Fix broken wandb import crashing unsloth startup (#4147)

* Fix broken wandb import crashing unsloth startup

When wandb is installed but broken (e.g., wandb < 0.19.11 with
protobuf >= 6.0), the import chain unsloth -> trl -> transformers ->
is_wandb_available() -> import wandb crashes with:

  ImportError: cannot import name 'Imports' from
  'wandb.proto.wandb_telemetry_pb2'

This happens because transformers' is_wandb_available() has no
try/except around `import wandb`. The error propagates up and kills
`from unsloth import FastLanguageModel` even though wandb is optional.

Add disable_broken_wandb() following the same pattern as
disable_torchcodec_if_broken(). It proactively tries importing wandb
during early init, and if the import fails, patches
is_wandb_available() to return False and sets WANDB_DISABLED=true.

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

for more information, see https://pre-commit.ci

---------

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

unsloth/__init__.py

@@ -151,6 +151,7 @@ from .import_fixes import (
     patch_vllm_for_notebooks,
     patch_torchcodec_audio_decoder,
     disable_torchcodec_if_broken,
+    disable_broken_wandb,
 )
 
 fix_xformers_performance_issue()
@@ -172,6 +173,7 @@ fix_executorch()
 patch_vllm_for_notebooks()
 patch_torchcodec_audio_decoder()
 disable_torchcodec_if_broken()
+disable_broken_wandb()
 
 del fix_xformers_performance_issue
 del fix_vllm_aimv2_issue
@@ -191,6 +193,7 @@ del fix_executorch
 del patch_vllm_for_notebooks
 del patch_torchcodec_audio_decoder
 del disable_torchcodec_if_broken
+del disable_broken_wandb
 
 # Torch 2.4 has including_emulation
 if DEVICE_TYPE == "cuda":

unsloth/import_fixes.py

@@ -1290,6 +1290,38 @@ def disable_torchcodec_if_broken():
             pass
 
 
+def disable_broken_wandb():
+    """Disable wandb if it's installed but cannot actually import.
+
+    wandb can fail to import when there's a protobuf version mismatch
+    (e.g., wandb < 0.19.11 with protobuf >= 6.0). This causes a cascading
+    import failure through trl -> transformers -> wandb that crashes
+    unsloth's import chain.
+
+    This function tests if wandb can actually import and if not, patches
+    transformers' is_wandb_available() to return False.
+    """
+    if importlib.util.find_spec("wandb") is None:
+        return  # wandb not installed, nothing to do
+
+    try:
+        import wandb
+    except Exception:
+        # wandb is installed but broken - patch transformers to skip it
+        logger.info(
+            "Unsloth: wandb is installed but broken (likely a protobuf version mismatch). "
+            "Disabling wandb to prevent import errors. To fix, run: pip install --upgrade wandb"
+        )
+        try:
+            import transformers.integrations.integration_utils as tf_integration
+
+            tf_integration.is_wandb_available = lambda: False
+        except (ImportError, AttributeError):
+            pass
+        # Also set env var as fallback for any other code path
+        os.environ["WANDB_DISABLED"] = "true"
+
+
 CAUSAL_CONV1D_BROKEN = False
 _CAUSAL_CONV1D_PREFIX = "causal_conv1d"
 _CAUSAL_CONV1D_BLOCKER_SENTINEL = "_unsloth_causal_conv1d_blocker"