[Routine - VT] fix: preserve sourceScopeId when duplicating a group

.gitignore

@@ -43,3 +43,4 @@ test-results/
 /coverage
 test-ui-output.txt
 docs/assets/fix_rounded_corners.py
+docs/_archive/**

CHANGELOG.md

@@ -2,6 +2,17 @@
 
 All notable changes to the "VirtualTabs" extension will be documented in this file.
 
+## [0.7.5] - Drag-and-Drop DataTransfer Fixes - 2026-06-21
+
+### 🐛 Bug Fix
+
+- **Folder drops from VS Code Explorer** ([#60](https://github.com/winterdrive/vscode-virtual-tabs/issues/60)): External folder drops now handle VS Code's special `files` DataTransfer MIME entries in addition to `text/uri-list`, so folders dragged from Explorer or the OS can be expanded and added to a VirtualTabs group.
+- **Group drags to AI chat sidebars** ([#60](https://github.com/winterdrive/vscode-virtual-tabs/issues/60)): Dragging a VirtualTabs group now also provides `text/plain` file references, giving chat inputs such as GitHub Copilot a readable fallback when they do not consume `text/uri-list` from extension tree items.
+
+### 🧪 Tests
+
+- Added unit coverage for URI-list parsing, external DataTransfer file URI extraction, duplicate URI handling, and chat-friendly drag text formatting.
+
 ## [0.7.4] - Skill Installer UX - 2026-06-16
 
 ### 🧠 Skill Installer UX (closes #25)

package.json

@@ -2,7 +2,7 @@
     "name": "virtual-tabs",
     "displayName": "VirtualTabs - Virtual File Directories & AI context management",
     "description": "%extension.description%",
-    "version": "0.7.4",
+    "version": "0.7.5",
     "publisher": "winterdrive",
     "icon": "docs/assets/virtualtabs_icon_128.png",
     "categories": [

src/commands.ts

@@ -543,7 +543,8 @@ export function registerCommands(
         provider.groups.push({
             id: Date.now().toString() + Math.random().toString(36).substring(2, 9),
             name: newName,
-            files: group.files ? [...group.files] : []
+            files: group.files ? [...group.files] : [],
+            sourceScopeId: group.sourceScopeId
         });
         provider.refresh();
     }));

src/core/DropUriParser.ts

@@ -0,0 +1,39 @@
+export interface DataTransferFileLike {
+    readonly uri?: { toString(): string };
+}
+
+export function parseUriList(value: unknown): string[] {
+    if (typeof value !== 'string') {
+        return [];
+    }
+
+    return value
+        .split(/\r?\n/)
+        .map(value => value.trim())
+        .filter(value => value.length > 0 && !value.startsWith('#'));
+}
+
+export function extractDataTransferFileUris(files: readonly DataTransferFileLike[]): string[] {
+    return files
+        .map(file => file.uri?.toString())
+        .filter((uri): uri is string => typeof uri === 'string' && uri.length > 0);
+}
+
+export function uniqueUriStrings(uris: readonly string[]): string[] {
+    const unique = new Set<string>();
+    for (const uri of uris) {
+        unique.add(uri);
+    }
+    return Array.from(unique);
+}
+
+export function formatDraggedFilesPlainText(paths: readonly string[]): string {
+    if (paths.length === 0) {
+        return '';
+    }
+
+    return [
+        'Use these files as context:',
+        ...paths.map(path => `#file:${path}`)
+    ].join('\n');
+}

src/dragAndDrop.ts

@@ -1,23 +1,27 @@
 import * as vscode from 'vscode';
 import { TempFoldersProvider } from './provider';
-import { TempFolderItem, TempFileItem, ScopeHeaderItem } from './treeItems';
+import { TempFolderItem, TempFileItem, ScopeHeaderItem, EditorGroupItem } from './treeItems';
 import { I18n } from './i18n';
+import { extractDataTransferFileUris, formatDraggedFilesPlainText, parseUriList, uniqueUriStrings } from './core/DropUriParser';
 
 // Drag-and-drop controller, allows files to be dragged into groups AND groups to be nested
 export class TempFoldersDragAndDropController implements vscode.TreeDragAndDropController<vscode.TreeItem> {
     constructor(private provider: TempFoldersProvider) { }
 
     public readonly supportedTypes = [
+        'files',
         'text/uri-list',
         'application/vnd.code.tree.virtualTabsView',
         'application/vnd.code.tree.virtualTabsView.files'
     ];
     public readonly dropMimeTypes = [
+        'files',
         'text/uri-list',
         'application/vnd.code.tree.virtualTabsView',
         'application/vnd.code.tree.virtualTabsView.files'
     ];
     public readonly dragMimeTypes = [
+        'text/plain',
         'text/uri-list',
         'application/vnd.code.tree.virtualTabsView',
         'application/vnd.code.tree.virtualTabsView.files'
@@ -27,6 +31,7 @@ export class TempFoldersDragAndDropController implements vscode.TreeDragAndDropC
         // Handle multi-file drag from the tree view
         const fileItems = source.filter((item): item is TempFileItem => item instanceof TempFileItem);
         const groupItems = source.filter((item): item is TempFolderItem => item instanceof TempFolderItem);
+        const editorGroupItems = source.filter((item): item is EditorGroupItem => item instanceof EditorGroupItem);
 
         const uriSet = new Set<string>();
 
@@ -42,7 +47,9 @@ export class TempFoldersDragAndDropController implements vscode.TreeDragAndDropC
         if (groupItems.length > 0) {
             for (const item of groupItems) {
                 const group = this.provider.groups[item.groupIdx];
-                if (!group || group.builtIn || !group.id) continue;
+                // Skip only groups without a valid id (builtIn groups are now allowed
+                // so that "Currently Open Files" can produce a drag payload).
+                if (!group || !group.id) continue;
                 const groupFiles = this.collectGroupFilesRecursive(group.id);
                 for (const uri of groupFiles) {
                     uriSet.add(uri);
@@ -53,10 +60,22 @@ export class TempFoldersDragAndDropController implements vscode.TreeDragAndDropC
             dataTransfer.set('application/vnd.code.tree.virtualTabsView', new vscode.DataTransferItem(groupItems));
         }
 
+        // Handle EditorGroupItem (split-editor sub-nodes under the built-in group).
+        // These are not TempFolderItem instances, so they need separate handling.
+        if (editorGroupItems.length > 0) {
+            for (const item of editorGroupItems) {
+                const files = this.provider.getEditorGroupFiles(item.viewColumn);
+                for (const uri of files) {
+                    uriSet.add(uri);
+                }
+            }
+        }
+
         if (uriSet.size > 0) {
             const uriList = Array.from(uriSet).join('\r\n');
             // Set drag data
             dataTransfer.set('text/uri-list', new vscode.DataTransferItem(uriList));
+            dataTransfer.set('text/plain', new vscode.DataTransferItem(this.createDraggedFilesPlainText(Array.from(uriSet))));
         }
     }
 
@@ -88,21 +107,23 @@ export class TempFoldersDragAndDropController implements vscode.TreeDragAndDropC
             }
         }
 
-        // Priority 2: Check for external file drag (uri-list)
-        // Condition: uri-list exists AND we did NOT successfully extract internal file items
+        // Priority 2: Check for external file drag.
+        // Condition: external URIs exist AND we did NOT successfully extract internal file items
         // Note: We do NOT use `!fileData` because fileData may exist but contain an invalid/serialized value
         const uriList = dataTransfer.get('text/uri-list');
-        if (uriList && !draggedFiles) {
+        const uriListText = uriList ? await this.readDataTransferString(uriList) : undefined;
+        const externalUris = uniqueUriStrings([
+            ...parseUriList(uriListText),
+            ...this.extractExternalFileUris(dataTransfer)
+        ]);
+        if (externalUris.length > 0 && !draggedFiles) {
             const targetGroup = this.determineTargetGroup(target);
             if (targetGroup || target instanceof ScopeHeaderItem) {
-                // Fix: support both \n and \r\n, trim whitespace and control characters from each URI
-                const uris = uriList.value.split(/\r?\n/).map((s: string) => s.trim()).filter(Boolean);
-
                 // Expand directories to get all files
                 const allFileUris: string[] = [];
-                for (const uriStr of uris) {
+                for (const uriStr of externalUris) {
                     try {
-                        const uri = vscode.Uri.parse(uriStr);
+                        const uri = this.toDroppedUri(uriStr);
                         const stat = await vscode.workspace.fs.stat(uri);
 
                         if (stat.type === vscode.FileType.Directory) {
@@ -111,7 +132,7 @@ export class TempFoldersDragAndDropController implements vscode.TreeDragAndDropC
                             allFileUris.push(...filesInDir.map(f => f.toString()));
                         } else if (stat.type === vscode.FileType.File) {
                             // It's a file - add directly
-                            allFileUris.push(uriStr);
+                            allFileUris.push(uri.toString());
                         }
                     } catch (e) {
                         // If we can't stat it, try adding it directly (might be a valid file)
@@ -172,6 +193,45 @@ export class TempFoldersDragAndDropController implements vscode.TreeDragAndDropC
         return value as TempFileItem[];
     }
 
+    private async readDataTransferString(item: vscode.DataTransferItem): Promise<unknown> {
+        try {
+            return await item.asString();
+        } catch {
+            return item.value;
+        }
+    }
+
+    private extractExternalFileUris(dataTransfer: vscode.DataTransfer): string[] {
+        const files: vscode.DataTransferFile[] = [];
+        for (const [, item] of dataTransfer) {
+            const file = item.asFile();
+            if (file) {
+                files.push(file);
+            }
+        }
+        return extractDataTransferFileUris(files);
+    }
+
+    private toDroppedUri(uriStr: string): vscode.Uri {
+        if (/^[a-zA-Z]:[\\/]/.test(uriStr) || uriStr.startsWith('\\\\') || uriStr.startsWith('/')) {
+            return vscode.Uri.file(uriStr);
+        }
+        return vscode.Uri.parse(uriStr);
+    }
+
+    private createDraggedFilesPlainText(uriStrings: readonly string[]): string {
+        const paths = uriStrings.map(uriString => {
+            try {
+                const uri = vscode.Uri.parse(uriString);
+                return vscode.workspace.asRelativePath(uri, false);
+            } catch {
+                return uriString;
+            }
+        });
+
+        return formatDraggedFilesPlainText(paths);
+    }
+
     private determineTargetGroup(target: vscode.TreeItem | undefined): TempFolderItem | undefined {
         if (target instanceof TempFolderItem) {
             return target;

src/provider.ts

@@ -701,6 +701,16 @@ export class TempFoldersProvider implements vscode.TreeDataProvider<vscode.TreeI
             .filter(group => group.files.length > 0);
     }
 
+    /**
+     * Get the file URI strings for a specific editor group by viewColumn.
+     * Used by the drag controller to collect files when dragging EditorGroupItem nodes
+     * without directly accessing the private builtInEditorGroups array.
+     */
+    getEditorGroupFiles(viewColumn: number): string[] {
+        const eg = this.builtInEditorGroups.find(g => g.viewColumn === viewColumn);
+        return eg ? [...eg.files] : [];
+    }
+
     /**
      * Returns true if the new editor group snapshot differs from the current one
      * in either count, column assignment, or file distribution.

src/test/unit/DropUriParser.test.ts

@@ -0,0 +1,59 @@
+import { extractDataTransferFileUris, formatDraggedFilesPlainText, parseUriList, uniqueUriStrings } from '../../core/DropUriParser';
+
+describe('DropUriParser', () => {
+    test('parses text/uri-list with comments, blank lines, and CRLF', () => {
+        const result = parseUriList([
+            '# copied from explorer',
+            'file:///workspace/project/src/index.ts',
+            '',
+            ' file:///workspace/project/package.json ',
+            ''
+        ].join('\r\n'));
+
+        expect(result).toEqual([
+            'file:///workspace/project/src/index.ts',
+            'file:///workspace/project/package.json'
+        ]);
+    });
+
+    test('returns no URIs for non-string uri-list values', () => {
+        expect(parseUriList(undefined)).toEqual([]);
+        expect(parseUriList(['file:///tmp/a.ts'])).toEqual([]);
+    });
+
+    test('extracts URI strings from DataTransferFile-like entries', () => {
+        const result = extractDataTransferFileUris([
+            { uri: { toString: () => 'file:///workspace/project' } },
+            { uri: undefined },
+            { uri: { toString: () => '' } }
+        ]);
+
+        expect(result).toEqual(['file:///workspace/project']);
+    });
+
+    test('deduplicates URI strings while preserving first-seen order', () => {
+        expect(uniqueUriStrings([
+            'file:///workspace/a.ts',
+            'file:///workspace/b.ts',
+            'file:///workspace/a.ts'
+        ])).toEqual([
+            'file:///workspace/a.ts',
+            'file:///workspace/b.ts'
+        ]);
+    });
+
+    test('formats dragged files as chat-friendly file references', () => {
+        expect(formatDraggedFilesPlainText([
+            'src/extension.ts',
+            'src/dragAndDrop.ts'
+        ])).toBe([
+            'Use these files as context:',
+            '#file:src/extension.ts',
+            '#file:src/dragAndDrop.ts'
+        ].join('\n'));
+    });
+
+    test('returns empty text when no dragged files are present', () => {
+        expect(formatDraggedFilesPlainText([])).toBe('');
+    });
+});