[eric] canvas: drags flag canvas interaction, idle-canvas drags skip tether work, the toolbar selector stops minting arrays

frontend/src/app/pages/AgentChat/ChatInput/toolbar/ToolbarActions.tsx

@@ -20,6 +20,9 @@ import { useElementSelection } from '@/app/components/editor/ElementSelectionCon
 import { ClaudeTokens } from '@/shared/styles/claudeTokens';
 import { ComposerPlusMenu, ActiveTogglePills, PlusMenuItem } from './ComposerPlusMenu';
 
+// Stable empty: minting [] inside the selector re-rendered the toolbar on every store commit.
+const EMPTY_MCPS: string[] = [];
+
 interface Props {
   c: ClaudeTokens;
   elementSelection: ReturnType<typeof useElementSelection>;
@@ -48,7 +51,7 @@ export const ToolbarActions: React.FC<Props> = ({
   // Lazy-load the skills list the first time the menu could need it; cheap and cached in the slice.
   const skills = useAppSelector((s) => s.skills.items);
   const skillsLoaded = useAppSelector((s) => s.skills.loaded);
-  const activeMcps = useAppSelector((s) => (sessionId ? s.agents.sessions[sessionId]?.active_mcps : undefined) ?? []);
+  const activeMcps = useAppSelector((s) => (sessionId ? s.agents.sessions[sessionId]?.active_mcps : undefined) ?? EMPTY_MCPS);
   React.useEffect(() => { if (!skillsLoaded) dispatch(fetchSkills()); }, [skillsLoaded, dispatch]);
   // Every composer action collapses into one "+" so the bar reads empty at rest; active toggles
   // (web search, selecting) still surface as a pill so their state stays visible. New capabilities

frontend/src/app/pages/Dashboard/canvas/TetherLayerHost.tsx

@@ -9,7 +9,12 @@ import TetherLayer from './TetherLayer';
 // whole dashboard tree (the ENG-88 input delay).
 const TetherLayerHost: React.FC<{ inputs: TetherInputs; c: ClaudeTokens }> = ({ inputs, c }) => {
   const [liveDrag, setLiveDrag] = useState<LiveDragInfo | null>(null);
-  useEffect(() => subscribeLiveDrag(setLiveDrag), []);
+  // Tethers only exist while something glows; on an idle canvas a drag frame should cost zero React work, so don't even subscribe.
+  const hasTethers = Object.keys(inputs.glowingAgentCards).length > 0 || Object.keys(inputs.glowingBrowserCards).length > 0;
+  useEffect(() => {
+    if (!hasTethers) { setLiveDrag(null); return undefined; }
+    return subscribeLiveDrag(setLiveDrag);
+  }, [hasTethers]);
   const tethers = useTethers(inputs, liveDrag);
   return <TetherLayer tethers={tethers} c={c} />;
 };

frontend/src/app/pages/Dashboard/hooks/interaction/useCardDrag.ts

@@ -5,6 +5,7 @@ import { moveCards } from '@/shared/state/dashboardLayoutSlice';
 import type { CardType, useDashboardSelection } from '../state/useDashboardSelection';
 import type { CanvasActions } from './useCanvasControls';
 import { publishLiveDrag } from './liveDragChannel';
+import { setCanvasInteractionActive } from '@/shared/canvasInteractionState';
 
 type Selection = ReturnType<typeof useDashboardSelection>;
 
@@ -98,6 +99,8 @@ export function useCardDrag({
     }
     // Arm the webview shield on the first real MOVE, not on pointerdown: a plain click also arms the drag machinery, and shielding then made the click-to-focus camera fit skip (it saw a "drag in progress"), so focusing a card took two clicks. On a real drag the shield still goes up before the pointer travels, so the webview neutralization + no-nudge + release-over-webview fixes all hold. Idempotent add.
     document.body.classList.add('dashboard-marquee-active');
+    // Card drags count as canvas interaction: without this, a mid-drag transcript resize re-rendered the whole controller per change (the ResizeObserver bail never engaged).
+    setCanvasInteractionActive(true);
     // Start edge panning only once actual dragging begins; a live frame handle means the loop is already running.
     if (edgePanFrameRef.current === null) {
       edgePanFrameRef.current = requestAnimationFrame(tickEdgePan);
@@ -116,6 +119,7 @@ export function useCardDrag({
     canvasActions.commit();
     activeDragCardRef.current = null;
     document.body.classList.remove('dashboard-marquee-active');
+    setCanvasInteractionActive(false);
     isMultiDragRef.current = false;
     setMultiDragDelta(null);
     publishLiveDrag(null);