diff --git a/lib/maptool/livetrack_client.rb b/lib/maptool/livetrack_client.rb
index 9f1b494..a28b944 100644
--- a/lib/maptool/livetrack_client.rb
+++ b/lib/maptool/livetrack_client.rb
@@ -1,5 +1,6 @@
 require "net/http"
 require "json"
+require "time"
 
 module Maptool
   # Fetches a Garmin LiveTrack session's track and metadata.
@@ -44,10 +45,22 @@ module Maptool
     # totals are cumulative for the whole session), name/type from the
     # session details — nil-safe throughout since either can be missing.
     #
-    # "active": Garmin doesn't set a session's `end` until the activity is
-    # actually stopped, so its absence means the session is still recording
-    # — inferred from the one (already-ended) session this was built
-    # against, not verified against a session actually caught mid-activity.
+    # "active": originally `session["end"].nil?`, on the assumption Garmin
+    # doesn't set `end` until the activity actually stops — disproven
+    # against a real still-recording session (2026-09-20): `end` was
+    # already non-nil, set to exactly `start + 24h`, the share link's own
+    # expiry, not an actual end time (a genuinely ended session's `end`
+    # instead reflects its real end — ~2h after start for the 2026-09-06
+    # session this was originally, and only, verified against). Recency of
+    # the last track point is a directly-observable signal instead of
+    # trying to reverse-engineer what a given `end` value means: Garmin
+    # posts one roughly every `postTrackPointFrequency` seconds (~15,
+    # observed) while genuinely still recording, so a point older than
+    # ACTIVE_WITHIN means the activity has actually stopped (or, at worst,
+    # lost signal for a while — same "looks ended until it isn't" behavior
+    # Garmin's own LiveTrack page shows in that case).
+    ACTIVE_WITHIN = 30 * 60 # seconds
+
     def self.summarize(result)
       last = result.points.last || {}
       session = result.session || {}
@@ -56,12 +69,20 @@ module Maptool
         "activity_type" => last["activityType"],
         "distance_meters" => last["totalDistanceMeters"],
         "duration_secs" => last["totalDurationSecs"],
-        "active" => session["end"].nil?,
+        "active" => active?(last["dateTime"]),
         "start" => session["start"],
         "end" => session["end"],
       }
     end
 
+    def self.active?(last_point_time)
+      return false unless last_point_time
+
+      Time.parse(last_point_time) > Time.now.utc - ACTIVE_WITHIN
+    rescue ArgumentError, TypeError
+      false
+    end
+
     private
 
     # The RSC payload serializes an absent field as the literal string
diff --git a/test/test_livetrack_client.rb b/test/test_livetrack_client.rb
index d699241..8c6ffa2 100644
--- a/test/test_livetrack_client.rb
+++ b/test/test_livetrack_client.rb
@@ -49,13 +49,22 @@ class LiveTrackClientTest < Minitest::Test
     assert_equal "Test Ride", summary["session_name"]
     assert_equal "CYCLING", summary["activity_type"]
     assert_equal 5000, summary["distance_meters"]
-    refute summary["active"], "session has an end timestamp"
+    refute summary["active"], "last track point is long in the past"
   end
 
-  def test_summarize_marks_active_when_session_has_no_end
+  # Not session["end"].nil? (the original signal, before 2026-09-20 — see
+  # LiveTrackClient's own comment): verified live against a real,
+  # still-recording session that day, Garmin had already set `end` to
+  # exactly start + 24h (the share link's own expiry, not an end time),
+  # so that check called an active session "ended".
+  def test_summarize_marks_active_when_last_point_is_recent
     payloads = @client.send(:parse_payloads, FAKE_PAGE)
     points = @client.send(:clean, @client.send(:search, payloads) { |n| n["trackPoints"] if n["trackPoints"].is_a?(Array) })
-    session = @client.send(:clean, @client.send(:search, payloads) { |n| n if n["sessionName"] }).merge("end" => nil)
+    points[-1] = points[-1].merge("dateTime" => Time.now.utc.iso8601)
+    # end present and in the future, same shape Garmin actually sends for a
+    # session that's still live — active must come from the point, not this.
+    session = @client.send(:clean, @client.send(:search, payloads) { |n| n if n["sessionName"] })
+                      .merge("end" => (Time.now.utc + 24 * 60 * 60).iso8601)
     result = Maptool::LiveTrackClient::Result.new(points: points, session: session)
 
     assert Maptool::LiveTrackClient.summarize(result)["active"]