feat: migrate to React 19

Upgrade React 18.3.1 → 19.2.4 with full type compatibility.

Changes:
- react, react-dom → ^19.0.0
- @types/react, @types/react-dom → ^19.0.0
- lucide-react → ^0.577.0 (React 19 type fixes)
- @tiptap/* → ^3.20.4 (React 19 support)
- useRef calls now require explicit initial value (undefined)
- RefObject types updated for React 19 (includes null)
- MutableRefObject → RefObject (deprecated in 19)
- act() import moved from react-dom/test-utils to react
- Scoped JSX namespace imports added where needed

package.json

@@ -112,11 +112,11 @@
     "@sentry/electron": "^7.10.0",
     "@sentry/react": "^10.45.0",
     "@tanstack/react-virtual": "^3.10.8",
-    "@tiptap/extension-placeholder": "^3.20.1",
-    "@tiptap/markdown": "^3.20.1",
-    "@tiptap/pm": "^3.20.1",
-    "@tiptap/react": "^3.20.1",
-    "@tiptap/starter-kit": "^3.20.1",
+    "@tiptap/extension-placeholder": "^3.20.4",
+    "@tiptap/markdown": "^3.20.4",
+    "@tiptap/pm": "^3.20.4",
+    "@tiptap/react": "^3.20.4",
+    "@tiptap/starter-kit": "^3.20.4",
     "@xterm/addon-fit": "^0.11.0",
     "@xterm/addon-web-links": "^0.12.0",
     "@xterm/xterm": "^6.0.0",
@@ -135,13 +135,13 @@
     "highlight.js": "^11.11.1",
     "idb-keyval": "^6.2.2",
     "isbinaryfile": "^6.0.0",
-    "lucide-react": "^0.562.0",
+    "lucide-react": "^0.577.0",
     "mdast-util-to-hast": "^13.2.1",
     "mermaid": "^11.12.3",
     "node-diff3": "^3.2.0",
     "node-pty": "^1.1.0",
-    "react": "^18.3.1",
-    "react-dom": "^18.3.1",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
     "react-grid-layout": "^2.2.2",
     "react-markdown": "^10.1.0",
     "react-resizable": "^3.1.3",
@@ -170,8 +170,8 @@
     "@types/hast": "^3.0.4",
     "@types/mdast": "^4.0.4",
     "@types/node": "^25.0.7",
-    "@types/react": "^18.3.3",
-    "@types/react-dom": "^18.3.0",
+    "@types/react": "^19.0.0",
+    "@types/react-dom": "^19.0.0",
     "@types/ssh2": "^1.15.5",
     "@vitejs/plugin-react": "^4.3.1",
     "@vitest/coverage-v8": "^3.1.4",

src/renderer/components/chat/ChatHistory.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { type JSX, useCallback, useEffect, useMemo, useRef, useState } from 'react';
 
 import { isNearBottom, useAutoScrollBottom } from '@renderer/hooks/useAutoScrollBottom';
 import { useTabNavigationController } from '@renderer/hooks/useTabNavigationController';

src/renderer/components/chat/ChatHistoryEmptyState.tsx

@@ -1,3 +1,4 @@
+import type { JSX } from 'react';
 /**
  * Empty state for ChatHistory when no conversation exists.
  */

src/renderer/components/chat/ChatHistoryItem.tsx

@@ -1,4 +1,4 @@
-import React from 'react';
+import React, { type JSX } from 'react';
 
 import {
   getHighlightProps,

src/renderer/components/chat/ChatHistoryLoadingState.tsx

@@ -1,3 +1,4 @@
+import type { JSX } from 'react';
 /**
  * Loading skeleton for ChatHistory while conversation is loading.
  * Industrial shimmer with organic line widths — no generic pulse.

src/renderer/components/report/AssessmentBadge.tsx

@@ -20,8 +20,8 @@ export const AssessmentBadge = ({ assessment, metricKey }: AssessmentBadgeProps)
   const [showTooltip, setShowTooltip] = useState(false);
   const [tooltipPos, setTooltipPos] = useState({ top: 0, left: 0 });
   const badgeRef = useRef<HTMLSpanElement>(null);
-  const enterTimer = useRef<ReturnType<typeof setTimeout>>();
-  const leaveTimer = useRef<ReturnType<typeof setTimeout>>();
+  const enterTimer = useRef<ReturnType<typeof setTimeout>>(undefined);
+  const leaveTimer = useRef<ReturnType<typeof setTimeout>>(undefined);
 
   const handleMouseEnter = useCallback(() => {
     if (!explanation) return;

src/renderer/components/settings/sections/AdvancedSection.tsx

@@ -37,7 +37,7 @@ export const AdvancedSection = ({
   const checkForUpdates = useStore((s) => s.checkForUpdates);
 
   // Auto-revert "not-available" / "error" status back to idle after a brief display
-  const revertTimerRef = useRef<ReturnType<typeof setTimeout>>();
+  const revertTimerRef = useRef<ReturnType<typeof setTimeout>>(undefined);
   useEffect(() => {
     if (updateStatus === 'not-available' || updateStatus === 'error') {
       revertTimerRef.current = setTimeout(() => {

src/renderer/components/settings/sections/ConfigEditorDialog.tsx

@@ -63,8 +63,8 @@ export const ConfigEditorDialog = ({
 }: ConfigEditorDialogProps): React.JSX.Element | null => {
   const editorRef = useRef<HTMLDivElement>(null);
   const viewRef = useRef<EditorView | null>(null);
-  const saveTimerRef = useRef<ReturnType<typeof setTimeout>>();
-  const savedRevertTimerRef = useRef<ReturnType<typeof setTimeout>>();
+  const saveTimerRef = useRef<ReturnType<typeof setTimeout>>(undefined);
+  const savedRevertTimerRef = useRef<ReturnType<typeof setTimeout>>(undefined);
   const [saveStatus, setSaveStatus] = useState<SaveStatus>('idle');
   const [jsonError, setJsonError] = useState<string | null>(null);
   const [loading, setLoading] = useState(true);

src/renderer/components/team/activity/AnimatedHeightReveal.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useRef, useState } from 'react';
+import { type JSX, useCallback, useEffect, useRef, useState } from 'react';
 
 import type { CSSProperties, MutableRefObject, PropsWithChildren, Ref } from 'react';
 

src/renderer/components/team/activity/LeadThoughtsGroup.tsx

@@ -1,4 +1,13 @@
-import { memo, useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react';
+import {
+  type JSX,
+  memo,
+  useCallback,
+  useEffect,
+  useLayoutEffect,
+  useMemo,
+  useRef,
+  useState,
+} from 'react';
 
 import { MemberBadge } from '@renderer/components/team/MemberBadge';
 import { Tooltip, TooltipContent, TooltipTrigger } from '@renderer/components/ui/tooltip';

src/renderer/components/team/activity/ThoughtBodyContent.tsx

@@ -1,4 +1,4 @@
-import { memo, useCallback, useMemo } from 'react';
+import { type JSX, memo, useCallback, useMemo } from 'react';
 
 import { MarkdownViewer } from '@renderer/components/chat/viewers/MarkdownViewer';
 import { CopyButton } from '@renderer/components/common/CopyButton';

src/renderer/components/team/editor/MarkdownSplitView.tsx

@@ -113,7 +113,6 @@ export const MarkdownSplitView = React.memo(function MarkdownSplitView({
           onMouseDown={handleMouseDown}
         />
       )}
-
       {/* Preview pane */}
       <div className="flex-1 overflow-hidden bg-surface">
         <MarkdownPreviewPane

src/renderer/components/team/editor/SearchInFilesPanel.tsx

@@ -50,7 +50,7 @@ export const SearchInFilesPanel = ({
   const [expandedFiles, setExpandedFiles] = useState<Set<string>>(new Set());
 
   const inputRef = useRef<HTMLInputElement>(null);
-  const debounceRef = useRef<ReturnType<typeof setTimeout>>();
+  const debounceRef = useRef<ReturnType<typeof setTimeout>>(undefined);
   // Monotonic request ID — prevents stale results from overwriting fresh ones
   const requestIdRef = useRef(0);
 

src/renderer/components/team/review/ChangeReviewDialog.tsx

@@ -150,7 +150,7 @@ export const ChangeReviewDialog = ({
   const [selectionInfo, setSelectionInfo] = useState<EditorSelectionInfo | null>(null);
   const [containerRect, setContainerRect] = useState<DOMRect>(new DOMRect());
   const diffContentRef = useRef<HTMLDivElement>(null);
-  const selectionTimerRef = useRef<ReturnType<typeof setTimeout>>();
+  const selectionTimerRef = useRef<ReturnType<typeof setTimeout>>(undefined);
   const activeSelectionFileRef = useRef<string | null>(null);
 
   // EditorView map for all visible file editors

src/renderer/components/team/review/CodeMirrorDiffView.tsx

@@ -225,7 +225,7 @@ export const CodeMirrorDiffView = ({
   const onContentChangedRef = useRef(onContentChanged);
   const onViewChangeRef = useRef(onViewChange);
   const onSelectionChangeRef = useRef(onSelectionChange);
-  const debounceTimer = useRef<ReturnType<typeof setTimeout>>();
+  const debounceTimer = useRef<ReturnType<typeof setTimeout>>(undefined);
   useEffect(() => {
     onAcceptRef.current = onHunkAccepted;
     onRejectRef.current = onHunkRejected;

src/renderer/components/team/review/ContinuousScrollView.tsx

@@ -59,9 +59,9 @@ interface ContinuousScrollViewProps {
   collapsedFiles?: Set<string>;
   onToggleCollapse?: (filePath: string) => void;
   onVisibleFileChange: (filePath: string) => void;
-  scrollContainerRef: React.RefObject<HTMLDivElement>;
+  scrollContainerRef: React.RefObject<HTMLDivElement | null>;
   editorViewMapRef: React.MutableRefObject<Map<string, EditorView>>;
-  isProgrammaticScroll: React.RefObject<boolean>;
+  isProgrammaticScroll: React.RefObject<boolean | null>;
   teamName: string;
   memberName: string | undefined;
   fetchFileContent: (

src/renderer/components/team/review/DiffErrorBoundary.tsx

@@ -1,4 +1,4 @@
-import { Component, type ReactNode } from 'react';
+import { Component, type JSX, type ReactNode } from 'react';
 
 import { AlertTriangle } from 'lucide-react';
 

src/renderer/components/team/review/ReviewFileTree.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useMemo, useState } from 'react';
+import { type JSX, useCallback, useEffect, useMemo, useState } from 'react';
 
 import { FileIcon } from '@renderer/components/team/editor/FileIcon';
 import { Tooltip, TooltipContent, TooltipTrigger } from '@renderer/components/ui/tooltip';

src/renderer/components/team/review/ScopeWarningBanner.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { type JSX, useState } from 'react';
 
 import { cn } from '@renderer/lib/utils';
 import { AlertTriangle, ChevronRight, Info, ShieldCheck, X } from 'lucide-react';

src/renderer/contexts/TabUIContext.tsx

@@ -17,7 +17,7 @@
  * ```
  */
 
-import { createContext, type ReactNode } from 'react';
+import { createContext, type JSX, type ReactNode } from 'react';
 
 // =============================================================================
 // Context Definition

src/renderer/hooks/useAutoScrollBottom.ts

@@ -40,7 +40,7 @@ interface UseAutoScrollBottomOptions {
    * ref instead of creating its own. Useful when the ref needs to be shared
    * with other hooks (e.g., navigation coordinator).
    */
-  externalRef?: React.RefObject<HTMLDivElement>;
+  externalRef?: React.RefObject<HTMLDivElement | null>;
 
   /**
    * When this value changes, reset isAtBottom state to true.
@@ -56,7 +56,7 @@ interface UseAutoScrollBottomReturn {
   /**
    * Ref to attach to the scroll container element.
    */
-  scrollContainerRef: React.RefObject<HTMLDivElement>;
+  scrollContainerRef: React.RefObject<HTMLDivElement | null>;
 
   /**
    * Get whether the user is currently at the bottom of the scroll container.

src/renderer/hooks/useContinuousScrollNav.ts

@@ -8,7 +8,7 @@ interface UseContinuousScrollNavOptions {
 
 interface UseContinuousScrollNavReturn {
   scrollToFile: (filePath: string) => void;
-  isProgrammaticScroll: RefObject<boolean>;
+  isProgrammaticScroll: RefObject<boolean | null>;
 }
 
 export function useContinuousScrollNav(

src/renderer/hooks/useLazyFileContent.ts

@@ -47,8 +47,8 @@ export function useLazyFileContent(options: UseLazyFileContentOptions): UseLazyF
   }, []);
 
   // Refs for loadFile/processQueue to avoid circular useCallback deps
-  const loadFileRef = useRef<(fp: string) => Promise<void>>();
-  const processQueueRef = useRef<() => void>();
+  const loadFileRef = useRef<(fp: string) => Promise<void>>(undefined);
+  const processQueueRef = useRef<() => void>(undefined);
 
   loadFileRef.current = async (filePath: string) => {
     if (!shouldLoad(filePath)) return;

src/renderer/hooks/useTabNavigationController.ts

@@ -64,15 +64,15 @@ interface UseTabNavigationControllerOptions {
   /** Tab ID for consuming navigation */
   tabId: string;
   /** Refs to AI group DOM elements */
-  aiGroupRefs: React.MutableRefObject<Map<string, HTMLElement>>;
+  aiGroupRefs: React.RefObject<Map<string, HTMLElement>>;
   /** Refs to individual chat item DOM elements */
-  chatItemRefs: React.MutableRefObject<Map<string, HTMLElement>>;
+  chatItemRefs: React.RefObject<Map<string, HTMLElement>>;
   /** Refs to individual tool item DOM elements */
-  toolItemRefs: React.MutableRefObject<Map<string, HTMLElement>>;
+  toolItemRefs: React.RefObject<Map<string, HTMLElement>>;
   /** Function to expand an AI group (per-tab state) */
   expandAIGroup: (groupId: string) => void;
   /** Ref to scroll container */
-  scrollContainerRef: React.RefObject<HTMLDivElement>;
+  scrollContainerRef: React.RefObject<HTMLDivElement | null>;
   /** Height of sticky elements at top of scroll container */
   stickyOffset?: number;
   /** Optional helper to ensure a target group is mounted (e.g., virtualized lists) */

src/renderer/hooks/useVisibleAIGroup.ts

@@ -4,7 +4,7 @@ interface UseVisibleAIGroupOptions {
   onVisibleChange: (aiGroupId: string) => void;
   threshold?: number; // Default 0.5
   /** Optional scroll container to observe against (important for nested scroll areas). */
-  rootRef?: RefObject<HTMLElement>;
+  rootRef?: RefObject<HTMLElement | null>;
 }
 
 interface UseVisibleAIGroupReturn {

src/renderer/hooks/useVisibleFileSection.ts

@@ -3,7 +3,7 @@ import { type RefObject, useCallback, useEffect, useRef } from 'react';
 interface UseVisibleFileSectionOptions {
   onVisibleFileChange: (filePath: string) => void;
   scrollContainerRef: RefObject<HTMLElement | null>;
-  isProgrammaticScroll: RefObject<boolean>;
+  isProgrammaticScroll: RefObject<boolean | null>;
 }
 
 interface UseVisibleFileSectionReturn {
@@ -18,7 +18,7 @@ export function useVisibleFileSection(
   const visibleFilePaths = useRef<Set<string>>(new Set());
   const elementRefs = useRef<Map<string, HTMLElement>>(new Map());
   const observerRef = useRef<IntersectionObserver | null>(null);
-  const debounceRef = useRef<ReturnType<typeof setTimeout>>();
+  const debounceRef = useRef<ReturnType<typeof setTimeout>>(undefined);
 
   const updateTopmostVisible = useCallback(() => {
     if (isProgrammaticScroll.current) return;

test/renderer/hooks/useVisibleAIGroup.test.ts

@@ -1,6 +1,5 @@
-import React from 'react';
+import React, { act } from 'react';
 import { createRoot } from 'react-dom/client';
-import { act } from 'react-dom/test-utils';
 import { afterEach, describe, expect, it, vi } from 'vitest';
 
 import { useVisibleAIGroup } from '../../../src/renderer/hooks/useVisibleAIGroup';
@@ -23,8 +22,9 @@ describe('useVisibleAIGroup', () => {
   });
 
   it('uses provided rootRef as IntersectionObserver root', async () => {
-    const observerSpy = vi.fn((cb: IntersectionObserverCallback, opts?: IntersectionObserverInit) =>
-      new FakeIntersectionObserver(cb, opts)
+    const observerSpy = vi.fn(
+      (cb: IntersectionObserverCallback, opts?: IntersectionObserverInit) =>
+        new FakeIntersectionObserver(cb, opts)
     );
 
     vi.stubGlobal('IntersectionObserver', observerSpy as unknown as typeof IntersectionObserver);