Fix Megatron rope theta compatibility

Author: Kovbo

src/art/megatron/provider.py

@@ -57,6 +57,21 @@ def has_glob(self, pattern: str) -> bool:
         return self._source.has_glob(pattern)
 
 
+def _ensure_rope_theta(bridge: AutoBridge) -> None:
+    config = bridge.hf_pretrained.config
+    if hasattr(config, "rope_theta"):
+        return
+
+    for rope_config_name in ("rope_scaling", "rope_parameters"):
+        rope_config = getattr(config, rope_config_name, None)
+        if not isinstance(rope_config, dict):
+            continue
+        rope_theta = rope_config.get("rope_theta")
+        if isinstance(rope_theta, int | float):
+            setattr(config, "rope_theta", float(rope_theta))
+            return
+
+
 def get_provider(
     model: str,
     *,
@@ -70,6 +85,7 @@ def get_provider(
     assert isinstance(bridge._model_bridge, Qwen3MoEBridge), (
         "Only Qwen3 MoE models are supported"
     )
+    _ensure_rope_theta(bridge)
     if torch_dtype != torch.bfloat16:
         model_name_or_path = bridge.hf_pretrained.model_name_or_path
         assert model_name_or_path is not None