diff --git a/openagent_eval/reports/base.py b/openagent_eval/reports/base.py
index 03682e4..073737e 100644
--- a/openagent_eval/reports/base.py
+++ b/openagent_eval/reports/base.py
@@ -107,8 +107,8 @@ def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
         """
         ...
 
-    def _ensure_output_dir(self, output_path: Path | str) -> Path:
-        """Ensure the output directory exists.
+    def _prepare_output_file(self, output_path: Path | str) -> Path:
+        """Ensure the parent directory exists and return the resolved file path.
 
         Args:
             output_path: Target file path.
diff --git a/openagent_eval/reports/comparison.py b/openagent_eval/reports/comparison.py
index 6ddfeea..eeaeb4b 100644
--- a/openagent_eval/reports/comparison.py
+++ b/openagent_eval/reports/comparison.py
@@ -173,7 +173,7 @@ def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
         Returns:
             Path to the written file.
         """
-        path = self._ensure_output_dir(output_path)
+        path = self._prepare_output_file(output_path)
         if not str(path).endswith(".txt"):
             path = path / "comparison.txt"
         content = self.generate(report)
diff --git a/openagent_eval/reports/html.py b/openagent_eval/reports/html.py
index 19a1f84..850e157 100644
--- a/openagent_eval/reports/html.py
+++ b/openagent_eval/reports/html.py
@@ -152,7 +152,7 @@ def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
             path = path / "report.html"
         elif path.suffix.lower() != ".html":
             path = path.with_suffix(".html")
-        path = self._ensure_output_dir(path)
+        path = self._prepare_output_file(path)
         content = self.generate(report)
         path.write_text(content, encoding="utf-8")
         return path
diff --git a/openagent_eval/reports/json_report.py b/openagent_eval/reports/json_report.py
index ce8020f..19a72f0 100644
--- a/openagent_eval/reports/json_report.py
+++ b/openagent_eval/reports/json_report.py
@@ -129,7 +129,7 @@ def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
         path = Path(output_path)
         if not str(path).endswith(".json"):
             path = path / "report.json"
-        path = self._ensure_output_dir(path)
+        path = self._prepare_output_file(path)
         content = self.generate(report)
         path.write_text(content, encoding="utf-8")
         return path
diff --git a/openagent_eval/reports/markdown.py b/openagent_eval/reports/markdown.py
index 81ee101..4f8ba35 100644
--- a/openagent_eval/reports/markdown.py
+++ b/openagent_eval/reports/markdown.py
@@ -179,7 +179,7 @@ def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
         path = Path(output_path)
         if not str(path).endswith(".md"):
             path = path / "report.md"
-        path = self._ensure_output_dir(path)
+        path = self._prepare_output_file(path)
         content = self.generate(report)
         path.write_text(content, encoding="utf-8")
         return path
diff --git a/openagent_eval/reports/terminal.py b/openagent_eval/reports/terminal.py
index 46717a9..bf9f936 100644
--- a/openagent_eval/reports/terminal.py
+++ b/openagent_eval/reports/terminal.py
@@ -107,7 +107,7 @@ def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
         Returns:
             Path to the written file.
         """
-        path = self._ensure_output_dir(output_path)
+        path = self._prepare_output_file(output_path)
         content = self.generate(report)
         path.write_text(content, encoding="utf-8")
         return path
diff --git a/tests/unit/test_reports/test_base.py b/tests/unit/test_reports/test_base.py
index 6d3d68a..94299ab 100644
--- a/tests/unit/test_reports/test_base.py
+++ b/tests/unit/test_reports/test_base.py
@@ -118,19 +118,19 @@ def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
         result = report_gen.generate(evaluation_report)
         assert result == "test report"
 
-    def test_ensure_output_dir(self, tmp_path: Path) -> None:
-        """_ensure_output_dir creates parent directories."""
+    def test_prepare_output_file(self, tmp_path: Path) -> None:
+        """_prepare_output_file creates parent directories."""
 
         class ConcreteReport(ReportGenerator):
             def generate(self, report: Any) -> str:
                 return ""
 
             def generate_to_file(self, report: Any, output_path: Path | str) -> Path:
-                return self._ensure_output_dir(output_path)
+                return self._prepare_output_file(output_path)
 
         report_gen = ConcreteReport()
         target = tmp_path / "subdir" / "report.txt"
-        result = report_gen._ensure_output_dir(target)
+        result = report_gen._prepare_output_file(target)
         assert result.parent.exists()
 
     def test_extract_metric_averages(self, pipeline_result_with_data: Any) -> None: