diff --git a/packages/react-native/ReactCommon/react/performance/timeline/PerformanceEntry.h b/packages/react-native/ReactCommon/react/performance/timeline/PerformanceEntry.h
index 1b7275352173..291bb2ace829 100644
--- a/packages/react-native/ReactCommon/react/performance/timeline/PerformanceEntry.h
+++ b/packages/react-native/ReactCommon/react/performance/timeline/PerformanceEntry.h
@@ -80,7 +80,7 @@ using PerformanceEntry = std::variant<
     PerformanceResourceTiming>;
 
 struct PerformanceEntrySorter {
-  bool operator()(const PerformanceEntry &lhs, const PerformanceEntry &rhs)
+  bool operator()(const PerformanceEntry &lhs, const PerformanceEntry &rhs) const
   {
     return std::visit(
         [](const auto &left, const auto &right) {
diff --git a/packages/react-native/ReactCommon/react/performance/timeline/tests/PerformanceEntryTest.cpp b/packages/react-native/ReactCommon/react/performance/timeline/tests/PerformanceEntryTest.cpp
new file mode 100644
index 000000000000..b6c6d7f9205d
--- /dev/null
+++ b/packages/react-native/ReactCommon/react/performance/timeline/tests/PerformanceEntryTest.cpp
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <type_traits>
+#include <vector>
+
+#include "../PerformanceEntry.h"
+
+using namespace facebook::react;
+
+// Verify that PerformanceEntrySorter::operator() is const-qualified.
+// Without const, std::stable_sort may fail to compile on toolchains where
+// the comparator is passed through a const-qualified code path (e.g.
+// libc++ __insertion_sort on NDK 19.x), causing SIGSEGV at runtime on
+// others. See T263807207.
+TEST(PerformanceEntry, SorterOperatorIsConst) {
+  static_assert(
+      std::is_invocable_v<
+          const PerformanceEntrySorter,
+          const PerformanceEntry&,
+          const PerformanceEntry&>,
+      "PerformanceEntrySorter::operator() must be const-qualified");
+}
+
+TEST(PerformanceEntry, SortEntriesByStartTimeThenDuration) {
+  auto t0 = HighResTimeStamp::now();
+  auto t1 = t0 + HighResDuration::fromMilliseconds(1);
+  auto t2 = t0 + HighResDuration::fromMilliseconds(2);
+
+  std::vector<PerformanceEntry> entries = {
+      PerformanceMark{{.name = "c", .startTime = t2}},
+      PerformanceMark{{.name = "a", .startTime = t0}},
+      PerformanceMeasure{
+          {.name = "b",
+           .startTime = t0,
+           .duration = HighResDuration::fromMilliseconds(5)}},
+      PerformanceMark{
+          {.name = "d", .startTime = t1, .duration = HighResDuration::zero()}},
+  };
+
+  std::stable_sort(entries.begin(), entries.end(), PerformanceEntrySorter{});
+
+  // Entries with same startTime are ordered by duration (ascending).
+  // "a" (t0, dur=0) < "b" (t0, dur=5) < "d" (t1, dur=0) < "c" (t2, dur=0)
+  ASSERT_EQ(4, entries.size());
+
+  auto getName = [](const PerformanceEntry& e) {
+    return std::visit([](const auto& x) { return x.name; }, e);
+  };
+
+  EXPECT_EQ("a", getName(entries[0]));
+  EXPECT_EQ("b", getName(entries[1]));
+  EXPECT_EQ("d", getName(entries[2]));
+  EXPECT_EQ("c", getName(entries[3]));
+}