diff --git a/desktop/src/shared/lib/channelSwitchPerf.test.mjs b/desktop/src/shared/lib/channelSwitchPerf.test.mjs
index b5a3872880..90eadea58f 100644
--- a/desktop/src/shared/lib/channelSwitchPerf.test.mjs
+++ b/desktop/src/shared/lib/channelSwitchPerf.test.mjs
@@ -471,6 +471,9 @@ test("the trace anchors at the input event, not handler dispatch", async () => {
     globalThis.window.event = { timeStamp: performance.now() - 550 };
     begin("aaaa1111aaaa1111");
     delete globalThis.window.event;
+    const startMark = performance
+      .getEntriesByName("buzz:channel-switch:start")
+      .at(-1);
     settle("aaaa1111aaaa1111");
     flush();
     const measure = performance
@@ -481,6 +484,9 @@ test("the trace anchors at the input event, not handler dispatch", async () => {
       measure.duration >= 550,
       `input delay must be inside the measure (got ${measure.duration})`,
     );
+    // The mark and the measure must share the anchor, or the Performance
+    // panel shows two different switch durations for the same switch.
+    assert.equal(startMark?.startTime, measure.startTime);
   });
 });
 
diff --git a/desktop/src/shared/lib/channelSwitchPerf.ts b/desktop/src/shared/lib/channelSwitchPerf.ts
index 9307daf19a..d970e04bb0 100644
--- a/desktop/src/shared/lib/channelSwitchPerf.ts
+++ b/desktop/src/shared/lib/channelSwitchPerf.ts
@@ -280,7 +280,13 @@ export function beginChannelSwitchTrace(channelId: string): void {
   performance.clearMarks(CHANNEL_SWITCH_START_MARK);
   performance.clearMarks(CHANNEL_SWITCH_SETTLED_MARK);
   performance.clearMeasures(CHANNEL_SWITCH_MEASURE);
-  performance.mark(CHANNEL_SWITCH_START_MARK, { detail: { channelId } });
+  // startTime keeps the mark on the same anchor as the measure — without it
+  // the Performance panel would show the measure starting before its own
+  // start mark by the input delay.
+  performance.mark(CHANNEL_SWITCH_START_MARK, {
+    detail: { channelId },
+    startTime: startedAt,
+  });
 }
 
 export function markChannelSwitchRouteCommit(channelId: string): void {