diff --git a/codex-rs/core/src/codex/rollout_reconstruction.rs b/codex-rs/core/src/codex/rollout_reconstruction.rs
index e8e9c730c8..928afe4b9d 100644
--- a/codex-rs/core/src/codex/rollout_reconstruction.rs
+++ b/codex-rs/core/src/codex/rollout_reconstruction.rs
@@ -170,6 +170,9 @@ impl Session {
                         active_segment.turn_id.as_deref(),
                         ctx.turn_id.as_deref(),
                     ) {
+                        // Reverse replay walks newest-to-oldest, so the first surviving
+                        // `TurnContextItem` we see for this turn segment is the newest
+                        // surviving context snapshot for the turn.
                         if active_segment.previous_turn_settings.is_none() {
                             active_segment.previous_turn_settings = Some(PreviousTurnSettings {
                                 model: ctx.model.clone(),