fix(studio): shell UX — data-loss guards, error surfacing, dialog contracts, toasts (#1964)

2026-09-03 12:54:29 +00:00 · 2026-07-06 16:56:06 -07:00
parent ccc1308839
commit 89e36da13d
23 changed files with 700 additions and 281 deletions
@@ -27,6 +27,7 @@ import { useFrameCapture } from "./hooks/useFrameCapture";
 import { useLintModal } from "./hooks/useLintModal";
 import { useCompositionDimensions } from "./hooks/useCompositionDimensions";
 import { useToast } from "./hooks/useToast";
+import { useCompositionContentLoader } from "./hooks/useCompositionContentLoader";
 import { useStudioUrlState } from "./hooks/useStudioUrlState";
 import {
  buildStudioContextValue,
@@ -132,7 +133,7 @@ export function StudioApp() {
      return !v;
    });
  }, []);
-  const { appToast, showToast, dismissToast } = useToast();
+  const { toasts, showToast, dismissToast } = useToast();
  const panelLayout = usePanelLayout({
    rightCollapsed: initialUrlStateRef.current.rightCollapsed,
    rightPanelTab: initialUrlStateRef.current.rightPanelTab,
@@ -389,17 +390,13 @@ export function StudioApp() {
    },
    [appHotkeys, resetConsoleErrors, refreshPreviewDocumentVersion],
  );
-  const handleSelectComposition = useCallback(
-    (comp: string) => {
-      setActiveCompPath(comp.endsWith(".html") ? comp : null);
-      fileManager.setEditingFile({ path: comp, content: null });
-      fetch(`/api/projects/${projectId}/files/${comp}`)
-        .then((r) => r.json())
-        .then((data) => fileManager.setEditingFile({ path: comp, content: data.content }))
-        .catch(() => {});
-    },
-    [projectId, fileManager],
-  );
+  const { setEditingFile } = fileManager;
+  const handleSelectComposition = useCompositionContentLoader({
+    projectId,
+    setEditingFile,
+    setActiveCompPath,
+    showToast,
+  });
  const {
    designPanelActive,
    inspectorPanelActive,
@@ -484,6 +481,7 @@ export function StudioApp() {
                    captureFrameFilename={frameCapture.captureFrameFilename}
                    handleCaptureFrameClick={frameCapture.handleCaptureFrameClick}
                    refreshCaptureFrameTime={frameCapture.refreshCaptureFrameTime}
+                    capturing={frameCapture.capturing}
                    inspectorButtonActive={inspectorButtonActive}
                    inspectorPanelActive={inspectorPanelActive}
                    onExport={() => {
@@ -496,7 +494,7 @@ export function StudioApp() {
                  {previewPersistence.domEditSaveQueuePaused && (
                    <SaveQueuePausedBanner
                      message={previewPersistence.domEditSaveQueuePaused}
-                      onDismiss={previewPersistence.resetDomEditSaveQueueBreaker}
+                      onRetry={previewPersistence.resetDomEditSaveQueueBreaker}
                    />
                  )}
                  {viewModeValue.viewMode === "storyboard" && (
@@ -578,6 +576,7 @@ export function StudioApp() {
                  </div>
                  <StudioOverlays
                    projectId={projectId}
+                    projectDir={fileManager.projectDir}
                    lintModal={lintModal}
                    closeLintModal={closeLintModal}
                    consoleErrors={consoleErrors}
@@ -585,7 +584,7 @@ export function StudioApp() {
                    domEditSession={domEditSession}
                    activeCompPath={activeCompPath}
                    dragOverlayActive={dragOverlay.active}
-                    appToast={appToast}
+                    toasts={toasts}
                    dismissToast={dismissToast}
                  />
                </div>
@@ -1,6 +1,7 @@
 import { useState, useRef, type CSSProperties } from "react";
 import { useMountEffect } from "../hooks/useMountEffect";
 import { type AgentModalAnchorPoint, clampNumber } from "../utils/studioHelpers";
+import { useDialogBehavior } from "./ui/useDialogBehavior";

 function getAgentModalPositionStyle(
  anchorPoint: AgentModalAnchorPoint | null,
@@ -39,7 +40,16 @@ export function AskAgentModal({
 }) {
  const [value, setValue] = useState("");
  const inputRef = useRef<HTMLTextAreaElement>(null);
+  const containerRef = useRef<HTMLDivElement>(null);
  const modalPositionStyle = getAgentModalPositionStyle(anchorPoint);
+  // A dirty draft vetoes Escape/backdrop closes — a stray click must not
+  // discard typed instructions. The X button and Copy still close directly.
+  const { requestClose } = useDialogBehavior({
+    open: true,
+    onClose,
+    containerRef,
+    canClose: () => !value.trim(),
+  });

  useMountEffect(() => {
    requestAnimationFrame(() => inputRef.current?.focus());
@@ -54,13 +64,18 @@ export function AskAgentModal({
    <div
      className={
        anchorPoint
-          ? "fixed inset-0 z-[100] bg-black/60 backdrop-blur-sm"
-          : "fixed inset-0 z-[100] flex items-center justify-center bg-black/60 backdrop-blur-sm"
+          ? "hf-backdrop-in fixed inset-0 z-[100] bg-black/60 backdrop-blur-sm"
+          : "hf-backdrop-in fixed inset-0 z-[100] flex items-center justify-center bg-black/60 backdrop-blur-sm"
      }
-      onClick={onClose}
+      onClick={requestClose}
    >
      <div
-        className={`w-[480px] rounded-2xl border border-neutral-800 bg-neutral-950 shadow-2xl ${
+        ref={containerRef}
+        role="dialog"
+        aria-modal="true"
+        aria-label="Copy prompt to AI agent"
+        tabIndex={-1}
+        className={`w-[480px] rounded-2xl border border-neutral-800 bg-neutral-950 shadow-2xl outline-none ${
          anchorPoint ? "fixed" : ""
        }`}
        style={modalPositionStyle}
@@ -74,8 +89,9 @@ export function AskAgentModal({
            </p>
          </div>
          <button
-            className="p-1 rounded-md text-neutral-500 hover:text-neutral-300 hover:bg-neutral-800/50"
+            className="p-1 rounded-md text-neutral-500 hover:text-neutral-300 hover:bg-neutral-800/50 active:scale-[0.98]"
            onClick={onClose}
+            aria-label="Close"
          >
            <svg
              width="14"
@@ -100,7 +116,8 @@ export function AskAgentModal({
            onChange={(e) => setValue(e.target.value)}
            onKeyDown={(e) => {
              if (e.key === "Enter" && (e.metaKey || e.ctrlKey)) handleSubmit();
-              if (e.key === "Escape") onClose();
+              // Escape is handled at the document level by useDialogBehavior,
+              // guarded against discarding a dirty draft.
            }}
          />
          {contextPreview && (
@@ -1,6 +1,7 @@
-import { useState } from "react";
+import { useRef, useState } from "react";
 import { XIcon, WarningIcon, CheckCircleIcon, CaretRightIcon } from "@phosphor-icons/react";
 import { copyTextToClipboard } from "../utils/clipboard";
+import { useDialogBehavior } from "./ui/useDialogBehavior";

 export interface LintFinding {
  severity: "error" | "warning";
@@ -12,16 +13,28 @@ export interface LintFinding {
 export function LintModal({
  findings,
  projectId,
+  projectDir,
+  title = "HyperFrame Lint Results",
+  promptIntro = "Fix these HyperFrames lint issues",
  onClose,
 }: {
  findings: LintFinding[];
  projectId: string;
+  /** Real on-disk project directory for the agent prompt (not the browser URL). */
+  projectDir?: string | null;
+  /** Header subtitle — parameterize so console errors don't masquerade as lint results. */
+  title?: string;
+  /** First line of the copied agent prompt. */
+  promptIntro?: string;
  onClose: () => void;
 }) {
  const errors = findings.filter((f) => f.severity === "error");
  const warnings = findings.filter((f) => f.severity === "warning");
  const hasIssues = findings.length > 0;
  const [copied, setCopied] = useState(false);
+  const [copyFailed, setCopyFailed] = useState(false);
+  const containerRef = useRef<HTMLDivElement>(null);
+  const { requestClose } = useDialogBehavior({ open: true, onClose, containerRef });

  const handleCopyToAgent = async () => {
    const lines = findings.map((f) => {
@@ -30,21 +43,31 @@ export function LintModal({
      if (f.fixHint) line += `\n  Fix: ${f.fixHint}`;
      return line;
    });
-    const text = `Fix these HyperFrames lint issues for project "${projectId}":\n\nProject path: ${window.location.href}\n\n${lines.join("\n\n")}`;
+    const pathLine = projectDir ? `Project path: ${projectDir}\n\n` : "";
+    const text = `${promptIntro} for project "${projectId}":\n\n${pathLine}${lines.join("\n\n")}`;
    const copiedText = await copyTextToClipboard(text);
    if (copiedText) {
      setCopied(true);
+      setCopyFailed(false);
      setTimeout(() => setCopied(false), 2000);
+    } else {
+      setCopyFailed(true);
+      setTimeout(() => setCopyFailed(false), 3000);
    }
  };

  return (
    <div
-      className="fixed inset-0 z-[100] flex items-center justify-center bg-black/60 backdrop-blur-sm"
-      onClick={onClose}
+      className="hf-backdrop-in fixed inset-0 z-[100] flex items-center justify-center bg-black/60 backdrop-blur-sm"
+      onClick={requestClose}
    >
      <div
-        className="bg-neutral-950 border border-neutral-800 rounded-xl shadow-2xl w-full max-w-xl max-h-[80vh] flex flex-col overflow-hidden"
+        ref={containerRef}
+        role="dialog"
+        aria-modal="true"
+        aria-label={title}
+        tabIndex={-1}
+        className="bg-neutral-950 border border-neutral-800 rounded-xl shadow-2xl w-full max-w-xl max-h-[80vh] flex flex-col overflow-hidden outline-none"
        onClick={(e) => e.stopPropagation()}
      >
        {/* Header */}
@@ -65,12 +88,13 @@ export function LintModal({
                  ? `${errors.length} error${errors.length !== 1 ? "s" : ""}, ${warnings.length} warning${warnings.length !== 1 ? "s" : ""}`
                  : "All checks passed"}
              </h2>
-              <p className="text-xs text-neutral-500">HyperFrame Lint Results</p>
+              <p className="text-xs text-neutral-500">{title}</p>
            </div>
          </div>
          <button
            onClick={onClose}
-            className="p-1.5 rounded-lg text-neutral-500 hover:text-neutral-200 hover:bg-neutral-800 transition-colors"
+            aria-label="Close"
+            className="p-1.5 rounded-lg text-neutral-500 hover:text-neutral-200 hover:bg-neutral-800 transition-colors active:scale-[0.98]"
          >
            <XIcon size={16} />
          </button>
@@ -81,13 +105,19 @@ export function LintModal({
          <div className="flex items-center justify-end px-5 py-2 border-b border-neutral-800/50">
            <button
              onClick={handleCopyToAgent}
-              className={`px-3 py-1 text-xs font-medium rounded-lg transition-colors ${
+              className={`px-3 py-1 text-xs font-medium rounded-lg transition-colors active:scale-[0.98] ${
                copied
                  ? "bg-green-600 text-white"
-                  : "bg-studio-accent hover:bg-studio-accent/80 text-white"
+                  : copyFailed
+                    ? "bg-red-600 text-white"
+                    : "bg-studio-accent hover:bg-studio-accent/80 text-white"
              }`}
            >
-              {copied ? "Copied!" : "Copy to Agent"}
+              {copied
+                ? "Copied!"
+                : copyFailed
+                  ? "Copy failed — check permissions"
+                  : "Copy to Agent"}
            </button>
          </div>
        )}
@@ -1,8 +1,41 @@
+import { useState } from "react";
 import { IMAGE_EXT, VIDEO_EXT, AUDIO_EXT } from "../utils/mediaTypes";

+function MediaErrorPanel({ name, filePath }: { name: string; filePath: string }) {
+  return (
+    <div className="flex flex-col items-center justify-center h-full p-4 bg-neutral-950 gap-2">
+      <svg
+        width="40"
+        height="40"
+        viewBox="0 0 24 24"
+        fill="none"
+        stroke="currentColor"
+        strokeWidth="1.5"
+        className="text-neutral-600"
+        aria-hidden="true"
+      >
+        <circle cx="12" cy="12" r="10" />
+        <line x1="12" y1="8" x2="12" y2="12" strokeLinecap="round" />
+        <line x1="12" y1="16" x2="12.01" y2="16" strokeLinecap="round" />
+      </svg>
+      <span className="text-sm text-neutral-400 font-medium">{name}</span>
+      <span className="text-[11px] text-neutral-600 font-mono">{filePath}</span>
+      <span className="text-[10px] text-neutral-500">
+        Couldn't load this file — it may be missing or corrupt
+      </span>
+    </div>
+  );
+}
+
 export function MediaPreview({ projectId, filePath }: { projectId: string; filePath: string }) {
  const serveUrl = `/api/projects/${projectId}/preview/${filePath}`;
  const name = filePath.split("/").pop() ?? filePath;
+  // Keyed by path so switching to another file clears a previous failure.
+  const [failedPath, setFailedPath] = useState<string | null>(null);
+  const failed = failedPath === filePath;
+  const setFailed = () => setFailedPath(filePath);
+
+  if (failed) return <MediaErrorPanel name={name} filePath={filePath} />;

  if (IMAGE_EXT.test(filePath)) {
    return (
@@ -10,6 +43,7 @@ export function MediaPreview({ projectId, filePath }: { projectId: string; fileP
        <img
          src={serveUrl}
          alt={name}
+          onError={setFailed}
          className="max-w-full max-h-[70%] object-contain rounded border border-neutral-800"
        />
        <span className="mt-3 text-[11px] text-neutral-500 font-mono">{filePath}</span>
@@ -23,6 +57,7 @@ export function MediaPreview({ projectId, filePath }: { projectId: string; fileP
        <video
          src={serveUrl}
          controls
+          onError={setFailed}
          className="max-w-full max-h-[70%] rounded border border-neutral-800"
        />
        <span className="mt-3 text-[11px] text-neutral-500 font-mono">{filePath}</span>
@@ -46,7 +81,7 @@ export function MediaPreview({ projectId, filePath }: { projectId: string; fileP
          <circle cx="6" cy="18" r="3" />
          <circle cx="18" cy="16" r="3" />
        </svg>
-        <audio src={serveUrl} controls className="w-full max-w-[280px]" />
+        <audio src={serveUrl} controls onError={setFailed} className="w-full max-w-[280px]" />
        <span className="text-[11px] text-neutral-500 font-mono">{filePath}</span>
      </div>
    );
@@ -1,22 +1,23 @@
 interface SaveQueuePausedBannerProps {
  message: string;
-  onDismiss: () => void;
+  /** Resets the save-queue circuit breaker so persistence resumes. */
+  onRetry: () => void;
 }

 /** Alert shown when the DOM-edit save queue circuit breaker pauses persistence. */
-export function SaveQueuePausedBanner({ message, onDismiss }: SaveQueuePausedBannerProps) {
+export function SaveQueuePausedBanner({ message, onRetry }: SaveQueuePausedBannerProps) {
  return (
    <div
-      className="absolute left-1/2 top-14 z-[92] flex max-w-[calc(100vw-32px)] -translate-x-1/2 items-center gap-3 rounded-md border border-red-500/30 bg-red-950/85 px-4 py-2 text-[12px] font-medium text-red-100 shadow-lg shadow-black/30"
+      className="hf-backdrop-in absolute left-1/2 top-14 z-[92] flex max-w-[calc(100vw-32px)] -translate-x-1/2 items-center gap-3 rounded-md border border-red-500/30 bg-red-950/85 px-4 py-2 text-[12px] font-medium text-red-100 shadow-lg shadow-black/30"
      role="alert"
    >
      <span>{message}</span>
      <button
        type="button"
-        onClick={onDismiss}
-        className="rounded border border-red-300/20 px-2 py-1 text-[11px] text-red-100 transition-colors hover:bg-red-400/10"
+        onClick={onRetry}
+        className="rounded border border-red-300/20 px-2 py-1 text-[11px] text-red-100 transition-colors hover:bg-red-400/10 active:scale-[0.98]"
      >
-        Dismiss
+        Retry saving
      </button>
    </div>
  );
@@ -30,39 +30,27 @@ export class StudioErrorBoundary extends Component<Props, State> {
    if (!this.state.error) return this.props.children;

    return (
-      <div
-        style={{
-          position: "fixed",
-          inset: 0,
-          display: "flex",
-          flexDirection: "column",
-          alignItems: "center",
-          justifyContent: "center",
-          background: "#0a0a0a",
-          color: "#e5e5e5",
-          fontFamily: "system-ui, -apple-system, sans-serif",
-          gap: 16,
-        }}
-      >
-        <div style={{ fontSize: 18, fontWeight: 600 }}>Something went wrong</div>
-        <div style={{ fontSize: 13, color: "#888", maxWidth: 480, textAlign: "center" }}>
+      <div className="fixed inset-0 flex flex-col items-center justify-center gap-4 bg-neutral-950 font-sans text-neutral-200">
+        <div className="text-lg font-semibold">Something went wrong</div>
+        <div className="max-w-[480px] text-center text-[13px] text-neutral-500">
          {this.state.error.message}
        </div>
-        <button
-          onClick={() => this.setState({ error: null })}
-          style={{
-            marginTop: 8,
-            padding: "8px 20px",
-            background: "#2563eb",
-            color: "#fff",
-            border: "none",
-            borderRadius: 6,
-            fontSize: 14,
-            cursor: "pointer",
-          }}
-        >
-          Try again
-        </button>
+        <div className="mt-2 flex items-center gap-2">
+          <button
+            onClick={() => this.setState({ error: null })}
+            className="rounded-md bg-studio-accent px-5 py-2 text-sm font-medium text-neutral-950 transition-[filter] hover:brightness-110 active:scale-[0.98]"
+          >
+            Try again
+          </button>
+          {/* If the error recurs immediately, "Try again" loops — a full reload
+              is the recovery path that always works. */}
+          <button
+            onClick={() => window.location.reload()}
+            className="rounded-md border border-neutral-700 px-5 py-2 text-sm font-medium text-neutral-300 transition-colors hover:bg-neutral-800 active:scale-[0.98]"
+          >
+            Reload Studio
+          </button>
+        </div>
      </div>
    );
  }
@@ -69,6 +69,7 @@ function markPrompted(): void {
 // fallow-ignore-next-line complexity
 export const StudioFeedbackBar = memo(function StudioFeedbackBar() {
  const [visible, setVisible] = useState(false);
+  const [entered, setEntered] = useState(false);
  const [rating, setRating] = useState<number | null>(null);
  const [comment, setComment] = useState("");
  const [submitted, setSubmitted] = useState(false);
@@ -88,6 +89,14 @@ export const StudioFeedbackBar = memo(function StudioFeedbackBar() {
    return () => clearTimeout(showTimer);
  }, []);

+  // Animate height in on entrance — appearing 3s after load, an instant 32px
+  // bar shoves the whole preview stack up mid-task.
+  useEffect(() => {
+    if (!visible) return;
+    const raf = requestAnimationFrame(() => setEntered(true));
+    return () => cancelAnimationFrame(raf);
+  }, [visible]);
+
  // Auto-dismiss timer — reset when user interacts (sets rating)
  useEffect(() => {
    if (!visible || rating !== null || submitted) return;
@@ -141,8 +150,8 @@ export const StudioFeedbackBar = memo(function StudioFeedbackBar() {
  return (
    <div
      className={[
-        "flex items-center gap-3 px-4 h-8 border-t border-neutral-800/50 bg-neutral-900/80 text-[11px] transition-all duration-300",
-        exiting ? "opacity-0 translate-y-2" : "opacity-100 translate-y-0",
+        "flex items-center gap-3 px-4 overflow-hidden border-t border-neutral-800/50 bg-neutral-900/80 text-[11px] transition-all duration-300 motion-reduce:transition-none",
+        entered && !exiting ? "h-8 opacity-100" : "h-0 opacity-0 border-t-transparent",
      ].join(" ")}
    >
      {submitted ? (
@@ -1,6 +1,6 @@
 export function StudioGlobalDragOverlay() {
  return (
-    <div className="absolute inset-0 z-[90] flex items-center justify-center bg-black/50 backdrop-blur-sm pointer-events-none">
+    <div className="hf-backdrop-in absolute inset-0 z-[90] flex items-center justify-center bg-black/50 backdrop-blur-sm pointer-events-none">
      <div className="flex flex-col items-center gap-3 px-8 py-6 rounded-xl border-2 border-dashed border-studio-accent/60 bg-studio-accent/[0.06]">
        <svg
          width="32"
@@ -1,4 +1,4 @@
-import type { MouseEvent } from "react";
+import { useRef, type MouseEvent } from "react";
 import { RotateCcw, RotateCw, Camera } from "../icons/SystemIcons";
 import {
  STUDIO_INSPECTOR_PANELS_ENABLED,
@@ -9,12 +9,14 @@ import { useStudioShellContext } from "../contexts/StudioContext";
 import { usePanelLayoutContext } from "../contexts/PanelLayoutContext";
 import { useViewMode, type StudioViewMode } from "../contexts/ViewModeContext";
 import { trackStudioEvent } from "../utils/studioTelemetry";
+import { Tooltip } from "./ui";

 export interface StudioHeaderProps {
  captureFrameHref: string;
  captureFrameFilename: string;
  handleCaptureFrameClick: (event: MouseEvent<HTMLAnchorElement>) => void;
  refreshCaptureFrameTime: () => void;
+  capturing?: boolean;
  inspectorButtonActive: boolean;
  inspectorPanelActive: boolean;
  onExport?: () => void;
@@ -149,26 +151,45 @@ const VIEW_MODE_OPTIONS: Array<{ mode: StudioViewMode; label: string }> = [
 /** Segmented control switching the main stage between storyboard and preview. */
 function ViewModeToggle() {
  const { viewMode, setViewMode } = useViewMode();
+  const tabRefs = useRef<Array<HTMLButtonElement | null>>([]);
+
+  const selectMode = (mode: StudioViewMode) => {
+    if (mode === viewMode) return;
+    trackStudioEvent("view_mode_toggle", { mode });
+    setViewMode(mode);
+  };
+
+  // Complete APG tabs pattern: roving tabIndex + arrow-key navigation.
+  const handleKeyDown = (e: React.KeyboardEvent, index: number) => {
+    if (e.key !== "ArrowLeft" && e.key !== "ArrowRight") return;
+    e.preventDefault();
+    const dir = e.key === "ArrowLeft" ? -1 : 1;
+    const next = (index + dir + VIEW_MODE_OPTIONS.length) % VIEW_MODE_OPTIONS.length;
+    tabRefs.current[next]?.focus();
+    selectMode(VIEW_MODE_OPTIONS[next].mode);
+  };
+
  return (
    <div
      className="flex items-center gap-0.5 rounded-md bg-neutral-800 p-0.5"
      role="tablist"
      aria-label="Studio view"
    >
-      {VIEW_MODE_OPTIONS.map(({ mode, label }) => {
+      {VIEW_MODE_OPTIONS.map(({ mode, label }, index) => {
        const active = viewMode === mode;
        return (
          <button
            key={mode}
+            ref={(el) => {
+              tabRefs.current[index] = el;
+            }}
            type="button"
            role="tab"
            aria-selected={active}
-            onClick={() => {
-              if (active) return;
-              trackStudioEvent("view_mode_toggle", { mode });
-              setViewMode(mode);
-            }}
-            className={`rounded px-3 py-1 text-[11px] font-medium transition-colors ${
+            tabIndex={active ? 0 : -1}
+            onClick={() => selectMode(mode)}
+            onKeyDown={(e) => handleKeyDown(e, index)}
+            className={`rounded px-3 py-1 text-[11px] font-medium transition-colors active:scale-[0.98] outline-none focus-visible:outline focus-visible:outline-2 focus-visible:outline-studio-accent ${
              active ? "bg-neutral-200 text-neutral-900" : "text-neutral-400 hover:text-neutral-200"
            }`}
          >
@@ -186,12 +207,14 @@ export function StudioHeader({
  captureFrameFilename,
  handleCaptureFrameClick,
  refreshCaptureFrameTime,
+  capturing,
  inspectorButtonActive,
  inspectorPanelActive,
  onExport,
 }: StudioHeaderProps) {
-  const { projectId, editHistory, handleUndo, handleRedo } = useStudioShellContext();
+  const { projectId, editHistory, handleUndo, handleRedo, renderQueue } = useStudioShellContext();
  const { rightCollapsed, setRightCollapsed, setRightPanelTab } = usePanelLayoutContext();
+  const isRendering = renderQueue.isRendering;

  return (
    <div className="flex items-center justify-between h-10 px-3 bg-neutral-900 border-b border-neutral-800 flex-shrink-0">
@@ -207,118 +230,173 @@ export function StudioHeader({
      <ViewModeToggle />
      {/* Right: toolbar buttons */}
      <div className="flex items-center gap-1.5">
-        <button
-          type="button"
-          onClick={() => {
-            trackStudioEvent("toolbar_action", { action: "undo" });
-            void handleUndo();
-          }}
-          disabled={!editHistory.canUndo}
-          className={`h-7 w-7 flex items-center justify-center rounded-md transition-colors ${
-            editHistory.canUndo
-              ? "text-neutral-400 hover:text-neutral-200 hover:bg-neutral-800"
-              : "text-neutral-700 cursor-default"
-          }`}
-          title={
+        <Tooltip
+          label={
            editHistory.undoLabel
              ? `Undo ${editHistory.undoLabel} (${getHistoryShortcutLabel("undo")})`
              : `Undo (${getHistoryShortcutLabel("undo")})`
          }
-          aria-label="Undo"
+          side="bottom"
        >
-          <RotateCcw size={14} />
-        </button>
-        <button
-          type="button"
-          onClick={() => {
-            trackStudioEvent("toolbar_action", { action: "redo" });
-            void handleRedo();
-          }}
-          disabled={!editHistory.canRedo}
-          className={`h-7 w-7 flex items-center justify-center rounded-md transition-colors ${
-            editHistory.canRedo
-              ? "text-neutral-400 hover:text-neutral-200 hover:bg-neutral-800"
-              : "text-neutral-700 cursor-default"
-          }`}
-          title={
+          <button
+            type="button"
+            onClick={() => {
+              trackStudioEvent("toolbar_action", { action: "undo" });
+              void handleUndo();
+            }}
+            disabled={!editHistory.canUndo}
+            className={`h-7 w-7 flex items-center justify-center rounded-md transition-colors active:scale-[0.98] ${
+              editHistory.canUndo
+                ? "text-neutral-400 hover:text-neutral-200 hover:bg-neutral-800"
+                : "text-neutral-700 cursor-default"
+            }`}
+            aria-label="Undo"
+          >
+            <RotateCcw size={14} />
+          </button>
+        </Tooltip>
+        <Tooltip
+          label={
            editHistory.redoLabel
              ? `Redo ${editHistory.redoLabel} (${getHistoryShortcutLabel("redo")})`
              : `Redo (${getHistoryShortcutLabel("redo")})`
          }
-          aria-label="Redo"
+          side="bottom"
        >
-          <RotateCw size={14} />
-        </button>
-        <a
-          href={captureFrameHref}
-          download={captureFrameFilename}
-          onClick={(e) => {
-            trackStudioEvent("toolbar_action", { action: "capture_frame" });
-            handleCaptureFrameClick(e);
-          }}
-          onFocus={refreshCaptureFrameTime}
-          onPointerDown={refreshCaptureFrameTime}
-          className="h-7 flex items-center gap-1.5 px-2.5 rounded-md text-[11px] font-medium text-neutral-400 transition-colors hover:text-neutral-200 hover:bg-neutral-800"
-          title="Capture current frame"
-          aria-label="Capture current frame"
-        >
-          <Camera size={14} />
-          <span>Capture</span>
-        </a>
-        <button
-          type="button"
-          onClick={() => {
-            if (!STUDIO_INSPECTOR_PANELS_ENABLED) return;
-            if (rightCollapsed || !inspectorPanelActive) {
-              trackStudioEvent("panel_toggle", { panel: "inspector", collapsed: false });
-              setRightPanelTab("design");
-              setRightCollapsed(false);
-              return;
-            }
-            trackStudioEvent("panel_toggle", { panel: "inspector", collapsed: true });
-            // Keep the current selection when collapsing the Inspector — closing
-            // the panel shouldn't deselect the element.
-            setRightCollapsed(true);
-          }}
-          disabled={!STUDIO_INSPECTOR_PANELS_ENABLED}
-          className={`h-7 flex items-center gap-1.5 px-2.5 rounded-md text-[11px] font-medium border transition-colors ${
-            inspectorButtonActive
-              ? "text-studio-accent bg-studio-accent/10 border-studio-accent/30"
-              : STUDIO_INSPECTOR_PANELS_ENABLED
-                ? "text-neutral-500 hover:text-neutral-300 hover:bg-neutral-800 border-transparent"
-                : "cursor-not-allowed border-transparent text-neutral-700"
-          }`}
-          title={
-            STUDIO_INSPECTOR_PANELS_ENABLED ? "Inspector" : STUDIO_MANUAL_EDITING_DISABLED_TITLE
-          }
-          aria-label={
-            STUDIO_INSPECTOR_PANELS_ENABLED ? "Inspector" : STUDIO_MANUAL_EDITING_DISABLED_TITLE
-          }
-        >
-          <svg
-            width="12"
-            height="12"
-            viewBox="0 0 24 24"
-            fill="none"
-            stroke="currentColor"
-            strokeWidth="2"
+          <button
+            type="button"
+            onClick={() => {
+              trackStudioEvent("toolbar_action", { action: "redo" });
+              void handleRedo();
+            }}
+            disabled={!editHistory.canRedo}
+            className={`h-7 w-7 flex items-center justify-center rounded-md transition-colors active:scale-[0.98] ${
+              editHistory.canRedo
+                ? "text-neutral-400 hover:text-neutral-200 hover:bg-neutral-800"
+                : "text-neutral-700 cursor-default"
+            }`}
+            aria-label="Redo"
          >
-            <circle cx="12" cy="12" r="10" />
-            <polygon points="10 8 16 12 10 16" fill="currentColor" stroke="none" />
-          </svg>
-          Inspector
-        </button>
-        <button
-          type="button"
-          onClick={() => {
-            setRightPanelTab("renders");
-            setRightCollapsed(false);
-            onExport?.();
-          }}
-          className="h-7 flex items-center gap-1.5 px-3 rounded-md text-[11px] font-semibold bg-studio-accent text-[#09090B] hover:brightness-110 transition-colors"
+            <RotateCw size={14} />
+          </button>
+        </Tooltip>
+        <Tooltip label={capturing ? "Capturing frame…" : "Capture current frame"} side="bottom">
+          <a
+            href={captureFrameHref}
+            download={captureFrameFilename}
+            onClick={(e) => {
+              if (capturing) {
+                e.preventDefault();
+                return;
+              }
+              trackStudioEvent("toolbar_action", { action: "capture_frame" });
+              handleCaptureFrameClick(e);
+            }}
+            onFocus={refreshCaptureFrameTime}
+            onPointerDown={refreshCaptureFrameTime}
+            aria-disabled={capturing || undefined}
+            className={`h-7 flex items-center gap-1.5 px-2.5 rounded-md text-[11px] font-medium transition-colors ${
+              capturing
+                ? "text-neutral-600 cursor-default"
+                : "text-neutral-400 hover:text-neutral-200 hover:bg-neutral-800 active:scale-[0.98]"
+            }`}
+            aria-label={capturing ? "Capturing frame" : "Capture current frame"}
+          >
+            {capturing ? (
+              <svg
+                className="animate-spin motion-reduce:animate-none h-3.5 w-3.5"
+                viewBox="0 0 24 24"
+                fill="none"
+                aria-hidden="true"
+              >
+                <circle
+                  className="opacity-25"
+                  cx="12"
+                  cy="12"
+                  r="10"
+                  stroke="currentColor"
+                  strokeWidth="4"
+                />
+                <path
+                  className="opacity-75"
+                  fill="currentColor"
+                  d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4z"
+                />
+              </svg>
+            ) : (
+              <Camera size={14} />
+            )}
+            <span>{capturing ? "Capturing…" : "Capture"}</span>
+          </a>
+        </Tooltip>
+        <Tooltip
+          label={
+            STUDIO_INSPECTOR_PANELS_ENABLED ? "Inspector" : STUDIO_MANUAL_EDITING_DISABLED_TITLE
+          }
+          side="bottom"
        >
-          Export
-        </button>
+          <button
+            type="button"
+            onClick={() => {
+              if (!STUDIO_INSPECTOR_PANELS_ENABLED) return;
+              if (rightCollapsed || !inspectorPanelActive) {
+                trackStudioEvent("panel_toggle", { panel: "inspector", collapsed: false });
+                setRightPanelTab("design");
+                setRightCollapsed(false);
+                return;
+              }
+              trackStudioEvent("panel_toggle", { panel: "inspector", collapsed: true });
+              // Keep the current selection when collapsing the Inspector — closing
+              // the panel shouldn't deselect the element.
+              setRightCollapsed(true);
+            }}
+            disabled={!STUDIO_INSPECTOR_PANELS_ENABLED}
+            aria-pressed={inspectorButtonActive}
+            className={`h-7 flex items-center gap-1.5 px-2.5 rounded-md text-[11px] font-medium border transition-colors active:scale-[0.98] ${
+              inspectorButtonActive
+                ? "text-studio-accent bg-studio-accent/10 border-studio-accent/30"
+                : STUDIO_INSPECTOR_PANELS_ENABLED
+                  ? "text-neutral-500 hover:text-neutral-300 hover:bg-neutral-800 border-transparent"
+                  : "cursor-not-allowed border-transparent text-neutral-700"
+            }`}
+            aria-label={
+              STUDIO_INSPECTOR_PANELS_ENABLED ? "Inspector" : STUDIO_MANUAL_EDITING_DISABLED_TITLE
+            }
+          >
+            <svg
+              width="12"
+              height="12"
+              viewBox="0 0 24 24"
+              fill="none"
+              stroke="currentColor"
+              strokeWidth="2"
+            >
+              <circle cx="12" cy="12" r="10" />
+              <polygon points="10 8 16 12 10 16" fill="currentColor" stroke="none" />
+            </svg>
+            Inspector
+          </button>
+        </Tooltip>
+        <Tooltip
+          label={
+            isRendering ? "A render is already in progress" : "Render and export this composition"
+          }
+          side="bottom"
+        >
+          <button
+            type="button"
+            disabled={isRendering}
+            onClick={() => {
+              if (isRendering) return;
+              setRightPanelTab("renders");
+              setRightCollapsed(false);
+              onExport?.();
+            }}
+            className="h-7 flex items-center gap-1.5 px-3 rounded-md text-[11px] font-semibold bg-studio-accent text-[#09090B] enabled:hover:brightness-110 transition-[filter,transform] enabled:active:scale-[0.98] disabled:opacity-50 disabled:cursor-not-allowed"
+          >
+            {isRendering ? "Rendering…" : "Export"}
+          </button>
+        </Tooltip>
      </div>
    </div>
  );
@@ -34,6 +34,7 @@ export function StudioLeftSidebar({
  const {
    leftCollapsed,
    leftWidth,
+    setLeftWidth,
    toggleLeftSidebar,
    handlePanelResizeStart,
    handlePanelResizeMove,
@@ -114,14 +115,22 @@ export function StudioLeftSidebar({
        onRenameFile={handleRenameFile}
        onDuplicateFile={handleDuplicateFile}
        onMoveFile={handleMoveFile}
-        onImportFiles={handleImportFiles}
+        onImportFiles={async (files, dir) => {
+          await handleImportFiles(files, dir);
+        }}
        codeChildren={
          editingFile ? (
            isMediaFile(editingFile.path) ? (
              <MediaPreview projectId={projectId} filePath={editingFile.path} />
+            ) : editingFile.content == null ? (
+              // Never mount the editor on unloaded content: a keystroke would
+              // autosave an empty document over the real file.
+              <div className="flex h-full items-center justify-center text-[11px] text-neutral-600">
+                Loading {editingFile.path}…
+              </div>
            ) : (
              <SourceEditor
-                content={editingFile.content ?? ""}
+                content={editingFile.content}
                filePath={editingFile.path}
                onChange={handleContentChange}
                revealOffset={revealSourceOffset}
@@ -140,11 +149,23 @@ export function StudioLeftSidebar({
        onPreviewBlock={onPreviewBlock}
      />
      <div
-        className="group w-2 flex-shrink-0 cursor-col-resize flex items-center justify-center"
+        role="separator"
+        aria-label="Resize sidebar"
+        aria-orientation="vertical"
+        tabIndex={0}
+        className="group w-2 flex-shrink-0 cursor-col-resize flex items-center justify-center outline-none focus-visible:bg-studio-accent/20"
        style={{ touchAction: "none" }}
        onPointerDown={(e) => handlePanelResizeStart("left", e)}
        onPointerMove={handlePanelResizeMove}
        onPointerUp={handlePanelResizeEnd}
+        onPointerCancel={handlePanelResizeEnd}
+        onKeyDown={(e) => {
+          if (e.key !== "ArrowLeft" && e.key !== "ArrowRight") return;
+          e.preventDefault();
+          const delta = e.key === "ArrowLeft" ? -16 : 16;
+          const maxLeft = Math.floor(window.innerWidth * 0.5);
+          setLeftWidth(Math.max(160, Math.min(maxLeft, leftWidth + delta)));
+        }}
      >
        <div className="h-[52px] w-px bg-white/12 transition-colors group-hover:bg-white/18 group-active:bg-white/24" />
      </div>
@@ -11,6 +11,7 @@ type LintFindings = ComponentProps<typeof LintModal>["findings"];

 export interface StudioOverlaysProps {
  projectId: string;
+  projectDir?: string | null;
  lintModal: LintFindings | null;
  closeLintModal: () => void;
  consoleErrors: LintFindings | null;
@@ -18,8 +19,8 @@ export interface StudioOverlaysProps {
  domEditSession: ReturnType<typeof useDomEditSession>;
  activeCompPath: string | null;
  dragOverlayActive: boolean;
-  appToast: ReturnType<typeof useToast>["appToast"];
-  dismissToast: () => void;
+  toasts: ReturnType<typeof useToast>["toasts"];
+  dismissToast: (id: number) => void;
 }

 /**
@@ -30,6 +31,7 @@ export interface StudioOverlaysProps {
 // fallow-ignore-next-line complexity
 export function StudioOverlays({
  projectId,
+  projectDir,
  lintModal,
  closeLintModal,
  consoleErrors,
@@ -37,16 +39,30 @@ export function StudioOverlays({
  domEditSession,
  activeCompPath,
  dragOverlayActive,
-  appToast,
+  toasts,
  dismissToast,
 }: StudioOverlaysProps) {
  return (
    <>
      {lintModal !== null && (
-        <LintModal findings={lintModal} projectId={projectId} onClose={closeLintModal} />
+        <LintModal
+          findings={lintModal}
+          projectId={projectId}
+          projectDir={projectDir}
+          onClose={closeLintModal}
+        />
      )}
-      {consoleErrors !== null && consoleErrors.length > 0 && (
-        <LintModal findings={consoleErrors} projectId={projectId} onClose={clearConsoleErrors} />
+      {/* One modal at a time — console errors wait behind an open lint modal
+          instead of stacking two full-screen overlays. */}
+      {lintModal === null && consoleErrors !== null && consoleErrors.length > 0 && (
+        <LintModal
+          findings={consoleErrors}
+          projectId={projectId}
+          projectDir={projectDir}
+          title="Console errors in preview"
+          promptIntro="Fix these runtime console errors from the composition preview"
+          onClose={clearConsoleErrors}
+        />
      )}
      {domEditSession.agentModalOpen && domEditSession.domEditSelection && (
        <AskAgentModal
@@ -62,8 +78,18 @@ export function StudioOverlays({
        />
      )}
      {dragOverlayActive && <StudioGlobalDragOverlay />}
-      {appToast && (
-        <StudioToast message={appToast.message} tone={appToast.tone} onDismiss={dismissToast} />
+      {toasts.length > 0 && (
+        <div className="absolute bottom-6 right-6 z-[91] flex flex-col items-end gap-2">
+          {toasts.map((toast) => (
+            <StudioToast
+              key={toast.id}
+              message={toast.message}
+              tone={toast.tone}
+              leaving={toast.leaving}
+              onDismiss={() => dismissToast(toast.id)}
+            />
+          ))}
+        </div>
      )}
    </>
  );
@@ -77,6 +77,7 @@ export function StudioRightPanel({
 }: StudioRightPanelProps) {
  const {
    rightWidth,
+    setRightWidth,
    rightPanelTab,
    setRightPanelTab,
    rightInspectorPanes,
@@ -400,6 +401,11 @@ export function StudioRightPanel({
      jobs={renderJobs}
      projectId={projectId}
      onDelete={renderQueue.deleteRender}
+      onCancel={renderQueue.cancelRender}
+      loadError={renderQueue.loadError}
+      onRetryLoad={renderQueue.reloadRenders}
+      actionError={renderQueue.actionError}
+      onDismissActionError={renderQueue.dismissActionError}
      onClearCompleted={renderQueue.clearCompleted}
      onStartRender={async (format, quality, resolution, fps) => {
        await waitForPendingDomEditSaves();
@@ -421,11 +427,23 @@ export function StudioRightPanel({
  return (
    <>
      <div
-        className="group w-2 flex-shrink-0 cursor-col-resize flex items-center justify-center"
+        role="separator"
+        aria-label="Resize inspector panel"
+        aria-orientation="vertical"
+        tabIndex={0}
+        className="group w-2 flex-shrink-0 cursor-col-resize flex items-center justify-center outline-none focus-visible:bg-studio-accent/20"
        style={{ touchAction: "none" }}
        onPointerDown={(e) => handlePanelResizeStart("right", e)}
        onPointerMove={handlePanelResizeMove}
        onPointerUp={handlePanelResizeEnd}
+        onPointerCancel={handlePanelResizeEnd}
+        onKeyDown={(e) => {
+          if (e.key !== "ArrowLeft" && e.key !== "ArrowRight") return;
+          e.preventDefault();
+          // Panel is right-anchored: ArrowLeft grows it, ArrowRight shrinks it.
+          const delta = e.key === "ArrowLeft" ? 16 : -16;
+          setRightWidth(Math.max(160, Math.min(600, rightWidth + delta)));
+        }}
      >
        <div className="h-[52px] w-px bg-white/12 transition-colors group-hover:bg-white/18 group-active:bg-white/24" />
      </div>
@@ -444,7 +462,8 @@ export function StudioRightPanel({
                    <button
                      type="button"
                      onClick={() => handleInspectorPaneButtonClick("design")}
-                      className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors ${
+                      aria-pressed={designPaneOpen}
+                      className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors active:scale-[0.98] ${
                        designPaneOpen
                          ? "bg-neutral-800 text-white"
                          : "text-neutral-500 hover:bg-neutral-800/70 hover:text-neutral-200"
@@ -457,7 +476,8 @@ export function StudioRightPanel({
                    <button
                      type="button"
                      onClick={() => handleInspectorPaneButtonClick("layers")}
-                      className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors ${
+                      aria-pressed={layersPaneOpen}
+                      className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors active:scale-[0.98] ${
                        layersPaneOpen
                          ? "bg-neutral-800 text-white"
                          : "text-neutral-500 hover:bg-neutral-800/70 hover:text-neutral-200"
@@ -472,7 +492,8 @@ export function StudioRightPanel({
                <button
                  type="button"
                  onClick={() => setRightPanelTab("renders")}
-                  className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors ${
+                  aria-pressed={rightPanelTab === "renders"}
+                  className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors active:scale-[0.98] ${
                    rightPanelTab === "renders"
                      ? "bg-neutral-800 text-white"
                      : "text-neutral-500 hover:bg-neutral-800/70 hover:text-neutral-200"
@@ -485,7 +506,8 @@ export function StudioRightPanel({
                <button
                  type="button"
                  onClick={() => setRightPanelTab("slideshow")}
-                  className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors ${
+                  aria-pressed={rightPanelTab === "slideshow"}
+                  className={`h-8 rounded-xl px-3 text-[11px] font-medium transition-colors active:scale-[0.98] ${
                    rightPanelTab === "slideshow"
                      ? "bg-neutral-800 text-white"
                      : "text-neutral-500 hover:bg-neutral-800/70 hover:text-neutral-200"
@@ -537,6 +559,24 @@ export function StudioRightPanel({
                <LayersPanel />
              ) : designPaneOpen ? (
                propertyPanel
+              ) : inspectorTabActive ? (
+                // Inspector tab selected but no pane can render (panes toggled
+                // off, or inspector inactive during playback/recording): show an
+                // explanation instead of silently rendering the render queue
+                // under a highlighted inspector tab.
+                <div className="flex h-full flex-col items-center justify-center gap-3 px-6 text-center">
+                  <p className="text-xs text-neutral-500">
+                    Inspector is unavailable right now — select the Design or Layers pane above, or
+                    pause playback/recording to inspect elements.
+                  </p>
+                  <button
+                    type="button"
+                    onClick={() => setRightPanelTab("renders")}
+                    className="h-7 rounded-md border border-neutral-800 px-3 text-[11px] font-medium text-neutral-400 transition-colors hover:border-neutral-700 hover:text-neutral-200 active:scale-[0.98]"
+                  >
+                    Show Renders
+                  </button>
+                </div>
              ) : (
                renderQueuePanel
              )}
@@ -2,15 +2,18 @@ export function StudioSplash({ waiting }: { waiting?: boolean }) {
  return (
    <div className="h-full w-full bg-neutral-950 flex items-center justify-center">
      {waiting ? (
-        <div className="flex flex-col items-center gap-3 text-center px-6">
-          <div className="w-4 h-4 rounded-full border-2 border-neutral-700 border-t-neutral-500 animate-spin" />
+        <div className="flex flex-col items-center gap-3 text-center px-6" role="status">
+          <div className="w-4 h-4 rounded-full border-2 border-neutral-700 border-t-neutral-500 animate-spin motion-reduce:animate-none" />
          <p className="text-xs text-neutral-600">
            Waiting for preview server… run{" "}
            <code className="text-neutral-500 font-mono">npm run dev</code>
          </p>
        </div>
      ) : (
-        <div className="w-4 h-4 rounded-full bg-studio-accent animate-pulse" />
+        <div className="flex flex-col items-center gap-3 text-center px-6" role="status">
+          <div className="w-4 h-4 rounded-full bg-studio-accent animate-pulse motion-reduce:animate-none" />
+          <p className="text-xs text-neutral-600">Connecting to project…</p>
+        </div>
      )}
    </div>
  );
@@ -1,18 +1,17 @@
 interface StudioToastProps {
  message: string;
  tone?: "error" | "info";
+  /** Plays the exit animation when true (owner removes the node after ~160ms). */
+  leaving?: boolean;
  onDismiss?: () => void;
 }

-// fallow-ignore-next-line complexity
-export function StudioToast({ message, tone, onDismiss }: StudioToastProps) {
+export function StudioToast({ message, tone, leaving, onDismiss }: StudioToastProps) {
  const isError = tone === "error";
  return (
    <div
-      className="absolute bottom-6 right-6 z-[91] animate-in fade-in slide-in-from-bottom-2"
-      onClick={onDismiss}
-      role={onDismiss ? "button" : undefined}
-      style={onDismiss ? { cursor: "pointer" } : undefined}
+      role={isError ? "alert" : "status"}
+      className={`motion-reduce:animate-none ${leaving ? "hf-toast-exit" : "hf-toast-enter"}`}
    >
      <div
        className="relative flex max-w-[min(420px,calc(100vw-48px))] items-center gap-3 overflow-hidden rounded-2xl py-3 pl-4 pr-2 text-[12px]"
@@ -38,10 +37,7 @@ export function StudioToast({ message, tone, onDismiss }: StudioToastProps) {
        {onDismiss && (
          <button
            type="button"
-            onClick={(e) => {
-              e.stopPropagation();
-              onDismiss();
-            }}
+            onClick={onDismiss}
            className="flex h-5 w-5 flex-shrink-0 items-center justify-center rounded-md text-neutral-500 transition-colors hover:bg-white/10 hover:text-neutral-300"
            aria-label="Dismiss"
          >
@@ -30,21 +30,27 @@ function renderToolbar() {
 describe("TimelineToolbar — auto-keyframe toggle (#1808)", () => {
  it("renders enabled (pressed) by default with no selection", () => {
    const { host, root } = renderToolbar();
-    const btn = host.querySelector<HTMLButtonElement>('button[aria-pressed="true"]');
+    const btn = host.querySelector<HTMLButtonElement>(
+      'button[aria-label="Auto-record manual edits as keyframes"]',
+    );
    expect(btn).not.toBeNull();
+    expect(btn?.getAttribute("aria-pressed")).toBe("true");
    act(() => root.unmount());
  });

  it("flips autoKeyframeEnabled in the store when clicked", () => {
    const { host, root } = renderToolbar();
-    const btn = host.querySelector<HTMLButtonElement>('button[aria-pressed="true"]')!;
+    const btn = host.querySelector<HTMLButtonElement>(
+      'button[aria-label="Auto-record manual edits as keyframes"]',
+    );
+    if (!btn) throw new Error("auto-keyframe toggle not rendered");

    act(() => {
      btn.dispatchEvent(new MouseEvent("click", { bubbles: true }));
    });

    expect(usePlayerStore.getState().autoKeyframeEnabled).toBe(false);
-    expect(host.querySelector('button[aria-pressed="false"]')).not.toBeNull();
+    expect(btn.getAttribute("aria-pressed")).toBe("false");
    act(() => root.unmount());
  });
 });
@@ -112,7 +112,9 @@ export function TimelineToolbar({
                <button
                  type="button"
                  onClick={() => setActiveTool("select")}
-                  className={`flex h-6 w-6 items-center justify-center transition-colors ${
+                  aria-label="Selection tool"
+                  aria-pressed={activeTool === "select"}
+                  className={`flex h-6 w-6 items-center justify-center transition-colors active:scale-[0.98] ${
                    activeTool === "select"
                      ? "bg-neutral-700 text-neutral-200"
                      : "text-neutral-500 hover:text-neutral-300"
@@ -123,11 +125,13 @@ export function TimelineToolbar({
                  </svg>
                </button>
              </Tooltip>
-              <Tooltip label="Razor tool (B)">
+              <Tooltip label="Razor tool (B) — Shift+click splits all tracks">
                <button
                  type="button"
                  onClick={() => setActiveTool("razor")}
-                  className={`flex h-6 w-6 items-center justify-center transition-colors ${
+                  aria-label="Razor tool"
+                  aria-pressed={activeTool === "razor"}
+                  className={`flex h-6 w-6 items-center justify-center transition-colors active:scale-[0.98] ${
                    activeTool === "razor"
                      ? "bg-neutral-700 text-neutral-200"
                      : "text-neutral-500 hover:text-neutral-300"
@@ -153,7 +157,12 @@ export function TimelineToolbar({
              <button
                type="button"
                onClick={onToggleKeyframe}
-                className={`flex h-7 w-7 items-center justify-center rounded transition-colors ${
+                aria-label={
+                  keyframeState === "active"
+                    ? "Remove keyframe at playhead"
+                    : "Add keyframe at playhead"
+                }
+                className={`flex h-7 w-7 items-center justify-center rounded transition-colors active:scale-[0.98] ${
                  keyframeState === "active"
                    ? "text-studio-accent"
                    : keyframeState === "inactive"
@@ -187,8 +196,9 @@ export function TimelineToolbar({
              <button
                type="button"
                onClick={() => setAutoKeyframeEnabled(!autoKeyframeEnabled)}
+                aria-label="Auto-record manual edits as keyframes"
                aria-pressed={autoKeyframeEnabled}
-                className={`flex h-7 w-7 items-center justify-center rounded transition-colors ${
+                className={`flex h-7 w-7 items-center justify-center rounded transition-colors active:scale-[0.98] ${
                  autoKeyframeEnabled
                    ? "text-red-400 hover:text-red-300"
                    : "text-neutral-600 hover:text-neutral-400"
@@ -213,23 +223,35 @@ export function TimelineToolbar({
          )}
          {onSplitElement &&
            (() => {
+              // Render the button unconditionally (disabled when unusable):
+              // mounting/unmounting mid-task shifts the neighboring controls.
              const { selectedElementId, elements, currentTime } = usePlayerStore.getState();
              const el = selectedElementId
                ? elements.find((e) => (e.key ?? e.id) === selectedElementId)
                : null;
-              if (!el || !canSplitElement(el)) return null;
-              const canSplit = currentTime > el.start && currentTime < el.start + el.duration;
+              const splittable = el != null && canSplitElement(el);
+              const canSplit =
+                splittable && currentTime > el.start && currentTime < el.start + el.duration;
              return (
-                <Tooltip label="Split clip at playhead (S)">
+                <Tooltip
+                  label={
+                    canSplit
+                      ? "Split clip at playhead (S)"
+                      : splittable
+                        ? "Move the playhead inside the clip to split"
+                        : "Select a clip to split"
+                  }
+                >
                  <button
                    type="button"
                    disabled={!canSplit}
+                    aria-label="Split clip at playhead"
                    onClick={() => {
-                      if (canSplit) onSplitElement(el, currentTime);
+                      if (canSplit && el) onSplitElement(el, currentTime);
                    }}
                    className={`flex h-7 w-7 items-center justify-center rounded transition-colors ${
                      canSplit
-                        ? "text-neutral-500 hover:text-neutral-200"
+                        ? "text-neutral-500 hover:text-neutral-200 active:scale-[0.98]"
                        : "text-neutral-700 cursor-not-allowed"
                    }`}
                  >
@@ -239,26 +261,38 @@ export function TimelineToolbar({
              );
            })()}
          {beatAnalysisReady &&
-            canAddBeatAt(currentTime) &&
-            (() => (
-              <Tooltip label="Add beat at playhead">
-                <button
-                  type="button"
-                  onClick={() => addBeatAtCompositionTime(currentTime)}
-                  className="flex h-7 w-7 items-center justify-center rounded text-neutral-500 transition-colors hover:text-[#22c55e]"
+            (() => {
+              const canAdd = canAddBeatAt(currentTime);
+              return (
+                <Tooltip
+                  label={canAdd ? "Add beat at playhead" : "A beat already exists at the playhead"}
                >
-                  <svg width="16" height="16" viewBox="0 0 24 24" fill="none">
-                    <path
-                      d="M21 10C21 12.2091 16.9706 14 12 14M21 10C21 7.79086 16.9706 6 12 6C7.02944 6 3 7.79086 3 10M21 10V16C21 18.2091 16.9706 20 12 20M12 14C7.02944 14 3 12.2091 3 10M12 14V20M3 10V16C3 18.2091 7.02944 20 12 20M7 19.3264V13.3264M17 19.3264V13.3264M12 10L20 4"
-                      stroke="currentColor"
-                      strokeWidth="2"
-                      strokeLinecap="round"
-                      strokeLinejoin="round"
-                    />
-                  </svg>
-                </button>
-              </Tooltip>
-            ))()}
+                  <button
+                    type="button"
+                    disabled={!canAdd}
+                    aria-label="Add beat at playhead"
+                    onClick={() => {
+                      if (canAdd) addBeatAtCompositionTime(currentTime);
+                    }}
+                    className={`flex h-7 w-7 items-center justify-center rounded transition-colors ${
+                      canAdd
+                        ? "text-neutral-500 hover:text-[#22c55e] active:scale-[0.98]"
+                        : "text-neutral-700 cursor-not-allowed"
+                    }`}
+                  >
+                    <svg width="16" height="16" viewBox="0 0 24 24" fill="none">
+                      <path
+                        d="M21 10C21 12.2091 16.9706 14 12 14M21 10C21 7.79086 16.9706 6 12 6C7.02944 6 3 7.79086 3 10M21 10V16C21 18.2091 16.9706 20 12 20M12 14C7.02944 14 3 12.2091 3 10M12 14V20M3 10V16C3 18.2091 7.02944 20 12 20M7 19.3264V13.3264M17 19.3264V13.3264M12 10L20 4"
+                        stroke="currentColor"
+                        strokeWidth="2"
+                        strokeLinecap="round"
+                        strokeLinejoin="round"
+                      />
+                    </svg>
+                  </button>
+                </Tooltip>
+              );
+            })()}
        </div>
        <div className="flex items-center gap-1">
          <Tooltip label="Fit timeline to width">
@@ -16,6 +16,7 @@ export function PanelLayoutProvider({
    leftWidth,
    setLeftWidth,
    rightWidth,
+    setRightWidth,
    leftCollapsed,
    setLeftCollapsed,
    rightCollapsed,
@@ -39,6 +40,7 @@ export function PanelLayoutProvider({
      leftWidth,
      setLeftWidth,
      rightWidth,
+      setRightWidth,
      leftCollapsed,
      setLeftCollapsed,
      rightCollapsed,
@@ -56,6 +58,7 @@ export function PanelLayoutProvider({
      leftWidth,
      setLeftWidth,
      rightWidth,
+      setRightWidth,
      leftCollapsed,
      setLeftCollapsed,
      rightCollapsed,
@@ -0,0 +1,40 @@
+import { useCallback } from "react";
+
+/**
+ * Loads a composition file's content for the source editor when a composition
+ * is selected. Content stays null until the fetch resolves — the source editor
+ * must not mount on a null-content file, or its autosave would overwrite the
+ * real file with an empty document. Load failures surface as an error toast
+ * instead of silently rendering an empty (and autosave-armed) editor.
+ */
+export function useCompositionContentLoader({
+  projectId,
+  setEditingFile,
+  setActiveCompPath,
+  showToast,
+}: {
+  projectId: string | null;
+  setEditingFile: (file: { path: string; content: string | null }) => void;
+  setActiveCompPath: (path: string | null) => void;
+  showToast: (message: string, tone?: "error" | "info") => void;
+}) {
+  return useCallback(
+    (comp: string) => {
+      setActiveCompPath(comp.endsWith(".html") ? comp : null);
+      setEditingFile({ path: comp, content: null });
+      fetch(`/api/projects/${projectId}/files/${comp}`)
+        .then(async (r) => {
+          if (!r.ok) throw new Error(`Failed to load ${comp} (${r.status})`);
+          return r.json();
+        })
+        .then((data: { content?: string }) => {
+          if (typeof data.content !== "string") throw new Error(`No content returned for ${comp}`);
+          setEditingFile({ path: comp, content: data.content });
+        })
+        .catch((err) => {
+          showToast(err instanceof Error ? err.message : `Failed to load ${comp}`, "error");
+        });
+    },
+    [projectId, setEditingFile, setActiveCompPath, showToast],
+  );
+}
@@ -18,6 +18,7 @@ interface UseEditorSaveOptions {
  recordEdit: (input: RecordEditInput) => Promise<void>;
  domEditSaveTimestampRef: React.MutableRefObject<number>;
  setRefreshKey: React.Dispatch<React.SetStateAction<number>>;
+  showToast: (message: string, tone?: "error" | "info") => void;
 }

 export function useEditorSave({
@@ -28,9 +29,13 @@ export function useEditorSave({
  recordEdit,
  domEditSaveTimestampRef,
  setRefreshKey,
+  showToast,
 }: UseEditorSaveOptions) {
  const saveRafRef = useRef<number | null>(null);
  const refreshRafRef = useRef<number | null>(null);
+  // One error toast per burst of failures — every keystroke retries the save,
+  // and error toasts persist until dismissed, so don't stack duplicates.
+  const lastFailureToastAtRef = useRef(0);

  const handleContentChange = useCallback(
    (content: string) => {
@@ -61,6 +66,14 @@ export function useEditorSave({
              source: "code_editor",
              error_message: error instanceof Error ? error.message : "unknown",
            });
+            const now = Date.now();
+            if (now - lastFailureToastAtRef.current > 5000) {
+              lastFailureToastAtRef.current = now;
+              showToast(
+                `Couldn't save ${path} — your latest edits are NOT persisted. Check the preview server; editing again retries the save.`,
+                "error",
+              );
+            }
          });
      });
    },
@@ -71,6 +84,7 @@ export function useEditorSave({
      readProjectFile,
      recordEdit,
      setRefreshKey,
+      showToast,
      writeProjectFile,
    ],
  );
@@ -126,6 +126,7 @@ export function useFileManager({
    recordEdit,
    domEditSaveTimestampRef,
    setRefreshKey,
+    showToast,
  });

  // ── File select ──
@@ -133,26 +134,34 @@ export function useFileManager({
  const revealRequestIdRef = useRef(0);
  const revealAbortRef = useRef<AbortController | null>(null);

-  const handleFileSelect = useCallback((path: string) => {
-    const pid = projectIdRef.current;
-    if (!pid) return;
-    revealAbortRef.current?.abort();
-    revealAbortRef.current = null;
-    revealRequestIdRef.current++;
-    // Skip fetching binary content for media files — just set the path for preview
-    if (isMediaFile(path)) {
-      setEditingFile({ path, content: null });
-      return;
-    }
-    fetch(`/api/projects/${pid}/files/${encodeURIComponent(path)}`)
-      .then((r) => r.json())
-      .then((data: { content?: string }) => {
-        if (data.content != null) {
-          setEditingFile({ path, content: data.content });
-        }
-      })
-      .catch(() => {});
-  }, []);
+  const handleFileSelect = useCallback(
+    (path: string) => {
+      const pid = projectIdRef.current;
+      if (!pid) return;
+      revealAbortRef.current?.abort();
+      revealAbortRef.current = null;
+      revealRequestIdRef.current++;
+      // Skip fetching binary content for media files — just set the path for preview
+      if (isMediaFile(path)) {
+        setEditingFile({ path, content: null });
+        return;
+      }
+      fetch(`/api/projects/${pid}/files/${encodeURIComponent(path)}`)
+        .then((r) => {
+          if (!r.ok) throw new Error(`Failed to load ${path} (${r.status})`);
+          return r.json();
+        })
+        .then((data: { content?: string }) => {
+          if (data.content != null) {
+            setEditingFile({ path, content: data.content });
+          }
+        })
+        .catch((err: unknown) => {
+          showToast(err instanceof Error ? err.message : `Failed to load ${path}`, "error");
+        });
+    },
+    [showToast],
+  );

  // ── Click-to-source ──

@@ -253,9 +262,10 @@ export function useFileManager({
      } else {
        const err = await res.json().catch(() => ({ error: "unknown" }));
        console.error(`Create file failed: ${err.error}`);
+        showToast(`Couldn't create ${path}: ${err.error}`, "error");
      }
    },
-    [refreshFileTree, handleFileSelect],
+    [refreshFileTree, handleFileSelect, showToast],
  );

  const handleCreateFolder = useCallback(
@@ -275,9 +285,10 @@ export function useFileManager({
      } else {
        const err = await res.json().catch(() => ({ error: "unknown" }));
        console.error(`Create folder failed: ${err.error}`);
+        showToast(`Couldn't create folder ${path}: ${err.error}`, "error");
      }
    },
-    [refreshFileTree],
+    [refreshFileTree, showToast],
  );

  const handleDeleteFile = useCallback(
@@ -293,9 +304,10 @@ export function useFileManager({
      } else {
        const err = await res.json().catch(() => ({ error: "unknown" }));
        console.error(`Delete failed: ${err.error}`);
+        showToast(`Couldn't delete ${path}: ${err.error}`, "error");
      }
    },
-    [refreshFileTree],
+    [refreshFileTree, showToast],
  );

  const handleRenameFile = useCallback(
@@ -316,9 +328,10 @@ export function useFileManager({
      } else {
        const err = await res.json().catch(() => ({ error: "unknown" }));
        console.error(`Rename failed: ${err.error}`);
+        showToast(`Couldn't rename ${oldPath}: ${err.error}`, "error");
      }
    },
-    [refreshFileTree, handleFileSelect, setRefreshKey],
+    [refreshFileTree, handleFileSelect, setRefreshKey, showToast],
  );

  const handleDuplicateFile = useCallback(
@@ -337,9 +350,10 @@ export function useFileManager({
      } else {
        const err = await res.json().catch(() => ({ error: "unknown" }));
        console.error(`Duplicate failed: ${err.error}`);
+        showToast(`Couldn't duplicate ${path}: ${err.error}`, "error");
      }
    },
-    [refreshFileTree, handleFileSelect],
+    [refreshFileTree, handleFileSelect, showToast],
  );

  const handleMoveFile = handleRenameFile;
@@ -1,4 +1,4 @@
-import { useState, useCallback, type MouseEvent } from "react";
+import { useState, useCallback, useRef, type MouseEvent } from "react";
 import { useMountEffect } from "./useMountEffect";
 import { liveTime, usePlayerStore } from "../player";
 import { buildFrameCaptureFilename, buildFrameCaptureUrl } from "../utils/frameCapture";
@@ -17,6 +17,8 @@ export function useFrameCapture({
  waitForPendingDomEditSaves,
 }: UseFrameCaptureParams) {
  const [captureFrameTime, setCaptureFrameTime] = useState(0);
+  const [capturing, setCapturing] = useState(false);
+  const capturingRef = useRef(false);

  useMountEffect(() => {
    setCaptureFrameTime(usePlayerStore.getState().currentTime);
@@ -31,6 +33,11 @@ export function useFrameCapture({
    async (event: MouseEvent<HTMLAnchorElement>) => {
      if (!projectId) return;
      event.preventDefault();
+      // A capture can take up to ~35s (save drain + server render) — ignore
+      // re-entrant clicks instead of firing parallel captures.
+      if (capturingRef.current) return;
+      capturingRef.current = true;
+      setCapturing(true);
      try {
        const time = usePlayerStore.getState().currentTime;
        setCaptureFrameTime(time);
@@ -79,6 +86,9 @@ export function useFrameCapture({
        }
      } catch (err) {
        showToast(err instanceof Error ? err.message : "Capture failed", "error");
+      } finally {
+        capturingRef.current = false;
+        setCapturing(false);
      }
    },
    [activeCompPath, projectId, showToast, waitForPendingDomEditSaves],
@@ -98,5 +108,6 @@ export function useFrameCapture({
    captureFrameFilename,
    handleCaptureFrameClick,
    refreshCaptureFrameTime,
+    capturing,
  };
 }
@@ -100,6 +100,7 @@ export function usePanelLayout(initialState?: InitialPanelLayoutState) {
    leftWidth,
    setLeftWidth,
    rightWidth,
+    setRightWidth,
    leftCollapsed,
    setLeftCollapsed,
    rightCollapsed,
@@ -2,24 +2,77 @@ import { useState, useCallback, useRef } from "react";
 import { useMountEffect } from "./useMountEffect";
 import type { AppToast } from "../utils/studioHelpers";

-export function useToast() {
-  const [appToast, setAppToast] = useState<AppToast | null>(null);
-  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+interface ToastItem extends AppToast {
+  id: number;
+  /** True while the exit animation plays, just before removal. */
+  leaving?: boolean;
+}

-  const showToast = useCallback((message: string, tone: AppToast["tone"] = "error") => {
-    if (timerRef.current) clearTimeout(timerRef.current);
-    setAppToast({ message, tone });
-    timerRef.current = setTimeout(() => setAppToast(null), 4000);
+const AUTO_DISMISS_MS = 4000;
+const EXIT_MS = 160;
+const MAX_TOASTS = 3;
+
+let nextToastId = 1;
+
+/**
+ * Stacked toasts (max 3). Info toasts auto-dismiss after 4s; error toasts
+ * persist until explicitly dismissed so failures can't silently vanish.
+ */
+export function useToast() {
+  const [toasts, setToasts] = useState<ToastItem[]>([]);
+  const timersRef = useRef<Map<number, ReturnType<typeof setTimeout>>>(new Map());
+
+  const clearTimer = useCallback((id: number) => {
+    const timer = timersRef.current.get(id);
+    if (timer) {
+      clearTimeout(timer);
+      timersRef.current.delete(id);
+    }
  }, []);

+  const removeToast = useCallback(
+    (id: number) => {
+      clearTimer(id);
+      setToasts((prev) => prev.filter((t) => t.id !== id));
+    },
+    [clearTimer],
+  );
+
+  const dismissToast = useCallback(
+    (id: number) => {
+      clearTimer(id);
+      // Mark leaving so the exit animation plays, then remove.
+      setToasts((prev) => prev.map((t) => (t.id === id ? { ...t, leaving: true } : t)));
+      const timer = setTimeout(() => removeToast(id), EXIT_MS);
+      timersRef.current.set(id, timer);
+    },
+    [clearTimer, removeToast],
+  );
+
+  const showToast = useCallback(
+    (message: string, tone: AppToast["tone"] = "error") => {
+      const id = nextToastId++;
+      setToasts((prev) => {
+        const next = [...prev, { id, message, tone }];
+        // Cap the stack; drop the oldest (and its pending timer).
+        while (next.length > MAX_TOASTS) {
+          const dropped = next.shift();
+          if (dropped) clearTimer(dropped.id);
+        }
+        return next;
+      });
+      if (tone !== "error") {
+        const timer = setTimeout(() => dismissToast(id), AUTO_DISMISS_MS);
+        timersRef.current.set(id, timer);
+      }
+    },
+    [clearTimer, dismissToast],
+  );
+
  useMountEffect(() => () => {
-    if (timerRef.current) clearTimeout(timerRef.current);
+    for (const timer of timersRef.current.values()) clearTimeout(timer);
+    timersRef.current.clear();
  });

-  const dismissToast = useCallback(() => {
-    if (timerRef.current) clearTimeout(timerRef.current);
-    setAppToast(null);
-  }, []);
-
-  return { appToast, showToast, dismissToast };
+  return { toasts, showToast, dismissToast };
 }