From c1a5415a65c96bc4067539d12764c16c0d1f605b Mon Sep 17 00:00:00 2001
From: Aditya Garud <153842990+yashranaway@users.noreply.github.com>
Date: Sat, 17 Oct 2026 17:16:01 +0000
Subject: [PATCH] fix(project): keep legacy captions at the timeline end

---
 crates/project/src/caption_timing.rs | 77 ++++++++++++++++++++++++++--
 crates/verify/expectations.toml      |  7 ---
 2 files changed, 72 insertions(+), 12 deletions(-)

diff --git a/crates/project/src/caption_timing.rs b/crates/project/src/caption_timing.rs
index aa7661afb46..63700fc2abd 100644
--- a/crates/project/src/caption_timing.rs
+++ b/crates/project/src/caption_timing.rs
@@ -369,7 +369,12 @@ pub fn synchronize_captions(project: &mut ProjectConfiguration, recording_durati
     if !captions.source_timed {
         let holds = timeline.hold_windows();
         let mappings = build_source_to_edited_mappings(timeline, recording_durations);
-        let to_source = |output: f64| -> Option<f32> {
+        let output_end = timeline.duration() as f32;
+        let to_source = |output: f32| -> Option<f32> {
+            if output == output_end {
+                return mappings.last().map(|mapping| mapping.source_end as f32);
+            }
+            let output = f64::from(output);
             let effective = output
                 - holds
                     .iter()
@@ -388,16 +393,16 @@ pub fn synchronize_captions(project: &mut ProjectConfiguration, recording_durati
             .segments
             .iter()
             .filter_map(|caption| {
-                let start = to_source(f64::from(caption.start))?;
-                let end = to_source(f64::from(caption.end))?;
+                let start = to_source(caption.start)?;
+                let end = to_source(caption.end)?;
                 let words = caption
                     .words
                     .iter()
                     .filter_map(|word| {
                         Some(CaptionWord {
                             text: word.text.clone(),
-                            start: to_source(f64::from(word.start))?,
-                            end: to_source(f64::from(word.end))?,
+                            start: to_source(word.start)?,
+                            end: to_source(word.end)?,
                         })
                     })
                     .collect();
@@ -466,6 +471,68 @@ mod tests {
         assert_eq!(track[0].end, 10.0);
     }
 
+    #[test]
+    fn legacy_caption_migration_preserves_rounded_timeline_end() {
+        let durations = [41.0 / 15.0, 82.0 / 15.0];
+        for (timescale, hold_duration) in [
+            (1.0, 0.0),
+            (2.0, 0.0),
+            (0.5, 0.0),
+            (1.0, 0.1),
+            (1.0, 10000.1),
+        ] {
+            let mut timeline: TimelineConfiguration = serde_json::from_value(serde_json::json!({
+                "segments": [
+                    {"recordingSegment": 0, "start": 0.0, "end": durations[0], "timescale": timescale},
+                    {"recordingSegment": 1, "start": 0.0, "end": durations[1], "timescale": timescale}
+                ],
+                "transitions": [{"segmentIndex": 1, "type": "cross-fade", "duration": 0.2}],
+                "zoomSegments": []
+            }))
+            .unwrap();
+            if hold_duration > 0.0 {
+                timeline.text_segments.push(
+                    serde_json::from_value(serde_json::json!({
+                        "start": 1.0, "end": 1.0 + hold_duration, "layout": "fullscreen"
+                    }))
+                    .unwrap(),
+                );
+            }
+            let end = timeline.duration() as f32;
+            let mut project = project(false, end - 0.5, end);
+            project.timeline = Some(timeline);
+
+            synchronize_captions(&mut project, &durations);
+
+            let captions = project.captions.as_ref().unwrap();
+            assert_eq!(captions.segments.len(), 1, "{timescale}, {hold_duration}");
+            let source_end = durations.iter().sum::<f64>() as f32;
+            assert_eq!(captions.segments[0].end, source_end);
+            assert_eq!(captions.segments[0].words[0].end, source_end);
+            let track = &project.timeline.as_ref().unwrap().caption_segments;
+            assert_eq!(track.len(), 1);
+            assert!((track[0].end - f64::from(end)).abs() <= f64::from(end * f32::EPSILON));
+            let saved = serde_json::to_string(&project).unwrap();
+            synchronize_captions(&mut project, &durations);
+            assert_eq!(serde_json::to_string(&project).unwrap(), saved);
+        }
+    }
+
+    #[test]
+    fn legacy_caption_migration_rejects_times_beyond_rounded_timeline_end() {
+        let mut project = project(false, 8.0, 9.0_f32.next_up());
+        synchronize_captions(&mut project, &[10.0]);
+        assert!(project.captions.as_ref().unwrap().segments.is_empty());
+        assert!(
+            project
+                .timeline
+                .as_ref()
+                .unwrap()
+                .caption_segments
+                .is_empty()
+        );
+    }
+
     #[test]
     fn stale_caption_tracks_are_replaced_and_styles_preserved() {
         let mut project = project(true, 8.0, 9.0);
diff --git a/crates/verify/expectations.toml b/crates/verify/expectations.toml
index b6b97fa360a..511cd9bea32 100644
--- a/crates/verify/expectations.toml
+++ b/crates/verify/expectations.toml
@@ -172,13 +172,6 @@ bound = { count = 1, missing = 30 }
 reason = "NEW: same as editing/mapping/duration-covered, end to end: a 1 s fullscreen text at 5.4 s and the clip trimmed to 3.2 s give a 4.2 s timeline, but the export stops at the first unmapped frame: 96 frames instead of 126, and the text card is never rendered"
 link = ""
 
-[[xfail]]
-case = "captions/legacy-migration/ends-at-timeline-end"
-class = "caption-migration"
-bound = { count = 1 }
-reason = "NEW (minor): loading a legacy (output-timed) project drops a caption that ends exactly at the timeline end: synchronize_captions maps each end through source_start + (end - start) / timescale, which rounds just below the timeline end after a clip transition (clips 41/15 s and 82/15 s, 0.2 s transition: 7.9999999 < 8.0), so the end does not map and the whole caption is discarded"
-link = ""
-
 [[xfail]]
 case = "playback/basic/cuts-speeds-reorder/realtime30-from25/avf"
 class = "stale"