From 565437fec566c88ce78a9ca37724edc2556dbb39 Mon Sep 17 00:00:00 2001
From: Saturday-boyi <2174084306@qq.com>
Date: Mon, 7 Sep 2026 13:25:34 +0800
Subject: [PATCH] Fix negative durations from clock-skewed transcripts

---
 agentrace/parse.py |  3 ++-
 tests/test_cli.py  | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/agentrace/parse.py b/agentrace/parse.py
index 582f399..162e1ab 100644
--- a/agentrace/parse.py
+++ b/agentrace/parse.py
@@ -39,7 +39,8 @@ class AgentRun:
     @property
     def duration_s(self) -> float | None:
         if self.started_at and self.ended_at:
-            return (self.ended_at - self.started_at).total_seconds()
+            duration = (self.ended_at - self.started_at).total_seconds()
+            return duration if duration >= 0 else None
         return None
 
     @property
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 1489d5c..ba17ee4 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -56,6 +56,27 @@ def test_stats_median(durations, expected, monkeypatch, capsys):
         assert " ".join(median_rows[0].split()) == f"median run {expected}"
 
 
+def test_stats_excludes_clock_skewed_duration(monkeypatch, capsys):
+    start = datetime(2026, 1, 1, tzinfo=UTC)
+    runs = [
+        AgentRun(
+            tool_use_id=str(i),
+            description="test",
+            prompt="prompt",
+            result="result",
+            started_at=start,
+            ended_at=start + timedelta(seconds=duration),
+        )
+        for i, duration in enumerate([-5, 10, 20])
+    ]
+    monkeypatch.setattr(cli, "_load", lambda args: runs)
+    assert cli.cmd_stats(Namespace(json=True)) == 0
+    output = capsys.readouterr().out
+    assert '"total_seconds": 30.0' in output
+    assert "median run 15 s" in " ".join(output.split())
+    assert runs[0].duration_s is None
+
+
 def test_file_and_dir_are_mutually_exclusive(tmp_path):
     transcript = tmp_path / "session.jsonl"
     transcript.write_text("")