diff --git a/src/vs/workbench/api/browser/mainThreadWebview.ts b/src/vs/workbench/api/browser/mainThreadWebview.ts
index 99c2aaeff52..e9889040ffc 100644
--- a/src/vs/workbench/api/browser/mainThreadWebview.ts
+++ b/src/vs/workbench/api/browser/mainThreadWebview.ts
@@ -289,7 +289,7 @@ export class MainThreadWebviews extends Disposable implements extHostProtocol.Ma
 
 				try {
 					await this._proxy.$resolveWebviewEditor(
-						webviewInput.getResource(),
+						{ resource: webviewInput.getResource(), edits: model.currentEdits },
 						handle,
 						viewType,
 						webviewInput.getTitle(),
@@ -299,6 +299,7 @@ export class MainThreadWebviews extends Disposable implements extHostProtocol.Ma
 				} catch (error) {
 					onUnexpectedError(error);
 					webviewInput.webview.html = MainThreadWebviews.getDeserializationFailedContents(viewType);
+					return;
 				}
 			}
 		}));
diff --git a/src/vs/workbench/api/common/extHost.protocol.ts b/src/vs/workbench/api/common/extHost.protocol.ts
index fd400006266..414ce05d910 100644
--- a/src/vs/workbench/api/common/extHost.protocol.ts
+++ b/src/vs/workbench/api/common/extHost.protocol.ts
@@ -592,7 +592,7 @@ export interface ExtHostWebviewsShape {
 	$onDidDisposeWebviewPanel(handle: WebviewPanelHandle): Promise<void>;
 
 	$deserializeWebviewPanel(newWebviewHandle: WebviewPanelHandle, viewType: string, title: string, state: any, position: EditorViewColumn, options: modes.IWebviewOptions & modes.IWebviewPanelOptions): Promise<void>;
-	$resolveWebviewEditor(resource: UriComponents, newWebviewHandle: WebviewPanelHandle, viewType: string, title: string, position: EditorViewColumn, options: modes.IWebviewOptions & modes.IWebviewPanelOptions): Promise<void>;
+	$resolveWebviewEditor(input: { resource: UriComponents, edits: readonly any[] }, newWebviewHandle: WebviewPanelHandle, viewType: string, title: string, position: EditorViewColumn, options: modes.IWebviewOptions & modes.IWebviewPanelOptions): Promise<void>;
 
 	$undoEdits(handle: WebviewPanelHandle, edits: readonly any[]): void;
 	$applyEdits(handle: WebviewPanelHandle, edits: readonly any[]): void;
diff --git a/src/vs/workbench/api/common/extHostWebview.ts b/src/vs/workbench/api/common/extHostWebview.ts
index 68405468573..bbe3fe187d0 100644
--- a/src/vs/workbench/api/common/extHostWebview.ts
+++ b/src/vs/workbench/api/common/extHostWebview.ts
@@ -248,11 +248,11 @@ export class ExtHostWebviewEditor extends Disposable implements vscode.WebviewPa
 		}
 	}
 
-	_undoEdits(edits: string[]): void {
+	_undoEdits(edits: readonly any[]): void {
 		assertIsDefined(this._capabilities).editingCapability?.undoEdits(edits);
 	}
 
-	_redoEdits(edits: string[]): void {
+	_redoEdits(edits: readonly any[]): void {
 		assertIsDefined(this._capabilities).editingCapability?.applyEdits(edits);
 	}
 
@@ -432,7 +432,7 @@ export class ExtHostWebviews implements ExtHostWebviewsShape {
 	}
 
 	async $resolveWebviewEditor(
-		resource: UriComponents,
+		input: { resource: UriComponents, edits: readonly any[] },
 		handle: WebviewPanelHandle,
 		viewType: string,
 		title: string,
@@ -448,8 +448,13 @@ export class ExtHostWebviews implements ExtHostWebviewsShape {
 		const webview = new ExtHostWebview(handle, this._proxy, options, this.initData, this.workspace, extension, this._logService);
 		const revivedPanel = new ExtHostWebviewEditor(handle, this._proxy, viewType, title, typeof position === 'number' && position >= 0 ? typeConverters.ViewColumn.to(position) : undefined, options, webview);
 		this._webviewPanels.set(handle, revivedPanel);
-		const capabilities = await provider.resolveWebviewEditor({ resource: URI.revive(resource) }, revivedPanel);
+		const capabilities = await provider.resolveWebviewEditor({ resource: URI.revive(input.resource) }, revivedPanel);
 		revivedPanel._setCapabilities(capabilities);
+
+		// TODO: the first set of edits should likely be passed when resolving
+		if (input.edits.length) {
+			revivedPanel._redoEdits(input.edits);
+		}
 	}
 
 	$undoEdits(handle: WebviewPanelHandle, edits: string[]): void {
diff --git a/src/vs/workbench/contrib/customEditor/browser/customEditorInput.ts b/src/vs/workbench/contrib/customEditor/browser/customEditorInput.ts
index a6d5a037799..673d8f3b96d 100644
--- a/src/vs/workbench/contrib/customEditor/browser/customEditorInput.ts
+++ b/src/vs/workbench/contrib/customEditor/browser/customEditorInput.ts
@@ -52,6 +52,10 @@ export class CustomFileEditorInput extends LazilyResolvedWebviewEditorInput {
 		return this._editorResource;
 	}
 
+	public supportsSplitEditor() {
+		return true;
+	}
+
 	@memoize
 	getName(): string {
 		return basename(this.labelService.getUriLabel(this.getResource()));
@@ -142,6 +146,7 @@ export class CustomFileEditorInput extends LazilyResolvedWebviewEditorInput {
 	public async resolve(): Promise<IEditorModel> {
 		this._model = await this.customEditorService.models.loadOrCreate(this.getResource(), this.viewType);
 		this._register(this._model.onDidChangeDirty(() => this._onDidChangeDirty.fire()));
+		this._onDidChangeDirty.fire();
 		return await super.resolve();
 	}
 
diff --git a/src/vs/workbench/contrib/customEditor/common/customEditor.ts b/src/vs/workbench/contrib/customEditor/common/customEditor.ts
index 087e4e9a17d..9162ab0e3d2 100644
--- a/src/vs/workbench/contrib/customEditor/common/customEditor.ts
+++ b/src/vs/workbench/contrib/customEditor/common/customEditor.ts
@@ -65,6 +65,8 @@ export interface ICustomEditorModel extends IWorkingCopy {
 	readonly onWillSave: Event<CustomEditorSaveEvent>;
 	readonly onWillSaveAs: Event<CustomEditorSaveAsEvent>;
 
+	readonly currentEdits: readonly CustomEditorEdit[];
+
 	undo(): void;
 	redo(): void;
 	revert(options?: IRevertOptions): Promise<boolean>;
diff --git a/src/vs/workbench/contrib/customEditor/common/customEditorModel.ts b/src/vs/workbench/contrib/customEditor/common/customEditorModel.ts
index df42f0c3f0c..bbf355c0377 100644
--- a/src/vs/workbench/contrib/customEditor/common/customEditorModel.ts
+++ b/src/vs/workbench/contrib/customEditor/common/customEditorModel.ts
@@ -53,6 +53,10 @@ export class CustomEditorModel extends Disposable implements ICustomEditorModel
 	protected readonly _onWillSaveAs = this._register(new Emitter<CustomEditorSaveAsEvent>());
 	readonly onWillSaveAs = this._onWillSaveAs.event;
 
+	get currentEdits(): readonly CustomEditorEdit[] {
+		return this._edits.slice(0, Math.max(0, this._currentEditIndex + 1));
+	}
+
 	public makeEdit(edit: CustomEditorEdit): void {
 		this._edits.splice(this._currentEditIndex + 1, this._edits.length - this._currentEditIndex, edit.data);
 		this._currentEditIndex = this._edits.length - 1;