Handle broken causal_conv1d at import time (#4047)

* Handle broken causal_conv1d import at runtime

Add a startup import-time probe for causal_conv1d and disable the fast path when the shared library is ABI broken. This keeps Falcon H1/model loading resilient without requiring env flags.

- Add disable_broken_causal_conv1d in import_fixes.
- Invoke it early from unsloth/__init__ during package init.
- Make Falcon H1 optional imports in loader and models/__init__ soft-fail instead of failing hard.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Enforce unavailable semantics for broken causal_conv1d

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Remove Falcon H1 import swallowing

* Restore optional Falcon H1 import guard

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Remove causal_conv1d regression tests

* Trim FA2 fallback messaging

---------

Co-authored-by: Daniel Hanchen <danielhanchen@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

unsloth/__init__.py

@@ -28,16 +28,19 @@ already_imported = [mod for mod in critical_modules if mod in sys.modules]
 from .import_fixes import (
     fix_message_factory_issue,
     check_fbgemm_gpu_version,
+    disable_broken_causal_conv1d,
     torchvision_compatibility_check,
     fix_diffusers_warnings,
     fix_huggingface_hub,
 )
 
+disable_broken_causal_conv1d()
 fix_message_factory_issue()
 check_fbgemm_gpu_version()
 torchvision_compatibility_check()
 fix_diffusers_warnings()
 fix_huggingface_hub()
+del disable_broken_causal_conv1d
 del fix_message_factory_issue
 del check_fbgemm_gpu_version
 del torchvision_compatibility_check

unsloth/import_fixes.py

@@ -13,6 +13,8 @@
 # limitations under the License.
 
 import os
+import importlib.abc
+import importlib.machinery
 import importlib.util
 from pathlib import Path
 from importlib.metadata import version as importlib_version
@@ -21,6 +23,7 @@ import re
 import logging
 import textwrap
 import warnings
+import sys
 
 # We cannot do from unsloth_zoo.log import logger since FBGEMM might cause seg faults.
 UNSLOTH_ENABLE_LOGGING = os.environ.get("UNSLOTH_ENABLE_LOGGING", "0") in (
@@ -1163,3 +1166,157 @@ def disable_torchcodec_if_broken():
             tf_import_utils._torchcodec_available = False
         except (ImportError, AttributeError):
             pass
+
+
+CAUSAL_CONV1D_BROKEN = False
+_CAUSAL_CONV1D_PREFIX = "causal_conv1d"
+_CAUSAL_CONV1D_BLOCKER_SENTINEL = "_unsloth_causal_conv1d_blocker"
+
+
+def _is_causal_conv1d_name(module_name: str) -> bool:
+    return module_name == _CAUSAL_CONV1D_PREFIX or module_name.startswith(
+        _CAUSAL_CONV1D_PREFIX + "."
+    )
+
+
+def _resolve_module_name(module_name, package):
+    if not isinstance(module_name, str):
+        return module_name
+    if module_name.startswith("."):
+        try:
+            return importlib.util.resolve_name(module_name, package)
+        except Exception:
+            return module_name
+    return module_name
+
+
+def _is_broken_causal_conv1d_error(error) -> bool:
+    checked = set()
+    current = error
+    while current is not None and id(current) not in checked:
+        checked.add(id(current))
+        message = str(current).lower()
+        if (
+            ("causal_conv1d_cuda" in message and "undefined symbol" in message)
+            or ("_zn3c103hip28c10_hip_check_implementation" in message)
+            or ("causal_conv1d" in message and "undefined symbol" in message)
+        ):
+            return True
+        current = getattr(current, "__cause__", None) or getattr(
+            current, "__context__", None
+        )
+    return False
+
+
+class _CausalConv1dImportBlockerLoader(importlib.abc.Loader):
+    __slots__ = ("module_name",)
+
+    def __init__(self, module_name):
+        self.module_name = module_name
+
+    def create_module(self, spec):
+        return None
+
+    def exec_module(self, module):
+        raise ModuleNotFoundError(f"No module named '{self.module_name}'")
+
+
+class _CausalConv1dImportBlockerFinder(importlib.abc.MetaPathFinder):
+    __slots__ = (_CAUSAL_CONV1D_BLOCKER_SENTINEL,)
+
+    def __init__(self):
+        setattr(self, _CAUSAL_CONV1D_BLOCKER_SENTINEL, True)
+
+    def find_spec(self, fullname, path = None, target = None):
+        if not CAUSAL_CONV1D_BROKEN or not _is_causal_conv1d_name(fullname):
+            return None
+        return importlib.machinery.ModuleSpec(
+            name = fullname,
+            loader = _CausalConv1dImportBlockerLoader(fullname),
+            is_package = fullname == _CAUSAL_CONV1D_PREFIX,
+        )
+
+
+def _patch_find_spec_for_causal_conv1d():
+    current_find_spec = importlib.util.find_spec
+    if getattr(current_find_spec, "_unsloth_causal_conv1d_find_spec_patch", False):
+        return
+
+    def _blocked_find_spec(name, package = None):
+        resolved_name = _resolve_module_name(name, package)
+        if CAUSAL_CONV1D_BROKEN and isinstance(resolved_name, str):
+            if _is_causal_conv1d_name(resolved_name):
+                return None
+        return current_find_spec(name, package)
+
+    _blocked_find_spec._unsloth_causal_conv1d_find_spec_patch = True
+    _blocked_find_spec._unsloth_original_find_spec = current_find_spec
+    importlib.util.find_spec = _blocked_find_spec
+
+
+def _install_causal_conv1d_blocker():
+    _patch_find_spec_for_causal_conv1d()
+    for finder in sys.meta_path:
+        if getattr(finder, _CAUSAL_CONV1D_BLOCKER_SENTINEL, False):
+            return
+    sys.meta_path.insert(0, _CausalConv1dImportBlockerFinder())
+
+
+def _clear_causal_conv1d_modules():
+    for module_name in list(sys.modules):
+        if _is_causal_conv1d_name(module_name):
+            sys.modules.pop(module_name, None)
+
+
+def _disable_transformers_causal_conv1d():
+    try:
+        import transformers.utils.import_utils as tf_import_utils
+    except Exception:
+        return
+
+    if hasattr(tf_import_utils, "is_causal_conv1d_available"):
+        tf_import_utils.is_causal_conv1d_available = lambda: False
+
+    for attr_name in (
+        "_causal_conv1d_available",
+        "_is_causal_conv1d_available",
+    ):
+        if hasattr(tf_import_utils, attr_name):
+            setattr(tf_import_utils, attr_name, False)
+
+
+def disable_broken_causal_conv1d():
+    """Disable causal_conv1d dynamically when its shared library is ABI-broken.
+
+    This mirrors Unsloth's FlashAttention fallback behavior: if importing causal_conv1d
+    fails with a known binary symbol error, we disable it at startup so model imports do
+    not hard-fail.
+    """
+    global CAUSAL_CONV1D_BROKEN
+    if CAUSAL_CONV1D_BROKEN:
+        _install_causal_conv1d_blocker()
+        _disable_transformers_causal_conv1d()
+        return
+
+    try:
+        if importlib.util.find_spec("causal_conv1d") is None:
+            return
+    except Exception:
+        return
+
+    try:
+        import causal_conv1d  # noqa: F401
+
+        return
+    except Exception as error:
+        if not _is_broken_causal_conv1d_error(error):
+            return
+
+    CAUSAL_CONV1D_BROKEN = True
+    _clear_causal_conv1d_modules()
+    _install_causal_conv1d_blocker()
+    _disable_transformers_causal_conv1d()
+    print(
+        "Unsloth: Detected broken causal_conv1d binary; "
+        "disabling causal_conv1d fast path and continuing import."
+    )

unsloth/models/_utils.py

@@ -845,8 +845,7 @@ if DEVICE_TYPE == "cuda":
                     "Unsloth: Your Flash Attention 2 installation seems to be broken?\n"
                     "A possible explanation is you have a new CUDA version which isn't\n"
                     "yet compatible with FA2? Please file a ticket to Unsloth or FA2.\n"
-                    "We shall now use Xformers instead, which does not have any performance hits!\n"
-                    "We found this negligible impact by benchmarking on 1x A100."
+                    "We shall now use Xformers instead, which does not have any performance hits!"
                 )
 
                 # Stop Flash Attention from importing!
@@ -897,8 +896,7 @@ elif DEVICE_TYPE == "hip":
                 "Unsloth: Your Flash Attention 2 installation seems to be broken?\n"
                 "A possible explanation is you have a new CUDA version which isn't\n"
                 "yet compatible with FA2? Please file a ticket to Unsloth or FA2.\n"
-                "We shall now use Xformers instead, which does not have any performance hits!\n"
-                "We found this negligible impact by benchmarking on 1x A100."
+                "We shall now use Xformers instead, which does not have any performance hits!"
             )
 
             # Stop Flash Attention from importing!