diff --git a/quest/m1/test-flakes-2/ts-duration-fidelity.md b/quest/m1/test-flakes-2/ts-duration-fidelity.md
index ac4c232c95..483e927c5d 100644
--- a/quest/m1/test-flakes-2/ts-duration-fidelity.md
+++ b/quest/m1/test-flakes-2/ts-duration-fidelity.md
@@ -18,3 +18,17 @@ without it. No longer timeout and no lower duration threshold.
 Check against #5147 (export ts follows announcements), which may change how an export ends.
 
 Public API: none expected. Wire: none expected.
+
+Investigation (2026-10-10):
+
+On 2026-10-10, an isolated `nix develop --command just test ts` against
+main at `6559065b8` captured 20.47 s of the 20.06 s source (ratio 1.021).
+The publisher exited 0 and duration-fidelity passed. The run failed a separate
+T-STD check (PID 257 held over one second); its subscriber log also contained
+missed-deadline drops. That does not reproduce the reported 3.3 s capture.
+
+The capture remains bounded by the existing harness timeout, and no duration
+threshold or timeout was changed. #5147 still owns the export announcement/end
+lifecycle, while #5175 owns groups left in flight when a relay track ends.
+A truncating capture with both process exit statuses and relay/publisher/
+subscriber logs is still needed to distinguish these paths before a fix.