diff --git a/strix/report/state.py b/strix/report/state.py
index 1eff2850..6f111178 100644
--- a/strix/report/state.py
+++ b/strix/report/state.py
@@ -351,6 +351,15 @@ class ReportState:
             for key in ("requests", "input_tokens", "output_tokens", "total_tokens", "cost")
         }
 
+    def get_process_duration_seconds(self) -> float:
+        """Return this process's elapsed wall time for telemetry."""
+        try:
+            start = datetime.fromisoformat(self.process_start_time.replace("Z", "+00:00"))
+            duration = (datetime.now(start.tzinfo) - start).total_seconds()
+            return max(0.0, duration)
+        except (ValueError, TypeError, AttributeError):
+            return 0.0
+
     def get_total_llm_cost(self) -> float:
         """Live accumulated LLM cost, independent of the persisted run-record snapshot."""
         return self._llm_usage.total_cost
diff --git a/strix/telemetry/posthog.py b/strix/telemetry/posthog.py
index fa89fd0b..756f163c 100644
--- a/strix/telemetry/posthog.py
+++ b/strix/telemetry/posthog.py
@@ -1,5 +1,4 @@
 import logging
-from datetime import datetime
 from typing import TYPE_CHECKING, Any
 
 import requests
@@ -105,13 +104,7 @@ def end(report_state: "ReportState", exit_reason: str = "completed") -> None:
         if sev in vulnerabilities_counts:
             vulnerabilities_counts[sev] += 1
 
-    duration = 0.0
-    try:
-        start = datetime.fromisoformat(report_state.process_start_time.replace("Z", "+00:00"))
-        end_iso = report_state.end_time or datetime.now(start.tzinfo).isoformat()
-        duration = (datetime.fromisoformat(end_iso.replace("Z", "+00:00")) - start).total_seconds()
-    except (ValueError, TypeError, AttributeError):
-        pass
+    duration = report_state.get_process_duration_seconds()
 
     llm_props: dict[str, int | float] = {}
     try:
diff --git a/strix/telemetry/scarf.py b/strix/telemetry/scarf.py
index 495c0f65..22767424 100644
--- a/strix/telemetry/scarf.py
+++ b/strix/telemetry/scarf.py
@@ -2,7 +2,6 @@ from __future__ import annotations
 
 import logging
 import urllib.parse
-from datetime import datetime
 from typing import TYPE_CHECKING, Any
 
 import requests
@@ -114,15 +113,7 @@ def end(report_state: ReportState, exit_reason: str = "completed") -> None:
         if sev in vulnerabilities_counts:
             vulnerabilities_counts[sev] += 1
 
-    duration = 0.0
-    try:
-        scan_start = datetime.fromisoformat(report_state.process_start_time.replace("Z", "+00:00"))
-        end_iso = report_state.end_time or datetime.now(scan_start.tzinfo).isoformat()
-        duration = (
-            datetime.fromisoformat(end_iso.replace("Z", "+00:00")) - scan_start
-        ).total_seconds()
-    except (ValueError, TypeError, AttributeError):
-        pass
+    duration = report_state.get_process_duration_seconds()
 
     llm_props: dict[str, int | float] = {}
     try:
diff --git a/tests/test_telemetry_resume.py b/tests/test_telemetry_resume.py
index 60804bc7..9a0f92fd 100644
--- a/tests/test_telemetry_resume.py
+++ b/tests/test_telemetry_resume.py
@@ -40,6 +40,8 @@ def test_scan_ended_reports_resumed_usage_delta(
         model="unknown",
     )
     initial.record_observed_llm_cost(1.25)
+    initial.end_time = (datetime.now(UTC) - timedelta(hours=1)).isoformat()
+    initial.run_record["end_time"] = initial.end_time
     initial.save_run_data()
 
     resumed = ReportState(run_name="resumed")
@@ -50,7 +52,6 @@ def test_scan_ended_reports_resumed_usage_delta(
         model="unknown",
     )
     resumed.record_observed_llm_cost(0.75)
-    resumed.end_time = (datetime.now(UTC) + timedelta(seconds=2)).isoformat()
 
     sent: list[dict[str, Any]] = []
     monkeypatch.setattr(telemetry, "_send", lambda _event, props: _capture(sent, props))
@@ -61,7 +62,7 @@ def test_scan_ended_reports_resumed_usage_delta(
     assert sent[0]["llm_output_tokens"] == 50
     assert sent[0]["llm_tokens"] == 350
     assert sent[0]["llm_cost"] == pytest.approx(0.75)
-    assert sent[0]["duration_seconds"] <= 2
+    assert 0 <= sent[0]["duration_seconds"] <= 2
 
 
 @pytest.mark.parametrize("telemetry", [posthog, scarf])