config: keep runtime hicache and weight-version updates off ServerArgs (#33336)

The scheduler's runtime HiCache attach/detach wrote its own ServerArgs so the
internal-state readback would show the change; that readback already reports
the resolved config, so the writes become get_context().override(...) and the
namespace readers see them too.

The tokenizer side is per-engine — several Engines can share one process — so
its control-plane updates (weight version, model path + load format, HiCache
attach/detach) stay with the manager instead of moving to the process-global
bags. TokenizerManager gains record_config_updates / config_value /
resolved_config_dict, and the readbacks that used to observe the instance write
(/server_info, /model_info, the HiCache status endpoint, the gRPC bridge) now
overlay those updates onto the startup config.

test_server_info's stub grew the real manager instead of a SimpleNamespace, so
the overlay it now exercises cannot drift from production.

Writer ratchet 26 -> 19.

python/sglang/srt/entrypoints/engine.py

@@ -1271,7 +1271,9 @@ class Engine(EngineScoreMixin, EngineBase):
         )
         return msgspec_to_builtins(
             {
-                **dataclasses.asdict(self.tokenizer_manager.server_args),
+                **self.tokenizer_manager.resolved_config_dict(
+                    dataclasses.asdict(self.tokenizer_manager.server_args)
+                ),
                 **self._scheduler_init_result.scheduler_infos[0],
                 "internal_states": internal_states,
                 "version": __version__,

python/sglang/srt/entrypoints/grpc_bridge.py

@@ -379,7 +379,7 @@ class RuntimeHandle:
             "model_path": self.tokenizer_manager.model_path,
             "tokenizer_path": self.tokenizer_manager.server_args.tokenizer_path,
             "is_generation": self.tokenizer_manager.is_generation,
-            "weight_version": self.tokenizer_manager.server_args.weight_version,
+            "weight_version": self.tokenizer_manager.config_value("weight_version"),
             "model_type": getattr(model_config.hf_config, "model_type", None),
             "architectures": getattr(model_config.hf_config, "architectures", None),
         }
@@ -393,7 +393,9 @@ class RuntimeHandle:
         return json.dumps(result, default=str)
 
     def get_server_info(self) -> str:
-        result: Dict[str, Any] = dataclasses.asdict(self.server_args)
+        result: Dict[str, Any] = self.tokenizer_manager.resolved_config_dict(
+            dataclasses.asdict(self.tokenizer_manager.server_args)
+        )
         result.update(self.scheduler_info)
         return json.dumps(msgspec_to_builtins(result), default=str)
 

python/sglang/srt/entrypoints/http_server.py

@@ -710,12 +710,13 @@ async def model_info():
         "tokenizer_path": _global_state.tokenizer_manager.server_args.tokenizer_path,
         "is_generation": _global_state.tokenizer_manager.is_generation,
         "preferred_sampling_params": _global_state.tokenizer_manager.server_args.preferred_sampling_params,
-        "weight_version": _global_state.tokenizer_manager.server_args.weight_version,
+        "weight_version": _global_state.tokenizer_manager.config_value(
+            "weight_version"
+        ),
         "has_image_understanding": model_config.is_image_understandable_model,
         "has_audio_understanding": model_config.is_audio_understandable_model,
         "model_type": getattr(model_config.hf_config, "model_type", None),
         "architectures": getattr(model_config.hf_config, "architectures", None),
-        "weight_version": _global_state.tokenizer_manager.server_args.weight_version,
         # "hf_config": model_config.hf_config.to_dict(),
     }
     embedding_model_spec = getattr(model_config, "embedding_model_spec", None)
@@ -761,7 +762,9 @@ async def server_info():
     # server_args.model_config is not serializable but should be excluded by asdict.
     return msgspec_to_builtins(
         {
-            **dataclasses.asdict(server_args),
+            **_global_state.tokenizer_manager.resolved_config_dict(
+                dataclasses.asdict(server_args)
+            ),
             **_global_state.scheduler_info,
             "internal_states": internal_states,
             "version": __version__,
@@ -1091,10 +1094,13 @@ async def hicache_storage_backend_status():
         return _admin_api_key_missing_response()
 
     return {
-        "hicache_storage_backend": _global_state.tokenizer_manager.server_args.hicache_storage_backend,
-        "hicache_storage_backend_extra_config": _global_state.tokenizer_manager.server_args.hicache_storage_backend_extra_config,
-        "hicache_storage_prefetch_policy": _global_state.tokenizer_manager.server_args.hicache_storage_prefetch_policy,
-        "hicache_write_policy": _global_state.tokenizer_manager.server_args.hicache_write_policy,
+        name: _global_state.tokenizer_manager.config_value(name)
+        for name in (
+            "hicache_storage_backend",
+            "hicache_storage_backend_extra_config",
+            "hicache_storage_prefetch_policy",
+            "hicache_write_policy",
+        )
     }
 
 
@@ -1385,8 +1391,7 @@ async def update_weight_version(
     # Use a simple approach without the complex lock mechanism for now
     # since weight_version update is a simple operation that doesn't affect model weights
     try:
-        # Update the weight version in server args (the single source of truth)
-        _global_state.tokenizer_manager.server_args.override(
+        _global_state.tokenizer_manager.record_config_updates(
             "http.update_weight_version", weight_version=obj.new_version
         )
 

python/sglang/srt/entrypoints/openai/realtime/session.py

@@ -338,12 +338,12 @@ class RealtimeConnection:
         if (
             transcription is not None
             and transcription.model
-            and transcription.model != self.server_args.served_model_name
+            and transcription.model != self.tokenizer_manager.served_model_name
         ):
             await self._send_error(
                 "not_supported",
                 f"Model {transcription.model!r} is not served by this endpoint "
-                f"(serving {self.server_args.served_model_name!r}); set "
+                f"(serving {self.tokenizer_manager.served_model_name!r}); set "
                 f"transcription.model to null or to the server's model name.",
                 param="session.audio.input.transcription.model",
             )

python/sglang/srt/entrypoints/openai/serving_chat.py

@@ -1279,7 +1279,7 @@ class OpenAIServingChat(OpenAIServingBase):
                     logger.warning(
                         "Model '%s' supports only 'low' reasoning effort; "
                         "requested '%s' treated as default thinking",
-                        self.tokenizer_manager.server_args.served_model_name,
+                        self.tokenizer_manager.served_model_name,
                         request.reasoning_effort,
                     )
 

python/sglang/srt/entrypoints/openai/serving_classify.py

@@ -39,7 +39,7 @@ class OpenAIServingClassify(OpenAIServingBase):
         self.model_name = (
             self.tokenizer_manager.served_model_name
             if self.tokenizer_manager.served_model_name
-            else self.tokenizer_manager.server_args.model_path
+            else self.tokenizer_manager.model_path
         )
         if not self.id2label:
             raise ValueError("id2label mapping is missing")

python/sglang/srt/managers/scheduler.py

@@ -4009,7 +4009,7 @@ class Scheduler(
                 )
             if recv_req.hicache_write_policy is not None:
                 hicache_fields["hicache_write_policy"] = recv_req.hicache_write_policy
-            self.server_args.override("scheduler.attach_hicache", **hicache_fields)
+            get_context().override("scheduler.attach_hicache", **hicache_fields)
             logger.info(
                 f"Attached HiCache storage backend: {recv_req.hicache_storage_backend}"
             )
@@ -4050,7 +4050,7 @@ class Scheduler(
         if ok or (not self.enable_hicache_storage):
             # Treat "already disabled / nothing to do" as success for idempotence.
             self.enable_hicache_storage = False
-            self.server_args.override(
+            get_context().override(
                 "scheduler.detach_hicache",
                 hicache_storage_backend=None,
                 hicache_storage_backend_extra_config=None,

python/sglang/srt/managers/tokenizer_control_mixin.py

@@ -343,7 +343,7 @@ class TokenizerControlMixin:
                 )
             if hicache_write_policy is not None:
                 hicache_fields["hicache_write_policy"] = hicache_write_policy
-            self.server_args.override("tokenizer.attach_hicache", **hicache_fields)
+            self.record_config_updates("tokenizer.attach_hicache", **hicache_fields)
         return out
 
     async def detach_hicache_storage(
@@ -359,7 +359,7 @@ class TokenizerControlMixin:
         out = DetachHiCacheStorageReqOutput(success=all_success, message=all_message)
         # TODO: partial rollback if failed
         if all_success:
-            self.server_args.override(
+            self.record_config_updates(
                 "tokenizer.detach_hicache",
                 hicache_storage_backend=None,
                 hicache_storage_backend_extra_config=None,
@@ -920,6 +920,6 @@ class TokenizerControlMixin:
     ) -> None:
         """Update weight version if provided."""
         if weight_version is not None:
-            self.server_args.override(
+            self.record_config_updates(
                 "tokenizer.weight_version", weight_version=weight_version
             )

python/sglang/srt/managers/tokenizer_manager.py

@@ -364,6 +364,11 @@ class InputFormat(Enum):
     CROSS_ENCODER_PAIRS = 3  # Cross-encoder pairs like [["query", "document"]]
 
 
+_SERVER_ARGS_FIELDS = frozenset(f.name for f in dataclasses.fields(ServerArgs))
+
+_MANAGER_OWNED_FIELDS = ("model_path", "served_model_name")
+
+
 class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
     """TokenizerManager is a process that tokenizes the text."""
 
@@ -386,6 +391,7 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
     ):
         # Parse args
         self.server_args = server_args
+        self._config_updates: List[Tuple[str, Dict[str, Any]]] = []
         self.elastic_worker_count = server_args.dp_size
         self.elastic_pending_ep_size = None
         self.elastic_scale_phase = "idle"
@@ -1888,9 +1894,8 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
     ) -> Tuple[bool, str]:
         self.auto_create_handle_loop()
 
-        # default the load format to the server_args
         if obj.load_format is None:
-            obj.load_format = self.server_args.load_format
+            obj.load_format = self.config_value("load_format")
         logger.info("Start update_weights. Load format=%s", obj.load_format)
 
         if obj.abort_all_requests:
@@ -1914,11 +1919,57 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
 
         return success, message, num_paused_requests
 
+    def record_config_updates(self, source: str, **fields) -> None:
+        """Record a control-plane config change for this engine.
+
+        Per-engine state: several ``Engine``s can share one tokenizer process.
+        The readback endpoints overlay these onto the startup config. The
+        process-global sibling is ``RuntimeContext.override`` /
+        ``resolved_server_args_dict``, which writes the config bags every
+        process shares.
+        """
+        unknown = sorted(f for f in fields if f not in _SERVER_ARGS_FIELDS)
+        if unknown:
+            raise ValueError(
+                f"{unknown} are not ServerArgs fields; the readback endpoints "
+                "overlay these onto a serialized ServerArgs, so an unknown key "
+                "would surface as a phantom config entry."
+            )
+        self._config_updates.append((source, dict(fields)))
+
+    def config_value(self, name: str):
+        """The value in effect for one config field, control-plane updates first."""
+        if name in _MANAGER_OWNED_FIELDS:
+            return getattr(self, name)
+        for _source, fields in reversed(self._config_updates):
+            if name in fields:
+                return fields[name]
+        return getattr(self.server_args, name)
+
+    def _dump_config_snapshot(self) -> Optional[Dict[str, Any]]:
+        """The config in effect, or None when it cannot be serialized.
+
+        A dump is worth having even when the config is not: request data is the
+        part that cannot be reconstructed afterwards.
+        """
+        try:
+            return self.resolved_config_dict(dataclasses.asdict(self.server_args))
+        except Exception as e:
+            logger.error(f"Failed to snapshot the resolved config for the dump: {e!r}")
+            return None
+
+    def resolved_config_dict(self, base: Dict[str, Any]) -> Dict[str, Any]:
+        """``base`` (a serialized ``ServerArgs``) with the control-plane updates on top."""
+        resolved = dict(base)
+        for _source, fields in self._config_updates:
+            resolved.update(fields)
+        for name in _MANAGER_OWNED_FIELDS:
+            resolved[name] = getattr(self, name)
+        return resolved
+
     def _update_model_path_info(self, model_path: str, load_format: str):
         self.served_model_name = model_path
-        self.server_args.override(
-            "tokenizer.update_weights", model_path=model_path, load_format=load_format
-        )
+        self.record_config_updates("tokenizer.update_weights", load_format=load_format)
         self.model_path = model_path
 
     async def _wait_for_model_update_from_disk(
@@ -2060,7 +2111,7 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
                 "id": rid,
                 "finish_reason": recv_obj.finished_reasons[i],
                 "prompt_tokens": recv_obj.prompt_tokens[i],
-                "weight_version": self.server_args.weight_version,
+                "weight_version": self.config_value("weight_version"),
                 "num_retractions": recv_obj.retraction_counts[i],
             }
 
@@ -2789,6 +2840,8 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
         logger.info(log_message)
         to_dump_with_server_args = {
             "server_args": self.server_args,
+            "config_updates": list(self._config_updates),
+            "resolved_config": self._dump_config_snapshot(),
             "requests": data_list.copy(),
         }
 
@@ -2808,6 +2861,8 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
                     f.seek(0)
                     f.truncate()
                     to_dump_with_server_args["server_args"] = None
+                    # The snapshot copies the same object field by field.
+                    to_dump_with_server_args["resolved_config"] = None
                     pickle.dump(to_dump_with_server_args, f)
 
         asyncio.create_task(asyncio.to_thread(background_task))
@@ -2870,6 +2925,8 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
                 # Write the data to the file
                 data_to_dump_with_server_args = {
                     "server_args": self.server_args,
+                    "config_updates": list(self._config_updates),
+                    "resolved_config": self._dump_config_snapshot(),
                     "requests": data_to_dump,
                     "launch_command": " ".join(sys.argv),
                 }
@@ -2887,6 +2944,8 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
                         f.seek(0)
                         f.truncate()
                         data_to_dump_with_server_args["server_args"] = None
+                        # The snapshot copies the same object field by field.
+                        data_to_dump_with_server_args["resolved_config"] = None
                         pickle.dump(data_to_dump_with_server_args, f)
                 logger.error(
                     f"Dumped {len(self.crash_dump_request_list)} finished and {len(unfinished_requests)} unfinished requests before crash to {filename}"
@@ -2999,7 +3058,7 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
         meta_info = {
             "id": recv_obj.rid,
             "finish_reason": finish_reason,
-            "weight_version": self.server_args.weight_version,
+            "weight_version": self.config_value("weight_version"),
             "e2e_latency": state.time_stats.get_e2e_latency(),
         }
         is_stream = getattr(state.obj, "stream", False)

python/sglang/srt/runtime_context.py

@@ -912,17 +912,23 @@ class RuntimeContext:
         """Serialize the *resolved* config: the pristine ``server_args`` fields
         with every post-publish ``override`` overlaid.
 
-        Reporting endpoints (``/server_info``, ``get_internal_state``) surface
-        the config the process is *currently* running, not the startup record,
-        so they read this rather than serializing ``server_args`` directly —
-        otherwise runtime updates (weight version, model path, tunables set via
-        ``/set_internal_state``) never show up in the readback.
+        ``get_internal_state`` reports this, and ``/server_info`` carries it in
+        the ``internal_states`` block, so scheduler-side runtime changes show up
+        in a readback: HiCache attach/detach, the generated forward-pass-metrics
+        endpoint, tunables set via ``/set_internal_state``.
 
         ``base`` defaults to ``dict(vars(server_args))`` (matching the legacy
         ``vars`` dump); pass ``dataclasses.asdict(server_args)`` when nested
-        dataclass fields must be expanded first (``/server_info``). Override
-        leaves are flat ``ServerArgs`` field names, so overlaying them onto the
-        top level of either base is exact.
+        dataclass fields must be expanded first. Override leaves are flat
+        ``ServerArgs`` field names, so overlaying them onto the top level of
+        either base is exact.
+
+        This covers the process-global bags only. Per-engine control-plane
+        changes (weight version, model path, the tokenizer's HiCache mirror)
+        live on the tokenizer manager — several ``Engine``s can share one
+        process — and ``TokenizerManager.resolved_config_dict`` overlays those
+        for the top-level ``/server_info`` body. The two are separate logs, not
+        one merged dict.
         """
         d = dict(vars(self.server_args)) if base is None else dict(base)
         for _source, fields in self._overrides_log:

test/registered/unit/entrypoints/openai/test_serving_chat.py

@@ -48,6 +48,9 @@ class _MockTokenizerManager:
             stream_response_default_include_usage=False,
             default_chat_template_kwargs=None,
         )
+        # The manager tracks the served name itself; a weight update rewrites it.
+        self.served_model_name = "test-model"
+
         # Mock hf_config for _resolve_chat_encoding_spec check
         mock_hf_config = Mock()
         mock_hf_config.architectures = ["LlamaForCausalLM"]

test/registered/unit/entrypoints/test_server_info.py

@@ -28,6 +28,7 @@ from types import SimpleNamespace
 
 from sglang.srt.entrypoints import http_server
 from sglang.srt.lora.lora_registry import LoRARef
+from sglang.srt.managers.tokenizer_manager import TokenizerManager
 from sglang.srt.server_args import ServerArgs
 from sglang.test.ci.ci_register import register_cpu_ci
 from sglang.test.test_utils import CustomTestCase
@@ -36,7 +37,9 @@ register_cpu_ci(est_time=5, suite="base-a-test-cpu")
 
 
 def _call_server_info_with(
-    server_args: ServerArgs, internal_states: list[dict] | None = None
+    server_args: ServerArgs,
+    internal_states: list[dict] | None = None,
+    config_updates: dict | None = None,
 ) -> dict:
     """Invoke `http_server.server_info()` against a stub global state.
 
@@ -50,11 +53,16 @@ def _call_server_info_with(
     async def _fake_internal_state():
         return internal_states or [{"max_req_input_len": 1024}]
 
+    tokenizer_manager = TokenizerManager.__new__(TokenizerManager)
+    tokenizer_manager.server_args = server_args
+    tokenizer_manager.model_path = server_args.model_path
+    tokenizer_manager.served_model_name = server_args.served_model_name
+    tokenizer_manager._config_updates = (
+        [("test", dict(config_updates))] if config_updates else []
+    )
+    tokenizer_manager.get_internal_state = _fake_internal_state
     stub_state = SimpleNamespace(
-        tokenizer_manager=SimpleNamespace(
-            server_args=server_args,
-            get_internal_state=_fake_internal_state,
-        ),
+        tokenizer_manager=tokenizer_manager,
         scheduler_info={"max_req_input_len": 1024},
     )
     prior_state = http_server.get_global_state()
@@ -233,6 +241,18 @@ class TestServerInfoKvEventsField(CustomTestCase):
                 self.assertIsNone(info["kv_events"])
 
 
+class TestServerInfoControlPlaneUpdates(CustomTestCase):
+    """Runtime control-plane updates live on the manager, not on ServerArgs."""
+
+    def test_recorded_updates_win_over_the_startup_config(self):
+        server_args = ServerArgs(model_path="dummy", weight_version="v1")
+        payload = _call_server_info_with(
+            server_args, config_updates={"weight_version": "v2"}
+        )
+        self.assertEqual(payload["weight_version"], "v2")
+        self.assertEqual(server_args.weight_version, "v1")
+
+
 class TestServerInfoExistingFieldsPreserved(CustomTestCase):
     """Regression guard: the new `kv_events` field is additive — none of
     the fields existing consumers depend on may be silently dropped.

test/registered/unit/managers/test_scheduler_hicache_attach.py

@@ -0,0 +1,76 @@
+"""Runtime HiCache attach/detach lands on the config bags.
+
+The attach RPC used to mutate the scheduler's ServerArgs so the readback would
+show the change; the namespace readers never saw it. Both now go through
+get_context().override, so get_memory() and the resolved-config readback agree
+and the published instance stays as the launcher left it.
+"""
+
+import unittest
+from types import SimpleNamespace
+
+from sglang.srt.managers.io_struct import (
+    AttachHiCacheStorageReqInput,
+    DetachHiCacheStorageReqInput,
+)
+from sglang.srt.managers.scheduler import Scheduler
+from sglang.srt.runtime_context import get_context, get_memory
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.test_utils import CustomTestCase
+
+register_cpu_ci(est_time=5, suite="base-a-test-cpu")
+
+
+class TestSchedulerHiCacheAttach(CustomTestCase):
+    def _scheduler(self, **fields):
+        override = get_context().override_server_args(
+            enable_hierarchical_cache=True, **fields
+        )
+        self.server_args = override.install()
+        self.addCleanup(override.restore)
+
+        scheduler = Scheduler.__new__(Scheduler)
+        scheduler.server_args = self.server_args
+        scheduler.enable_hierarchical_cache = True
+        scheduler.enable_hicache_storage = False
+        scheduler.is_fully_idle = lambda: True
+        scheduler.tree_cache = SimpleNamespace(
+            attach_storage_backend=lambda **kwargs: (True, "attached"),
+            detach_storage_backend=lambda: (True, "detached"),
+        )
+        return scheduler
+
+    def test_attach_reaches_the_namespace_readers(self):
+        scheduler = self._scheduler(hicache_storage_backend=None)
+        out = scheduler.attach_hicache_storage_wrapped(
+            AttachHiCacheStorageReqInput(
+                hicache_storage_backend="file",
+                hicache_write_policy="write_through",
+            )
+        )
+
+        self.assertTrue(out.success)
+        self.assertEqual(get_memory().hicache_storage_backend, "file")
+        self.assertEqual(get_memory().hicache_write_policy, "write_through")
+        self.assertEqual(
+            get_context().resolved_server_args_dict()["hicache_storage_backend"],
+            "file",
+        )
+        self.assertIsNone(self.server_args.hicache_storage_backend)
+
+    def test_detach_clears_the_backend_for_the_same_readers(self):
+        scheduler = self._scheduler(hicache_storage_backend="file")
+        scheduler.enable_hicache_storage = True
+
+        out = scheduler.detach_hicache_storage_wrapped(DetachHiCacheStorageReqInput())
+
+        self.assertTrue(out.success)
+        self.assertIsNone(get_memory().hicache_storage_backend)
+        self.assertIsNone(
+            get_context().resolved_server_args_dict()["hicache_storage_backend"]
+        )
+        self.assertEqual(self.server_args.hicache_storage_backend, "file")
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/managers/test_tokenizer_config_updates.py

@@ -0,0 +1,216 @@
+"""Control-plane config updates stay on the tokenizer manager.
+
+Regression: runtime updates (weight version, model path, HiCache attach) were
+written onto the manager's ServerArgs instance so that the readback endpoints
+would show them. They are per-engine — several Engines can share a tokenizer
+process — so they live on the manager and the endpoints overlay them.
+"""
+
+import re
+import unittest
+from pathlib import Path
+
+import sglang
+from sglang.srt.managers.tokenizer_manager import TokenizerManager
+from sglang.srt.server_args import ServerArgs
+from sglang.test.ci.ci_register import register_cpu_ci
+from sglang.test.test_utils import CustomTestCase
+
+register_cpu_ci(est_time=5, suite="base-a-test-cpu")
+
+
+def _manager(**fields):
+    manager = TokenizerManager.__new__(TokenizerManager)
+    manager.server_args = ServerArgs(model_path="dummy", **fields)
+    manager._config_updates = []
+    return manager
+
+
+class TestTokenizerConfigUpdates(CustomTestCase):
+    def test_startup_config_shows_through_until_something_updates_it(self):
+        manager = _manager(weight_version="v1")
+        self.assertEqual(manager.config_value("weight_version"), "v1")
+
+        manager.record_config_updates("test", weight_version="v2")
+        self.assertEqual(manager.config_value("weight_version"), "v2")
+
+    def test_the_serverargs_instance_is_not_written(self):
+        manager = _manager(weight_version="v1")
+        manager.record_config_updates("test", weight_version="v2")
+        self.assertEqual(manager.server_args.weight_version, "v1")
+
+    def test_two_engines_keep_their_own_updates(self):
+        first, second = _manager(weight_version="v1"), _manager(weight_version="v1")
+        first.record_config_updates("test", weight_version="v2")
+        self.assertEqual(second.config_value("weight_version"), "v1")
+
+    def test_the_readback_dict_carries_the_updates(self):
+        manager = _manager(hicache_storage_backend=None)
+        manager.record_config_updates(
+            "test", hicache_storage_backend="file", hicache_write_policy="write_through"
+        )
+        manager.model_path = "dummy"
+        manager.served_model_name = "dummy"
+        resolved = manager.resolved_config_dict(
+            {"hicache_storage_backend": None, "model_path": "dummy"}
+        )
+        self.assertEqual(resolved["hicache_storage_backend"], "file")
+        self.assertEqual(resolved["hicache_write_policy"], "write_through")
+        self.assertEqual(resolved["model_path"], "dummy")
+
+    def test_detach_reports_the_backend_as_gone(self):
+        manager = _manager(hicache_storage_backend="file")
+        manager.record_config_updates(
+            "test",
+            hicache_storage_backend=None,
+            hicache_storage_backend_extra_config=None,
+        )
+        self.assertIsNone(manager.config_value("hicache_storage_backend"))
+
+    def test_an_unknown_field_is_refused(self):
+        manager = _manager()
+        with self.assertRaisesRegex(ValueError, "not ServerArgs fields"):
+            manager.record_config_updates("test", waight_version="v2")
+
+    def test_the_source_is_kept_for_provenance(self):
+        manager = _manager(weight_version="v1")
+        manager.record_config_updates("http.update_weight_version", weight_version="v2")
+        self.assertEqual(
+            manager._config_updates,
+            [("http.update_weight_version", {"weight_version": "v2"})],
+        )
+
+    def test_the_dump_snapshot_identifies_the_running_checkpoint(self):
+        import dataclasses
+
+        manager = _manager(load_format="auto")
+        manager.model_path = "at-startup"
+        manager.served_model_name = "at-startup"
+        manager._update_model_path_info("after-reload", "dummy")
+
+        snapshot = manager.resolved_config_dict(dataclasses.asdict(manager.server_args))
+        self.assertEqual(snapshot["model_path"], "after-reload")
+        self.assertEqual(snapshot["served_model_name"], "after-reload")
+        self.assertEqual(snapshot["load_format"], "dummy")
+        self.assertEqual(manager.server_args.model_path, "dummy")
+
+    def test_an_unsnapshotable_config_does_not_lose_the_dump(self):
+        class Hostile:
+            def __deepcopy__(self, memo):
+                raise RuntimeError("refuses to be copied")
+
+        manager = _manager()
+        manager.model_path = "dummy"
+        manager.served_model_name = "dummy"
+        manager.server_args.custom_sigquit_handler = Hostile()
+
+        self.assertIsNone(manager._dump_config_snapshot())
+
+    def test_an_unpickleable_field_does_not_lose_the_dump(self):
+        import dataclasses
+        import pickle
+
+        manager = _manager()
+        manager.model_path = "dummy"
+        manager.served_model_name = "dummy"
+        # What --custom-sigquit-handler leaves on a real ServerArgs.
+        manager.server_args.custom_sigquit_handler = lambda *_: None
+
+        payload = {
+            "server_args": manager.server_args,
+            "config_updates": list(manager._config_updates),
+            "resolved_config": manager.resolved_config_dict(
+                dataclasses.asdict(manager.server_args)
+            ),
+            "requests": [],
+        }
+        with self.assertRaises(Exception):
+            pickle.dumps(payload)
+
+        # The fallback drops both copies of the offending object, not just one.
+        payload["server_args"] = None
+        payload["resolved_config"] = None
+        self.assertTrue(pickle.dumps(payload))
+
+    def test_the_model_path_readback_follows_the_manager(self):
+        manager = _manager()
+        manager.model_path = "after-update"
+        manager.served_model_name = "after-update"
+        resolved = manager.resolved_config_dict({"model_path": "at-startup"})
+        self.assertEqual(resolved["model_path"], "after-update")
+        self.assertEqual(resolved["served_model_name"], "after-update")
+
+
+CONTROL_PLANE_FIELDS = (
+    "weight_version",
+    "model_path",
+    "served_model_name",
+    "load_format",
+    "hicache_storage_backend",
+    "hicache_storage_backend_extra_config",
+    "hicache_storage_prefetch_policy",
+    "hicache_write_policy",
+)
+
+# Modules that answer readbacks or fill responses; the tokenizer manager's own
+# __init__ seeds attributes from the constructor argument, which is not a
+# readback and not matched by the patterns below. Prometheus label sets are
+# exempt: a label must stay fixed for the lifetime of the series, so the metrics
+# collector keeps the name the server started with.
+EXEMPT_LINES = (
+    (
+        "srt/managers/tokenizer_manager.py",
+        '"model_name": self.server_args.served_model_name',
+    ),
+)
+READBACK_MODULES = (
+    "srt/managers/tokenizer_manager.py",
+    "srt/managers/tokenizer_control_mixin.py",
+    "srt/managers/multi_tokenizer_mixin.py",
+    "srt/entrypoints/http_server.py",
+    "srt/entrypoints/grpc_bridge.py",
+    "srt/entrypoints/engine.py",
+    "srt/entrypoints/openai",
+)
+
+
+class TestControlPlaneFieldsAreNotReadFromTheInstance(CustomTestCase):
+    def test_readbacks_go_through_the_manager(self):
+        root = Path(next(iter(sglang.__path__)))
+        patterns = [
+            re.compile(
+                rf"self\.server_args\.{f}\b|tokenizer_manager\.server_args\.{f}\b"
+            )
+            for f in CONTROL_PLANE_FIELDS
+        ]
+        stale = []
+        for rel in READBACK_MODULES:
+            paths = (
+                sorted((root / rel).rglob("*.py"))
+                if (root / rel).is_dir()
+                else [root / rel]
+            )
+            for path in paths:
+                for number, line in enumerate(path.read_text().split("\n"), 1):
+                    if any(
+                        rel_exempt == path.relative_to(root).as_posix()
+                        and needle in line
+                        for rel_exempt, needle in EXEMPT_LINES
+                    ):
+                        continue
+                    if any(p.search(line) for p in patterns):
+                        stale.append(
+                            f"{path.relative_to(root)}:{number}: {line.strip()}"
+                        )
+        self.assertEqual(
+            stale,
+            [],
+            "control-plane fields change at runtime and the update lives on the "
+            "TokenizerManager; read them with config_value() / "
+            "resolved_config_dict() so the readback reflects the change:\n"
+            + "\n".join(stale),
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()

test/registered/unit/managers/test_tokenizer_manager_rid_cleanup.py

@@ -98,6 +98,7 @@ def _make_tokenizer_manager() -> TokenizerManager:
     """Create a TokenizerManager with mocked dependencies, bypassing __init__."""
     tm = TokenizerManager.__new__(TokenizerManager)
     tm.server_args = MagicMock()
+    tm._config_updates = []
     tm.server_args.enable_trace = False
     tm.server_args.enable_metrics = False
     tm.server_args.enable_lora = False

test/registered/unit/test_server_args_writer_ratchet.py

@@ -49,7 +49,7 @@ _EXCLUDED = (
     "multimodal_gen",
 )
 
-_BASELINE = 26
+_BASELINE = 19
 
 
 class TestServerArgsWriterRatchet(CustomTestCase):