(attn_tp_size=4):
+
+        with self.assertRaises(ValueError) as caught:
+            with get_parallel().override(tp_size=2):
+                pass
+        self.assertIn(
+            "tp_size == attn_tp_size * attn_dp_size * attn_cp_size",
+            str(caught.exception),
+        )
+
+        with get_parallel().override(tp_size=2, attn_tp_size=2, moe_tp_size=2):
+            self.assertEqual(get_parallel().tp_size, 2)
+            self.assertEqual(get_parallel().attn_tp_size, 2)
+        with get_parallel().override(attn_tp_size=4, tp_size=4, moe_tp_size=4):
             self.assertEqual(get_parallel().attn_tp_size, 4)
 
     def test_an_unstated_topology_still_fails(self):
@@ -2127,17 +2239,11 @@ class TestDerivedWidths(_IsolatedOverrides):
                 )
                 self.assertEqual(published, recomputed)
 
-    def test_initialize_model_parallel_no_longer_touches_the_bag(self):
-        """`initialize_model_parallel` used to recompute and
-        permanently override the six derived widths on `get_parallel()`
-        after building its groups; that call is gone. Publish a placeholder
-        config (tp_size defaults to 1), then build real groups at a
-        different width -- the published leaf must now stay exactly what it
-        was, because nothing corrects it. This is the behavior a caller
-        relies on being told about, loudly, the first time it publishes and
-        builds inconsistently -- see
-        `test_recomputing_from_published_leaves_matches_the_publish_bag`
-        for why every real caller must not do that.
+    def test_initialize_model_parallel_builds_at_the_published_widths(self):
+        """The build takes every width from the context rather than from an
+        argument, so "published one width, built another" is no longer a state
+        a caller can reach -- there is nothing left to translate, and nothing
+        to correct afterwards either.
         """
         from unittest.mock import Mock
 
@@ -2145,11 +2251,11 @@ class TestDerivedWidths(_IsolatedOverrides):
 
         reset_context()
         self.addCleanup(reset_context)
-        publish(ServerArgs(model_path="dummy"), role="test")
-        self.assertEqual(get_parallel().attn_tp_size, 1)
-        self.assertEqual(get_parallel().moe_ep_size, 1)
-
         world_size = 8
+        publish(ServerArgs(model_path="dummy", tp_size=world_size), role="test")
+        self.assertEqual(get_parallel().attn_tp_size, world_size)
+
+        built_at = []
         with (
             patch.object(parallel_state, "_WORLD", None),
             patch.object(parallel_state, "_TP", None),
@@ -2168,25 +2274,20 @@ class TestDerivedWidths(_IsolatedOverrides):
             patch.object(
                 parallel_state,
                 "init_model_parallel_group",
-                return_value=Mock(device_group=Mock()),
+                side_effect=lambda group_ranks, *a, **k: (
+                    built_at.append(group_ranks),
+                    Mock(device_group=Mock()),
+                )[1],
             ),
             patch.object(parallel_state, "get_world_group") as mock_world_group,
         ):
             mock_world_group.return_value = Mock(device_group=Mock(), local_rank=0)
-            parallel_state.initialize_model_parallel(
-                tensor_model_parallel_size=world_size,
-                expert_model_parallel_size=world_size,
-            )
+            parallel_state.initialize_model_parallel()
         self.addCleanup(parallel_state.destroy_model_parallel)
 
-        self.assertEqual(
-            get_parallel().attn_tp_size,
-            1,
-            "initialize_model_parallel must not touch the published leaf -- "
-            "a caller that needs it corrected must publish a config that "
-            "already matches the width it is about to build",
-        )
-        self.assertEqual(get_parallel().moe_ep_size, 1)
+        # The first group built is TP, one group spanning the published width.
+        self.assertEqual(built_at[0], [list(range(world_size))])
+        self.assertEqual(get_parallel().attn_tp_size, world_size)
 
 
 class TestTheDerivedHalfIsDeclared(CustomTestCase):
@@ -2294,6 +2395,225 @@ class TestAnEntryThatBuildsARunnerHandsOverItsPlacement(CustomTestCase):
         )
 
 
+class TestTheAccessorsHaveNoCallersOutsideTheirPackage(CustomTestCase):
+    """`parallel_state`'s getters are the definition, not a second spelling.
+
+    Business code asks `get_parallel()`; a call that goes straight to the getter
+    is a read the context cannot redirect, which is what a scope needs it to be
+    able to do. The package that defines them is exempt -- a read there would
+    go through the context back into itself -- and so is `multimodal_gen`, which
+    has its own parallel state.
+    """
+
+    #: Not topology. `get_self_pp_group` builds the single-rank group a draft
+    #: pipeline scope installs, so there is nothing for the context to answer
+    #: with until the scope has installed it.
+    ALLOWED = {
+        "get_self_pp_group",
+        "get_default_distributed_backend",
+        "get_mooncake_transfer_engine",
+    }
+
+    def _accessors(self):
+        """Derived from the source, not listed here: a guard whose subject set
+        is written by hand stops watching whatever gets added next."""
+        from sglang.srt.distributed import parallel_state as parallel_state_module
+
+        source = _pathlib.Path(parallel_state_module.__file__).read_text().splitlines()
+        return {
+            line[len("def ") : line.index("(")]
+            for line in source
+            if line.startswith("def get_") or line.startswith("def is_")
+        }
+
+    def _callers(self, name):
+        import re
+
+        from sglang.srt.distributed import parallel_state as parallel_state_module
+
+        root = _pathlib.Path(parallel_state_module.__file__).parents[2]
+        pattern = re.compile(rf"(?<![.\w]){re.escape(name)}\(")
+        hits = []
+        for path in root.rglob("*.py"):
+            rel = path.relative_to(root).as_posix()
+            if rel.startswith(("srt/distributed/", "multimodal_gen/", "test/")):
+                continue
+            for number, line in enumerate(path.read_text().splitlines(), 1):
+                if line.lstrip().startswith(("def ", "#")):
+                    continue
+                if pattern.search(line):
+                    hits.append(f"{rel}:{number}")
+        return hits
+
+    def test_no_business_code_calls_them(self):
+        offenders = {}
+        for name in sorted(self._accessors() - self.ALLOWED):
+            callers = self._callers(name)
+            if callers:
+                offenders[name] = callers
+        self.assertEqual(
+            offenders,
+            {},
+            "read these through get_parallel() instead, or say here why the "
+            "context cannot answer them",
+        )
+
+    def test_the_guard_would_notice_a_caller(self):
+        """The subject set is derived, so this checks the search finds a real
+        call rather than that the list happens to be empty: `get_self_pp_group`
+        is exempt and does have one caller."""
+        self.assertTrue(self._callers("get_self_pp_group"))
+
+
+class TestTheTopologyIdentities(CustomTestCase):
+    """One set of identities, checked wherever the layout is written.
+
+    Each one is injected in the direction that breaks it and in the direction
+    that keeps it: a guard that only ever fires is as uninformative as one that
+    never does. They hold unconditionally -- a caller that states one leaf owes
+    the quotients that follow from it, because a namespace describing no real
+    layout is what the guard exists to refuse.
+    """
+
+    def _publish_square(self):
+        """tp=4 over two attention-DP replicas of two: every identity holds."""
+        reset_context()
+        self.addCleanup(reset_context)
+        publish(
+            ServerArgs(
+                model_path="dummy", tp_size=4, dp_size=2, enable_dp_attention=True
+            ),
+            role="scheduler",
+            ranks=SpawnRanks(world_rank=3, dp_rank=1),
+        )
+
+    def test_a_published_topology_is_consistent(self):
+        """The quiet direction, and the reason publish can check everything:
+        it is the one write that establishes the whole layout."""
+        self._publish_square()
+        parallel = get_parallel()
+        self.assertEqual(parallel.tp_size, 4)
+        self.assertEqual(parallel.attn_dp_size, 2)
+        self.assertEqual(parallel.attn_tp_size, 2)
+        self.assertEqual(parallel.tp_rank, 3)
+
+    def test_a_width_that_does_not_factor_is_refused(self):
+        self._publish_square()
+        with self.assertRaises(ValueError) as caught:
+            with get_parallel().override(
+                tp_size=4, attn_tp_size=3, attn_dp_size=1, attn_cp_size=1
+            ):
+                pass
+        message = str(caught.exception)
+        self.assertIn("set by override", message)
+        self.assertIn("attn_tp_size * attn_dp_size * attn_cp_size", message)
+        self.assertIn("4 != 3 * 1 * 1", message)
+
+    def test_a_rank_at_its_width_is_refused(self):
+        self._publish_square()
+        with self.assertRaises(ValueError) as caught:
+            with get_parallel().override(tp_rank=4, tp_size=4):
+                pass
+        self.assertIn("0 <= tp_rank < tp_size", str(caught.exception))
+
+    def test_a_moe_width_that_does_not_factor_is_refused(self):
+        self._publish_square()
+        with self.assertRaises(ValueError) as caught:
+            with get_parallel().override(
+                tp_size=4, moe_ep_size=1, moe_dp_size=1, moe_tp_size=3
+            ):
+                pass
+        message = str(caught.exception)
+        self.assertIn("moe_ep_size * moe_dp_size * moe_tp_size", message)
+        self.assertIn("4 != 1 * 1 * 3", message)
+
+    def test_a_rank_the_attention_layout_cannot_produce_is_refused(self):
+        """`tp_rank` is not free of the attention ranks: the layout derives one
+        from the other, so a set that does not satisfy it places this process
+        in two different seats at once."""
+        self._publish_square()
+        with self.assertRaises(ValueError) as caught:
+            with get_parallel().override(
+                tp_rank=0,
+                attn_dp_rank=1,
+                attn_cp_rank=0,
+                attn_tp_rank=0,
+                attn_cp_size=1,
+                attn_tp_size=2,
+            ):
+                pass
+        self.assertIn("attn_tp_size + attn_tp_rank", str(caught.exception))
+
+    def test_the_published_ranks_satisfy_the_layout(self):
+        """The quiet direction for the same identity: publish derives the
+        attention ranks from `tp_rank` through that very equation, so a
+        published process always sits in one seat."""
+        self._publish_square()
+        parallel = get_parallel()
+        self.assertEqual(
+            parallel.tp_rank,
+            (parallel.attn_dp_rank * parallel.attn_cp_size + parallel.attn_cp_rank)
+            * parallel.attn_tp_size
+            + parallel.attn_tp_rank,
+        )
+
+    def test_a_refused_write_leaves_nothing_behind(self):
+        """The scope never opened, so the value it tried to state must not be
+        readable afterwards -- a half-applied override is the state this guard
+        exists to prevent."""
+        self._publish_square()
+        with self.assertRaises(ValueError):
+            with get_parallel().override(
+                tp_size=4, attn_tp_size=3, attn_dp_size=1, attn_cp_size=1
+            ):
+                pass
+        self.assertEqual(get_parallel().attn_tp_size, 2)
+
+    def test_a_group_built_at_another_width_is_refused(self):
+        """The other end of the same identity: what the configuration says and
+        what the coordinators were actually built at, checked where the
+        disagreement is still attributable to the build."""
+        from sglang.srt.distributed import parallel_state
+        from sglang.srt.distributed.parallel_state import GroupCoordinator
+
+        self._publish_square()
+        wrong = GroupCoordinator.__new__(GroupCoordinator)
+        wrong.world_size = 8
+        wrong.rank_in_group = 0
+        with patch.object(parallel_state, "_TP", wrong):
+            with self.assertRaises(ValueError) as caught:
+                _validate_parallel(get_parallel(), "group build")
+        message = str(caught.exception)
+        self.assertIn("set by group build", message)
+        self.assertIn("tp_group.world_size == tp_size", message)
+        self.assertIn("built 8, configured 4", message)
+
+    def test_a_group_built_at_the_configured_width_is_quiet(self):
+        from sglang.srt.distributed import parallel_state
+        from sglang.srt.distributed.parallel_state import GroupCoordinator
+
+        self._publish_square()
+        right = GroupCoordinator.__new__(GroupCoordinator)
+        right.world_size = 4
+        right.rank_in_group = 3
+        with patch.object(parallel_state, "_TP", right):
+            _validate_parallel(get_parallel(), "group build")
+
+    def test_a_draft_scope_states_a_consistent_topology(self):
+        """The scope narrows four names at once, so the identity applies to it
+        -- and holds, which is what step lets the guard stay on."""
+        from sglang.srt.distributed import parallel_state
+        from sglang.srt.distributed.parallel_state import GroupCoordinator
+
+        self._publish_square()
+        group = GroupCoordinator.__new__(GroupCoordinator)
+        group.world_size = 2
+        group.rank_in_group = 1
+        with patch.object(parallel_state, "_TP", group):
+            with parallel_state.patch_tensor_parallel_group(group, owns_attention=True):
+                self.assertEqual(get_parallel().attn_tp_size, 2)
+
+
 class TestWhoAnswersDuringADraftScope(CustomTestCase):
     """A draft worker runs in one process with the target, under a scope.
 
@@ -2397,29 +2717,36 @@ class TestWhoAnswersDuringADraftScope(CustomTestCase):
         worker states it, and a caller that forgets is the bug this catches --
         `owns_attention` has no default, but a missing one is a TypeError only
         on the path that runs, and these paths need a GPU and a draft model."""
-        import ast
+        self.assertEqual(
+            _scope_entries_that_say_nothing(_sources()),
+            [],
+            "these enter the draft scope without saying",
+        )
 
-        package = _pathlib.Path(next(iter(_sglang.__path__))).resolve()
-        checkout = package.parents[1]
-        roots = [package] + [
-            checkout / name for name in ("test",) if (checkout / name).is_dir()
-        ]
-        missing = []
-        for path in (q for root in roots for q in root.rglob("*.py")):
-            try:
-                tree = ast.parse(path.read_text(encoding="utf-8"))
-            except (SyntaxError, UnicodeDecodeError):
-                continue
-            for node in ast.walk(tree):
-                if not isinstance(node, ast.Call):
-                    continue
-                func = node.func
-                name = getattr(func, "attr", None) or getattr(func, "id", None)
-                if name not in ("draft_tp_context", "patch_tensor_parallel_group"):
-                    continue
-                if not any(kw.arg == "owns_attention" for kw in node.keywords):
-                    missing.append(f"{path}:{node.lineno}")
-        self.assertEqual(missing, [], "these enter the draft scope without saying")
+    def test_the_census_would_notice_one(self):
+        """Two ways for it to report zero and still be wrong: the matcher does
+        not recognise the call, or the walk never reaches the file. A draft
+        scope entered from `benchmark/` breaks the same way as one in the
+        package and no suite covers it, so the roots are part of the check."""
+        trees = {
+            part
+            for path in _sources()
+            for part in ("benchmark", "examples", "scripts", "test")
+            if f"/{part}/" in path.as_posix()
+        }
+        self.assertEqual(
+            trees,
+            {"benchmark", "examples", "scripts", "test"},
+            "the walk misses a tree that can enter the scope",
+        )
+
+        with tempfile.TemporaryDirectory() as tmp:
+            probe = _pathlib.Path(tmp) / "probe.py"
+            probe.write_text(
+                "with self.draft_tp_context(runner.tp_group):\n    pass\n",
+                encoding="utf-8",
+            )
+            self.assertEqual(_scope_entries_that_say_nothing([probe]), [f"{probe}:1"])
 
     def test_a_full_width_swap_leaves_the_attention_layout_alone(self):
         """The other caller. A draft built outside any scope carries the