[diffusion] rl: extract post-training weight apis into mixins and add tensor update/checker paths (#22817)

Co-authored-by: dreamyang-liu <nikolaliu@icloud.com>
Co-authored-by: Xiaole Guo <vera0315@connect.hku.hk>
Co-authored-by: zhaochenyang20 <zhaochen20@outlook.com>
Co-authored-by: Xiaole Guo <119391905+gxlvera@users.noreply.github.com>
Co-authored-by: zhihengy <zhihengy@andrew.cmu.edu>
Co-authored-by: MikukuOvO <MikukuOvO@users.noreply.github.com>

python/sglang/multimodal_gen/runtime/entrypoints/post_training/io_struct.py

@@ -17,6 +17,23 @@ class UpdateWeightFromDiskReqInput:
     target_modules: list[str] | None = None
 
 
+@dataclass
+class UpdateWeightFromTensorReqInput:
+    """Request to update model weights from tensor payloads for diffusion models."""
+
+    serialized_named_tensors: list[str | bytes]
+    load_format: str | None = None
+    target_modules: list[str] | None = None
+
+
+@dataclass
+class UpdateWeightFromTensorCheckerReqInput:
+    """Request to verify live module weights against expected SHA-256 values."""
+
+    target_module: str
+    expected_named_tensors_sha256: dict[str, str]
+
+
 @dataclass
 class GetWeightsChecksumReqInput:
     """Compute SHA-256 checksum of loaded module weights for verification."""

python/sglang/multimodal_gen/runtime/entrypoints/post_training/weights_api.py

@@ -5,6 +5,8 @@ from fastapi import APIRouter, Request
 from sglang.multimodal_gen.runtime.entrypoints.post_training.io_struct import (
     GetWeightsChecksumReqInput,
     UpdateWeightFromDiskReqInput,
+    UpdateWeightFromTensorCheckerReqInput,
+    UpdateWeightFromTensorReqInput,
 )
 from sglang.multimodal_gen.runtime.scheduler_client import async_scheduler_client
 from sglang.srt.utils.json_response import orjson_response
@@ -29,6 +31,82 @@ async def update_weights_from_disk(request: Request):
         target_modules=body.get("target_modules"),
     )
 
+    try:
+        response = await async_scheduler_client.forward(req)
+    except Exception as e:
+        return orjson_response(
+            {"success": False, "message": str(e)},
+            status_code=500,
+        )
+
+    result = response.output
+    return orjson_response(
+        result,
+        status_code=200 if result["success"] else 400,
+    )
+
+
+@router.post("/update_weights_from_tensor")
+async def update_weights_from_tensor(request: Request):
+    """Update model weights from serialized tensor payloads."""
+    body = await request.json()
+    serialized_named_tensors = body.get("serialized_named_tensors")
+    if not serialized_named_tensors:
+        return orjson_response(
+            {"success": False, "message": "serialized_named_tensors is required"},
+            status_code=400,
+        )
+
+    req = UpdateWeightFromTensorReqInput(
+        serialized_named_tensors=serialized_named_tensors,
+        load_format=body.get("load_format"),
+        target_modules=body.get("target_modules"),
+    )
+
+    try:
+        response = await async_scheduler_client.forward(req)
+    except Exception as e:
+        return orjson_response(
+            {"success": False, "message": str(e)},
+            status_code=500,
+        )
+
+    result = response.output
+    return orjson_response(
+        result,
+        status_code=200 if result["success"] else 400,
+    )
+
+
+@router.post("/update_weights_from_tensor_checker")
+async def update_weights_from_tensor_checker(request: Request):
+    """Verify live module weights against expected SHA-256 values."""
+    body = await request.json()
+    target_module = body.get("target_module")
+    if not target_module:
+        return orjson_response(
+            {"success": False, "message": "target_module is required"},
+            status_code=400,
+        )
+
+    expected_named_tensors_sha256 = body.get("expected_named_tensors_sha256")
+    if (
+        not isinstance(expected_named_tensors_sha256, dict)
+        or not expected_named_tensors_sha256
+    ):
+        return orjson_response(
+            {
+                "success": False,
+                "message": "expected_named_tensors_sha256 is required",
+            },
+            status_code=400,
+        )
+
+    req = UpdateWeightFromTensorCheckerReqInput(
+        target_module=target_module,
+        expected_named_tensors_sha256=expected_named_tensors_sha256,
+    )
+
     try:
         response = await async_scheduler_client.forward(req)
     except Exception as e:

python/sglang/multimodal_gen/runtime/managers/gpu_worker.py

@@ -37,14 +37,8 @@ from sglang.multimodal_gen.runtime.entrypoints.utils import (
     post_process_sample,
     save_outputs,
 )
-from sglang.multimodal_gen.runtime.loader.weight_utils import compute_weights_checksum
-from sglang.multimodal_gen.runtime.loader.weights_updater import (
-    WeightsUpdater,
-    get_updatable_modules,
-)
 from sglang.multimodal_gen.runtime.managers.memory_managers.layerwise_offload import (
     configure_layerwise_offload_modules,
-    iter_materialized_weights,
 )
 from sglang.multimodal_gen.runtime.pipelines_core import (
     ComposedPipelineBase,
@@ -54,6 +48,9 @@ from sglang.multimodal_gen.runtime.pipelines_core import (
 )
 from sglang.multimodal_gen.runtime.pipelines_core.schedule_batch import OutputBatch
 from sglang.multimodal_gen.runtime.platforms import current_platform
+from sglang.multimodal_gen.runtime.post_training.gpu_worker_post_training_mixin import (
+    GPUWorkerPostTrainingMixin,
+)
 from sglang.multimodal_gen.runtime.realtime.session import (
     RealtimeSessionCache,
 )
@@ -102,7 +99,7 @@ class _ExpandedOutputParts:
     trajectory_decoded_parts: list[list[torch.Tensor]] | None = None
 
 
-class GPUWorker:
+class GPUWorker(GPUWorkerPostTrainingMixin):
     """
     A worker that executes the model on a single GPU.
     """
@@ -894,48 +891,6 @@ class GPUWorker:
         status = self.pipeline.get_lora_status()
         return OutputBatch(output=status)
 
-    def update_weights_from_disk(
-        self,
-        model_path: str,
-        flush_cache: bool = True,
-        target_modules: list[str] | None = None,
-    ) -> tuple[bool, str]:
-        """Update model weights from disk inplace without restarting the server."""
-        if not self.pipeline:
-            return False, "Pipeline is not initialized"
-
-        updater = WeightsUpdater(self.pipeline)
-        success, message = updater.update_weights_from_disk(
-            model_path,
-            flush_cache=flush_cache,
-            target_modules=target_modules,
-        )
-        if success:
-            self.server_args.model_path = model_path
-            self.pipeline.model_path = model_path
-        return success, message
-
-    def get_weights_checksum(
-        self, module_names: list[str] | None = None
-    ) -> dict[str, str]:
-        """Compute SHA-256 checksum of each module's weights."""
-        if not self.pipeline:
-            return {"error": "Pipeline is not initialized"}
-
-        all_modules = get_updatable_modules(self.pipeline)
-        names = module_names if module_names is not None else list(all_modules.keys())
-
-        checksums: dict[str, str] = {}
-        for name in names:
-            module = all_modules.get(name)
-            if module is None:
-                checksums[name] = "not_found"
-                continue
-            checksums[name] = compute_weights_checksum(
-                iter_materialized_weights(module)
-            )
-        return checksums
-
 
 OOM_MSG = """
 OOM detected. Possible solutions:

python/sglang/multimodal_gen/runtime/managers/scheduler.py

@@ -20,6 +20,8 @@ from sglang.multimodal_gen.runtime.distributed import get_world_group
 from sglang.multimodal_gen.runtime.entrypoints.post_training.io_struct import (
     GetWeightsChecksumReqInput,
     UpdateWeightFromDiskReqInput,
+    UpdateWeightFromTensorCheckerReqInput,
+    UpdateWeightFromTensorReqInput,
 )
 from sglang.multimodal_gen.runtime.entrypoints.utils import (
     GetDisaggStatsReq,
@@ -44,6 +46,9 @@ from sglang.multimodal_gen.runtime.pipelines_core.schedule_batch import (
     BatchMetricsWindow,
     OutputBatch,
 )
+from sglang.multimodal_gen.runtime.post_training.scheduler_post_training_mixin import (
+    SchedulerPostTrainingMixin,
+)
 from sglang.multimodal_gen.runtime.server_args import (
     PortArgs,
     ServerArgs,
@@ -69,7 +74,7 @@ _MAX_RECV_REQS_PER_POLL = 1024
 _BATCH_METRICS_LOG_INTERVAL = 5
 
 
-class Scheduler(SchedulerDisaggMixin):
+class Scheduler(SchedulerPostTrainingMixin, SchedulerDisaggMixin):
     """
     Runs the main event loop for the rank 0 worker.
     It listens for external requests via ZMQ and coordinates with other workers.
@@ -132,6 +137,10 @@ class Scheduler(SchedulerDisaggMixin):
             ReleaseRealtimeSessionReq: self._handle_release_realtime_session,
             GetDisaggStatsReq: self._handle_get_disagg_stats,
             UpdateWeightFromDiskReqInput: self._handle_update_weights_from_disk,
+            UpdateWeightFromTensorReqInput: self._handle_update_weights_from_tensor,
+            UpdateWeightFromTensorCheckerReqInput: (
+                self._handle_update_weights_from_tensor_checker
+            ),
             GetWeightsChecksumReqInput: self._handle_get_weights_checksum,
         }
 
@@ -211,25 +220,6 @@ class Scheduler(SchedulerDisaggMixin):
         req = reqs[0]
         return self.worker.release_realtime_session(req.session_id)
 
-    def _handle_update_weights_from_disk(self, reqs: List[Any]) -> OutputBatch:
-        """Handle update_weights_from_disk request for RL workflows."""
-        req = reqs[0]
-        success, message = self.worker.update_weights_from_disk(
-            model_path=req.model_path,
-            flush_cache=req.flush_cache,
-            target_modules=req.target_modules,
-        )
-        return OutputBatch(
-            output={"success": success, "message": message},
-            error=None if success else message,
-        )
-
-    def _handle_get_weights_checksum(self, reqs: List[Any]) -> OutputBatch:
-        """Handle get_weights_checksum request."""
-        req = reqs[0]
-        checksums = self.worker.get_weights_checksum(module_names=req.module_names)
-        return OutputBatch(output=checksums)
-
     @staticmethod
     def _normalize_generation_reqs(reqs: list[Any]) -> list[Req]:
         if len(reqs) == 1 and isinstance(reqs[0], list):

python/sglang/multimodal_gen/runtime/post_training/gpu_worker_post_training_mixin.py

@@ -0,0 +1,172 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from sglang.multimodal_gen.runtime.distributed import get_tp_rank, get_tp_world_size
+from sglang.multimodal_gen.runtime.loader.weight_utils import compute_weights_checksum
+from sglang.multimodal_gen.runtime.managers.memory_managers.layerwise_offload import (
+    iter_materialized_weights,
+)
+from sglang.multimodal_gen.runtime.post_training.tensor_update_checker import (
+    TensorUpdateChecker,
+)
+from sglang.multimodal_gen.runtime.post_training.weights_updater import (
+    WeightsUpdater,
+    get_updatable_modules,
+)
+from sglang.srt.utils import MultiprocessingSerializer
+from sglang.srt.utils.patch_torch import monkey_patch_torch_reductions
+
+if TYPE_CHECKING:
+    from sglang.multimodal_gen.runtime.entrypoints.post_training.io_struct import (
+        UpdateWeightFromTensorCheckerReqInput,
+        UpdateWeightFromTensorReqInput,
+    )
+
+
+class GPUWorkerPostTrainingMixin:
+    def update_weights_from_disk(
+        self,
+        model_path: str,
+        flush_cache: bool = True,
+        target_modules: list[str] | None = None,
+    ) -> tuple[bool, str]:
+        if not self.pipeline:
+            return False, "Pipeline is not initialized"
+
+        updater = WeightsUpdater(self.pipeline)
+        success, message = updater.update_weights_from_disk(
+            model_path,
+            flush_cache=flush_cache,
+            target_modules=target_modules,
+        )
+        if success:
+            self.server_args.model_path = model_path
+            self.pipeline.model_path = model_path
+        return success, message
+
+    def update_weights_from_tensor(
+        self,
+        req: UpdateWeightFromTensorReqInput,
+    ) -> tuple[bool, str]:
+        if not self.pipeline:
+            return False, "Pipeline is not initialized"
+
+        payload, error = self._select_rank_scoped_payload(
+            payloads=req.serialized_named_tensors,
+            field_name="serialized_named_tensors",
+        )
+        if error is not None:
+            return False, error
+
+        monkey_patch_torch_reductions()
+        try:
+            named_tensors = MultiprocessingSerializer.deserialize(payload)
+        except Exception as e:
+            return False, f"Failed to deserialize serialized_named_tensors: {e}"
+
+        updater = WeightsUpdater(self.pipeline)
+        return updater.update_weights_from_tensor(
+            named_tensors=named_tensors,
+            load_format=req.load_format,
+            target_modules=req.target_modules,
+        )
+
+    def update_weights_from_tensor_checker(
+        self,
+        req: UpdateWeightFromTensorCheckerReqInput,
+    ) -> tuple[bool, str]:
+        if not self.pipeline:
+            return False, "Pipeline is not initialized"
+
+        checker = TensorUpdateChecker(self.pipeline)
+        result = checker.verify_across_tp(
+            target_module=req.target_module,
+            expected_named_tensors_sha256=req.expected_named_tensors_sha256,
+            tp_rank=get_tp_rank(),
+            tp_world_size=get_tp_world_size(),
+            tp_cpu_group=self.tp_cpu_group,
+            tp_root_rank=self.tp_group.first_rank,
+        )
+        if self.sp_group.world_size == 1:
+            return result
+
+        import torch
+
+        is_sp_root = self.sp_group.rank_in_group == 0
+        gathered_results = [None] * self.sp_group.world_size if is_sp_root else None
+        torch.distributed.gather_object(
+            result,
+            gathered_results,
+            dst=self.sp_group.first_rank,
+            group=self.sp_cpu_group,
+        )
+
+        final_result = None
+        if is_sp_root:
+            failures = [
+                (rank, message)
+                for rank, (success, message) in enumerate(gathered_results)
+                if not success
+            ]
+            if failures:
+                rank, message = failures[0]
+                if len(failures) == 1:
+                    final_result = (False, f"SP rank {rank}: {message}")
+                else:
+                    final_result = (
+                        False,
+                        f"{len(failures)} SP ranks failed update_weight_from_tensor_checker; "
+                        f"first failure on rank {rank}: {message}",
+                    )
+            else:
+                final_result = result
+
+        final_result_holder = [final_result]
+        torch.distributed.broadcast_object_list(
+            final_result_holder,
+            src=self.sp_group.first_rank,
+            group=self.sp_cpu_group,
+        )
+        return final_result_holder[0]
+
+    def get_weights_checksum(
+        self, module_names: list[str] | None = None
+    ) -> dict[str, str]:
+        if not self.pipeline:
+            return {"error": "Pipeline is not initialized"}
+
+        all_modules = get_updatable_modules(self.pipeline)
+        names = module_names if module_names is not None else list(all_modules.keys())
+
+        checksums: dict[str, str] = {}
+        for name in names:
+            module = all_modules.get(name)
+            if module is None:
+                checksums[name] = "not_found"
+                continue
+            checksums[name] = compute_weights_checksum(
+                iter_materialized_weights(module)
+            )
+        return checksums
+
+    def _select_rank_scoped_payload(
+        self,
+        payloads: list,
+        field_name: str,
+    ) -> tuple[object | None, str | None]:
+        if not isinstance(payloads, list):
+            return None, f"{field_name} must be a list"
+        if not payloads:
+            return None, f"{field_name} is required"
+
+        tp_world_size = get_tp_world_size()
+        if len(payloads) not in (1, tp_world_size):
+            return (
+                None,
+                f"{field_name} size must be 1 or tp_size ({tp_world_size}), "
+                f"got {len(payloads)}",
+            )
+
+        payload_idx = get_tp_rank() if len(payloads) == tp_world_size else 0
+        return payloads[payload_idx], None

python/sglang/multimodal_gen/runtime/post_training/scheduler_post_training_mixin.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+from typing import Any, List
+
+from sglang.multimodal_gen.runtime.pipelines_core.schedule_batch import OutputBatch
+
+
+class SchedulerPostTrainingMixin:
+    def _handle_update_weights_from_disk(self, reqs: List[Any]) -> OutputBatch:
+        req = reqs[0]
+        success, message = self.worker.update_weights_from_disk(
+            model_path=req.model_path,
+            flush_cache=req.flush_cache,
+            target_modules=req.target_modules,
+        )
+        return OutputBatch(
+            output={"success": success, "message": message},
+            error=None if success else message,
+        )
+
+    def _handle_update_weights_from_tensor(self, reqs: List[Any]) -> OutputBatch:
+        req = reqs[0]
+        success, message = self.worker.update_weights_from_tensor(req)
+        if self.server_args.tp_size > 1:
+            import torch
+
+            torch.distributed.barrier(group=self.worker.tp_cpu_group)
+        return OutputBatch(
+            output={"success": success, "message": message},
+            error=None if success else message,
+        )
+
+    def _handle_update_weights_from_tensor_checker(
+        self, reqs: List[Any]
+    ) -> OutputBatch:
+        req = reqs[0]
+        success, message = self.worker.update_weights_from_tensor_checker(req)
+        return OutputBatch(
+            output={"success": success, "message": message},
+            error=None if success else message,
+        )
+
+    def _handle_get_weights_checksum(self, reqs: List[Any]) -> OutputBatch:
+        req = reqs[0]
+        checksums = self.worker.get_weights_checksum(module_names=req.module_names)
+        return OutputBatch(output=checksums)

python/sglang/multimodal_gen/runtime/post_training/tensor_update_checker.py

@@ -0,0 +1,263 @@
+"""Verification helpers for diffusion update_weights_from_tensor workflows."""
+
+from __future__ import annotations
+
+import hashlib
+from collections.abc import Iterable
+
+import torch
+from torch.distributed.tensor import DTensor
+
+from sglang.multimodal_gen.runtime.managers.memory_managers.layerwise_offload import (
+    iter_materialized_weights,
+)
+
+_MAX_DISPLAY_TENSORS = 5
+
+
+def _materialize_local_tensor(tensor: torch.Tensor) -> torch.Tensor:
+    if isinstance(tensor, DTensor):
+        tensor = tensor._local_tensor
+    return tensor.detach().cpu().contiguous()
+
+
+def compute_tensor_sha256(tensor: torch.Tensor) -> str:
+    tensor = _materialize_local_tensor(tensor)
+    hasher = hashlib.sha256()
+    hasher.update(str(tensor.dtype).encode("utf-8"))
+    hasher.update(repr(tuple(tensor.shape)).encode("utf-8"))
+    hasher.update(tensor.view(torch.uint8).numpy().tobytes())
+    return hasher.hexdigest()
+
+
+def build_named_tensor_sha256(
+    named_tensors: Iterable[tuple[str, torch.Tensor]],
+) -> dict[str, str]:
+    sha256_by_name: dict[str, str] = {}
+    for name, tensor in named_tensors:
+        sha256_by_name[name] = compute_tensor_sha256(tensor)
+    return sha256_by_name
+
+
+class TensorUpdateChecker:
+    def __init__(self, pipeline):
+        self.pipeline = pipeline
+
+    def verify_across_tp(
+        self,
+        target_module: str,
+        expected_named_tensors_sha256: dict[str, str],
+        tp_rank: int,
+        tp_world_size: int,
+        tp_cpu_group,
+        tp_root_rank: int,
+    ) -> tuple[bool, str]:
+        if tp_world_size == 1:
+            return self.verify(
+                target_module=target_module,
+                expected_named_tensors_sha256=expected_named_tensors_sha256,
+            )
+
+        module = self.pipeline.get_module(target_module)
+        if module is None:
+            return False, f"Module '{target_module}' is not initialized"
+
+        local_named_tensors = dict(
+            self._iter_module_named_tensors(
+                module, expected_named_tensors_sha256.keys()
+            )
+        )
+        reference_tensors = dict(module.named_parameters())
+        reference_tensors.update(dict(module.named_buffers()))
+        actual_named_tensors_sha256: dict[str, str] | None = (
+            {} if tp_rank == 0 else None
+        )
+
+        for name, expected_sha256 in expected_named_tensors_sha256.items():
+            gathered_tensors: list[torch.Tensor | None] | None = (
+                [None] * tp_world_size if tp_rank == 0 else None
+            )
+            torch.distributed.gather_object(
+                (
+                    _materialize_local_tensor(local_named_tensors[name])
+                    if name in local_named_tensors
+                    else None
+                ),
+                gathered_tensors,
+                dst=tp_root_rank,
+                group=tp_cpu_group,
+            )
+            if tp_rank != 0:
+                continue
+
+            valid_tensors = [
+                tensor for tensor in gathered_tensors if tensor is not None
+            ]
+            if len(valid_tensors) != len(gathered_tensors):
+                continue
+
+            local_sha256s = [compute_tensor_sha256(tensor) for tensor in valid_tensors]
+            if all(local_sha256 == expected_sha256 for local_sha256 in local_sha256s):
+                actual_named_tensors_sha256[name] = expected_sha256
+                continue
+
+            reference_tensor = reference_tensors.get(name)
+            candidate_dims: list[int] = []
+            if isinstance(reference_tensor, DTensor):
+                for placement in reference_tensor.placements:
+                    shard_dim = getattr(placement, "dim", None)
+                    if isinstance(shard_dim, int) and shard_dim not in candidate_dims:
+                        candidate_dims.append(shard_dim)
+            for attr in ("input_dim", "output_dim"):
+                shard_dim = getattr(reference_tensor, attr, None)
+                if isinstance(shard_dim, int) and shard_dim not in candidate_dims:
+                    candidate_dims.append(shard_dim)
+
+            reconstructed_sha256 = None
+            first_tensor = valid_tensors[0]
+            for shard_dim in candidate_dims:
+                if first_tensor.ndim == 0:
+                    break
+
+                shard_dim %= first_tensor.ndim
+                compatible = True
+                for tensor in valid_tensors[1:]:
+                    if (
+                        tensor.ndim != first_tensor.ndim
+                        or tensor.dtype != first_tensor.dtype
+                    ):
+                        compatible = False
+                        break
+                    if any(
+                        lhs != rhs
+                        for dim, (lhs, rhs) in enumerate(
+                            zip(first_tensor.shape, tensor.shape)
+                        )
+                        if dim != shard_dim
+                    ):
+                        compatible = False
+                        break
+                if not compatible:
+                    continue
+
+                reconstructed = torch.cat(valid_tensors, dim=shard_dim).contiguous()
+                if compute_tensor_sha256(reconstructed) == expected_sha256:
+                    reconstructed_sha256 = expected_sha256
+                    break
+
+            actual_named_tensors_sha256[name] = reconstructed_sha256 or local_sha256s[0]
+
+        final_result: tuple[bool, str] | None = None
+        if tp_rank == 0:
+            final_result = self._compare_manifests(
+                target_module=target_module,
+                expected_named_tensors_sha256=expected_named_tensors_sha256,
+                actual_named_tensors_sha256=actual_named_tensors_sha256,
+            )
+            if final_result[0]:
+                final_result = (
+                    True,
+                    f"Verified module '{target_module}' update across {tp_world_size} TP ranks.",
+                )
+
+        final_result_holder = [final_result]
+        torch.distributed.broadcast_object_list(
+            final_result_holder,
+            src=tp_root_rank,
+            group=tp_cpu_group,
+        )
+        final_result = final_result_holder[0]
+        assert final_result is not None
+        return final_result
+
+    def verify(
+        self,
+        target_module: str,
+        expected_named_tensors_sha256: dict[str, str],
+    ) -> tuple[bool, str]:
+        module = self.pipeline.get_module(target_module)
+        if module is None:
+            return False, f"Module '{target_module}' is not initialized"
+
+        actual_named_tensors_sha256 = build_named_tensor_sha256(
+            self._iter_module_named_tensors(
+                module, expected_named_tensors_sha256.keys()
+            )
+        )
+        return self._compare_manifests(
+            target_module=target_module,
+            expected_named_tensors_sha256=expected_named_tensors_sha256,
+            actual_named_tensors_sha256=actual_named_tensors_sha256,
+        )
+
+    def _iter_module_named_tensors(
+        self,
+        module: torch.nn.Module,
+        expected_names: Iterable[str],
+    ):
+        expected_name_set = set(expected_names)
+        seen_names: set[str] = set()
+
+        for name, tensor in iter_materialized_weights(module):
+            if name not in expected_name_set:
+                continue
+            seen_names.add(name)
+            yield name, tensor
+
+        for name, tensor in module.named_buffers():
+            if name in seen_names or name not in expected_name_set:
+                continue
+            seen_names.add(name)
+            yield name, tensor
+
+    def _compare_manifests(
+        self,
+        *,
+        target_module: str,
+        expected_named_tensors_sha256: dict[str, str],
+        actual_named_tensors_sha256: dict[str, str],
+    ) -> tuple[bool, str]:
+        missing_names = sorted(
+            name
+            for name in expected_named_tensors_sha256
+            if name not in actual_named_tensors_sha256
+        )
+        mismatched_names = sorted(
+            name
+            for name, expected_sha256 in expected_named_tensors_sha256.items()
+            if name in actual_named_tensors_sha256
+            and actual_named_tensors_sha256[name] != expected_sha256
+        )
+
+        if missing_names or mismatched_names:
+            parts: list[str] = []
+            if missing_names:
+                parts.append(
+                    "missing "
+                    f"{len(missing_names)} tensor(s): "
+                    f"{self._format_tensor_names(missing_names)}"
+                )
+            if mismatched_names:
+                parts.append(
+                    "checksum mismatch for "
+                    f"{len(mismatched_names)} tensor(s): "
+                    f"{self._format_tensor_names(mismatched_names)}"
+                )
+            return (
+                False,
+                f"Module '{target_module}' update weight check failed: "
+                + "; ".join(parts),
+            )
+
+        return (
+            True,
+            f"Verified module '{target_module}' update for "
+            f"{len(expected_named_tensors_sha256)} tensor(s).",
+        )
+
+    def _format_tensor_names(self, names: list[str]) -> str:
+        displayed = names[:_MAX_DISPLAY_TENSORS]
+        formatted = ", ".join(displayed)
+        if len(names) > _MAX_DISPLAY_TENSORS:
+            formatted += f", ... (+{len(names) - _MAX_DISPLAY_TENSORS} more)"
+        return formatted

python/sglang/multimodal_gen/runtime/post_training/weights_updater.py

@@ -42,6 +42,7 @@ from __future__ import annotations
 
 import gc
 from pathlib import Path
+from typing import Any
 
 import torch
 from torch.distributed.tensor import DTensor, distribute_tensor
@@ -49,6 +50,7 @@ from torch.distributed.tensor import DTensor, distribute_tensor
 from sglang.multimodal_gen.runtime.cache.teacache import TeaCacheMixin
 from sglang.multimodal_gen.runtime.loader.utils import (
     _list_safetensors_files,
+    get_param_names_mapping,
 )
 from sglang.multimodal_gen.runtime.loader.weight_utils import (
     safetensors_weights_iterator,
@@ -59,8 +61,13 @@ from sglang.multimodal_gen.runtime.managers.memory_managers.layerwise_offload im
 from sglang.multimodal_gen.runtime.pipelines.diffusers_pipeline import DiffusersPipeline
 from sglang.multimodal_gen.runtime.utils.hf_diffusers_utils import maybe_download_model
 from sglang.multimodal_gen.runtime.utils.logging_utils import init_logger
+from sglang.srt.weight_sync.tensor_bucket import (
+    FlattenedTensorBucket,
+    FlattenedTensorMetadata,
+)
 
 logger = init_logger(__name__)
+_DEFAULT_TENSOR_TARGET_MODULE = "transformer"
 
 
 def get_updatable_modules(pipeline) -> dict[str, torch.nn.Module]:
@@ -115,6 +122,9 @@ def _load_weights_into_module(module: torch.nn.Module, weights_iter) -> None:
     For offloaded modules, updates CPU buffers directly via
     update_cpu_weights(); non-offloaded parameters use in-place copy.
     """
+    model_params = dict(module.named_parameters())
+    weights_iter = _iter_module_weight_updates(module, weights_iter, model_params)
+
     offload_managers: list = []
     if is_layerwise_offloaded_module(module):
         offload_managers = [m for m in module.layerwise_offload_managers if m.enabled]
@@ -125,30 +135,92 @@ def _load_weights_into_module(module: torch.nn.Module, weights_iter) -> None:
         for manager in offload_managers:
             offloaded_names.update(manager.update_cpu_weights(weight_dict))
         remaining = ((n, w) for n, w in weight_dict.items() if n not in offloaded_names)
-        load_weights_into_model(remaining, dict(module.named_parameters()))
+        load_weights_into_model(remaining, model_params)
     else:
-        load_weights_into_model(weights_iter, dict(module.named_parameters()))
+        load_weights_into_model(weights_iter, model_params)
 
 
-def load_weights_into_model(weights_iter, model_params: dict) -> None:
+def _build_module_weight_name_mapper(module: torch.nn.Module):
+    """Build a chained regex mapper from mapping dicts exposed by the module."""
+    mapping_fns = []
+    for attr in ("lora_param_names_mapping", "param_names_mapping"):
+        mapping = getattr(module, attr, None)
+        if not mapping:
+            continue
+        mapping_fns.append(get_param_names_mapping(mapping))
+
+    if not mapping_fns:
+        return None
+
+    def map_name(name: str) -> str:
+        mapped_name = name
+        for mapping_fn in mapping_fns:
+            mapped_name = mapping_fn(mapped_name)[0]
+        return mapped_name
+
+    return map_name
+
+
+def _iter_module_weight_updates(
+    module: torch.nn.Module,
+    weights_iter,
+    model_params: dict,
+):
+    map_name = _build_module_weight_name_mapper(module)
+    module_name = type(module).__name__
+
+    for name, loaded_weight in weights_iter:
+        if name in model_params:
+            yield name, loaded_weight
+            continue
+
+        mapped_name = map_name(name) if map_name is not None else name
+        if mapped_name in model_params:
+            yield mapped_name, loaded_weight
+            continue
+
+        logger.warning(
+            "Skipping weight update for %s: parameter %r not found after mapping to %r",
+            module_name,
+            name,
+            mapped_name,
+        )
+
+
+def load_weights_into_model(
+    weights_iter, model_params: dict, module_name: str | None = None
+) -> None:
     """Copy weights from weights_iter into model_params in-place."""
     for name, loaded_weight in weights_iter:
         if name not in model_params:
+            logger.warning("Skipping weight update: parameter %r not found", name)
             continue
         param = model_params[name]
-        if param.shape != loaded_weight.shape:
-            raise ValueError(
-                f"Shape mismatch for {name}: model={param.shape}, loaded={loaded_weight.shape}"
-            )
-        if isinstance(param, DTensor):
-            distributed_weight = distribute_tensor(
-                loaded_weight.to(param.dtype),
-                param.device_mesh,
-                param.placements,
-            )
-            param._local_tensor.copy_(distributed_weight._local_tensor)
+        weight_loader = getattr(param, "weight_loader", None)
+        if callable(weight_loader):
+            weight_loader(param, loaded_weight.to(param.dtype))
         else:
-            param.data.copy_(loaded_weight.to(param.dtype))
+            dtensor_param = param if isinstance(param, DTensor) else None
+            if dtensor_param is None and isinstance(
+                getattr(param, "data", None), DTensor
+            ):
+                dtensor_param = param.data
+
+            if dtensor_param is not None:
+                distributed_weight = distribute_tensor(
+                    loaded_weight.to(param.dtype),
+                    dtensor_param.device_mesh,
+                    dtensor_param.placements,
+                )
+                dtensor_param._local_tensor.copy_(distributed_weight._local_tensor)
+            else:
+                if param.shape != loaded_weight.shape:
+                    module_prefix = f"{module_name}." if module_name else ""
+                    raise ValueError(
+                        f"Shape mismatch for {module_prefix}{name}: "
+                        f"model={param.shape}, loaded={loaded_weight.shape}"
+                    )
+                param.data.copy_(loaded_weight.to(param.dtype))
 
 
 class WeightsUpdater:
@@ -293,3 +365,142 @@ class WeightsUpdater:
                 continue
             weights_iter = _get_weights_iter(str(weights_dir))
             _load_weights_into_module(module, weights_iter)
+
+    def update_weights_from_tensor(
+        self,
+        named_tensors: Any,
+        load_format: str | None = None,
+        target_modules: list[str] | None = None,
+    ) -> tuple[bool, str]:
+        if target_modules is None:
+            target_modules = [_DEFAULT_TENSOR_TARGET_MODULE]
+        try:
+            modules_to_update = self._collect_modules(target_modules)
+        except ValueError as e:
+            logger.error(str(e))
+            return False, str(e)
+
+        if not modules_to_update:
+            error_msg = (
+                f"No matching modules found for update. "
+                f"Requested: {target_modules}. "
+                f"Available nn.Module(s): {list(get_updatable_modules(self.pipeline).keys())}"
+            )
+            logger.error(error_msg)
+            return False, error_msg
+
+        try:
+            module_payloads = self._resolve_module_payloads(
+                named_tensors=named_tensors,
+                modules_to_update=modules_to_update,
+            )
+        except ValueError as e:
+            logger.error(str(e))
+            return False, str(e)
+
+        updated_modules: list[str] = []
+        for module_name, module in modules_to_update:
+            try:
+                payload = module_payloads[module_name]
+                weights_iter = self._materialize_weights_iter(payload, load_format)
+                _load_weights_into_module(module, weights_iter)
+                updated_modules.append(module_name)
+            except Exception as e:
+                error_msg = (
+                    f"Failed to update module '{module_name}' from tensor: {e}. "
+                    f"The pipeline may be partially updated. "
+                    f"Please discard the whole weights and reload from a known-good checkpoint."
+                )
+                logger.error(error_msg, exc_info=True)
+                return False, error_msg
+
+        gc.collect()
+        torch.cuda.empty_cache()
+        names = ", ".join(updated_modules)
+        message = f"Updated {len(updated_modules)} modules from tensor ({names})."
+        logger.info(message)
+        return True, message
+
+    def _resolve_module_payloads(
+        self,
+        named_tensors: Any,
+        modules_to_update: list[tuple[str, torch.nn.Module]],
+    ) -> dict[str, Any]:
+        module_names = [name for name, _ in modules_to_update]
+        if isinstance(named_tensors, dict):
+            missing = [name for name in module_names if name not in named_tensors]
+            if missing:
+                raise ValueError(
+                    f"Missing tensor payload for module(s): {missing}. "
+                    f"Provided modules: {list(named_tensors.keys())}"
+                )
+            return {name: named_tensors[name] for name in module_names}
+
+        if len(module_names) == 1:
+            return {module_names[0]: named_tensors}
+
+        raise ValueError(
+            "Ambiguous tensor payload for multi-module update. "
+            "Provide a dict mapping module_name -> module payload, "
+            f"requested modules: {module_names}."
+        )
+
+    def _materialize_weights_iter(self, module_payload: Any, load_format: str | None):
+        if load_format == "flattened_bucket":
+            if not isinstance(module_payload, dict):
+                raise ValueError(
+                    "flattened_bucket payload must be a dict with "
+                    "'flattened_tensor' and 'metadata'."
+                )
+            flattened_tensor = module_payload.get("flattened_tensor")
+            metadata = module_payload.get("metadata")
+            if flattened_tensor is None or metadata is None:
+                raise ValueError(
+                    "flattened_bucket payload missing 'flattened_tensor' or 'metadata'."
+                )
+            return self._reconstruct_from_flattened_bucket(flattened_tensor, metadata)
+
+        if isinstance(module_payload, (list, tuple)):
+            return iter(module_payload)
+
+        raise ValueError(
+            f"Unsupported module payload type for load_format={load_format}: "
+            f"{type(module_payload).__name__}"
+        )
+
+    def _reconstruct_from_flattened_bucket(self, flattened_tensor: Any, metadata: Any):
+        if not isinstance(flattened_tensor, torch.Tensor):
+            raise ValueError(
+                "flattened_bucket 'flattened_tensor' must be a torch.Tensor."
+            )
+        if not isinstance(metadata, list):
+            raise ValueError("flattened_bucket 'metadata' must be a list.")
+
+        converted_metadata: list[FlattenedTensorMetadata] = []
+        for meta in metadata:
+            converted_metadata.append(
+                FlattenedTensorMetadata(
+                    name=meta.name,
+                    shape=torch.Size(meta.shape),
+                    dtype=self._normalize_torch_dtype(meta.dtype),
+                    start_idx=int(meta.start_idx),
+                    end_idx=int(meta.end_idx),
+                    numel=int(meta.numel),
+                )
+            )
+
+        bucket = FlattenedTensorBucket(
+            flattened_tensor=flattened_tensor,
+            metadata=converted_metadata,
+        )
+        return bucket.reconstruct_tensors()
+
+    def _normalize_torch_dtype(self, dtype: Any) -> torch.dtype:
+        if isinstance(dtype, torch.dtype):
+            return dtype
+        if isinstance(dtype, str):
+            name = dtype.split(".")[-1]
+            normalized = getattr(torch, name, None)
+            if isinstance(normalized, torch.dtype):
+                return normalized
+        raise ValueError(f"Unsupported dtype in flattened_bucket metadata: {dtype!r}")