From 8f14f0c1562b6dc887f2d4df54460d32ed7e6b0a Mon Sep 17 00:00:00 2001
From: maurycy <5383+maurycy@users.noreply.github.com>
Date: Sun, 27 Sep 2026 16:53:13 +0200
Subject: [PATCH 1/3] banal fix

---
 Modules/_remote_debugging/binary_io_writer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Modules/_remote_debugging/binary_io_writer.c b/Modules/_remote_debugging/binary_io_writer.c
index 6af81515e7131d1..bd9175701dcbded 100644
--- a/Modules/_remote_debugging/binary_io_writer.c
+++ b/Modules/_remote_debugging/binary_io_writer.c
@@ -950,7 +950,6 @@ process_thread_sample(BinaryWriter *writer, PyObject *thread_info,
 
     /* Calculate timestamp delta */
     uint64_t delta = timestamp_us - entry->prev_timestamp;
-    entry->prev_timestamp = timestamp_us;
 
     /* Process frames and build current stack */
     uint32_t curr_stack[MAX_STACK_DEPTH];
@@ -1006,6 +1005,7 @@ process_thread_sample(BinaryWriter *writer, PyObject *thread_info,
         entry->prev_stack_depth = curr_depth;
     }
 
+    entry->prev_timestamp = timestamp_us;
     writer->total_samples++;
     return 0;
 }

From e867c1d398ccb9a98ddbd532716625e36b3dfc3f Mon Sep 17 00:00:00 2001
From: maurycy <5383+maurycy@users.noreply.github.com>
Date: Sun, 27 Sep 2026 16:57:29 +0200
Subject: [PATCH 2/3] test

---
 .../test_binary_format.py                     | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py b/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
index ff944b3163ec3e8..92cf8c01351f031 100644
--- a/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
+++ b/Lib/test/test_profiling/test_sampling_profiler/test_binary_format.py
@@ -952,6 +952,26 @@ def test_writer_handles_mixed_empty_and_real_first_sample(self):
         self.assertIn((0, 1), reader_collector.by_thread)
         self.assertEqual(len(reader_collector.by_thread[(0, 1)]), 2)
 
+    def test_writer_failed_sample_does_not_advance_timestamp(self):
+        """A rejected frame must not shift later timestamps."""
+        with tempfile.NamedTemporaryFile(suffix=".bin", delete=False) as f:
+            filename = f.name
+        self.temp_files.append(filename)
+
+        good = [make_interpreter(0, [make_thread(1, [make_frame("a.py", 1, "f")])])]
+        bad = [make_interpreter(0, [make_thread(1, [make_frame(42, 1, "f")])])]
+
+        with _remote_debugging.BinaryWriter(filename, 1000, 0) as writer:
+            writer.write_sample(good, 1000)
+            with self.assertRaises(TypeError):
+                writer.write_sample(bad, 5000)
+            writer.write_sample(good, 6000)
+
+        collector = TimestampCollector()
+        with BinaryReader(filename) as reader:
+            reader.replay_samples(collector)
+        self.assertEqual(collector.all_timestamps, [1000, 6000])
+
     def test_writer_total_samples_after_finalize_matches_reader(self):
         """BinaryWriter.total_samples after finalize() matches the reader's count."""
         # Five IDENTICAL samples force every sample beyond the first into the

From 89f6e7cf019277bde30f9c6c047cbc2be4d8fab9 Mon Sep 17 00:00:00 2001
From: maurycy <5383+maurycy@users.noreply.github.com>
Date: Thu, 1 Oct 2026 09:17:37 +0200
Subject: [PATCH 3/3] news

---
 .../next/Library/2026-10-01-09-17-11.gh-issue-158550.cRIHW-.rst | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-10-01-09-17-11.gh-issue-158550.cRIHW-.rst

diff --git a/Misc/NEWS.d/next/Library/2026-10-01-09-17-11.gh-issue-158550.cRIHW-.rst b/Misc/NEWS.d/next/Library/2026-10-01-09-17-11.gh-issue-158550.cRIHW-.rst
new file mode 100644
index 000000000000000..d84eb292bb5b3de
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-10-01-09-17-11.gh-issue-158550.cRIHW-.rst
@@ -0,0 +1,2 @@
+Fix incorrect timestamps in Tachyon binary profiles after a sample fails to be
+written.  Patch by Maurycy Pawłowski-Wieronski.