app: link the rear halves when splitting an A/V pair at the playhead

The Cmd+K split ran the plain per-block split for every selected clip,
so an originally linked audio/video pair came out with its front halves
linked but the two rear halves unlinked — dragging one rear clip left
its mate behind and Link/Relink could not repair it.

Split the whole target set as ONE BlockSplitPreservingLinksCommand (the
same command the multicam path uses): any pair of originally linked
blocks split at the same time gets its new halves linked too. Adds a
gpui test asserting front and rear halves of a dropped A/V clip stay
linked after split_at_playhead.

crates/oak-app/src/oakui/graphops.rs

@@ -1421,6 +1421,41 @@ pub fn split_clip(p: &ProjectRef, clip: NodeId, time_ts: i64) -> Result<(), Stri
 	)
 }
 
+/// Split every clip of `blocks` at `time_ts` as ONE undoable
+/// `BlockSplitPreservingLinksCommand` (the Cmd+K path): originally linked
+/// pairs that are both split get their rear halves linked too — the
+/// per-block plain split left the rear half of an A/V pair unlinked.
+/// Blocks whose range does not strictly contain the time are skipped by
+/// the command itself.
+pub fn split_clips_preserving_links(
+	p: &ProjectRef,
+	blocks: &[NodeId],
+	time_ts: i64,
+) -> Result<(), String> {
+	let Some((&first, rest)) = blocks.split_first() else {
+		return Ok(());
+	};
+	let tb = {
+		let g = lock(p);
+		clip_track(&g.graph, first)
+			.and_then(|t| track_behavior(&g.graph, t))
+			.and_then(|t| t.track_list)
+			.and_then(|l| track_list_behavior(&g.graph, l))
+			.and_then(|l| l.sequence)
+			.and_then(|s| sequence_time_base(&g.graph, s))
+			.ok_or_else(|| "the clip's sequence has no valid frame rate".to_string())?
+	};
+	let point = ts_to_rational(time_ts, tb);
+	let mut refs = Vec::with_capacity(blocks.len());
+	refs.push(node_ref(p, first));
+	refs.extend(rest.iter().map(|&b| node_ref(p, b)));
+	let times = vec![point; refs.len()];
+	push(
+		oak_timeline::undosplit::BlockSplitPreservingLinksCommand::new(refs, times).to_command(),
+		"Split Clips",
+	)
+}
+
 /// Trim `clip`'s timeline range to `[new_in_ts, new_out_ts)` (undoable
 /// "Trim Clip"; the facade's `oakengine_clip_trim` semantics: one end at
 /// a time, trim-in anchors the OUT, trim-out anchors the IN — the

crates/oak-app/src/oakui/real.rs

@@ -3834,10 +3834,10 @@ impl AppEngine for RealEngine {
 				})
 			})
 			.collect();
-		let mut result = Ok(());
-		for block in targets {
-			result = graphops::split_clip(&project, block, frame.0);
-		}
+		// ONE preserving-links split for the whole set: linked pairs (the
+		// A/V drop) get their rear halves linked too — the per-block plain
+		// split left the rear halves unlinked.
+		let result = graphops::split_clips_preserving_links(&project, &targets, frame.0);
 		self.apply_edit(result, "split at playhead", cx);
 	}
 
@@ -7164,6 +7164,86 @@ mod tests {
 		);
 	}
 
+	/// Cmd+K split of an A/V pair: the front halves keep their link AND
+	/// the two rear halves are linked to each other (the old per-block
+	/// plain split left the rear halves unlinked).
+	#[gpui::test]
+	async fn split_at_playhead_links_the_rear_halves(cx: &mut gpui::TestAppContext) {
+		let _media = media_lock();
+		let engine = cx.update(|cx| cx.new(|cx| RealEngine::create(cx)));
+		cx.update(|app| engine.update(app, |engine, cx| engine.new_project(cx)));
+		let media = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/demo.mp4");
+		cx.update(|app| {
+			engine.update(app, |engine, cx| {
+				engine.import_footage(media.clone(), cx).expect("import")
+			})
+		});
+		let name = media.file_name().unwrap().to_string_lossy().into_owned();
+		let entry = cx
+			.read(|app| {
+				engine
+					.read(app)
+					.roots()
+					.into_iter()
+					.find(|e| e.name.as_ref() == name)
+			})
+			.expect("imported footage is listed");
+		cx.update(|app| {
+			engine.update(app, |engine, cx| {
+				engine.drop_footage(entry.id, TrackKind::Video, 0, Frame(0), cx)
+			})
+		});
+		cx.update(|app| {
+			engine.update(app, |engine, cx| engine.request_frame(Monitor::Program, Frame(20), cx))
+		});
+		cx.update(|app| engine.update(app, |engine, cx| engine.split_at_playhead(cx)));
+
+		// Front/rear clips of the video track and the audio track (matched
+		// by their start frame: front starts at 0, rear at 20).
+		let clips_of = |kind: TrackKind, cx: &mut gpui::TestAppContext| {
+			cx.read(|app| {
+				let engine = engine.read(app);
+				let mut clips: Vec<ClipId> = engine
+					.tracks
+					.iter()
+					.filter(|t| t.kind == kind)
+					.flat_map(|t| t.clips.iter().map(|c| c.id))
+					.collect();
+				clips.sort_by_key(|c| c.0);
+				clips
+			})
+		};
+		let by_start = |kind: TrackKind, start: i64, cx: &mut gpui::TestAppContext| {
+			cx.read(|app| {
+				let engine = engine.read(app);
+				engine
+					.tracks
+					.iter()
+					.filter(|t| t.kind == kind)
+					.flat_map(|t| t.clips.iter())
+					.find(|c| c.range.start.0 == start)
+					.map(|c| c.id)
+					.unwrap_or_else(|| panic!("a {kind:?} clip starts at {start}"))
+			})
+		};
+		let linked = |a: ClipId, b: ClipId, cx: &mut gpui::TestAppContext| {
+			cx.read(|app| {
+				let engine = engine.read(app);
+				let project = engine.project_ref().expect("project").clone();
+				let (Some(na), Some(nb)) = (graphops::id_of(a.0), graphops::id_of(b.0)) else {
+					return false;
+				};
+				let guard = graphops::lock(&project);
+				guard.graph.links_of(na).contains(&nb)
+			})
+		};
+		let _ = clips_of;
+		let (vf, vr) = (by_start(TrackKind::Video, 0, cx), by_start(TrackKind::Video, 20, cx));
+		let (af, ar) = (by_start(TrackKind::Audio, 0, cx), by_start(TrackKind::Audio, 20, cx));
+		assert!(linked(vf, af, cx), "the front halves stay linked");
+		assert!(linked(vr, ar, cx), "the rear halves are linked too");
+	}
+
 	/// Playback pre-render window (M15 S2): during playback the playhead
 	/// frame must come from the worker-rendered shm slot cache, NOT the
 	/// synchronous render path (the main thread blocking in