From 6c9384caabf5414b7135a660de20c9e4cb50fac3 Mon Sep 17 00:00:00 2001
From: Richie McIlroy <33632126+richiemcilroy@users.noreply.github.com>
Date: Fri, 16 Oct 2026 23:18:39 +0900
Subject: [PATCH] fix(recording): write segment start times off the async
 runtime

The start-time persister wrote the file and ran two fsyncs inside its
tokio task, blocking a runtime worker that capture pipelines also use.
The write now runs on a blocking thread.
---
 crates/recording/src/studio_recording.rs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/crates/recording/src/studio_recording.rs b/crates/recording/src/studio_recording.rs
index 762ae485795..60ed1c6e944 100644
--- a/crates/recording/src/studio_recording.rs
+++ b/crates/recording/src/studio_recording.rs
@@ -1496,7 +1496,15 @@ impl Pipeline {
                         firsts[3],
                     );
                     if written != Some(times) {
-                        match write_segment_start_times(&segment_dir, &times) {
+                        // A blocking write and two fsyncs: keep them off the
+                        // runtime workers the capture pipelines run on.
+                        let dir = segment_dir.clone();
+                        let result = tokio::task::spawn_blocking(move || {
+                            write_segment_start_times(&dir, &times)
+                        })
+                        .await
+                        .unwrap_or_else(|error| Err(std::io::Error::other(error)));
+                        match result {
                             Ok(()) => written = Some(times),
                             Err(error) => {
                                 failed_writes += 1;