diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9c8e01ccf..ed920d58a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -563,6 +563,10 @@
 
 - Dense finite-difference `observed_information` preflights package-owned objective-call and fixed-width workspace budgets before the first objective evaluation and replaces the dense identity workspace with a reusable trial vector.
 
+#### Rubric hostile iterable error redaction
+
+- Rubric collection materialization fails closed on hostile iterable setup and iteration exceptions with package-owned messages, while preserving `MemoryError` resource signals.
+
 #### Model-comparison hostile input redaction
 
 - Model-comparison parameter counts and casewise iterables redact hostile conversion and iteration callback failures into stable package-owned `ValueError` messages while preserving `MemoryError`.
diff --git a/docs/changelog.d/783-rubric-iterable-error-boundary.md b/docs/changelog.d/783-rubric-iterable-error-boundary.md
new file mode 100644
index 000000000..cd5079039
--- /dev/null
+++ b/docs/changelog.d/783-rubric-iterable-error-boundary.md
@@ -0,0 +1,5 @@
+# Rubric hostile iterable error redaction
+
+## Fixed
+
+- Rubric collection materialization fails closed on hostile iterable setup and iteration exceptions with package-owned messages, while preserving `MemoryError` resource signals.
diff --git a/python/fast_mlsirm/rubric/models.py b/python/fast_mlsirm/rubric/models.py
index 225aa0522..ca2b5112b 100644
--- a/python/fast_mlsirm/rubric/models.py
+++ b/python/fast_mlsirm/rubric/models.py
@@ -89,10 +89,20 @@ def _bounded_values(
         raise ValueError(f"{name} must be a collection")
     try:
         iterator = iter(values)
-    except TypeError as exc:
-        raise ValueError(f"{name} must be a collection") from exc
+    except MemoryError:
+        raise
+    except Exception:
+        raise ValueError(f"{name} must be a collection") from None
     materialized: list[Any] = []
-    for index, value in enumerate(iterator):
+    for index in range(maximum + 1):
+        try:
+            value = next(iterator)
+        except StopIteration:
+            break
+        except MemoryError:
+            raise
+        except Exception:
+            raise ValueError(f"{name} iteration failed") from None
         if index >= maximum:
             raise ValueError(f"{name} must contain at most {maximum} values")
         materialized.append(value)
diff --git a/tests/test_rubric_iterable_error_boundary.py b/tests/test_rubric_iterable_error_boundary.py
new file mode 100644
index 000000000..1818ac5e3
--- /dev/null
+++ b/tests/test_rubric_iterable_error_boundary.py
@@ -0,0 +1,100 @@
+"""Regression tests for fail-closed rubric iterable boundaries."""
+
+from __future__ import annotations
+
+import pytest
+
+from fast_mlsirm.rubric import ResponseFormat, RubricLevel, RubricSpecification
+
+
+class _ExplodingIterable:
+    """Yield a valid prefix before raising a caller-controlled runtime error."""
+
+    def __init__(self, values: tuple[object, ...]) -> None:
+        """Store the bounded prefix used before the hostile iterator failure."""
+        self._values = values
+
+    def __iter__(self):
+        """Yield valid values and then raise an error containing source-like text."""
+        yield from self._values
+        raise RuntimeError("sensitive_source_text_should_not_escape")
+
+
+class _ExplodingIteratorFactory:
+    """Raise a caller-controlled runtime error while creating an iterator."""
+
+    def __iter__(self):
+        """Fail before iteration begins so setup errors are covered separately."""
+        raise RuntimeError("sensitive_iterator_factory_text_should_not_escape")
+
+
+class _MemoryErrorIteratorFactory:
+    """Raise a memory exhaustion signal while creating an iterator."""
+
+    def __iter__(self):
+        """Preserve process-level memory exhaustion instead of redacting it."""
+        raise MemoryError("iterator allocation failed")
+
+
+class _MemoryErrorDuringIteration:
+    """Raise a memory exhaustion signal after one valid yielded level."""
+
+    def __iter__(self):
+        """Yield one value before preserving a subsequent memory failure."""
+        yield _level(0)
+        raise MemoryError("iterator advance allocation failed")
+
+
+def _level(score: int) -> RubricLevel:
+    """Return one minimal valid rubric level."""
+    return RubricLevel(
+        score=score,
+        label=f"Level {score}",
+        descriptor=f"Observed performance at score {score}.",
+        observable_indicators=(f"indicator {score}",),
+    )
+
+
+def _rubric_with_levels(levels: object) -> RubricSpecification:
+    """Construct one minimal rubric using a caller-controlled levels object."""
+    return RubricSpecification(
+        rubric_id="writing_rubric",
+        construct_id="argument_quality",
+        construct_definition="Quality of evidence-grounded argumentation.",
+        response_format=ResponseFormat.CONSTRUCTED_RESPONSE,
+        levels=levels,  # type: ignore[arg-type]
+        task_families=("essay_task",),
+        evidence_requirements=("Cites relevant evidence.",),
+    )
+
+
+def test_rubric_levels_iterator_failure_is_redacted_value_error() -> None:
+    """Caller iterator exceptions must not cross the public rubric boundary raw."""
+    hostile_levels = _ExplodingIterable((_level(0), _level(1)))
+
+    with pytest.raises(ValueError) as caught:
+        _rubric_with_levels(hostile_levels)
+
+    assert "levels" in str(caught.value)
+    assert "sensitive_source_text_should_not_escape" not in str(caught.value)
+
+
+def test_rubric_levels_iterator_factory_failure_is_redacted_value_error() -> None:
+    """Iterator-construction failures must be package-owned and non-reflective."""
+    with pytest.raises(ValueError) as caught:
+        _rubric_with_levels(_ExplodingIteratorFactory())
+
+    assert "levels" in str(caught.value)
+    assert "sensitive_iterator_factory_text_should_not_escape" not in str(caught.value)
+
+
+def test_rubric_levels_iterator_factory_memory_error_is_preserved() -> None:
+    """Memory exhaustion during iterator construction must remain distinguishable."""
+    with pytest.raises(MemoryError, match="iterator allocation failed"):
+        _rubric_with_levels(_MemoryErrorIteratorFactory())
+
+
+def test_rubric_levels_iteration_memory_error_is_preserved() -> None:
+    """Memory exhaustion while advancing an iterator must remain distinguishable."""
+    with pytest.raises(MemoryError, match="iterator advance allocation failed"):
+        _rubric_with_levels(_MemoryErrorDuringIteration())