[bugfix] MiniMax-H3: prepare compile after FP8 conversion

fastvideo/models/dits/minimax_h3.py

@@ -741,6 +741,13 @@ class MiniMaxH3Transformer3DModel(BaseDiT):
         compiled block forwards (H3 compiles per-block by default). Say so
         once instead of leaving the flag looking active.
         """
+        compile_state = next(self.parameters(), None)
+        if compile_state is None:
+            compile_state = next(self.buffers(), None)
+        if compile_state is None:
+            raise RuntimeError("MiniMax H3 has no materialized parameter or buffer to identify its compile device.")
+        compile_device = compile_state.device
+
         gate_states: list[bool] = []
         prepared_vsa_impls = 0
         for block in self.transformer_blocks:
@@ -751,7 +758,10 @@ class MiniMaxH3Transformer3DModel(BaseDiT):
                 gate_states.append(attention._gate_compress_active)
             prepare_vsa = getattr(attention.distributed_attention.attn_impl, "prepare_for_regional_compile", None)
             if callable(prepare_vsa):
-                prepare_vsa(attention.to_q.weight.device)
+                # Generic post-load quantization may replace to_q.weight with
+                # packed buffers before this hook runs. The transformer state
+                # remains materialized on the same local device.
+                prepare_vsa(compile_device)
                 prepared_vsa_impls += 1
         if gate_states:
             logger.info(

fastvideo/tests/inference/test_inference_regional_compile.py

@@ -117,13 +117,27 @@ def _gate_model(*weights: float) -> MiniMaxH3Transformer3DModel:
 
 def test_minimax_h3_prepare_for_compile_resolves_loaded_vsa_gates() -> None:
     model = _gate_model(0.0, 2.0)
+    expected_device = next(model.parameters()).device
 
     model.prepare_for_compile()
 
     assert [block.attn._gate_compress_active for block in model.transformer_blocks] == [False, True]
     for block in model.transformer_blocks:
         impl = block.attn.distributed_attention.attn_impl
-        assert impl.devices == [block.attn.to_q.weight.device]
+        assert impl.devices == [expected_device]
+
+
+def test_minimax_h3_prepare_for_compile_does_not_require_quantized_q_weight() -> None:
+    model = _gate_model(2.0)
+    attention = model.transformer_blocks[0].attn
+    removed_weight = attention.to_q._parameters.pop("weight")
+    attention.to_q.register_buffer("_fp8_weight", removed_weight.detach(), persistent=False)
+    expected_device = next(model.parameters()).device
+
+    model.prepare_for_compile()
+
+    impl = attention.distributed_attention.attn_impl
+    assert impl.devices == [expected_device]
 
 
 def test_unprepared_vsa_gate_cannot_mutate_cache_during_compile(monkeypatch) -> None: