diff --git a/studio/backend/core/inference/diffusion.py b/studio/backend/core/inference/diffusion.py
index a252e39790..7c632788e4 100644
--- a/studio/backend/core/inference/diffusion.py
+++ b/studio/backend/core/inference/diffusion.py
@@ -920,6 +920,7 @@ class DiffusionBackend:
         safetensors shard headers. Returns 0 when no ``transformer/*.safetensors`` shards
         are present (an uncached base, or a .bin-only transformer); the caller then gates
         the fast path on the plain plan."""
+
         def _params(d: Path) -> int:
             tdir = d / "transformer"
             if not tdir.is_dir():
diff --git a/studio/backend/tests/test_diffusion_backend.py b/studio/backend/tests/test_diffusion_backend.py
index 57f9e5a24c..3da7b8840c 100644
--- a/studio/backend/tests/test_diffusion_backend.py
+++ b/studio/backend/tests/test_diffusion_backend.py
@@ -2005,11 +2005,16 @@ def test_dense_quant_skipped_when_dense_transformer_does_not_fit(
     monkeypatch.setattr(
         DiffusionBackend,
         "_dense_transformer_resident_bytes",
-        staticmethod(lambda base: 40 * 1024 ** 3),
+        staticmethod(lambda base: 40 * 1024**3),
     )
     orig_plan = DiffusionBackend._plan_memory
 
-    def plan_wrap(self, *a, transformer_mib_override = None, **k):
+    def plan_wrap(
+        self,
+        *a,
+        transformer_mib_override = None,
+        **k,
+    ):
         # GGUF budget fits (real plan -> none); the dense-transformer preflight does not.
         if transformer_mib_override is not None:
             return types.SimpleNamespace(offload_policy = "model")
@@ -2029,9 +2034,9 @@ def test_dense_quant_skipped_when_dense_transformer_does_not_fit(
         family_override = "z-image",
         transformer_quant = "fp8",
     )
-    assert status["transformer_quant"] is None       # dense quant skipped
-    assert status["offload_policy"] == "none"         # GGUF loaded resident, not offloaded
-    assert _FakeTransformer.last["path"]              # GGUF path used
+    assert status["transformer_quant"] is None  # dense quant skipped
+    assert status["offload_policy"] == "none"  # GGUF loaded resident, not offloaded
+    assert _FakeTransformer.last["path"]  # GGUF path used
 
 
 def test_dense_quant_prequant_skips_dense_refit(fake_runtime, tmp_path, monkeypatch):
@@ -2051,12 +2056,17 @@ def test_dense_quant_prequant_skips_dense_refit(fake_runtime, tmp_path, monkeypa
     monkeypatch.setattr(
         DiffusionBackend,
         "_dense_transformer_resident_bytes",
-        staticmethod(lambda base: 999 * 1024 ** 3),
+        staticmethod(lambda base: 999 * 1024**3),
     )
     dense_refit_ran = []
     orig_plan = DiffusionBackend._plan_memory
 
-    def spy_plan(self, *a, transformer_mib_override = None, **k):
+    def spy_plan(
+        self,
+        *a,
+        transformer_mib_override = None,
+        **k,
+    ):
         if transformer_mib_override is not None:
             dense_refit_ran.append(True)
         return orig_plan(self, *a, **k)
@@ -2076,8 +2086,8 @@ def test_dense_quant_prequant_skips_dense_refit(fake_runtime, tmp_path, monkeypa
         family_override = "z-image",
         transformer_quant = "fp8",
     )
-    assert dense_refit_ran == []   # prequant -> dense re-check skipped
-    assert attempted == [True]     # fast path still attempted (with the prequant)
+    assert dense_refit_ran == []  # prequant -> dense re-check skipped
+    assert attempted == [True]  # fast path still attempted (with the prequant)
 
 
 def test_transformer_quant_unsupported_scheme_skips_dense_download(
diff --git a/studio/backend/tests/test_diffusion_training.py b/studio/backend/tests/test_diffusion_training.py
index 9233a54def..ff0b2f12ff 100644
--- a/studio/backend/tests/test_diffusion_training.py
+++ b/studio/backend/tests/test_diffusion_training.py
@@ -583,7 +583,7 @@ def test_diffusion_dataset_upload_over_cap_preserves_existing_file(
     (folder / "existing.png").write_bytes(b"ORIGINAL")  # from an earlier upload
     files = [
         ("files", ("existing.png", b"NEW", "image/png")),  # re-upload, small
-        ("files", ("big.png", b"y" * 200, "image/png")),   # trips the cap
+        ("files", ("big.png", b"y" * 200, "image/png")),  # trips the cap
     ]
     r = client.post("/api/train/diffusion/dataset", data = {"name": "keep"}, files = files)
     assert r.status_code == 413, r.text