Positron Notebooks: Add ghost cell suggestions for AI-powered next step hints

extensions/positron-assistant/package.json

@@ -210,6 +210,12 @@
         "title": "%commands.resetState.title%",
         "category": "%commands.category%",
         "enablement": "config.positron.assistant.enable"
+      },
+      {
+        "command": "positron-assistant.selectGhostCellModel",
+        "title": "%commands.selectGhostCellModel.title%",
+        "category": "%commands.category%",
+        "enablement": "config.positron.assistant.enable"
       }
     ],
     "configuration": [

extensions/positron-assistant/package.nls.json

@@ -12,6 +12,7 @@
 	"commands.managePromptFiles.title": "Manage Prompt Files",
 	"commands.collectDiagnostics.title": "Collect Diagnostics",
 	"commands.resetState.title": "Reset State",
+	"commands.selectGhostCellModel.title": "Select Ghost Cell Suggestion Model",
 	"commands.copilot.signin.title": "Copilot Sign In",
 	"commands.copilot.signout.title": "Copilot Sign Out",
 	"commands.category": "Positron Assistant",

extensions/positron-assistant/src/commands/ghostCellModelPicker.ts

@@ -0,0 +1,117 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (C) 2026 Posit Software, PBC. All rights reserved.
+ *  Licensed under the Elastic License 2.0. See LICENSE.txt for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+interface ModelQuickPickItem extends vscode.QuickPickItem {
+	modelId?: string;
+	isDefault?: boolean;
+}
+
+/**
+ * Opens a quick pick to select a model for ghost cell suggestions.
+ * Groups models by vendor and allows selecting "Use Default" to restore auto-select behavior.
+ */
+export async function selectGhostCellModel(): Promise<void> {
+	// Get all available models
+	const allModels = await vscode.lm.selectChatModels();
+
+	if (allModels.length === 0) {
+		vscode.window.showWarningMessage(
+			vscode.l10n.t('No language models available. Configure a model provider first.')
+		);
+		return;
+	}
+
+	// Get current setting to mark current selection
+	const config = vscode.workspace.getConfiguration('positron.assistant.notebook');
+	const currentPatterns = config.get<string[]>('ghostCellSuggestions.model') || [];
+	const currentModelId = currentPatterns.length > 0 ? currentPatterns[0] : null;
+	const isUsingDefault = !currentModelId ||
+		(currentPatterns.length === 2 &&
+			currentPatterns[0] === 'haiku' &&
+			currentPatterns[1] === 'mini');
+
+	// Group models by vendor
+	const modelsByVendor = new Map<string, vscode.LanguageModelChat[]>();
+	for (const model of allModels) {
+		const vendor = model.vendor;
+		if (!modelsByVendor.has(vendor)) {
+			modelsByVendor.set(vendor, []);
+		}
+		modelsByVendor.get(vendor)!.push(model);
+	}
+
+	// Build quick pick items
+	const items: ModelQuickPickItem[] = [];
+
+	// Add "Use Default" option at top
+	items.push({
+		label: isUsingDefault
+			? '$(check) Use Default (Auto-select)'
+			: 'Use Default (Auto-select)',
+		description: isUsingDefault ? '(current)' : undefined,
+		detail: 'Automatically selects a fast model (Haiku, Mini, etc.)',
+		isDefault: true
+	});
+
+	items.push({ label: '', kind: vscode.QuickPickItemKind.Separator });
+
+	// Add models grouped by vendor
+	const sortedVendors = Array.from(modelsByVendor.keys()).sort();
+	for (const vendor of sortedVendors) {
+		const models = modelsByVendor.get(vendor)!;
+
+		// Add vendor separator
+		items.push({
+			label: vendor,
+			kind: vscode.QuickPickItemKind.Separator
+		});
+
+		// Add models for this vendor
+		for (const model of models) {
+			const isCurrent = !isUsingDefault && currentModelId === model.id;
+			items.push({
+				label: isCurrent ? `$(check) ${model.name}` : model.name,
+				description: isCurrent ? '(current)' : undefined,
+				detail: model.id,
+				modelId: model.id
+			});
+		}
+	}
+
+	// Show quick pick
+	const selected = await vscode.window.showQuickPick(items, {
+		title: vscode.l10n.t('Select Model for Ghost Cell Suggestions'),
+		placeHolder: vscode.l10n.t('Choose a model or use default auto-selection'),
+		matchOnDetail: true
+	});
+
+	if (!selected) {
+		return; // User cancelled
+	}
+
+	// Update the setting
+	let newValue: string[];
+	let message: string;
+
+	if (selected.isDefault) {
+		newValue = ['haiku', 'mini'];
+		message = vscode.l10n.t('Ghost cell suggestions will use default model selection.');
+	} else if (selected.modelId) {
+		newValue = [selected.modelId];
+		message = vscode.l10n.t('Ghost cell suggestions will use {0}.', selected.label.replace('$(check) ', ''));
+	} else {
+		return; // Separator or invalid item
+	}
+
+	await config.update(
+		'ghostCellSuggestions.model',
+		newValue,
+		vscode.ConfigurationTarget.Global
+	);
+
+	vscode.window.showInformationMessage(message);
+}

extensions/positron-assistant/src/extension.ts

@@ -16,11 +16,13 @@ import { ALL_DOCUMENTS_SELECTOR, DEFAULT_MAX_TOKEN_OUTPUT } from './constants.js
 import { registerCodeActionProvider } from './codeActions.js';
 import { generateCommitMessage } from './git.js';
 import { generateNotebookSuggestions, type NotebookActionSuggestion, type NotebookSuggestionsResult } from './notebookSuggestions.js';
+import { generateGhostCellSuggestion, type GhostCellSuggestionResult } from './ghostCellSuggestions.js';
 import { TokenUsage, TokenTracker } from './tokens.js';
 import { exportChatToUserSpecifiedLocation, exportChatToFileInWorkspace } from './export.js';
 import { AnthropicModelProvider } from './providers/anthropic/anthropicProvider.js';
 import { registerParticipantDetectionProvider } from './participantDetection.js';
 import { registerAssistantCommands } from './commands/index.js';
+import { selectGhostCellModel } from './commands/ghostCellModelPicker.js';
 import { PositronAssistantApi } from './api.js';
 import { registerPromptManagement } from './promptRender.js';
 import { collectDiagnostics } from './diagnostics.js';
@@ -324,6 +326,53 @@ function registerGenerateNotebookSuggestionsCommand(
 	);
 }
 
+function registerGenerateGhostCellSuggestionCommand(
+	context: vscode.ExtensionContext,
+	participantService: ParticipantService,
+	log: vscode.LogOutputChannel,
+) {
+	context.subscriptions.push(
+		vscode.commands.registerCommand(
+			'positron-assistant.generateGhostCellSuggestion',
+			async (
+				notebookUri: string,
+				executedCellIndex: number,
+				progressCallbackCommand?: string,
+				skipConfigCheck?: boolean,
+				token?: vscode.CancellationToken
+			): Promise<GhostCellSuggestionResult | null> => {
+				// Create a token source only if no token is provided
+				let tokenSource: vscode.CancellationTokenSource | undefined;
+				const cancellationToken = token || (tokenSource = new vscode.CancellationTokenSource()).token;
+
+				// Progress callback handler that invokes the provided command
+				const onProgress = progressCallbackCommand
+					? (partial: Partial<GhostCellSuggestionResult>) => {
+						Promise.resolve(vscode.commands.executeCommand(progressCallbackCommand, partial)).catch(err => {
+							log.warn(`[ghost-cell] Progress callback failed: ${err}`);
+						});
+					}
+					: undefined;
+
+				try {
+					return await generateGhostCellSuggestion(
+						notebookUri,
+						executedCellIndex,
+						participantService,
+						log,
+						cancellationToken,
+						onProgress,
+						skipConfigCheck
+					);
+				} finally {
+					// Only dispose if we created the token
+					tokenSource?.dispose();
+				}
+			}
+		)
+	);
+}
+
 function registerExportChatCommands(context: vscode.ExtensionContext) {
 	context.subscriptions.push(
 		vscode.commands.registerCommand('positron-assistant.exportChatToFileInWorkspace', async () => {
@@ -410,6 +459,7 @@ function registerAssistant(context: vscode.ExtensionContext) {
 	registerConfigureModelsCommand(context);
 	registerGenerateCommitMessageCommand(context, participantService, log);
 	registerGenerateNotebookSuggestionsCommand(context, participantService, log);
+	registerGenerateGhostCellSuggestionCommand(context, participantService, log);
 	registerExportChatCommands(context);
 	registerToggleInlineCompletionsCommand(context);
 	registerCollectDiagnosticsCommand(context);
@@ -428,6 +478,11 @@ function registerAssistant(context: vscode.ExtensionContext) {
 	// Register chat commands
 	registerAssistantCommands();
 
+	// Register ghost cell model picker command
+	context.subscriptions.push(
+		vscode.commands.registerCommand('positron-assistant.selectGhostCellModel', selectGhostCellModel)
+	);
+
 	// Dispose cleanup
 	context.subscriptions.push({
 		dispose: () => {