diff --git a/src/kb/cli.py b/src/kb/cli.py
index 4816c5f..a70b50e 100644
--- a/src/kb/cli.py
+++ b/src/kb/cli.py
@@ -1904,6 +1904,13 @@ def correct(
     except ValueError as e:
         click.echo(f"Error: {e}", err=True)
         raise SystemExit(1) from None
+    except OSError as e:
+        # Batch write failed mid-apply; apply_corrections rolled the files back (#1 COW).
+        click.echo(
+            f"Error: correction failed and was rolled back — no files were changed ({e}).",
+            err=True,
+        )
+        raise SystemExit(1) from None
     finally:
         kb.close()
 
diff --git a/tests/test_correct.py b/tests/test_correct.py
index d160c0d..a4d7dad 100644
--- a/tests/test_correct.py
+++ b/tests/test_correct.py
@@ -369,6 +369,20 @@ def _invoke(self, runner: CliRunner, memory_tree: Path, args: list[str]):
         with patch("kb.cli._find_project_root", return_value=project_root):
             return runner.invoke(cli, ["correct", *args], catch_exceptions=False)
 
+    def test_apply_rollback_shows_graceful_error(
+        self, cli_runner: CliRunner, memory_tree: Path, monkeypatch
+    ):
+        """A rolled-back batch (OSError from apply) surfaces a clean message, not a traceback (#1)."""
+        from kb.api import KnowledgeBase
+
+        def boom(self, *a, **k):  # type: ignore[no-untyped-def]
+            raise OSError("disk full (simulated)")
+
+        monkeypatch.setattr(KnowledgeBase, "correct_term", boom)
+        result = self._invoke(cli_runner, memory_tree, ["Quartz Indexer", "Datalux", "--apply"])
+        assert result.exit_code == 1
+        assert "rolled back" in result.output.lower()
+
     def test_scan_json_output(self, cli_runner: CliRunner, memory_tree: Path):
         """kbx correct TERM --json returns structured scan output."""
         result = self._invoke(cli_runner, memory_tree, ["Quartz Indexer", "--json"])