diff --git a/agentrace/cli.py b/agentrace/cli.py
index 9c7a5b9..eedb373 100644
--- a/agentrace/cli.py
+++ b/agentrace/cli.py
@@ -30,7 +30,17 @@ def _load(args) -> list[AgentRun]:
     if args.file:
         sessions = [parse_session(Path(args.file))]
     else:
-        sessions = parse_all(Path(args.dir) if args.dir else None)
+        path = Path(args.dir) if args.dir else None
+
+        if path and path.is_file():
+            console.print(
+                f"[yellow]Hint:[/] {escape(str(path))} is a file. "
+                "Use [bold]--file[/] instead of [bold]--dir[/]."
+            )
+            return []
+
+        sessions = parse_all(path)
+
     runs = [r for s in sessions for r in s.runs]
     if not runs:
         source = args.file or args.dir or "~/.claude/projects"
diff --git a/tests/test_cli.py b/tests/test_cli.py
index c346408..28b0de3 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -125,7 +125,14 @@ def test_empty_result_names_selected_directory(tmp_path):
     assert "No subagent runs found." in result.stdout
     assert f"Looked in {tmp_path}." in result.stdout
 
+def test_dir_given_file_hints_to_use_file(tmp_path):
+    transcript = tmp_path / "session.jsonl"
+    transcript.write_text("")
+    result = run_cli("--dir", str(transcript), "list")
+    assert "--file" in result.stdout
+
+
 def test_version():
     result = run_cli("--version")
     assert result.returncode == 0
-    assert "0.1.0" in result.stdout
\ No newline at end of file
+    assert "0.1.0" in result.stdout