Fix invalid group reference in revert_checkpoint_conversion_mapping

auto_round/utils/common.py

@@ -1191,7 +1191,10 @@ def revert_checkpoint_conversion_mapping(name: str, key_mapping: dict[str, str])
             target_patterns = [target_patterns]
         for target_pattern in target_patterns:
             source_pattern = source_pattern.lstrip("^")  # strip off un-needed chars and patterns
-            source_pattern = re.sub(r"\(.*\)", "", source_pattern)
+            # Skip stripping the capture group if the target backreferences it,
+            # otherwise re.subn raises "invalid group reference".
+            if not re.search(r"\\g?<?\d+>?", target_pattern):
+                source_pattern = re.sub(r"\(.*\)", "", source_pattern)
 
             # Weight-conversion reverse mappings may expose bare tensor names
             # such as "weight" -> ".weight_packed". Treat those as terminal

test/test_cpu/utils/test_utils.py

@@ -56,6 +56,14 @@ def test_revert_checkpoint_conversion_mapping_does_not_rewrite_quantized_tensor_
     )
 
 
+def test_revert_checkpoint_conversion_mapping_handles_backreference_patterns():
+    mapping = {r"^model\.language_model\.(.+)$": r"model.\1"}
+
+    converted = revert_checkpoint_conversion_mapping("model.language_model.layers.0.self_attn.q_proj.weight", mapping)
+
+    assert converted == "model.layers.0.self_attn.q_proj.weight"
+
+
 def test_preserve_original_visual_block_name():
     # Single visual block name
     assert preserve_original_visual_block_name("model.visual.blocks", "visual.blocks") == "model.visual.blocks"