fix(studio): fix seek after code edit, improve scrub perf, add click-to-source (#881)

* feat(studio): html-backed motion panel — persist GSAP motion to element attributes

Re-architects the motion panel to store GSAP motion data as a JSON
data attribute (data-hf-studio-motion) on each element instead of a
.hyperframes/studio-motion.json sidecar file. Follows the same
pattern as position/resize/rotation edits: write to DOM, build patches,
persist to HTML source via commitPositionPatchToHtml.

Render pipeline: the studioPositionSeekReapplyRuntime now queries
[data-hf-studio-motion] elements after each seek, parses their JSON,
builds a GSAP timeline, and seeks it to the current frame time.

Studio preview: motion reapply is integrated into the manual edits seek
hook (reapplyPositionEditsAfterSeek). useManifestPersistence is slimmed
to only handle save queue and seek hooks.

* fix(studio): address PR review — html-escape attrs, cache timeline, migrate sidecar, add tests

Blocker: JSON attribute values are now HTML-entity-escaped before being
written into source HTML. Read-back unescapes automatically.

Perf: motion timeline is cached between seeks at render — only rebuilt
when the concatenated JSON key changes, not on every frame.

Migration: on mount, empties legacy .hyperframes/studio-motion.json so
the legacy render script no-ops.

Tests: 46 new tests for motion read/write/clear round-trips, JSON
attribute escaping, and source patcher entity handling.

Nits: removed unused activeCompositionPath param; tightened htmlCompiler
attribute substring check.

* fix(studio): fix seek after code edit, improve scrub performance, add click-to-source

Three issues addressed:

1. **Seek breaks after code edit**: During crossfade refreshes the retiring
   Player's cleanup unconditionally nulled `iframeRef.current`, clobbering the
   reference the new Player had already assigned. Guard the cleanup to only
   clear the ref when it still points to the retiring Player's own iframe.

2. **Scrubber/timeline drag jank**: Every pointermove during a drag called the
   full seek pipeline (adapter.seek + setCurrentTime + React re-render cascade).
   RAF-throttle the expensive onSeek call during drags while keeping slider and
   playhead visuals updated on every pointer event for instant feedback.

3. **Click-to-source**: Clicking an element in the preview now switches to the
   Code tab, opens the element's source file, and scrolls the editor to the
   element's opening tag. Uses the existing `findTagByTarget` source patcher to
   locate the element by id/selector in the HTML source.

* fix(studio): address PR review — gate click-to-source, fix fetch race, guard refs

- Gate click-to-source on Alt/Option+click so it doesn't steal the Code
  tab on every preview click, conflicting with select-to-inspect workflow
- Fix fetch race in openSourceForSelection: AbortController cancels the
  previous in-flight fetch, monotonic request ID prevents stale responses
  from applying the wrong file/offset
- Guard the callback-ref branch in Player cleanup (no-op — can't read
  back from a callback ref to check identity, and the path is unreachable
  today since the ref is always a MutableRefObject)
- Import SidebarTab type instead of duplicating the literal inline

packages/studio/src/App.tsx

@@ -1,5 +1,5 @@
 import { useState, useCallback, useRef, useMemo, useEffect } from "react";
-import type { LeftSidebarHandle } from "./components/sidebar/LeftSidebar";
+import type { LeftSidebarHandle, SidebarTab } from "./components/sidebar/LeftSidebar";
 import { useRenderQueue } from "./components/renders/useRenderQueue";
 import { usePlayerStore } from "./player";
 import { LintModal } from "./components/LintModal";
@@ -215,6 +215,8 @@ export function StudioApp() {
     syncPreviewHistoryHotkey: appHotkeys.syncPreviewHistoryHotkey,
     reloadPreview,
     setRefreshKey,
+    openSourceForSelection: fileManager.openSourceForSelection,
+    selectSidebarTab: (tab: SidebarTab) => leftSidebarRef.current?.selectTab(tab),
   });
 
   domEditSelectionBridgeRef.current = domEditSession.domEditSelection;

packages/studio/src/components/StudioLeftSidebar.tsx

@@ -35,6 +35,7 @@ export function StudioLeftSidebar({
     assets,
     editingFile,
     fileTree,
+    revealSourceOffset,
     handleFileSelect,
     handleCreateFile,
     handleCreateFolder,
@@ -113,6 +114,7 @@ export function StudioLeftSidebar({
                 content={editingFile.content ?? ""}
                 filePath={editingFile.path}
                 onChange={handleContentChange}
+                revealOffset={revealSourceOffset}
               />
             )
           ) : undefined

packages/studio/src/components/editor/SourceEditor.tsx

@@ -55,6 +55,7 @@ interface SourceEditorProps {
   language?: string;
   onChange?: (content: string) => void;
   readOnly?: boolean;
+  revealOffset?: number | null;
 }
 
 export const SourceEditor = memo(function SourceEditor({
@@ -63,6 +64,7 @@ export const SourceEditor = memo(function SourceEditor({
   language,
   onChange,
   readOnly = false,
+  revealOffset,
 }: SourceEditorProps) {
   const editorRef = useRef<EditorView | null>(null);
   const containerRef = useRef<HTMLDivElement | null>(null);
@@ -132,5 +134,17 @@ export const SourceEditor = memo(function SourceEditor({
     }
   }, [content]);
 
+  useEffect(() => {
+    const view = editorRef.current;
+    if (!view || revealOffset == null || revealOffset < 0) return;
+    const docLen = view.state.doc.length;
+    const pos = Math.min(revealOffset, docLen);
+    view.dispatch({
+      selection: { anchor: pos },
+      effects: EditorView.scrollIntoView(pos, { y: "center" }),
+    });
+    view.focus();
+  }, [revealOffset]);
+
   return <div ref={mountEditor} className="h-full w-full overflow-hidden" />;
 });

packages/studio/src/contexts/FileManagerContext.tsx

@@ -26,6 +26,8 @@ export function FileManagerProvider({
     readProjectFile,
     writeProjectFile,
     readOptionalProjectFile,
+    revealSourceOffset,
+    openSourceForSelection,
     handleFileSelect,
     handleContentChange,
     refreshFileTree,
@@ -62,6 +64,8 @@ export function FileManagerProvider({
       readProjectFile,
       writeProjectFile,
       readOptionalProjectFile,
+      revealSourceOffset,
+      openSourceForSelection,
       handleFileSelect,
       handleContentChange,
       refreshFileTree,
@@ -92,6 +96,8 @@ export function FileManagerProvider({
       readProjectFile,
       writeProjectFile,
       readOptionalProjectFile,
+      revealSourceOffset,
+      openSourceForSelection,
       handleFileSelect,
       handleContentChange,
       refreshFileTree,

packages/studio/src/hooks/useDomEditSession.ts

@@ -1,10 +1,12 @@
-import { useEffect } from "react";
+import { useCallback, useEffect } from "react";
 import type { TimelineElement } from "../player";
 import { STUDIO_INSPECTOR_PANELS_ENABLED } from "../components/editor/manualEditingAvailability";
-import { findElementForSelection } from "../components/editor/domEditing";
+import { findElementForSelection, type DomEditSelection } from "../components/editor/domEditing";
 import type { ImportedFontAsset } from "../components/editor/fontAssets";
 import type { EditHistoryKind } from "../utils/editHistory";
 import type { RightPanelTab } from "../utils/studioHelpers";
+import type { PatchTarget } from "../utils/sourcePatcher";
+import type { SidebarTab } from "../components/sidebar/LeftSidebar";
 import { useAskAgentModal } from "./useAskAgentModal";
 import { useDomSelection } from "./useDomSelection";
 import { usePreviewInteraction } from "./usePreviewInteraction";
@@ -52,6 +54,8 @@ export interface UseDomEditSessionParams {
   syncPreviewHistoryHotkey: (iframe: HTMLIFrameElement | null) => void;
   reloadPreview: () => void;
   setRefreshKey: React.Dispatch<React.SetStateAction<number>>;
+  openSourceForSelection?: (sourceFile: string, target: PatchTarget) => void;
+  selectSidebarTab?: (tab: SidebarTab) => void;
 }
 
 // ── Hook ──
@@ -87,8 +91,25 @@ export function useDomEditSession({
   syncPreviewHistoryHotkey,
   reloadPreview,
   setRefreshKey: _setRefreshKey,
+  openSourceForSelection,
+  selectSidebarTab,
 }: UseDomEditSessionParams) {
   void _setRefreshKey;
+
+  const onClickToSource = useCallback(
+    (selection: DomEditSelection) => {
+      if (!openSourceForSelection || !selectSidebarTab) return;
+      if (!selection.sourceFile) return;
+      selectSidebarTab("code");
+      openSourceForSelection(selection.sourceFile, {
+        id: selection.id,
+        selector: selection.selector,
+        selectorIndex: selection.selectorIndex,
+      });
+    },
+    [openSourceForSelection, selectSidebarTab],
+  );
+
   // ── Selection (delegated to useDomSelection) ──
 
   const {
@@ -164,6 +185,7 @@ export function useDomEditSession({
     setAgentPromptSelectionContext,
     setAgentModalAnchorPoint,
     setAgentModalOpen,
+    onClickToSource,
   });
 
   // ── Commit handlers (delegated to useDomEditCommits) ──

packages/studio/src/hooks/useFileManager.ts

@@ -4,6 +4,7 @@ import { FONT_EXT, isMediaFile } from "../utils/mediaTypes";
 import { fontFamilyFromAssetPath, type ImportedFontAsset } from "../components/editor/fontAssets";
 import { saveProjectFilesWithHistory } from "../utils/studioFileHistory";
 import type { EditHistoryKind } from "../utils/editHistory";
+import { findTagByTarget, type PatchTarget } from "../utils/sourcePatcher";
 
 // ── Types ──
 
@@ -37,6 +38,7 @@ export function useFileManager({
   const [projectDir, setProjectDir] = useState<string | null>(null);
   const [fileTree, setFileTree] = useState<string[]>([]);
   const [fileTreeLoaded, setFileTreeLoaded] = useState(false);
+  const [revealSourceOffset, setRevealSourceOffset] = useState<number | null>(null);
 
   // ── Refs ──
 
@@ -169,6 +171,42 @@ export function useFileManager({
     [domEditSaveTimestampRef, readProjectFile, recordEdit, setRefreshKey, writeProjectFile],
   );
 
+  // ── Open source for selection (click-to-source) ──
+
+  const revealRequestIdRef = useRef(0);
+  const revealAbortRef = useRef<AbortController | null>(null);
+
+  const openSourceForSelection = useCallback(
+    (sourceFile: string, target: PatchTarget) => {
+      const pid = projectIdRef.current;
+      if (!pid || !sourceFile) return;
+      revealAbortRef.current?.abort();
+      revealAbortRef.current = null;
+      if (editingPathRef.current === sourceFile && editingFile?.content != null) {
+        const match = findTagByTarget(editingFile.content, target);
+        setRevealSourceOffset(match ? match.start : null);
+        return;
+      }
+      const requestId = ++revealRequestIdRef.current;
+      const controller = new AbortController();
+      revealAbortRef.current = controller;
+      fetch(`/api/projects/${pid}/files/${encodeURIComponent(sourceFile)}`, {
+        signal: controller.signal,
+      })
+        .then((r) => r.json())
+        .then((data: { content?: string }) => {
+          if (requestId !== revealRequestIdRef.current) return;
+          if (data.content != null) {
+            setEditingFile({ path: sourceFile, content: data.content });
+            const match = findTagByTarget(data.content, target);
+            setRevealSourceOffset(match ? match.start : null);
+          }
+        })
+        .catch(() => {});
+    },
+    [editingFile?.content],
+  );
+
   // ── File tree refresh ──
 
   const refreshFileTree = useCallback(async () => {
@@ -418,6 +456,10 @@ export function useFileManager({
     writeProjectFile,
     readOptionalProjectFile,
 
+    // Click-to-source
+    revealSourceOffset,
+    openSourceForSelection,
+
     // Callbacks
     handleFileSelect,
     handleContentChange,

packages/studio/src/hooks/usePreviewInteraction.ts

@@ -37,6 +37,8 @@ export interface UsePreviewInteractionParams {
   setAgentPromptSelectionContext: (context: string | undefined) => void;
   setAgentModalAnchorPoint: (point: AgentModalAnchorPoint | null) => void;
   setAgentModalOpen: (open: boolean) => void;
+
+  onClickToSource?: (selection: DomEditSelection) => void;
 }
 
 // ── Hook ──
@@ -53,6 +55,7 @@ export function usePreviewInteraction({
   setAgentPromptSelectionContext,
   setAgentModalAnchorPoint,
   setAgentModalOpen,
+  onClickToSource,
 }: UsePreviewInteractionParams) {
   const handlePreviewCanvasMouseDown = useCallback(
     (e: React.MouseEvent<HTMLDivElement>, options?: { preferClipAncestor?: boolean }) => {
@@ -70,6 +73,9 @@ export function usePreviewInteraction({
         ? getPreviewLocalPointer(previewIframeRef.current, e.clientX, e.clientY)
         : null;
       applyDomSelection(nextSelection, { additive: e.shiftKey });
+      if (!e.shiftKey && e.altKey && onClickToSource) {
+        onClickToSource(nextSelection);
+      }
       if (
         !e.shiftKey &&
         localPointer &&
@@ -87,6 +93,7 @@ export function usePreviewInteraction({
       applyDomSelection,
       captionEditMode,
       compositionLoading,
+      onClickToSource,
       preloadAgentPromptSnippet,
       resolveDomSelectionFromPreviewPoint,
       previewIframeRef,

packages/studio/src/player/components/Player.tsx

@@ -268,11 +268,20 @@ export const Player = forwardRef<HTMLIFrameElement, PlayerProps>(
           if (assetPollRef.current) clearInterval(assetPollRef.current);
           assetPollRef.current = null;
           container.removeChild(player);
-          // Clear the forwarded ref
+          // Clear the forwarded ref only if it still points to THIS iframe.
+          // During crossfade refreshes the retiring Player unmounts after the
+          // new Player has already assigned its iframe to the same ref — blindly
+          // nulling it would break seeking in the new Player.
+          // Callback refs are skipped — we can't read back the current value to
+          // guard against clobbering a newer assignment. The mutable-ref branch
+          // (the only path used today) is guarded by identity check.
           if (typeof ref === "function") {
-            ref(null);
+            // no-op: can't safely guard callback refs
           } else if (ref) {
-            (ref as React.MutableRefObject<HTMLIFrameElement | null>).current = null;
+            const mutableRef = ref as React.MutableRefObject<HTMLIFrameElement | null>;
+            if (mutableRef.current === iframe) {
+              mutableRef.current = null;
+            }
           }
         };
       });

packages/studio/src/player/components/PlayerControls.tsx

@@ -207,12 +207,39 @@ export const PlayerControls = memo(function PlayerControls({
 
       seekFromClientX(e.clientX);
 
+      // During drag, update the slider visual immediately on every pointer
+      // event but RAF-throttle the actual onSeek call. The seek path triggers
+      // adapter.seek + setCurrentTime + React re-renders which can take >16ms
+      // on complex compositions — keeping visual feedback on the raw event and
+      // batching the expensive work to one call per frame keeps scrubbing at
+      // 60 fps.
+      let seekRafId = 0;
+      let pendingClientX = e.clientX;
       const onMove = (ev: PointerEvent) => {
-        if (ev.pointerId !== pointerId) return;
-        if (isDraggingRef.current) seekFromClientX(ev.clientX);
+        if (ev.pointerId !== pointerId || !isDraggingRef.current) return;
+        pendingClientX = ev.clientX;
+        const bar = seekBarRef.current;
+        const dur = durationRef.current;
+        if (bar && dur > 0) {
+          const rect = bar.getBoundingClientRect();
+          const pct = resolveSeekPercent(ev.clientX, rect.left, rect.width) * 100;
+          if (progressFillRef.current) progressFillRef.current.style.width = `${pct}%`;
+          if (progressThumbRef.current) progressThumbRef.current.style.left = `${pct}%`;
+        }
+        if (!seekRafId) {
+          seekRafId = requestAnimationFrame(() => {
+            seekRafId = 0;
+            if (isDraggingRef.current) seekFromClientX(pendingClientX);
+          });
+        }
       };
       const cleanup = () => {
         isDraggingRef.current = false;
+        if (seekRafId) {
+          cancelAnimationFrame(seekRafId);
+          seekRafId = 0;
+        }
+        seekFromClientX(pendingClientX);
         try {
           target.releasePointerCapture(pointerId);
         } catch {

packages/studio/src/player/components/useTimelineRangeSelection.ts

@@ -38,6 +38,9 @@ export function useTimelineRangeSelection({
     anchorY: number;
   } | null>(null);
 
+  const seekRafRef = useRef(0);
+  const pendingClientXRef = useRef(0);
+
   const handlePointerDown = useCallback(
     (e: React.PointerEvent) => {
       if (e.button !== 0) return;
@@ -80,8 +83,27 @@ export function useTimelineRangeSelection({
         return;
       }
       if (!isDragging.current) return;
-      seekFromX(e.clientX);
-      autoScrollDuringDrag(e.clientX);
+      pendingClientXRef.current = e.clientX;
+      // Update the playhead visual immediately via liveTime for smooth feedback,
+      // then RAF-throttle the full seek (adapter + React state sync).
+      const el = scrollRef.current;
+      if (el) {
+        const rect = el.getBoundingClientRect();
+        const x = e.clientX - rect.left + el.scrollLeft - GUTTER;
+        if (x >= 0) {
+          const dur = el.scrollWidth / pps;
+          liveTime.notify(Math.max(0, Math.min(dur, x / pps)));
+        }
+      }
+      if (!seekRafRef.current) {
+        seekRafRef.current = requestAnimationFrame(() => {
+          seekRafRef.current = 0;
+          if (isDragging.current) {
+            seekFromX(pendingClientXRef.current);
+            autoScrollDuringDrag(pendingClientXRef.current);
+          }
+        });
+      }
     },
     [seekFromX, autoScrollDuringDrag, pps, scrollRef, isDragging],
   );
@@ -104,9 +126,14 @@ export function useTimelineRangeSelection({
       });
       return;
     }
+    if (seekRafRef.current) {
+      cancelAnimationFrame(seekRafRef.current);
+      seekRafRef.current = 0;
+    }
+    seekFromX(pendingClientXRef.current);
     isDragging.current = false;
     cancelAnimationFrame(dragScrollRaf.current);
-  }, [isDragging, dragScrollRaf, setShowPopover]);
+  }, [isDragging, dragScrollRaf, setShowPopover, seekFromX]);
 
   return {
     rangeSelection,

packages/studio/src/utils/sourcePatcher.ts

@@ -232,7 +232,7 @@ function replaceTagAtMatch(html: string, match: TagMatch, newTag: string): strin
   return `${html.slice(0, match.start)}${newTag}${html.slice(match.end)}`;
 }
 
-function findTagByTarget(html: string, target: PatchTarget): TagMatch | null {
+export function findTagByTarget(html: string, target: PatchTarget): TagMatch | null {
   if (target.id) {
     const idPattern = new RegExp(`(<[^>]*\\bid=(["'])${escapeRegex(target.id)}\\2[^>]*)>`, "i");
     const match = idPattern.exec(html);