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This has been tested uptil 3 steps on DeepSWE workflows and seems to be working fine. This is very useful to rule out issues with Raiden. I will also try to follow up with chanages that add a single host based weight sync on lustre.
niting
requested review from
abheesht17,
hgao327,
jiangyangmu,
lc5211,
s-noghabi,
sizhit2,
tianshub and
wang2yn84
as code owners
September 18, 2026 19:33
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Description
This change introduces a GCS and shared-filesystem based weight synchronization transport (
GcsSyncHandler/FilesystemSyncHandler) to Tunix as an alternative/fallback to Raiden.Motivation
Raiden P2P weight sync can encounter issues with C++ FFI compatibility, complex mesh geometries, and timing drift across slices. This change provides a reliable, decoupled checkpoint-based weight sync mechanism that works over GCS and shared/parallel filesystems (e.g. Lustre / Parallelstore).
Key Changes
gcs_weight_sync.py: AddedGcsSyncHandler(implementingWeightSyncHandler),apply_checkpoint_to_runner(restoring via Orbax and patching runner state in-place), and monkey-patching forTPUWorker(load_gcs_weights/load_filesystem_weights).weight_sync.py&weight_sync_coordinator.py:WeightSyncMode.GCS = "gcs"and alias support forfilesystem.create_default_handlerto constructGcsSyncHandler.checkpoint_paththroughextra_configintoWeightSyncRequest.needs_manifest_preflightflag to bypass P2P manifest checks for checkpoint sync.VllmSamplerAdapterandRLVllmSamplerV2to load weights viaload_gcs_weights/load_filesystem_weightsinweight_sync().--weight_sync_modeflag torun_trainer_node.py,run_rollout_node.py, andk8s_launcher.sh.tests/experimental/weight_sync/gcs_weight_sync_test.py,tests/experimental/weight_sync/weight_sync_coordinator_test.py, andtests/experimental/rollout/vllm_sampler_adapter_test.py.Verification