diff --git a/gitm/importers/_common.py b/gitm/importers/_common.py
index 996f5d1..07882ea 100644
--- a/gitm/importers/_common.py
+++ b/gitm/importers/_common.py
@@ -3,11 +3,11 @@
 from __future__ import annotations
 
 import os
+import sys
 import tempfile
 import warnings
 from collections.abc import Iterable
 from dataclasses import dataclass, field
-import sys
 from pathlib import Path
 from typing import Any
 
diff --git a/gitm/importers/analyze.py b/gitm/importers/analyze.py
index 84a02ee..178799f 100644
--- a/gitm/importers/analyze.py
+++ b/gitm/importers/analyze.py
@@ -18,7 +18,7 @@
 from gitm.optimizer.qualification import QualificationResult, qualify
 from gitm.planner.context import peak_for_sku
 from gitm.tracer.capture import write_trace_jsonl
-from gitm.tracer.schema import KernelEvent, Trace
+from gitm.tracer.schema import Trace
 
 # Default catalogue peak when SKU is unknown (A100 PCIe figures; called out in caveats).
 _DEFAULT_PEAK = HardwarePeak(name="A100", peak_flops=312e12, peak_bw_bytes_s=1555e9)
diff --git a/gitm/importers/node_rollup.py b/gitm/importers/node_rollup.py
index d433d07..c30bfd4 100644
--- a/gitm/importers/node_rollup.py
+++ b/gitm/importers/node_rollup.py
@@ -11,7 +11,7 @@
 from typing import Any
 
 from gitm.optimizer.metrics import _merge_intervals
-from gitm.tracer.schema import KernelEvent, Trace
+from gitm.tracer.schema import Trace
 
 # Collective kernel name patterns (case-insensitive). One module-level table;
 # each entry is a substring match against the demangled/exported kernel name.
diff --git a/gitm/importers/nsys.py b/gitm/importers/nsys.py
index 68035bd..27a1af7 100644
--- a/gitm/importers/nsys.py
+++ b/gitm/importers/nsys.py
@@ -17,11 +17,8 @@
     ImportError,
     ImportStats,
     as_int,
-    device_count_from_events,
     file_mtime_ns,
-    filter_device,
     finish_trace,
-    per_device_kernel_counts,
 )
 from gitm.tracer.schema import KernelEvent, MemcpyEvent, SyncEvent, Trace, TraceEvent
 
diff --git a/gitm/importers/torch_trace.py b/gitm/importers/torch_trace.py
index c2c8be4..ff16f3a 100644
--- a/gitm/importers/torch_trace.py
+++ b/gitm/importers/torch_trace.py
@@ -24,7 +24,7 @@
     finish_trace,
     per_device_kernel_counts,
 )
-from gitm.tracer.schema import KernelEvent, MemcpyEvent, Trace, TraceEvent
+from gitm.tracer.schema import MemcpyEvent, Trace, TraceEvent
 
 # Max decompressed size for .json.gz (customer dumps can be multi-GB).
 DEFAULT_MAX_DECOMPRESSED_BYTES = 20 * 1024 ** 3  # 20 GiB
@@ -91,7 +91,7 @@ def _arg_get(args: dict[str, Any] | None, keys: tuple[str, ...]) -> Any:
 def _as_dims(val: Any) -> tuple[int, int, int]:
     if val is None:
         return (1, 1, 1)
-    if isinstance(val, (list, tuple)) and len(val) >= 1:
+    if isinstance(val, (list | tuple)) and len(val) >= 1:
         x = as_int(val[0], 1) if len(val) > 0 else 1
         y = as_int(val[1], 1) if len(val) > 1 else 1
         z = as_int(val[2], 1) if len(val) > 2 else 1
diff --git a/gitm/optimizer/metrics.py b/gitm/optimizer/metrics.py
index 47a0968..8d93542 100644
--- a/gitm/optimizer/metrics.py
+++ b/gitm/optimizer/metrics.py
@@ -26,7 +26,7 @@
 from collections.abc import Callable, Iterable
 from dataclasses import dataclass
 
-from gitm.tracer.schema import KernelEvent, MemcpyEvent, SyncEvent, Trace
+from gitm.tracer.schema import KernelEvent, Trace
 
 FlopsModel = Callable[[KernelEvent], float]
 
diff --git a/pyproject.toml b/pyproject.toml
index 230b098..40bb220 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,6 +55,7 @@ s3 = ["boto3>=1.34"]
 dev = [
     "pytest>=8.0",
     "pytest-cov>=4.1",
+    "hypothesis>=6.0",  # property-based fuzzing for the importers (tests/test_importers_hypothesis.py, _fuzz.py)
     "ruff>=0.4",
     "mypy>=1.10",
     "build>=1.0",  # `python -m build` for the wheel-build verification check
diff --git a/tests/test_importers_hypothesis.py b/tests/test_importers_hypothesis.py
index 7a343fb..3237c42 100644
--- a/tests/test_importers_hypothesis.py
+++ b/tests/test_importers_hypothesis.py
@@ -41,7 +41,7 @@ def test_prop_us_to_ns_monotonic(ts: float, dur: float):
         }
     )
     # Default import path uses LightKernel for scale; --strict uses KernelEvent.
-    assert isinstance(ev, (KernelEvent, LightKernel))
+    assert isinstance(ev, (KernelEvent | LightKernel))
     assert ev.start_ns == int(ts * 1000.0)
     assert ev.end_ns == int((ts + dur) * 1000.0)
     assert ev.end_ns >= ev.start_ns or dur == 0.0
@@ -74,7 +74,7 @@ def test_prop_missing_args_never_crash(cat, name, has_grid, has_stream, has_devi
     )
     # May be None for weird name/cat combos; must not raise.
     if ev is not None:
-        assert isinstance(ev, (KernelEvent, MemcpyEvent, LightKernel, LightMemcpy))
+        assert isinstance(ev, (KernelEvent | MemcpyEvent | LightKernel | LightMemcpy))
         assert getattr(ev, "kind", None) in ("kernel", "memcpy")
         assert ev.end_ns >= ev.start_ns
         # Light events are not pydantic; only validate the full Trace path