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fix(nnx): scope PartitionSpec default strictly to LoRA parameters in sharding analysis #4689

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copybara-service merged 1 commit into from
Aug 4, 2026
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fix(nnx): scope PartitionSpec default strictly to LoRA parameters in sharding analysis #4689

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12 changes: 6 additions & 6 deletions src/maxtext/utils/sharding.py
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Original file line number Diff line number Diff line change
Expand Up @@ -437,14 +437,14 @@ def _analyze_sharding(params, mesh, valid_target_mesh_axes):
for path, p_leaf in all_params_leaves: # Iterate over each parameter leaf
param_name_str = jax.tree_util.keystr(path) # Convert the tree path to a readable string

# Unwrap nnx.Variable / nnx.LoRAParam objects to access the underlying jax.Array
if hasattr(p_leaf, "value") and not isinstance(p_leaf, jax.Array):
# Default unannotated LoRA parameters to PartitionSpec P() while leaving standard parameters as None for strict assertions.
is_lora_param = isinstance(p_leaf, getattr(nnx, "LoRAParam", ()))
is_lora = is_lora_param or "lora" in param_name_str.lower()
if isinstance(p_leaf, nnx.Variable):
p_leaf = p_leaf.value

# Extract sharding spec, defaulting to PartitionSpec P() if sharding is unset or single-device
sharding = getattr(p_leaf, "sharding", None)
spec = getattr(sharding, "spec", None)
if spec is None:
spec = getattr(getattr(p_leaf, "sharding", None), "spec", None)
if spec is None and is_lora:
spec = P()
assert isinstance(spec, P), f"Expected '.sharding.spec' for parameter '{param_name_str}' to be a PartitionSpec."

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