diff --git a/src/components/ui-editor/NodeInspector.jsx b/src/components/ui-editor/NodeInspector.tsx
similarity index 100%
rename from src/components/ui-editor/NodeInspector.jsx
rename to src/components/ui-editor/NodeInspector.tsx
diff --git a/src/components/ui-editor/NodePicker.jsx b/src/components/ui-editor/NodePicker.tsx
similarity index 100%
rename from src/components/ui-editor/NodePicker.jsx
rename to src/components/ui-editor/NodePicker.tsx
diff --git a/src/components/ui-editor/TreePanel.jsx b/src/components/ui-editor/TreePanel.tsx
similarity index 100%
rename from src/components/ui-editor/TreePanel.jsx
rename to src/components/ui-editor/TreePanel.tsx
diff --git a/src/components/ui-editor/UiEditor.jsx b/src/components/ui-editor/UiEditor.tsx
similarity index 100%
rename from src/components/ui-editor/UiEditor.jsx
rename to src/components/ui-editor/UiEditor.tsx
diff --git a/src/components/ui-editor/ops.js b/src/components/ui-editor/ops.ts
similarity index 100%
rename from src/components/ui-editor/ops.js
rename to src/components/ui-editor/ops.ts
diff --git a/src/components/ui-tree/UiEditingProvider.jsx b/src/components/ui-tree/UiEditingProvider.tsx
similarity index 100%
rename from src/components/ui-tree/UiEditingProvider.jsx
rename to src/components/ui-tree/UiEditingProvider.tsx
diff --git a/src/components/ui-tree/UiNodeBoundary.jsx b/src/components/ui-tree/UiNodeBoundary.tsx
similarity index 81%
rename from src/components/ui-tree/UiNodeBoundary.jsx
rename to src/components/ui-tree/UiNodeBoundary.tsx
index e959ec5..681554b 100644
--- a/src/components/ui-tree/UiNodeBoundary.jsx
+++ b/src/components/ui-tree/UiNodeBoundary.tsx
@@ -25,7 +25,27 @@ import React from 'react';
  * the node it is holding changes, which is what makes removing the broken node
  * put the page right without a reload.
  */
-export class UiNodeBoundary extends React.Component {
+/**
+ * `node` is the one this boundary holds; `children` is what it renders while
+ * that node is fine. Both optional, because the placeholder path reads them
+ * with `?.` and has always tolerated their absence.
+ */
+interface UiNodeBoundaryProps {
+  node?: any;
+  children?: React.ReactNode;
+}
+
+/**
+ * `forNode` is how the reset works: it records which node the current `failed`
+ * belongs to, so a boundary does not stay latched after the broken node is
+ * hidden or removed. It is absent until the first `getDerivedStateFromProps`.
+ */
+interface UiNodeBoundaryState {
+  failed: boolean;
+  forNode?: any;
+}
+
+export class UiNodeBoundary extends React.Component<UiNodeBoundaryProps, UiNodeBoundaryState> {
   constructor(props) {
     super(props);
     this.state = { failed: false };
diff --git a/src/components/ui-tree/UiTreeRenderer.jsx b/src/components/ui-tree/UiTreeRenderer.tsx
similarity index 100%
rename from src/components/ui-tree/UiTreeRenderer.jsx
rename to src/components/ui-tree/UiTreeRenderer.tsx
diff --git a/src/components/ui-tree/chartNodeTypes.jsx b/src/components/ui-tree/chartNodeTypes.tsx
similarity index 100%
rename from src/components/ui-tree/chartNodeTypes.jsx
rename to src/components/ui-tree/chartNodeTypes.tsx
diff --git a/src/components/ui-tree/nodeTypes.jsx b/src/components/ui-tree/nodeTypes.tsx
similarity index 100%
rename from src/components/ui-tree/nodeTypes.jsx
rename to src/components/ui-tree/nodeTypes.tsx
diff --git a/src/components/ui-tree/sectionNodeTypes.jsx b/src/components/ui-tree/sectionNodeTypes.tsx
similarity index 100%
rename from src/components/ui-tree/sectionNodeTypes.jsx
rename to src/components/ui-tree/sectionNodeTypes.tsx