diff --git a/tests/trace/test_iterators.py b/tests/trace/test_iterators.py
new file mode 100644
index 000000000000..b70246b418e4
--- /dev/null
+++ b/tests/trace/test_iterators.py
@@ -0,0 +1,142 @@
+import threading
+
+import pytest
+
+from weave.utils.iterators import ThreadSafeInMemoryIteratorAsSequence
+
+
+def test_basic_sequence_operations():
+    # Test basic sequence operations
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(range(10)))
+    assert len(iterator) == 10
+    assert iterator[0] == 0
+    assert iterator[1:3] == [1, 2]
+    assert list(iterator) == list(range(10))
+
+
+def test_empty_iterator():
+    # Test behavior with empty iterator
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter([]))
+    assert len(iterator) == 0
+    with pytest.raises(IndexError):
+        _ = iterator[0]
+    assert list(iterator) == []
+
+
+def test_known_length():
+    # Test initialization with known length
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(range(5)), known_length=5)
+    assert len(iterator) == 5  # Should not need to exhaust iterator
+    assert iterator[4] == 4  # Access last element
+
+
+def test_multiple_iterations():
+    # Test multiple iterations return same results
+    data = list(range(5))
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(data))
+
+    assert list(iterator) == data  # First iteration
+    assert list(iterator) == data  # Second iteration
+    assert list(iterator) == data  # Third iteration
+
+
+def test_concurrent_access():
+    # Test thread-safe concurrent access
+    data = list(range(1000))
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(data))
+    results = []
+
+    def reader_thread():
+        results.append(list(iterator))
+
+    threads = [threading.Thread(target=reader_thread) for _ in range(5)]
+    for t in threads:
+        t.start()
+    for t in threads:
+        t.join()
+
+    # All threads should see the same data
+    assert all(r == data for r in results)
+
+
+def test_slicing():
+    # Test various slicing operations
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(range(10)))
+
+    assert iterator[2:5] == [2, 3, 4]
+    assert iterator[:3] == [0, 1, 2]
+    assert iterator[7:] == [7, 8, 9]
+    assert iterator[::2] == [0, 2, 4, 6, 8]
+    assert iterator[::-1] == [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
+
+
+def test_random_access():
+    # Test random access patterns
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(range(10)))
+
+    assert iterator[5] == 5  # Middle access
+    assert iterator[1] == 1  # Earlier access
+    assert iterator[8] == 8  # Later access
+    assert iterator[0] == 0  # First element
+    assert iterator[9] == 9  # Last element
+
+
+def test_concurrent_mixed_operations():
+    # Test concurrent mixed operations (reads, slices, iterations)
+    data = list(range(100))
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(data))
+    results = []
+
+    def mixed_ops_thread():
+        local_results = []
+        local_results.append(iterator[10])  # Single element access
+        local_results.append(list(iterator[20:25]))  # Slice access
+        local_results.append(iterator[50])  # Another single element
+        local_results.extend(iterator[90:])  # End slice
+        results.append(local_results)
+
+    threads = [threading.Thread(target=mixed_ops_thread) for _ in range(3)]
+    for t in threads:
+        t.start()
+    for t in threads:
+        t.join()
+
+    # Verify all threads got the same results
+    expected = [10, list(range(20, 25)), 50, list(range(90, 100))]
+    assert all(r == expected for r in results)
+
+
+def test_index_out_of_range():
+    # Test index out of range behavior
+    iterator = ThreadSafeInMemoryIteratorAsSequence(iter(range(5)))
+
+    with pytest.raises(IndexError):
+        _ = iterator[10]
+
+    assert iterator[-1] == 4  # Negative indices are supported
+
+
+def test_iterator_exhaustion():
+    # Test behavior when iterator is exhausted
+    class CountingIterator:
+        def __init__(self):
+            self.count = 0
+
+        def __iter__(self):
+            return self
+
+        def __next__(self):
+            if self.count < 5:
+                self.count += 1
+                return self.count - 1
+            raise StopIteration
+
+    iterator = ThreadSafeInMemoryIteratorAsSequence(CountingIterator())
+
+    # Access beyond iterator length should raise IndexError
+    assert len(iterator) == 5
+    with pytest.raises(IndexError):
+        _ = iterator[10]
+
+    # Verify original data is still accessible
+    assert list(iterator) == [0, 1, 2, 3, 4]
diff --git a/weave/utils/iterators.py b/weave/utils/iterators.py
index 3938f2a84a9b..5e52e8534fed 100644
--- a/weave/utils/iterators.py
+++ b/weave/utils/iterators.py
@@ -78,7 +78,10 @@ def __getitem__(self, index: int | slice) -> T | Sequence[T]:
             IndexError: If the index is out of range.
         """
         if isinstance(index, slice):
-            self._seek_to_index(index.stop)
+            if index.stop is None:
+                self._seek_to_end()
+            else:
+                self._seek_to_index(index.stop)
             return self._list[index]
         else:
             self._seek_to_index(index)