mcp: implement McpUiUpdateModelContextRequest handler

src/vs/workbench/contrib/chat/browser/attachments/chatAttachmentWidgets.ts

@@ -600,7 +600,7 @@ export class DefaultChatAttachmentWidget extends AbstractChatAttachmentWidget {
 		}
 
 		// Setup tooltip hover for string context attachments
-		if (isStringVariableEntry(attachment) && attachment.tooltip) {
+		if ((isStringVariableEntry(attachment) || attachment.kind === 'generic') && attachment.tooltip) {
 			this._setupTooltipHover(attachment.tooltip);
 		}
 

src/vs/workbench/contrib/chat/browser/widget/chatContentParts/toolInvocationParts/chatMcpAppModel.ts

@@ -9,6 +9,8 @@ import { disposableTimeout } from '../../../../../../../base/common/async.js';
 import { decodeBase64 } from '../../../../../../../base/common/buffer.js';
 import { CancellationToken, CancellationTokenSource } from '../../../../../../../base/common/cancellation.js';
 import { Emitter, Event } from '../../../../../../../base/common/event.js';
+import { hash } from '../../../../../../../base/common/hash.js';
+import { MarkdownString } from '../../../../../../../base/common/htmlContent.js';
 import { Disposable } from '../../../../../../../base/common/lifecycle.js';
 import { autorun, autorunSelfDisposable, derived, IObservable, observableValue } from '../../../../../../../base/common/observable.js';
 import { basename } from '../../../../../../../base/common/resources.js';
@@ -396,8 +398,12 @@ export class ChatMcpAppModel extends Disposable {
 					result = await this._handleUiMessage(request.params);
 					break;
 
+				case 'ui/update-model-context':
+					result = await this._handleUpdateModelContext(request.params);
+					break;
+
 				case 'notifications/message':
-					await this._mcpToolCallUI.log(request.params);
+					await this._mcpToolCallUI.log(request.params as MCP.LoggingMessageNotification['params']);
 					break;
 
 				default: {
@@ -474,8 +480,15 @@ export class ChatMcpAppModel extends Disposable {
 				logging: {},
 				sandbox: {
 					csp: this._latestCsp,
-					permissions: { clipboardWrite: true },
+					permissions: { clipboardWrite: {} },
 				},
+				updateModelContext: {
+					audio: {},
+					image: {},
+					resourceLink: {},
+					resource: {},
+					structuredContent: {},
+				}
 			},
 			hostContext: this.hostContext.get(),
 		} satisfies Required<McpApps.McpUiInitializeResult>;
@@ -520,6 +533,68 @@ export class ChatMcpAppModel extends Disposable {
 		return { isError: false };
 	}
 
+	private async _handleUpdateModelContext(params: McpApps.McpUiUpdateModelContextRequest['params']): Promise<MCP.EmptyResult> {
+		const widget = this._chatWidgetService.getWidgetBySessionResource(this.renderData.sessionResource);
+		if (!widget) {
+			return {};
+		}
+
+		const idPrefix = `mcpui-context-${hash(this.renderData.serverDefinitionId)}-`;
+		const toDelete = widget.attachmentModel.getAttachmentIDs();
+		const idsToDelete = Array.from(toDelete).filter(id => id.startsWith(idPrefix));
+		const entries: IChatRequestVariableEntry[] = [];
+		let entryIndex = 0;
+
+		if (params.content) {
+			for (const block of params.content) {
+				const id = `${idPrefix}${entryIndex++}`;
+				if (block.type === 'image') {
+					entries.push({
+						kind: 'image',
+						value: decodeBase64(block.data).buffer,
+						id,
+						name: 'Image',
+						mimeType: block.mimeType,
+					});
+				} else if (block.type === 'resource_link') {
+					const uri = McpResourceURI.fromServer({ id: this.renderData.serverDefinitionId, label: '' }, block.uri);
+					entries.push({
+						kind: 'file',
+						value: uri,
+						id,
+						name: basename(uri),
+					});
+				} else if (block.type === 'text') {
+					const preview = block.text.replaceAll(/\s+/g, ' ').trim();
+					const truncateTo = 20;
+					entries.push({
+						kind: 'generic',
+						value: block.text,
+						id,
+						tooltip: new MarkdownString().appendCodeblock('plaintext', block.text),
+						name: preview.length > truncateTo ? preview.slice(0, truncateTo) + '…' : preview,
+					});
+				}
+			}
+		}
+
+		if (params.structuredContent && Object.keys(params.structuredContent).length > 0) {
+			const id = `${idPrefix}structured`;
+			const value = JSON.stringify(params.structuredContent, null, 2);
+			entries.push({
+				kind: 'generic',
+				value,
+				tooltip: new MarkdownString().appendCodeblock('json', value),
+				id,
+				name: 'UI Data',
+			});
+		}
+
+		widget.attachmentModel.updateContext(idsToDelete, entries);
+
+		return {};
+	}
+
 	private _handleSizeChanged(params: McpApps.McpUiSizeChangedNotification['params']): void {
 		if (params.height !== undefined) {
 			this._height = params.height;

src/vs/workbench/contrib/chat/common/attachments/chatVariableEntries.ts

@@ -41,6 +41,7 @@ interface IBaseChatRequestVariableEntry {
 
 export interface IGenericChatRequestVariableEntry extends IBaseChatRequestVariableEntry {
 	kind: 'generic';
+	tooltip?: IMarkdownString;
 }
 
 export interface IChatRequestDirectoryEntry extends IBaseChatRequestVariableEntry {

src/vs/workbench/contrib/mcp/common/modelContextProtocolApps.ts

@@ -19,6 +19,7 @@ export namespace McpApps {
 		| MCP.ReadResourceRequest
 		| MCP.PingRequest
 		| (McpUiOpenLinkRequest & MCP.JSONRPCRequest)
+		| (McpUiUpdateModelContextRequest & MCP.JSONRPCRequest)
 		| (McpUiMessageRequest & MCP.JSONRPCRequest)
 		| (McpUiRequestDisplayModeRequest & MCP.JSONRPCRequest)
 		| (McpApps.McpUiInitializeRequest & MCP.JSONRPCRequest);
@@ -427,6 +428,28 @@ export namespace McpApps {
 		params: McpUiHostContext;
 	}
 
+	/**
+	 * @description Request to update the agent's context without requiring a follow-up action (Guest UI -> Host).
+	 *
+	 * Unlike `notifications/message` which is for debugging/logging, this request is intended
+	 * to update the Host's model context. Each request overwrites the previous context sent by the Guest UI.
+	 * Unlike messages, context updates do not trigger follow-ups.
+	 *
+	 * The host will typically defer sending the context to the model until the next user message
+	 * (including `ui/message`), and will only send the last update received.
+	 *
+	 * @see {@link app.App.updateModelContext} for the method that sends this request
+	 */
+	export interface McpUiUpdateModelContextRequest {
+		method: "ui/update-model-context";
+		params: {
+			/** @description Context content blocks (text, image, etc.). */
+			content?: ContentBlock[];
+			/** @description Structured content for machine-readable context data. */
+			structuredContent?: Record<string, unknown>;
+		};
+	}
+
 	/**
 	 * @description Request for graceful shutdown of the Guest UI (Host -> Guest UI).
 	 * @see {@link app-bridge.AppBridge.teardownResource} for the host method that sends this
@@ -447,6 +470,21 @@ export namespace McpApps {
 		[key: string]: unknown;
 	}
 
+	export interface McpUiSupportedContentBlockModalities {
+		/** @description Host supports text content blocks. */
+		text?: {};
+		/** @description Host supports image content blocks. */
+		image?: {};
+		/** @description Host supports audio content blocks. */
+		audio?: {};
+		/** @description Host supports resource content blocks. */
+		resource?: {};
+		/** @description Host supports resource link content blocks. */
+		resourceLink?: {};
+		/** @description Host supports structured content. */
+		structuredContent?: {};
+	}
+
 	/**
 	 * @description Capabilities supported by the host application.
 	 * @see {@link McpUiInitializeResult} for the initialization result that includes these capabilities
@@ -475,6 +513,10 @@ export namespace McpApps {
 			/** @description CSP domains approved by the host. */
 			csp?: McpUiResourceCsp;
 		};
+		/** @description Host accepts context updates (ui/update-model-context) to be included in the model's context for future turns. */
+		updateModelContext?: McpUiSupportedContentBlockModalities;
+		/** @description Host supports receiving content messages (ui/message) from the Guest UI. */
+		message?: McpUiSupportedContentBlockModalities;
 	}
 
 	/**
@@ -674,4 +716,6 @@ export namespace McpApps {
 		"ui/notifications/initialized";
 	export const REQUEST_DISPLAY_MODE_METHOD: McpUiRequestDisplayModeRequest["method"] =
 		"ui/request-display-mode";
+	export const UPDATE_MODEL_CONTEXT_METHOD: McpUiUpdateModelContextRequest["method"] =
+		"ui/update-model-context";
 }