fix: multi-file timeline drop spacing

packages/studio/src/App.tsx

@@ -957,7 +957,11 @@ export function StudioApp() {
   );
 
   const handleTimelineAssetDrop = useCallback(
-    async (assetPath: string, placement: Pick<TimelineElement, "start" | "track">) => {
+    async (
+      assetPath: string,
+      placement: Pick<TimelineElement, "start" | "track">,
+      durationOverride?: number,
+    ) => {
       const pid = projectIdRef.current;
       if (!pid) throw new Error("No active project");
 
@@ -983,9 +987,11 @@ export function StudioApp() {
         }
 
         const normalizedStart = Number(formatTimelineAttributeNumber(placement.start));
-        const normalizedDuration = Number(
-          formatTimelineAttributeNumber(await resolveDroppedAssetDuration(pid, assetPath, kind)),
-        );
+        const duration =
+          Number.isFinite(durationOverride) && durationOverride != null && durationOverride > 0
+            ? durationOverride
+            : await resolveDroppedAssetDuration(pid, assetPath, kind);
+        const normalizedDuration = Number(formatTimelineAttributeNumber(duration));
         const newId = buildTimelineAssetId(assetPath, collectHtmlIds(originalContent));
         const resolvedAssetSrc = resolveTimelineAssetSrc(targetPath, assetPath);
 
@@ -1064,17 +1070,40 @@ export function StudioApp() {
 
   const handleTimelineFileDrop = useCallback(
     async (files: File[], placement?: Pick<TimelineElement, "start" | "track">) => {
+      const pid = projectIdRef.current;
+      if (!pid) return;
       const uploaded = await uploadProjectFiles(files);
       if (uploaded.length === 0) return;
+      const durations: number[] = [];
+      for (const assetPath of uploaded) {
+        const kind = getTimelineAssetKind(assetPath);
+        const duration = kind ? await resolveDroppedAssetDuration(pid, assetPath, kind) : 0;
+        durations.push(Number(formatTimelineAttributeNumber(duration)));
+      }
       const placements = buildTimelineFileDropPlacements(
         placement ?? { start: 0, track: 0 },
-        uploaded.length,
+        durations,
+        timelineElements
+          .filter(
+            (timelineElement) =>
+              (timelineElement.sourceFile || activeCompPath || "index.html") ===
+              (activeCompPath || "index.html"),
+          )
+          .map((timelineElement) => ({
+            start: timelineElement.start,
+            duration: timelineElement.duration,
+            track: timelineElement.track,
+          })),
       );
       for (const [index, assetPath] of uploaded.entries()) {
-        await handleTimelineAssetDrop(assetPath, placements[index] ?? placements[0]);
+        await handleTimelineAssetDrop(
+          assetPath,
+          placements[index] ?? placements[0],
+          durations[index],
+        );
       }
     },
-    [handleTimelineAssetDrop, uploadProjectFiles],
+    [activeCompPath, handleTimelineAssetDrop, timelineElements, uploadProjectFiles],
   );
 
   // ── File Management Handlers ──

packages/studio/src/utils/timelineAssetDrop.test.ts

@@ -11,6 +11,8 @@ describe("getTimelineAssetKind", () => {
   it("detects image, video, and audio assets", () => {
     expect(getTimelineAssetKind("assets/photo.png")).toBe("image");
     expect(getTimelineAssetKind("assets/clip.mp4")).toBe("video");
+    expect(getTimelineAssetKind("assets/clip.mov")).toBe("video");
+    expect(getTimelineAssetKind("assets/music.mp3")).toBe("audio");
     expect(getTimelineAssetKind("assets/music.wav")).toBe("audio");
   });
 });
@@ -58,11 +60,69 @@ describe("resolveTimelineAssetSrc", () => {
 });
 
 describe("buildTimelineFileDropPlacements", () => {
-  it("uses the dropped start and stacks multiple files onto successive tracks", () => {
-    expect(buildTimelineFileDropPlacements({ start: 1.5, track: 2 }, 3)).toEqual([
+  it("returns no placements for an empty drop set", () => {
+    expect(buildTimelineFileDropPlacements({ start: 1.5, track: 2 }, [])).toEqual([]);
+  });
+
+  it("uses the dropped start and spaces multiple files by duration on the same track", () => {
+    expect(buildTimelineFileDropPlacements({ start: 1.5, track: 2 }, [1.2, 1.6, 1.1])).toEqual([
       { start: 1.5, track: 2 },
-      { start: 1.5, track: 3 },
-      { start: 1.5, track: 4 },
+      { start: 2.7, track: 2 },
+      { start: 4.3, track: 2 },
+    ]);
+  });
+
+  it("uses fallback spacing when a duration is unavailable", () => {
+    expect(buildTimelineFileDropPlacements({ start: 1.5, track: 2 }, [1.2, 0, 1.1])).toEqual([
+      { start: 1.5, track: 2 },
+      { start: 2.7, track: 2 },
+      { start: 7.7, track: 2 },
+    ]);
+  });
+
+  it("moves the spaced sequence to a clear track when the dropped row is occupied", () => {
+    expect(
+      buildTimelineFileDropPlacements(
+        { start: 1.5, track: 2 },
+        [1.2, 1.6, 1.1],
+        [
+          { start: 0, duration: 8, track: 2 },
+          { start: 0, duration: 4, track: 5 },
+        ],
+      ),
+    ).toEqual([
+      { start: 1.5, track: 6 },
+      { start: 2.7, track: 6 },
+      { start: 4.3, track: 6 },
+    ]);
+  });
+
+  it("keeps a requested track above occupied rows when that track is clear", () => {
+    expect(
+      buildTimelineFileDropPlacements(
+        { start: 1.5, track: 8 },
+        [1.2, 1.6],
+        [
+          { start: 0, duration: 8, track: 2 },
+          { start: 0, duration: 4, track: 5 },
+        ],
+      ),
+    ).toEqual([
+      { start: 1.5, track: 8 },
+      { start: 2.7, track: 8 },
+    ]);
+  });
+
+  it("moves a default-track drop to a clear row when track 0 is occupied at time 0", () => {
+    expect(
+      buildTimelineFileDropPlacements(
+        { start: 0, track: 0 },
+        [1.2, 1.6],
+        [{ start: 0, duration: 8, track: 0 }],
+      ),
+    ).toEqual([
+      { start: 0, track: 1 },
+      { start: 1.2, track: 1 },
     ]);
   });
 });

packages/studio/src/utils/timelineAssetDrop.ts

@@ -1,6 +1,7 @@
 import { AUDIO_EXT, IMAGE_EXT, VIDEO_EXT } from "./mediaTypes";
 
 export const TIMELINE_ASSET_MIME = "application/x-hyperframes-asset";
+const FALLBACK_TIMELINE_FILE_DROP_DURATION = 5;
 
 export type TimelineAssetKind = "image" | "video" | "audio";
 
@@ -46,12 +47,33 @@ export function resolveTimelineAssetSrc(targetPath: string, assetPath: string):
 
 export function buildTimelineFileDropPlacements(
   placement: { start: number; track: number },
-  count: number,
+  durations: number[],
+  occupiedClips: Array<{ start: number; duration: number; track: number }> = [],
 ): Array<{ start: number; track: number }> {
-  return Array.from({ length: Math.max(0, count) }, (_, index) => ({
-    start: placement.start,
-    track: placement.track + index,
-  }));
+  let nextStart = Math.round(Math.max(0, placement.start) * 100) / 100;
+  const sequenceStart = nextStart;
+  const resolvedDurations = durations.map((duration) =>
+    Number.isFinite(duration) && duration > 0 ? duration : FALLBACK_TIMELINE_FILE_DROP_DURATION,
+  );
+  const sequenceEnd = resolvedDurations.reduce(
+    (end, duration) => Math.round((end + duration) * 100) / 100,
+    sequenceStart,
+  );
+  const overlapsDropTrack = occupiedClips.some((clip) => {
+    if (clip.track !== placement.track) return false;
+    const clipStart = Math.max(0, clip.start);
+    const clipEnd = clipStart + Math.max(0, clip.duration);
+    return sequenceStart < clipEnd && sequenceEnd > clipStart;
+  });
+  const track = overlapsDropTrack
+    ? Math.max(placement.track, ...occupiedClips.map((clip) => clip.track)) + 1
+    : placement.track;
+
+  return resolvedDurations.map((duration) => {
+    const start = nextStart;
+    nextStart = Math.round((nextStart + duration) * 100) / 100;
+    return { start, track };
+  });
 }
 
 export function buildTimelineAssetInsertHtml(input: {