diff --git a/extensions/copilot/src/extension/tools/node/readFileTool.tsx b/extensions/copilot/src/extension/tools/node/readFileTool.tsx
index 06fb90b91920ce..359d5995dcdec3 100644
--- a/extensions/copilot/src/extension/tools/node/readFileTool.tsx
+++ b/extensions/copilot/src/extension/tools/node/readFileTool.tsx
@@ -22,6 +22,7 @@ import { IWorkspaceService } from '../../../platform/workspace/common/workspaceS
 import { getCachedSha256Hash } from '../../../util/common/crypto';
 import { clamp } from '../../../util/vs/base/common/numbers';
 import { dirname, extUriBiasedIgnorePathCase } from '../../../util/vs/base/common/resources';
+import { isHighSurrogate, isLowSurrogate } from '../../../util/vs/base/common/strings';
 import { sendSkillContentReadTelemetry } from '../common/skillTelemetry';
 import { URI } from '../../../util/vs/base/common/uri';
 import { IInstantiationService } from '../../../util/vs/platform/instantiation/common/instantiation';
@@ -432,7 +433,11 @@ class ReadFileResult extends PromptElement<ReadFileResultProps> {
 		let contents = rawContents.split('\n').map(line => {
 			if (line.length > MAX_LINE_LENGTH) {
 				hadLongLines = true;
-				return line.slice(0, MAX_LINE_LENGTH) + ' [truncated]';
+				let end = MAX_LINE_LENGTH;
+				if (isHighSurrogate(line.charCodeAt(end - 1)) && isLowSurrogate(line.charCodeAt(end))) {
+					end--;
+				}
+				return line.slice(0, end) + ' [truncated]';
 			}
 			return line;
 		}).join('\n');
diff --git a/extensions/copilot/src/extension/tools/node/test/readFile.spec.tsx b/extensions/copilot/src/extension/tools/node/test/readFile.spec.tsx
index 7e8206e2e4740d..548aeaf443bd1a 100644
--- a/extensions/copilot/src/extension/tools/node/test/readFile.spec.tsx
+++ b/extensions/copilot/src/extension/tools/node/test/readFile.spec.tsx
@@ -42,13 +42,15 @@ suite('ReadFile', () => {
 		const longLine = 'x'.repeat(2500);
 		const longLinesContent = `normal line\n${longLine}\nanother normal line\n${longLine}`;
 		const longLinesDoc = createTextDocumentData(URI.file('/workspace/longlines.ts'), longLinesContent, 'ts').document;
+		const surrogateBoundaryLine = 'x'.repeat(1999) + '\u{1F6E1}' + 'tail';
+		const surrogateBoundaryDoc = createTextDocumentData(URI.file('/workspace/surrogate-boundary.ts'), surrogateBoundaryLine, 'ts').document;
 
 		const services = createExtensionUnitTestingServices();
 		services.define(IWorkspaceService, new SyncDescriptor(
 			TestWorkspaceService,
 			[
 				[URI.file('/workspace')],
-				[testDoc, emptyDoc, whitespaceDoc, singleLineDoc, largeDoc, longLinesDoc],
+				[testDoc, emptyDoc, whitespaceDoc, singleLineDoc, largeDoc, longLinesDoc, surrogateBoundaryDoc],
 			]
 		));
 		accessor = services.createTestingAccessor();
@@ -208,6 +210,18 @@ suite('ReadFile', () => {
 			}
 		});
 
+		test('long line truncation does not split surrogate pairs', async () => {
+			const toolsService = accessor.get(IToolsService);
+			const input: IReadFileParamsV2 = {
+				filePath: '/workspace/surrogate-boundary.ts'
+			};
+			const result = await toolsService.invokeTool(ToolName.ReadFile, { input, toolInvocationToken: null as never }, CancellationToken.None);
+			const resultString = await toolResultToString(accessor, result);
+			const truncatedLine = resultString.split('\n').find(line => line.endsWith(' [truncated]'));
+
+			expect(truncatedLine).toBe('x'.repeat(1999) + ' [truncated]');
+		});
+
 		test('read file with offset beyond file line count should throw error', async () => {
 			const toolsService = accessor.get(IToolsService);
 
diff --git a/src/vs/base/browser/ui/list/listWidget.ts b/src/vs/base/browser/ui/list/listWidget.ts
index 4b191b9dd833e0..45458741adbd96 100644
--- a/src/vs/base/browser/ui/list/listWidget.ts
+++ b/src/vs/base/browser/ui/list/listWidget.ts
@@ -1560,6 +1560,7 @@ export class List<T> implements ISpliceable<T>, IDisposable {
 
 		this.onDidChangeFocus(this._onFocusChange, this, this.disposables);
 		this.onDidChangeSelection(this._onSelectionChange, this, this.disposables);
+		this.view.onDidScroll(this.onDidChangeActiveDescendant, this, this.disposables);
 
 		if (this.accessibilityProvider) {
 			const ariaLabel = this.accessibilityProvider.getWidgetAriaLabel();
@@ -2059,13 +2060,22 @@ export class List<T> implements ISpliceable<T>, IDisposable {
 		const focus = this.focus.get();
 
 		if (focus.length > 0) {
+			const index = focus[0];
 			let id: string | undefined;
 
 			if (this.accessibilityProvider?.getActiveDescendantId) {
-				id = this.accessibilityProvider.getActiveDescendantId(this.view.element(focus[0]));
+				id = this.accessibilityProvider.getActiveDescendantId(this.view.element(index));
 			}
 
-			this.view.domNode.setAttribute('aria-activedescendant', id || this.view.getElementDomId(focus[0]));
+			if (!id && this.view.domElement(index)) {
+				id = this.view.getElementDomId(index);
+			}
+
+			if (id) {
+				this.view.domNode.setAttribute('aria-activedescendant', id);
+			} else {
+				this.view.domNode.removeAttribute('aria-activedescendant');
+			}
 		} else {
 			this.view.domNode.removeAttribute('aria-activedescendant');
 		}
diff --git a/src/vs/base/test/browser/ui/list/listWidget.test.ts b/src/vs/base/test/browser/ui/list/listWidget.test.ts
index 98dc9d1ef51467..455baa025dc354 100644
--- a/src/vs/base/test/browser/ui/list/listWidget.test.ts
+++ b/src/vs/base/test/browser/ui/list/listWidget.test.ts
@@ -93,4 +93,58 @@ suite('ListWidget', function () {
 		await timeout(0);
 		assert.strictEqual(listWidget.getFocus()[0], 0, 'page up to next page');
 	});
+
+	test('aria-activedescendant references a rendered element', function () {
+		const element = document.createElement('div');
+		element.style.height = '20px';
+		element.style.width = '200px';
+
+		const delegate: IListVirtualDelegate<number> = {
+			getHeight() { return 20; },
+			getTemplateId() { return 'template'; }
+		};
+
+		const renderer: IListRenderer<number, void> = {
+			templateId: 'template',
+			renderTemplate() { },
+			renderElement() { },
+			disposeTemplate() { }
+		};
+
+		const listWidget = store.add(new List<number>('test', element, delegate, [renderer], {
+			accessibilityProvider: {
+				getAriaLabel: element => String(element),
+				getWidgetAriaLabel: () => 'Test list',
+				getActiveDescendantId: () => undefined
+			}
+		}));
+		listWidget.layout(20);
+		listWidget.splice(0, 0, range(100));
+
+		const listElement = element.querySelector<HTMLElement>('.monaco-list')!;
+		const focusedElementId = listWidget.getElementID(50);
+
+		listWidget.setFocus([50]);
+		const beforeReveal = {
+			activeDescendant: listElement.getAttribute('aria-activedescendant'),
+			focusedElementRendered: element.querySelector(`#${focusedElementId}`) !== null
+		};
+
+		listWidget.reveal(50);
+		const afterReveal = {
+			activeDescendant: listElement.getAttribute('aria-activedescendant'),
+			focusedElementRendered: element.querySelector(`#${focusedElementId}`) !== null
+		};
+
+		assert.deepStrictEqual({ beforeReveal, afterReveal }, {
+			beforeReveal: {
+				activeDescendant: null,
+				focusedElementRendered: false
+			},
+			afterReveal: {
+				activeDescendant: focusedElementId,
+				focusedElementRendered: true
+			}
+		});
+	});
 });
diff --git a/src/vs/platform/agentHost/common/agent.ts b/src/vs/platform/agentHost/common/agent.ts
index cc5ee6b72368c7..b895265c1c06df 100644
--- a/src/vs/platform/agentHost/common/agent.ts
+++ b/src/vs/platform/agentHost/common/agent.ts
@@ -1145,8 +1145,8 @@ export interface IAgent {
 	/** Optional lifecycle operation paired with {@link startMcpServer}. */
 	stopMcpServer?(session: URI, id: string): Promise<void>;
 
-	/** Optional `mcp://` router for providers that advertise MCP side-channel resources. */
-	handleMcpRequest?(session: URI, serverName: string, method: string, params: Record<string, unknown> | undefined): Promise<unknown>;
+	/** Optional `mcp://` router for providers that advertise chat-scoped MCP side-channel resources. */
+	handleMcpRequest?(chat: URI, serverName: string, method: string, params: Record<string, unknown> | undefined): Promise<unknown>;
 
 	/** Optional notification stream paired with {@link handleMcpRequest}. */
 	readonly onMcpNotification?: Event<IMcpNotification>;
diff --git a/src/vs/platform/agentHost/node/agentService.ts b/src/vs/platform/agentHost/node/agentService.ts
index 358049a9e71e1d..b3c9e9e5c77320 100644
--- a/src/vs/platform/agentHost/node/agentService.ts
+++ b/src/vs/platform/agentHost/node/agentService.ts
@@ -959,8 +959,7 @@ export class AgentService extends Disposable implements IAgentService {
 		if (!provider || !provider.handleMcpRequest) {
 			throw new Error(`Method not found: no provider for mcp:// channel ${channel}`);
 		}
-		const sessionUri = AgentSession.uri(route.providerId, route.sessionId);
-		return provider.handleMcpRequest(sessionUri, route.serverName, method, params);
+		return provider.handleMcpRequest(route.chatUri, route.serverName, method, params);
 	}
 
 	// ---- session management -------------------------------------------------
diff --git a/src/vs/platform/agentHost/node/codex/codexAgent.ts b/src/vs/platform/agentHost/node/codex/codexAgent.ts
index d25d334bb11f8e..99aef2aa2e5197 100644
--- a/src/vs/platform/agentHost/node/codex/codexAgent.ts
+++ b/src/vs/platform/agentHost/node/codex/codexAgent.ts
@@ -5636,8 +5636,10 @@ export class CodexAgent extends Disposable implements IAgent {
 			return [];
 		}
 		const controller = this._getOrCreateMcpController(session);
-		controller.applyAll(inventoryToSdkServers(this._mcpInventory));
-		this._refreshMcpCustomizationIds(session, controller);
+		controller?.applyAll(inventoryToSdkServers(this._mcpInventory));
+		if (controller) {
+			this._refreshMcpCustomizationIds(session, controller);
+		}
 		const [workspaceAgents, skillHookContainers] = await Promise.all([
 			discoverCodexWorkspaceAgents(this._workingDirectories(session), this._fileService),
 			this._fetchSkillHookContainers(session),
@@ -5648,7 +5650,7 @@ export class CodexAgent extends Disposable implements IAgent {
 		return [
 			...workspaceAgents.containers,
 			...session.clientCustomizations.toCustomizations(),
-			...controller.topLevelCustomizations(),
+			...(controller?.topLevelCustomizations() ?? []),
 			...skillHookContainers,
 		];
 	}
@@ -5709,11 +5711,14 @@ export class CodexAgent extends Disposable implements IAgent {
 	 * `Method not found` so the protocol server maps them to JSON-RPC
 	 * `-32601`.
 	 */
-	async handleMcpRequest(sessionUri: URI, serverName: string, method: string, params: Record<string, unknown> | undefined): Promise<unknown> {
-		const sessionId = AgentSession.id(sessionUri);
+	async handleMcpRequest(chat: URI, serverName: string, method: string, params: Record<string, unknown> | undefined): Promise<unknown> {
+		const sessionId = this._sessionIdByChatUri.get(chat.toString());
+		if (!sessionId) {
+			throw new Error(`Method not found: no active chat ${chat.toString()}`);
+		}
 		const session = this._sessions.get(sessionId);
-		if (!session) {
-			throw new Error(`Method not found: no active session ${sessionId}`);
+		if (!session || !session.chatChannel || !isEqual(session.chatChannel, chat)) {
+			throw new Error(`Method not found: no active chat ${chat.toString()}`);
 		}
 		const entry = this._mcpInventory.get(serverName);
 		if (!entry) {
@@ -5780,6 +5785,9 @@ export class CodexAgent extends Disposable implements IAgent {
 
 	private _resolveMcpServerName(session: ICodexSession, id: string): string | undefined {
 		const controller = this._getOrCreateMcpController(session);
+		if (!controller) {
+			return undefined;
+		}
 		controller.applyAll(inventoryToSdkServers(this._mcpInventory));
 		this._refreshMcpCustomizationIds(session, controller);
 		return controller.serverNameForCustomizationId(id);
@@ -5790,12 +5798,13 @@ export class CodexAgent extends Disposable implements IAgent {
 	 * registered on the agent (sessions come and go) — disposed explicitly
 	 * when the session is removed.
 	 */
-	private _getOrCreateMcpController(session: ICodexSession): McpCustomizationController {
+	private _getOrCreateMcpController(session: ICodexSession): McpCustomizationController | undefined {
+		if (!session.chatChannel) {
+			return undefined;
+		}
 		if (!session.mcpController) {
 			session.mcpController = this._instantiationService.createInstance(McpCustomizationController, {
-				providerId: this.id,
-				sessionId: session.sessionId,
-				sessionUri: session.sessionUri,
+				chatUri: session.chatChannel,
 				emit: action => this._fire(session.sessionUri, action),
 				capabilities: CODEX_MCP_APP_CAPABILITIES,
 				pluginMcpServerSources: () => codexPluginMcpServerSources(session.clientCustomizations.plugins()),
@@ -5816,6 +5825,9 @@ export class CodexAgent extends Disposable implements IAgent {
 				continue;
 			}
 			const controller = this._getOrCreateMcpController(session);
+			if (!controller) {
+				continue;
+			}
 			controller.applyAll(servers);
 			this._refreshMcpCustomizationIds(session, controller);
 		}
diff --git a/src/vs/platform/agentHost/node/copilot/copilotAgent.ts b/src/vs/platform/agentHost/node/copilot/copilotAgent.ts
index 5db3c597357070..58356715d2baa2 100644
--- a/src/vs/platform/agentHost/node/copilot/copilotAgent.ts
+++ b/src/vs/platform/agentHost/node/copilot/copilotAgent.ts
@@ -1283,10 +1283,10 @@ export class CopilotAgent extends Disposable implements IAgent {
 		return applyMcpServerEnablement(customizations, this._retainedHostCustomizations(session));
 	}
 
-	async handleMcpRequest(session: URI, serverName: string, method: string, params: Record<string, unknown> | undefined): Promise<unknown> {
-		const entry = this._findSessionChat(session);
+	async handleMcpRequest(chat: URI, serverName: string, method: string, params: Record<string, unknown> | undefined): Promise<unknown> {
+		const entry = this._findChatByUri(chat);
 		if (!entry) {
-			throw new Error(`Method not found: no active session ${AgentSession.id(session)}`);
+			throw new Error(`Method not found: no active chat ${chat.toString()}`);
 		}
 		return entry.handleMcpRequest(serverName, method, params);
 	}
@@ -2925,7 +2925,7 @@ export class CopilotAgent extends Disposable implements IAgent {
 				freeLongContext: this._isFreeLongContext(provisional.model?.id),
 				workspaceless: provisional.workspaceless,
 			};
-			const chatChannelUri = this._findBoundSessionChatUri(sdkSessionId) ?? sessionUri;
+			const chatChannelUri = this._findBoundSessionChatUri(sdkSessionId) ?? URI.parse(buildDefaultChatUri(sessionUri));
 			agentSession = this._createAgentSession(launchPlan, customizationDirectory, activeClient, {
 				sessionUri,
 				chatChannelUri,
@@ -4134,7 +4134,7 @@ export class CopilotAgent extends Disposable implements IAgent {
 	/** Instantiates a session; the caller must initialize and register it on success. */
 	private _createAgentSession(launchPlan: CopilotSessionLaunchPlan, customizationDirectory: URI | undefined, activeClient: ActiveClient, identity?: ICopilotAgentSessionIdentity): CopilotAgentSession {
 		const sessionUri = identity?.sessionUri ?? AgentSession.uri(this.id, launchPlan.sessionId);
-		const chatChannelUri = identity?.chatChannelUri ?? this._findBoundSessionChatUri(launchPlan.sessionId) ?? sessionUri;
+		const chatChannelUri = identity?.chatChannelUri ?? this._findBoundSessionChatUri(launchPlan.sessionId) ?? URI.parse(buildDefaultChatUri(sessionUri));
 
 		const agentSession = this._instantiationService.createInstance(
 			CopilotAgentSession,
@@ -4151,7 +4151,7 @@ export class CopilotAgent extends Disposable implements IAgent {
 				customizationDirectory,
 				clientSnapshot: launchPlan.snapshot,
 				activeClientToolSet: launchPlan.activeClientToolSet,
-				// Evaluate membership against the session's current chat channel; `bindChatChannel` can move it later.
+				// Evaluate membership against the session's chat channel.
 				clientReachesChat: (clientId, chat) => activeClient.contributesTo(clientId, chat.toString()),
 				// MCP reconcile has no host call of its own, so read the retained host snapshot lazily.
 				hostCustomizations: () => this._retainedHostCustomizations(sessionUri),
@@ -4211,7 +4211,6 @@ export class CopilotAgent extends Disposable implements IAgent {
 		this._throwIfClientReplaced(client, agentSession);
 		const boundChat = this._findBoundSessionChatUri(sessionId);
 		if (boundChat) {
-			agentSession.bindChatChannel?.(boundChat);
 			this._registerLiveChat(boundChat, agentSession, activeClient);
 			return;
 		}
diff --git a/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts b/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
index e897e99f70c699..2b18bec0477eb1 100644
--- a/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
+++ b/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
@@ -625,7 +625,7 @@ export class CopilotAgentSession extends Disposable {
 	get ownerSessionUri(): URI { return this._ownerSessionUri; }
 	/** @deprecated Compatibility alias for SDK callbacks; this is the exact persistence resource. */
 	get sessionUri(): URI { return this.resourceUri; }
-	private _chatChannelUri: URI;
+	private readonly _chatChannelUri: URI;
 	/** Fixed persistence scope for this chat; never re-derived from the mutable routing channel. Config reads/writes must use {@link _ownerSessionUri} instead — peer chats share that scope but have distinct storage. */
 	private readonly _storageUri: URI;
 
@@ -633,10 +633,6 @@ export class CopilotAgentSession extends Disposable {
 		return this._chatChannelUri;
 	}
 
-	bindChatChannel(chatChannelUri: URI): void {
-		this._chatChannelUri = chatChannelUri;
-	}
-
 	/** Working directory this session operates in, if any. */
 	get workingDirectory(): URI | undefined { return this._workingDirectory; }
 
@@ -954,9 +950,7 @@ export class CopilotAgentSession extends Disposable {
 			return sourceUri === undefined ? [] : plugin.mcpServers.map(server => [server.name, sourceUri.toString()] as const);
 		}));
 		this._mcpCustomizations = this._register(this._instantiationService.createInstance(McpCustomizationController, {
-			providerId: this.resourceUri.scheme,
-			sessionId: this.sessionId,
-			sessionUri: this.resourceUri,
+			chatUri: this._chatChannelUri,
 			emit: action => this._emitAction(action),
 			pluginMcpServerSources: () => pluginMcpServerSources,
 			resolveEnablement: (server, owningPluginUri) => {
@@ -2440,7 +2434,7 @@ export class CopilotAgentSession extends Disposable {
 		} catch {
 			// Database may not exist yet — that's fine
 		}
-		const result = await mapSessionEvents(this._storageUri, db, events, {
+		const result = await mapSessionEvents(this._storageUri, db, events, this._chatChannelUri, {
 			workingDirectory: this._workingDirectory,
 			model: this._launchPlan.kind === 'create'
 				? this._launchPlan.model
diff --git a/src/vs/platform/agentHost/node/copilot/mapSessionEvents.ts b/src/vs/platform/agentHost/node/copilot/mapSessionEvents.ts
index f621f9e9a1e134..282e3d80a51d9f 100644
--- a/src/vs/platform/agentHost/node/copilot/mapSessionEvents.ts
+++ b/src/vs/platform/agentHost/node/copilot/mapSessionEvents.ts
@@ -15,7 +15,7 @@ import { stripRedundantCdPrefix } from '../../common/commandLineHelpers.js';
 import { toToolCallMeta, type IToolCallUiMeta, type ToolKind } from '../../common/meta/agentToolCallMeta.js';
 import { IFileEditRecord, ISessionDatabase } from '../../common/sessionDataService.js';
 import { MessageAttachmentKind, type MessageAttachment } from '../../common/state/protocol/state.js';
-import { MessageKind, ResponsePartKind, ToolCallConfirmationReason, ToolCallContributorKind, ToolCallStatus, ToolResultContentType, TurnState, buildSubagentSessionUri, type AgentSelection, type ErrorInfo, type Message, type ModelSelection, type ResponsePart, type StringOrMarkdown, type TerminalCommandResult, type ToolCallCompletedState, type ToolResultContent, type ToolResultTerminalContent, type Turn, type UsageInfo } from '../../common/state/sessionState.js';
+import { MessageKind, ResponsePartKind, ToolCallConfirmationReason, ToolCallContributorKind, ToolCallStatus, ToolResultContentType, TurnState, buildSubagentSessionUri, parseChatUri, type AgentSelection, type ErrorInfo, type Message, type ModelSelection, type ResponsePart, type StringOrMarkdown, type TerminalCommandResult, type ToolCallCompletedState, type ToolResultContent, type ToolResultTerminalContent, type Turn, type UsageInfo } from '../../common/state/sessionState.js';
 import { buildNonPtyShellTerminalUri } from './copilotNonPtyShellTerminals.js';
 import { getInvocationMessage, getPastTenseMessage, getShellIntention, getShellLanguage, getSubagentMetadata, getTaskCompleteMarkdown, getToolDisplayName, getToolInputString, getToolKind, isEditTool, isHiddenTool, isTaskCompleteTool, synthesizeSkillToolCall } from './copilotToolDisplay.js';
 import { buildSessionDbUri } from '../../common/sessionDbUri.js';
@@ -310,11 +310,16 @@ export async function mapSessionEvents(
 	session: URI,
 	db: ISessionDatabase | undefined,
 	events: readonly SessionEvent[],
-	options: URI | IMapSessionEventsOptions | undefined = undefined,
+	routingChatUri: URI,
+	options: IMapSessionEventsOptions | undefined = undefined,
 ): Promise<{ turns: Turn[]; subagentTurnsByToolCallId: ReadonlyMap<string, Turn[]> }> {
-	const workingDirectory = options instanceof URI ? options : options?.workingDirectory;
-	let currentModel = options instanceof URI ? undefined : options?.model;
-	let currentAgent = options instanceof URI ? undefined : options?.agent;
+	const routingChat = parseChatUri(routingChatUri);
+	if (!routingChat) {
+		throw new Error(`Malformed AHP chat URI: ${routingChatUri.toString()}`);
+	}
+	const workingDirectory = options?.workingDirectory;
+	let currentModel = options?.model;
+	let currentAgent = options?.agent;
 	// First pass: collect tool-arg info and identify edit tool calls so we
 	// can batch-load their stored file edits before the second pass needs
 	// them at `tool.execution_complete` time. We also build the
@@ -387,8 +392,9 @@ export async function mapSessionEvents(
 	}
 
 	const sessionUriStr = session.toString();
-	const providerId = session.scheme;
-	const rawSessionId = AgentSession.id(session);
+	const routingSession = URI.parse(routingChat.session);
+	const providerId = routingSession.scheme;
+	const rawSessionId = AgentSession.id(routingSession);
 	const turns: Turn[] = [];
 
 	// Subagent state. Each subagent has its own active turn builder; only
@@ -664,7 +670,7 @@ export async function mapSessionEvents(
 					// No active turn to attach this completion to.
 					continue;
 				}
-				const completedPart = makeCompletedToolCallPart(d, info, sessionUriStr, providerId, rawSessionId, storedEdits, subagentInfoByToolCallId.get(d.toolCallId), workingDirectory);
+				const completedPart = makeCompletedToolCallPart(d, info, sessionUriStr, providerId, rawSessionId, routingChatUri, storedEdits, subagentInfoByToolCallId.get(d.toolCallId), workingDirectory);
 				builder.responseParts.push(completedPart);
 				// When a parent tool call that spawned a subagent completes,
 				// flush the subagent's accumulated turn.
@@ -755,6 +761,7 @@ export async function mapSessionEvents(
 				sessionUriStr,
 				providerId,
 				rawSessionId,
+				routingChatUri,
 				storedEdits,
 				subagentInfoByToolCallId.get(request.toolCallId),
 				workingDirectory,
@@ -858,6 +865,7 @@ function makeCompletedToolCallPart(
 	sessionUriStr: string,
 	providerId: string,
 	rawSessionId: string,
+	chatURI: URI,
 	storedEdits: Map<string, IFileEditRecord[]> | undefined,
 	subagent: ISubagentInfo | undefined,
 	workingDirectory: URI | undefined,
@@ -916,7 +924,7 @@ function makeCompletedToolCallPart(
 	const mcpUi: IToolCallUiMeta | undefined = mcpUiResourceUri
 		? {
 			resourceUri: mcpUiResourceUri,
-			...(mcpServerName ? { channel: buildMcpChannel(providerId, rawSessionId, mcpServerName) } : {}),
+			...(mcpServerName ? { channel: buildMcpChannel(chatURI, mcpServerName) } : {}),
 		}
 		: undefined;
 
diff --git a/src/vs/platform/agentHost/node/shared/mcpCustomizationController.ts b/src/vs/platform/agentHost/node/shared/mcpCustomizationController.ts
index e4e4984c446608..1798ba5d2134ea 100644
--- a/src/vs/platform/agentHost/node/shared/mcpCustomizationController.ts
+++ b/src/vs/platform/agentHost/node/shared/mcpCustomizationController.ts
@@ -6,10 +6,12 @@
 import { Disposable } from '../../../../base/common/lifecycle.js';
 import { derived, observableValue, transaction, type IObservable, type ITransaction } from '../../../../base/common/observable.js';
 import { URI } from '../../../../base/common/uri.js';
+import { AgentSession } from '../../common/agent.js';
 import { ActionType } from '../../common/state/protocol/common/actions.js';
 import { isCustomizationEnabled } from '../../common/customizationEnablement.js';
 import { CustomizationType, McpServerStatus, type AhpMcpUiHostCapabilities, type Customization, type CustomizationEnablement, type McpServerCustomization, type McpServerState } from '../../common/state/protocol/channels-session/state.js';
 import { DEFAULT_MCP_APP, DEFAULT_MCP_APP_CAPABILITIES } from '../../common/state/protocol/mcpAppDefaults.js';
+import { parseChatUri } from '../../common/state/sessionState.js';
 import type { SessionAction } from '../../common/state/sessionActions.js';
 import { AgentHostStateManager, IAgentHostStateManager } from '../agentHostStateManager.js';
 
@@ -49,12 +51,8 @@ export { DEFAULT_MCP_APP_CAPABILITIES, DEFAULT_MCP_APP };
  * Options for {@link McpCustomizationController}.
  */
 export interface IMcpCustomizationControllerOptions {
-	/** Provider id (e.g. `'copilotcli'`). Used as the channel URI authority. */
-	readonly providerId: string;
-	/** Session id (the raw id, not the full URI). Used as the channel path segment. */
-	readonly sessionId: string;
-	/** Canonical session URI used to resolve persisted customization state. */
-	readonly sessionUri: URI;
+	/** Concrete chat URI used for MCP App routing. */
+	readonly chatUri: URI;
 	/** Emits a {@link SessionAction} into the session's action stream. */
 	readonly emit: (action: SessionAction) => void;
 	/** Returns durable plugin source URIs for plugin-provided MCP servers. */
@@ -80,8 +78,9 @@ export function buildMcpTopLevelCustomizationId(providerId: string, sessionId: s
 	return `mcp-top-level:${providerId}:${sessionId}:${serverName}`;
 }
 
-export function buildMcpChannel(providerId: string, sessionId: string, serverName: string): string {
-	return `mcp://${providerId}/${encodeURIComponent(sessionId)}/${encodeURIComponent(serverName)}`;
+export function buildMcpChannel(chatUri: URI, serverName: string): string {
+	const providerId = getMcpChannelProviderId(chatUri);
+	return `mcp://${providerId}/${encodeURIComponent(chatUri.toString())}/${encodeURIComponent(serverName)}`;
 }
 
 /**
@@ -109,6 +108,11 @@ export function buildMcpChannel(providerId: string, sessionId: string, serverNam
  */
 export class McpCustomizationController extends Disposable {
 
+	private readonly _chatUri: URI;
+	private readonly _providerId: string;
+	private readonly _sessionId: string;
+	private readonly _sessionUri: URI;
+
 	/** Per-server live entries, keyed by server name. */
 	private readonly _live = observableValue<ReadonlyMap<string, ILiveEntry>>(this, new Map());
 
@@ -128,6 +132,17 @@ export class McpCustomizationController extends Disposable {
 		@IAgentHostStateManager private readonly _stateManager: AgentHostStateManager,
 	) {
 		super();
+		this._chatUri = this._options.chatUri;
+		const chat = parseChatUri(this._chatUri);
+		if (!chat) {
+			throw new Error(`Malformed AHP chat URI: ${this._chatUri.toString()}`);
+		}
+		this._sessionUri = URI.parse(chat.session);
+		this._providerId = AgentSession.provider(this._sessionUri) ?? '';
+		this._sessionId = AgentSession.id(this._sessionUri);
+		if (!this._providerId || !this._sessionId) {
+			throw new Error(`Malformed Agent Host session URI: ${chat.session}`);
+		}
 		this.runtimeStates = derived(this, reader => {
 			const out = new Map<string, IMcpServerRuntimeState>();
 			for (const entry of this._live.read(reader).values()) {
@@ -365,7 +380,7 @@ export class McpCustomizationController extends Disposable {
 	}
 
 	private _mintTopLevelId(serverName: string): string {
-		return buildMcpTopLevelCustomizationId(this._options.providerId, this._options.sessionId, serverName);
+		return buildMcpTopLevelCustomizationId(this._providerId, this._sessionId, serverName);
 	}
 
 	private _resolveChildId(serverName: string): string | undefined {
@@ -373,7 +388,7 @@ export class McpCustomizationController extends Disposable {
 	}
 
 	private _findPublishedMcpCustomization(serverName: string): { readonly topLevelId?: string; readonly childId?: string } | undefined {
-		const customizations = this._stateManager.getSessionState(this._options.sessionUri.toString())?.customizations ?? [];
+		const customizations = this._stateManager.getSessionState(this._sessionUri.toString())?.customizations ?? [];
 		const topLevel = customizations.find(customization => customization.type === CustomizationType.McpServer && customization.name === serverName);
 		if (topLevel?.type === CustomizationType.McpServer) {
 			return { topLevelId: topLevel.id };
@@ -386,7 +401,7 @@ export class McpCustomizationController extends Disposable {
 		if (state.kind !== McpServerStatus.Ready) {
 			return undefined;
 		}
-		return buildMcpChannel(this._options.providerId, this._options.sessionId, serverName);
+		return buildMcpChannel(this._chatUri, serverName);
 	}
 
 	private _buildTopLevel(id: string, serverName: string, state: McpServerState, enabled: boolean): McpServerCustomization {
@@ -400,7 +415,7 @@ export class McpCustomizationController extends Disposable {
 		const mcpApp = this._options.capabilities
 			? { capabilities: this._options.capabilities }
 			: DEFAULT_MCP_APP;
-		const existing = getMcpServerCustomizations(this._stateManager.getSessionState(this._options.sessionUri.toString())?.customizations ?? [])
+		const existing = getMcpServerCustomizations(this._stateManager.getSessionState(this._sessionUri.toString())?.customizations ?? [])
 			.find(customization => customization.id === id);
 		const customization: McpServerCustomization = {
 			type: CustomizationType.McpServer,
@@ -504,22 +519,32 @@ export function findMcpServerName(customizations: readonly Customization[], id:
 }
 
 /**
- * Parsed `mcp://<providerId>/<sessionId>/<serverName>` URI as minted by
+ * Parsed `mcp://<providerId>/<chatUri>/<serverName>` URI as minted by
  * {@link McpCustomizationController}. The path segments are
  * URL-decoded.
  */
 export interface IMcpChannelRoute {
 	readonly providerId: string;
-	readonly sessionId: string;
+	readonly chatUri: URI;
 	readonly serverName: string;
 }
 
+function getMcpChannelProviderId(chatUri: URI): string {
+	const chat = parseChatUri(chatUri);
+	if (!chat) {
+		throw new Error(`Malformed AHP chat URI: ${chatUri.toString()}`);
+	}
+	const providerId = AgentSession.provider(chat.session);
+	if (!providerId) {
+		throw new Error(`Malformed Agent Host session URI: ${chat.session}`);
+	}
+	return providerId;
+}
+
 /**
  * Decodes a channel URI string into a {@link IMcpChannelRoute}, or
  * returns `undefined` when the URI is not an `mcp://` channel or the
- * path is malformed. Intentionally uses string parsing rather than
- * `URI.parse` so the helper stays usable from layers (e.g. agentService
- * test fixtures) without a full URI dependency.
+ * path is malformed.
  */
 export function parseMcpChannelUri(uri: string): IMcpChannelRoute | undefined {
 	const prefix = 'mcp://';
@@ -533,24 +558,29 @@ export function parseMcpChannelUri(uri: string): IMcpChannelRoute | undefined {
 	}
 	const providerId = rest.slice(0, slash);
 	const tail = rest.slice(slash + 1);
-	const sep = tail.indexOf('/');
-	if (sep <= 0 || sep === tail.length - 1) {
+	const segments = tail.split('/');
+	if (segments.length !== 2 || !segments[0] || !segments[1]) {
 		return undefined;
 	}
-	let sessionId: string;
+	let chatUri: URI;
 	let serverName: string;
 	try {
-		// `decodeURIComponent` throws `URIError` on malformed percent
-		// escapes (e.g. a lone `%`). Treat any decode failure as a
-		// malformed channel rather than letting it escape — the caller
-		// translates `undefined` into a clean `Method not found`.
-		sessionId = decodeURIComponent(tail.slice(0, sep));
-		serverName = decodeURIComponent(tail.slice(sep + 1));
+		chatUri = URI.parse(decodeURIComponent(segments[0]));
+		serverName = decodeURIComponent(segments[1]);
+	} catch {
+		return undefined;
+	}
+	if (!providerId || !serverName) {
+		return undefined;
+	}
+	let routedProviderId: string;
+	try {
+		routedProviderId = getMcpChannelProviderId(chatUri);
 	} catch {
 		return undefined;
 	}
-	if (!providerId || !sessionId || !serverName) {
+	if (routedProviderId !== providerId) {
 		return undefined;
 	}
-	return { providerId, sessionId, serverName };
+	return { providerId, chatUri, serverName };
 }
diff --git a/src/vs/platform/agentHost/test/node/buildSessionEvents.test.ts b/src/vs/platform/agentHost/test/node/buildSessionEvents.test.ts
index e14d254eeb668f..889001cde9056a 100644
--- a/src/vs/platform/agentHost/test/node/buildSessionEvents.test.ts
+++ b/src/vs/platform/agentHost/test/node/buildSessionEvents.test.ts
@@ -5,11 +5,12 @@
 
 import assert from 'assert';
 import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../base/test/common/utils.js';
+import { URI } from '../../../../base/common/uri.js';
 import { generateUuid, isUUID } from '../../../../base/common/uuid.js';
 import { AgentSession } from '../../common/agent.js';
-import { MessageKind, ResponsePartKind, ToolCallConfirmationReason, ToolCallStatus, ToolResultContentType, TurnState, type ResponsePart, type ToolCallCompletedState, type Turn } from '../../common/state/sessionState.js';
+import { MessageKind, ResponsePartKind, ToolCallConfirmationReason, ToolCallStatus, ToolResultContentType, TurnState, buildChatUri, type ResponsePart, type ToolCallCompletedState, type Turn } from '../../common/state/sessionState.js';
 import { buildSessionEventLogFromTurns, buildSessionEventsFromTurns, serializeSessionEventsToJsonl } from '../../node/copilot/buildSessionEvents.js';
-import { mapSessionEvents } from '../../node/copilot/mapSessionEvents.js';
+import { mapSessionEvents as mapSessionEventsWithRouting } from '../../node/copilot/mapSessionEvents.js';
 import type { SessionEvent } from '@github/copilot-sdk';
 
 suite('buildSessionEventsFromTurns — reverse of mapSessionEvents', () => {
@@ -19,6 +20,10 @@ suite('buildSessionEventsFromTurns — reverse of mapSessionEvents', () => {
 	const session = AgentSession.uri('copilot', 'test-session');
 	const sessionId = 'test-session';
 
+	function mapSessionEvents(session: URI, db: undefined, events: Parameters<typeof mapSessionEventsWithRouting>[2]) {
+		return mapSessionEventsWithRouting(session, db, events, URI.parse(buildChatUri(session, 'default')));
+	}
+
 	function markdown(content: string): ResponsePart {
 		return { kind: ResponsePartKind.Markdown, id: 'ignored', content };
 	}
diff --git a/src/vs/platform/agentHost/test/node/codex/codexAgent.test.ts b/src/vs/platform/agentHost/test/node/codex/codexAgent.test.ts
index 2d1430b7ac8f61..d4d94d7123846e 100644
--- a/src/vs/platform/agentHost/test/node/codex/codexAgent.test.ts
+++ b/src/vs/platform/agentHost/test/node/codex/codexAgent.test.ts
@@ -35,6 +35,7 @@ interface ICodexConversationResolverHarness {
 interface ICodexMcpControllerSession {
 	readonly sessionId: string;
 	readonly sessionUri: URI;
+	chatChannel: URI | undefined;
 	readonly clientCustomizations: CodexClientCustomizationStore;
 	mcpController: McpCustomizationController | undefined;
 }
@@ -57,9 +58,9 @@ function resolveConversationSession(harness: ICodexConversationResolverHarness,
 	return resolver.call(harness, address, context);
 }
 
-function getOrCreateMcpController(harness: ICodexMcpControllerHarness, session: ICodexMcpControllerSession): McpCustomizationController {
+function getOrCreateMcpController(harness: ICodexMcpControllerHarness, session: ICodexMcpControllerSession): McpCustomizationController | undefined {
 	const getOrCreate = (CodexAgent.prototype as unknown as {
-		_getOrCreateMcpController(this: ICodexMcpControllerHarness, session: ICodexMcpControllerSession): McpCustomizationController;
+		_getOrCreateMcpController(this: ICodexMcpControllerHarness, session: ICodexMcpControllerSession): McpCustomizationController | undefined;
 	})._getOrCreateMcpController;
 	return getOrCreate.call(harness, session);
 }
@@ -117,13 +118,14 @@ suite('CodexAgent', () => {
 		});
 	});
 
-	test('keeps fresh plugin MCP ownership after client customization resyncs, including disabled plugins', () => {
+	test('creates MCP customization state only after a concrete chat is bound', () => {
 		const store = new DisposableStore();
 		const stateManager = store.add(new AgentHostStateManager(new NullLogService()));
 		const customizations = new CodexClientCustomizationStore();
 		const session: ICodexMcpControllerSession = {
 			sessionId: 'session-1',
 			sessionUri: AgentSession.uri('codex', 'session-1'),
+			chatChannel: undefined,
 			clientCustomizations: customizations,
 			mcpController: undefined,
 		};
@@ -145,7 +147,10 @@ suite('CodexAgent', () => {
 			},
 			_fire: () => { },
 		};
+		const beforeChatBinding = getOrCreateMcpController(harness, session);
+		session.chatChannel = URI.parse(buildDefaultChatUri(session.sessionUri));
 		const controller = getOrCreateMcpController(harness, session);
+		assert.ok(controller);
 		const plugin = {
 			synced: { customization: { id: 'azure-plugin', uri: pluginUri } },
 			parsed: { mcpServers: [{ name: 'azure' }] },
@@ -171,11 +176,13 @@ suite('CodexAgent', () => {
 		const topLevelEnablement = controller.topLevelCustomizations()[0]?.enablement;
 
 		assert.deepStrictEqual({
+			beforeChatBinding,
 			owner,
 			topLevelKey: getCustomizationEnablementKey(targetForMcpServer(topLevel, owner, false), CustomizationEnablementKind.Global),
 			nestedKey: getCustomizationEnablementKey(targetForMcpServer(nested, pluginUri, false), CustomizationEnablementKind.Global),
 			topLevelEnablement,
 		}, {
+			beforeChatBinding: undefined,
 			owner: pluginUri,
 			topLevelKey: `${pluginUri}#mcp=azure`,
 			nestedKey: `${pluginUri}#mcp=azure`,
diff --git a/src/vs/platform/agentHost/test/node/copilotAgent.test.ts b/src/vs/platform/agentHost/test/node/copilotAgent.test.ts
index 532fde1ea8e410..5aeb1c57c6e7f8 100644
--- a/src/vs/platform/agentHost/test/node/copilotAgent.test.ts
+++ b/src/vs/platform/agentHost/test/node/copilotAgent.test.ts
@@ -6808,7 +6808,7 @@ suite('CopilotAgent', () => {
 
 				assert.deepStrictEqual({
 					mcpCalls,
-					mcpRequest: await agent.handleMcpRequest(session, 'srv', 'tools/list', undefined),
+					mcpRequest: await agent.handleMcpRequest(defaultChatUri(session), 'srv', 'tools/list', undefined),
 					customizations: await getDefaultChatCustomizations(agent, session),
 					// Constructing the agent never touched the state manager.
 					sessions: stateManager.getSessionUris().length,
@@ -6823,15 +6823,11 @@ suite('CopilotAgent', () => {
 			}
 		});
 
-		test('session-addressed lookups resolve the session-backed chat by its host-chosen scope, not a rebuilt default-chat URI', async () => {
+		test('MCP requests route to the exact host chat instead of the owning session', async () => {
 			const agent = createTestAgent(disposables);
 			try {
 				const session = AgentSession.uri('copilotcli', 'scope-resolved-session');
-				// Bound to a NON-default chat URI with an SDK id unrelated to
-				// the AH session id: neither `buildDefaultChatUri(session)` nor
-				// an `AgentSession.id(session)` SDK lookup would find it. Only
-				// the host-chosen persistence scope (`resourceUri === session`)
-				// identifies it as the session-backed chat.
+				// The Agent Host session id, chat id, and SDK id intentionally differ.
 				const boundChat = URI.parse(buildChatUri(session, 'host-picked'));
 				setLiveChatStub(agent, 'unrelated-sdk-id', {
 					sessionId: 'unrelated-sdk-id',
@@ -6844,19 +6840,19 @@ suite('CopilotAgent', () => {
 					dispose: () => { },
 				}, boundChat);
 
-				assert.strictEqual(await agent.handleMcpRequest(session, 'srv', 'tools/call', undefined), 'srv/tools/call');
+				assert.strictEqual(await agent.handleMcpRequest(boundChat, 'srv', 'tools/call', undefined), 'srv/tools/call');
 			} finally {
 				await disposeAgent(agent);
 			}
 		});
 
-		test('handleMcpRequest rejects when the session has no live session-backed chat', async () => {
+		test('handleMcpRequest rejects when the exact chat has no live runtime', async () => {
 			const agent = createTestAgent(disposables);
 			try {
 				const session = AgentSession.uri('copilotcli', 'no-live-chat');
 				await assert.rejects(
-					() => agent.handleMcpRequest(session, 'srv', 'tools/list', undefined),
-					/Method not found: no active session no-live-chat/,
+					() => agent.handleMcpRequest(defaultChatUri(session), 'srv', 'tools/list', undefined),
+					/Method not found: no active chat/,
 				);
 			} finally {
 				await disposeAgent(agent);
@@ -9196,7 +9192,7 @@ suite('CopilotAgent', () => {
 			const sharedTool: ToolDefinition = { name: 'shared', description: 'Shared tool', inputSchema: { type: 'object', properties: {} } };
 			// Both clients provide the tool; the host fans A out to this chat
 			// and B out to a different one only.
-			agent.getOrCreateActiveClient(session, session, { clientId: 'client-A' }).tools = [sharedTool];
+			agent.getOrCreateActiveClient(defaultChatUri(session), session, { clientId: 'client-A' }).tools = [sharedTool];
 			agent.getOrCreateActiveClient(otherChat, session, { clientId: 'client-B' }).tools = [sharedTool];
 
 			const mockSession = new MockCopilotSession();
diff --git a/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts b/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
index f86e33c0393f97..65de73ef9bb3ee 100644
--- a/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
+++ b/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
@@ -41,6 +41,7 @@ import { STREAMING_TOOL_DISPLAY_INTERVAL_MS } from '../../common/streamingToolCa
 import { CustomizationEnablementKind, CustomizationType, McpAuthRequiredReason, McpServerStatus, type Customization } from '../../common/state/protocol/channels-session/state.js';
 import { CopilotAgentSession } from '../../node/copilot/copilotAgentSession.js';
 import { buildNonPtyShellTerminalUri } from '../../node/copilot/copilotNonPtyShellTerminals.js';
+import { buildMcpChannel } from '../../node/shared/mcpCustomizationController.js';
 import { buildSandboxConfigForSdk } from '../../node/copilot/sandboxConfigForSdk.js';
 import { ActiveClientToolSet } from '../../node/activeClientState.js';
 import { type CopilotSessionLaunchPlan, type IActiveClientSnapshot, type ICopilotSessionLauncher, type ICopilotSessionRuntime } from '../../node/copilot/copilotSessionLauncher.js';
@@ -682,7 +683,7 @@ async function createAgentSession(disposables: DisposableStore, options?: {
 
 	const parentSessionUri = AgentSession.uri('copilot', 'test-session-1');
 	const sessionUri = options?.sessionUri ?? parentSessionUri;
-	const chatChannelUri = options?.chatChannelUri ?? URI.parse(buildDefaultChatUri(parentSessionUri));
+	const chatChannelUri = options?.chatChannelUri ?? URI.parse(buildDefaultChatUri(sessionUri));
 	const mockSession = new MockCopilotSession();
 	options?.configureMockSession?.(mockSession);
 
@@ -4864,7 +4865,7 @@ suite('CopilotAgentSession', () => {
 						mcpServerName: 'docs',
 						ui: {
 							resourceUri: 'ui://docs',
-							channel: 'mcp://copilot/test-session-1/docs',
+							channel: buildMcpChannel(URI.parse(buildDefaultChatUri(AgentSession.uri('copilot', 'test-session-1'))), 'docs'),
 						},
 					},
 				});
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-accepts-an-open-session-link.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-accepts-an-open-session-link.yaml
new file mode 100644
index 00000000000000..54d5c23cc05e0a
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-accepts-an-open-session-link.yaml
@@ -0,0 +1,54 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+    response:
+      content: LINK_READY
+      stopReason: end_turn
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+        - role: assistant
+          content: LINK_READY
+        - role: user
+          content: Call get_session_context exactly once with session "agent-host-session://claude/${uuid_0}", then reply exactly "read".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__get_session_context
+          input:
+            session: agent-host-session://claude/${uuid_0}
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+        - role: assistant
+          content: LINK_READY
+        - role: user
+          content: Call get_session_context exactly once with session "agent-host-session://claude/${uuid_0}", then reply exactly "read".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: mcp__host__get_session_context
+              input:
+                session: agent-host-session://claude/${uuid_0}
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"claude:/${uuid_0}","openLink":"agent-host-session://claude/${uuid_0}","detail":"summary","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"LINK_READY\".","assistant":"LINK_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"agent-host-session://claude/${uuid_0}\", then reply exactly \"read\"."}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-accepts-explicit-summary-detail.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-accepts-explicit-summary-detail.yaml
new file mode 100644
index 00000000000000..7685abef8e7ca2
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-accepts-explicit-summary-detail.yaml
@@ -0,0 +1,56 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+    response:
+      content: SUMMARY_READY
+      stopReason: end_turn
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+        - role: assistant
+          content: SUMMARY_READY
+        - role: user
+          content: Call get_session_context exactly once with session "claude:/${uuid_0}" and detail "summary", then reply exactly "read".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__get_session_context
+          input:
+            session: claude:/${uuid_0}
+            detail: summary
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+        - role: assistant
+          content: SUMMARY_READY
+        - role: user
+          content: Call get_session_context exactly once with session "claude:/${uuid_0}" and detail "summary", then reply exactly "read".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: mcp__host__get_session_context
+              input:
+                session: claude:/${uuid_0}
+                detail: summary
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"claude:/${uuid_0}","openLink":"agent-host-session://claude/${uuid_0}","detail":"summary","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"SUMMARY_READY\".","assistant":"SUMMARY_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"claude:/${uuid_0}\" and detail \"summary\", then reply exactly \"read\"."}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-digest-includes-completed-response-text.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-digest-includes-completed-response-text.yaml
new file mode 100644
index 00000000000000..fe5d5c0b77d212
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-get-session-context-digest-includes-completed-response-text.yaml
@@ -0,0 +1,56 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+    response:
+      content: DIGEST_READY
+      stopReason: end_turn
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+        - role: assistant
+          content: DIGEST_READY
+        - role: user
+          content: Call get_session_context exactly once with session "claude:/${uuid_0}" and detail "digest", then reply exactly "read".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__get_session_context
+          input:
+            session: claude:/${uuid_0}
+            detail: digest
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+        - role: assistant
+          content: DIGEST_READY
+        - role: user
+          content: Call get_session_context exactly once with session "claude:/${uuid_0}" and detail "digest", then reply exactly "read".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: mcp__host__get_session_context
+              input:
+                session: claude:/${uuid_0}
+                detail: digest
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"claude:/${uuid_0}","openLink":"agent-host-session://claude/${uuid_0}","detail":"digest","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"DIGEST_READY\".","assistant":"DIGEST_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"claude:/${uuid_0}\" and detail \"digest\", then reply exactly \"read\".","toolCalls":["mcp__host__get_session_context"]}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml
new file mode 100644
index 00000000000000..8d192a1255db58
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml
@@ -0,0 +1,37 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdAfter "2999-01-01T00:00:00Z", then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__list_sessions
+          input:
+            createdAfter: '2999-01-01T00:00:00Z'
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdAfter "2999-01-01T00:00:00Z", then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: mcp__host__list_sessions
+              input:
+                createdAfter: '2999-01-01T00:00:00Z'
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml
new file mode 100644
index 00000000000000..23f093f1a7cf62
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml
@@ -0,0 +1,37 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdBefore "2999-01-01T00:00:00Z", then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__list_sessions
+          input:
+            createdBefore: '2999-01-01T00:00:00Z'
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdBefore "2999-01-01T00:00:00Z", then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: mcp__host__list_sessions
+              input:
+                createdBefore: '2999-01-01T00:00:00Z'
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"claude:/${uuid_0}","title":"Call list_sessions exactly once with createdBefore \"2999-01-01T00:00:00Z\", then reply exactly \"filtered\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-16T00:05:45.643Z","modifiedAt":"2026-08-16T00:05:45.208Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"claude:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"claude:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-hides-archived-sessions-by-default.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-hides-archived-sessions-by-default.yaml
new file mode 100644
index 00000000000000..69cab21d83a2b4
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-hides-archived-sessions-by-default.yaml
@@ -0,0 +1,50 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "ARCHIVED_HIDDEN_READY".
+    response:
+      content: ARCHIVED_HIDDEN_READY
+      stopReason: end_turn
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}", then reply exactly "listed".
+    response:
+      content:
+        - type: text
+          text: I'll list the sessions for that workspace.
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__list_sessions
+          input:
+            workspace: ${workdir}
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}", then reply exactly "listed".
+        - role: assistant
+          content:
+            - type: text
+              text: I'll list the sessions for that workspace.
+            - type: tool_use
+              name: mcp__host__list_sessions
+              input:
+                workspace: ${workdir}
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"claude:/${uuid_0}","title":"Call list_sessions exactly once with workspace \"${workdir}\", then reply exactly \"listed\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:03:36.971Z","modifiedAt":"2026-08-15T23:03:36.554Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"claude:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"claude:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: listed
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml
new file mode 100644
index 00000000000000..d2e04d522a968a
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml
@@ -0,0 +1,48 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "ARCHIVED_INCLUDED_READY".
+    response:
+      content: ARCHIVED_INCLUDED_READY
+      stopReason: end_turn
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}" and includeArchived true, then reply exactly "listed".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__list_sessions
+          input:
+            workspace: ${workdir}
+            includeArchived: true
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}" and includeArchived true, then reply exactly "listed".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: mcp__host__list_sessions
+              input:
+                workspace: ${workdir}
+                includeArchived: true
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"claude:/${uuid_0}","title":"Call list_sessions exactly once with workspace \"${workdir}\" and includeArchived true, then reply exactly \"listed","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:11:26.581Z","modifiedAt":"2026-08-15T23:11:26.168Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"claude:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"claude:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]},{"session":"claude:/${uuid_1}","title":"Reply exactly \"ARCHIVED_INCLUDED_READY\".","status":"idle,archived","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:11:24.281Z","modifiedAt":"2026-08-15T23:11:26.162Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"claude:/${uuid_1}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"claude:/${uuid_1}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: listed
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml
new file mode 100644
index 00000000000000..96709bea7195e9
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/claude-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml
@@ -0,0 +1,50 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "COMBINED_TARGET_READY".
+    response:
+      content: COMBINED_TARGET_READY
+      stopReason: end_turn
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with status ["inProgress", "archived"], then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: mcp__host__list_sessions
+          input:
+            status:
+              - inProgress
+              - archived
+      stopReason: tool_use
+  - request:
+      model: claude-opus-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with status ["inProgress", "archived"], then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: mcp__host__list_sessions
+              input:
+                status:
+                  - inProgress
+                  - archived
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"claude:/${uuid_0}","title":"Call list_sessions exactly once with status [\"inProgress\", \"archived\"], then reply exactly \"filtered\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:39:43.777Z","modifiedAt":"2026-08-15T23:39:43.354Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"claude:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"claude:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]},{"session":"claude:/${uuid_1}","title":"Reply exactly \"COMBINED_TARGET_READY\".","status":"idle,archived","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:39:41.314Z","modifiedAt":"2026-08-15T23:39:43.346Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"claude:/${uuid_1}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"claude:/${uuid_1}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-accepts-an-open-session-link.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-accepts-an-open-session-link.yaml
new file mode 100644
index 00000000000000..7167d6e2ab5839
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-accepts-an-open-session-link.yaml
@@ -0,0 +1,58 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+    response:
+      content: LINK_READY
+      stopReason: end_turn
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+        - role: assistant
+          content: LINK_READY
+        - role: user
+          content: Call get_session_context exactly once with session "agent-host-session://codex/${uuid_0}", then reply exactly "read".
+    response:
+      content:
+        - type: text
+          text: I’ll fetch that session context now.
+        - type: tool_use
+          id: toolcall_0
+          name: get_session_context
+          input:
+            session: agent-host-session://codex/${uuid_0}
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+        - role: assistant
+          content: LINK_READY
+        - role: user
+          content: Call get_session_context exactly once with session "agent-host-session://codex/${uuid_0}", then reply exactly "read".
+        - role: assistant
+          content: I’ll fetch that session context now.
+        - role: assistant
+          content:
+            - type: tool_use
+              name: get_session_context
+              input:
+                session: agent-host-session://codex/${uuid_0}
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"codex:/${uuid_0}","openLink":"agent-host-session://codex/${uuid_0}","detail":"summary","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"LINK_READY\".","assistant":"LINK_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"agent-host-session://codex/${uuid_0}\", then reply exactly \"read\".","assistant":"I’ll fetch that session context now."}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-accepts-explicit-summary-detail.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-accepts-explicit-summary-detail.yaml
new file mode 100644
index 00000000000000..a06b4929f13204
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-accepts-explicit-summary-detail.yaml
@@ -0,0 +1,60 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+    response:
+      content: SUMMARY_READY
+      stopReason: end_turn
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+        - role: assistant
+          content: SUMMARY_READY
+        - role: user
+          content: Call get_session_context exactly once with session "codex:/${uuid_0}" and detail "summary", then reply exactly "read".
+    response:
+      content:
+        - type: text
+          text: Got it — I’ll fetch that session summary once now.
+        - type: tool_use
+          id: toolcall_0
+          name: get_session_context
+          input:
+            session: codex:/${uuid_0}
+            detail: summary
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+        - role: assistant
+          content: SUMMARY_READY
+        - role: user
+          content: Call get_session_context exactly once with session "codex:/${uuid_0}" and detail "summary", then reply exactly "read".
+        - role: assistant
+          content: Got it — I’ll fetch that session summary once now.
+        - role: assistant
+          content:
+            - type: tool_use
+              name: get_session_context
+              input:
+                session: codex:/${uuid_0}
+                detail: summary
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"codex:/${uuid_0}","openLink":"agent-host-session://codex/${uuid_0}","detail":"summary","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"SUMMARY_READY\".","assistant":"SUMMARY_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"codex:/${uuid_0}\" and detail \"summary\", then reply exactly \"read\".","assistant":"Got it — I’ll fetch that session summary once now."}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-digest-includes-completed-response-text.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-digest-includes-completed-response-text.yaml
new file mode 100644
index 00000000000000..d7374a0c390cdc
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-get-session-context-digest-includes-completed-response-text.yaml
@@ -0,0 +1,60 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+    response:
+      content: DIGEST_READY
+      stopReason: end_turn
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+        - role: assistant
+          content: DIGEST_READY
+        - role: user
+          content: Call get_session_context exactly once with session "codex:/${uuid_0}" and detail "digest", then reply exactly "read".
+    response:
+      content:
+        - type: text
+          text: I’ll fetch that session digest now, then return the exact reply.
+        - type: tool_use
+          id: toolcall_0
+          name: get_session_context
+          input:
+            session: codex:/${uuid_0}
+            detail: digest
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+        - role: assistant
+          content: DIGEST_READY
+        - role: user
+          content: Call get_session_context exactly once with session "codex:/${uuid_0}" and detail "digest", then reply exactly "read".
+        - role: assistant
+          content: I’ll fetch that session digest now, then return the exact reply.
+        - role: assistant
+          content:
+            - type: tool_use
+              name: get_session_context
+              input:
+                session: codex:/${uuid_0}
+                detail: digest
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"codex:/${uuid_0}","openLink":"agent-host-session://codex/${uuid_0}","detail":"digest","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"DIGEST_READY\".","assistant":"DIGEST_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"codex:/${uuid_0}\" and detail \"digest\", then reply exactly \"read\".","assistant":"I’ll fetch that session digest now, then return the exact reply.","toolCalls":["get_session_context"]}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml
new file mode 100644
index 00000000000000..3b2965c2d55c45
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml
@@ -0,0 +1,37 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdAfter "2999-01-01T00:00:00Z", then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            createdAfter: '2999-01-01T00:00:00Z'
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdAfter "2999-01-01T00:00:00Z", then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                createdAfter: '2999-01-01T00:00:00Z'
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml
new file mode 100644
index 00000000000000..ea63eb7d4f2d52
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml
@@ -0,0 +1,37 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdBefore "2999-01-01T00:00:00Z", then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            createdBefore: '2999-01-01T00:00:00Z'
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdBefore "2999-01-01T00:00:00Z", then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                createdBefore: '2999-01-01T00:00:00Z'
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"codex:/${uuid_0}","title":"Call list_sessions exactly once with createdBefore \"2999-01-01T00:00:00Z\", then reply exactly \"filtered\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-16T00:07:45.791Z","modifiedAt":"2026-08-16T00:07:45.848Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"codex:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"codex:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-hides-archived-sessions-by-default.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-hides-archived-sessions-by-default.yaml
new file mode 100644
index 00000000000000..70b6b488f5dbda
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-hides-archived-sessions-by-default.yaml
@@ -0,0 +1,50 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "ARCHIVED_HIDDEN_READY".
+    response:
+      content: ARCHIVED_HIDDEN_READY
+      stopReason: end_turn
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}", then reply exactly "listed".
+    response:
+      content:
+        - type: text
+          text: Got it — I’ll run that one `list_sessions` call now.
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            workspace: ${workdir}
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}", then reply exactly "listed".
+        - role: assistant
+          content: Got it — I’ll run that one `list_sessions` call now.
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                workspace: ${workdir}
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"codex:/${uuid_0}","title":"Call list_sessions exactly once with workspace \"${workdir}\", then reply exactly \"listed\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:04:23.686Z","modifiedAt":"2026-08-15T23:04:25.853Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"codex:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"codex:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: listed
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml
new file mode 100644
index 00000000000000..d5a3dd0d4664b3
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml
@@ -0,0 +1,48 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "ARCHIVED_INCLUDED_READY".
+    response:
+      content: ARCHIVED_INCLUDED_READY
+      stopReason: end_turn
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}" and includeArchived true, then reply exactly "listed".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            workspace: ${workdir}
+            includeArchived: true
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}" and includeArchived true, then reply exactly "listed".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                workspace: ${workdir}
+                includeArchived: true
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"codex:/${uuid_0}","title":"Call list_sessions exactly once with workspace \"${workdir}\" and includeArchived true, then reply exactly \"listed","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:11:39.997Z","modifiedAt":"2026-08-15T23:11:42.015Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"codex:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"codex:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]},{"session":"codex:/${uuid_1}","title":"Reply exactly \"ARCHIVED_INCLUDED_READY\".","status":"idle,archived","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:11:40.132Z","modifiedAt":"2026-08-15T23:11:42.012Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"codex:/${uuid_1}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"codex:/${uuid_1}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: listed
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml
new file mode 100644
index 00000000000000..85ea9fb6b4e3c0
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/codex-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml
@@ -0,0 +1,54 @@
+version: 1
+dialect: responses
+exchanges:
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "COMBINED_TARGET_READY".
+    response:
+      content: COMBINED_TARGET_READY
+      stopReason: end_turn
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with status ["inProgress", "archived"], then reply exactly "filtered".
+    response:
+      content:
+        - type: text
+          text: Got it — I’ll run that exact session filter now.
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            status:
+              - inProgress
+              - archived
+      stopReason: tool_use
+  - request:
+      model: gpt-5.3-codex
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with status ["inProgress", "archived"], then reply exactly "filtered".
+        - role: assistant
+          content: Got it — I’ll run that exact session filter now.
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                status:
+                  - inProgress
+                  - archived
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"codex:/${uuid_0}","title":"Call list_sessions exactly once with status [\"inProgress\", \"archived\"], then reply exactly \"filtered\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:39:55.468Z","modifiedAt":"2026-08-15T23:39:57.604Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"codex:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"codex:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]},{"session":"codex:/${uuid_1}","title":"Reply exactly \"COMBINED_TARGET_READY\".","status":"idle,archived","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:39:55.588Z","modifiedAt":"2026-08-15T23:39:57.601Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"codex:/${uuid_1}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"codex:/${uuid_1}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-accepts-an-open-session-link.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-accepts-an-open-session-link.yaml
new file mode 100644
index 00000000000000..4a44c4fe1a7a1e
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-accepts-an-open-session-link.yaml
@@ -0,0 +1,54 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+    response:
+      content: LINK_READY
+      stopReason: end_turn
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+        - role: assistant
+          content: LINK_READY
+        - role: user
+          content: Call get_session_context exactly once with session "agent-host-session://copilotcli/e2e-server-tools-context-link", then reply exactly "read".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: get_session_context
+          input:
+            session: agent-host-session://copilotcli/e2e-server-tools-context-link
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "LINK_READY".
+        - role: assistant
+          content: LINK_READY
+        - role: user
+          content: Call get_session_context exactly once with session "agent-host-session://copilotcli/e2e-server-tools-context-link", then reply exactly "read".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: get_session_context
+              input:
+                session: agent-host-session://copilotcli/e2e-server-tools-context-link
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"copilotcli:/e2e-server-tools-context-link","openLink":"agent-host-session://copilotcli/e2e-server-tools-context-link","detail":"summary","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"LINK_READY\".","assistant":"LINK_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"agent-host-session://copilotcli/e2e-server-tools-context-link\", then reply exactly \"read\"."}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-accepts-explicit-summary-detail.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-accepts-explicit-summary-detail.yaml
new file mode 100644
index 00000000000000..13dcb2bcec2b51
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-accepts-explicit-summary-detail.yaml
@@ -0,0 +1,56 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+    response:
+      content: SUMMARY_READY
+      stopReason: end_turn
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+        - role: assistant
+          content: SUMMARY_READY
+        - role: user
+          content: Call get_session_context exactly once with session "copilotcli:/e2e-server-tools-context-explicit-summary" and detail "summary", then reply exactly "read".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: get_session_context
+          input:
+            session: copilotcli:/e2e-server-tools-context-explicit-summary
+            detail: summary
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "SUMMARY_READY".
+        - role: assistant
+          content: SUMMARY_READY
+        - role: user
+          content: Call get_session_context exactly once with session "copilotcli:/e2e-server-tools-context-explicit-summary" and detail "summary", then reply exactly "read".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: get_session_context
+              input:
+                session: copilotcli:/e2e-server-tools-context-explicit-summary
+                detail: summary
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"copilotcli:/e2e-server-tools-context-explicit-summary","openLink":"agent-host-session://copilotcli/e2e-server-tools-context-explicit-summary","detail":"summary","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"SUMMARY_READY\".","assistant":"SUMMARY_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"copilotcli:/e2e-server-tools-context-explicit-summary\" and detail \"summary\", then reply exactly \"read\"."}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-digest-includes-completed-response-text.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-digest-includes-completed-response-text.yaml
new file mode 100644
index 00000000000000..f04fd5375350c5
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-get-session-context-digest-includes-completed-response-text.yaml
@@ -0,0 +1,56 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+    response:
+      content: DIGEST_READY
+      stopReason: end_turn
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+        - role: assistant
+          content: DIGEST_READY
+        - role: user
+          content: Call get_session_context exactly once with session "copilotcli:/e2e-server-tools-context-digest" and detail "digest", then reply exactly "read".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: get_session_context
+          input:
+            session: copilotcli:/e2e-server-tools-context-digest
+            detail: digest
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "DIGEST_READY".
+        - role: assistant
+          content: DIGEST_READY
+        - role: user
+          content: Call get_session_context exactly once with session "copilotcli:/e2e-server-tools-context-digest" and detail "digest", then reply exactly "read".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: get_session_context
+              input:
+                session: copilotcli:/e2e-server-tools-context-digest
+                detail: digest
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"session":"copilotcli:/e2e-server-tools-context-digest","openLink":"agent-host-session://copilotcli/e2e-server-tools-context-digest","detail":"digest","transcript":[{"turn":1,"state":"complete","user":"Reply exactly \"DIGEST_READY\".","assistant":"DIGEST_READY"},{"turn":2,"state":"inProgress","user":"Call get_session_context exactly once with session \"copilotcli:/e2e-server-tools-context-digest\" and detail \"digest\", then reply exactly \"read\".","toolCalls":["get_session_context"]}],"hasMoreHistory":false,"truncated":false}'
+    response:
+      content: read
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml
new file mode 100644
index 00000000000000..e6b8a7ee829656
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-createdafter-excludes-sessions-before-the-boundary.yaml
@@ -0,0 +1,37 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdAfter "2999-01-01T00:00:00Z", then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            createdAfter: '2999-01-01T00:00:00Z'
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdAfter "2999-01-01T00:00:00Z", then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                createdAfter: '2999-01-01T00:00:00Z'
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml
new file mode 100644
index 00000000000000..b7b9b3f82ad118
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-createdbefore-accepts-sessions-before-a-future-boundary.yaml
@@ -0,0 +1,37 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdBefore "2999-01-01T00:00:00Z", then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            createdBefore: '2999-01-01T00:00:00Z'
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with createdBefore "2999-01-01T00:00:00Z", then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                createdBefore: '2999-01-01T00:00:00Z'
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"copilotcli:/${uuid_0}","title":"Call list_sessions exactly once with createdBefore \"2999-01-01T00:00:00Z\", then reply exactly \"filtered\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-16T00:06:20.199Z","modifiedAt":"2026-08-16T00:06:19.758Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"copilotcli:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"copilotcli:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-hides-archived-sessions-by-default.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-hides-archived-sessions-by-default.yaml
new file mode 100644
index 00000000000000..6867f8c6d80a98
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-hides-archived-sessions-by-default.yaml
@@ -0,0 +1,46 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "ARCHIVED_HIDDEN_READY".
+    response:
+      content: ARCHIVED_HIDDEN_READY
+      stopReason: end_turn
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}", then reply exactly "listed".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            workspace: ${workdir}
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}", then reply exactly "listed".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                workspace: ${workdir}
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"copilotcli:/${uuid_0}","title":"Call list_sessions exactly once with workspace \"${workdir}\", then reply exactly \"listed\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:05:12.573Z","modifiedAt":"2026-08-15T23:05:12.170Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"copilotcli:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"copilotcli:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: listed
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml
new file mode 100644
index 00000000000000..e6dd8ff1be3732
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-includearchived-returns-active-and-archived-sessions.yaml
@@ -0,0 +1,48 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "ARCHIVED_INCLUDED_READY".
+    response:
+      content: ARCHIVED_INCLUDED_READY
+      stopReason: end_turn
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}" and includeArchived true, then reply exactly "listed".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            workspace: ${workdir}
+            includeArchived: true
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with workspace "${workdir}" and includeArchived true, then reply exactly "listed".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                workspace: ${workdir}
+                includeArchived: true
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"copilotcli:/${uuid_0}","title":"Call list_sessions exactly once with workspace \"${workdir}\" and includeArchived true, then reply exactly \"listed","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:12:01.625Z","modifiedAt":"2026-08-15T23:12:01.153Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"copilotcli:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"copilotcli:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]},{"session":"copilotcli:/${uuid_1}","title":"Reply exactly \"ARCHIVED_INCLUDED_READY\".","status":"idle,archived","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:11:59.721Z","modifiedAt":"2026-08-15T23:12:01.137Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"copilotcli:/${uuid_1}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"copilotcli:/${uuid_1}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: listed
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml
new file mode 100644
index 00000000000000..508c4427ab9d01
--- /dev/null
+++ b/src/vs/platform/agentHost/test/node/e2e/captures/copilotcli-server-tool-list-sessions-status-filter-combines-active-and-archived-sessions.yaml
@@ -0,0 +1,50 @@
+version: 1
+dialect: anthropic
+exchanges:
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Reply exactly "COMBINED_TARGET_READY".
+    response:
+      content: COMBINED_TARGET_READY
+      stopReason: end_turn
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with status ["inProgress", "archived"], then reply exactly "filtered".
+    response:
+      content:
+        - type: tool_use
+          id: toolcall_0
+          name: list_sessions
+          input:
+            status:
+              - inProgress
+              - archived
+      stopReason: tool_use
+  - request:
+      model: claude-sonnet-5
+      system: ${system}
+      messages:
+        - role: user
+          content: Call list_sessions exactly once with status ["inProgress", "archived"], then reply exactly "filtered".
+        - role: assistant
+          content:
+            - type: tool_use
+              name: list_sessions
+              input:
+                status:
+                  - inProgress
+                  - archived
+        - role: user
+          content:
+            - type: tool_result
+              tool_use_id: toolcall_0
+              content: '{"sessions":[{"session":"copilotcli:/${uuid_0}","title":"Call list_sessions exactly once with status [\"inProgress\", \"archived\"], then reply exactly \"filtered\".","status":"inProgress","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:40:12.159Z","modifiedAt":"2026-08-15T23:40:11.847Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"copilotcli:/${uuid_0}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"copilotcli:/${uuid_0}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]},{"session":"copilotcli:/${uuid_1}","title":"Reply exactly \"COMBINED_TARGET_READY\".","status":"idle,archived","workingDirectory":"file://${workdir}","unread":true,"createdAt":"2026-08-15T23:40:10.640Z","modifiedAt":"2026-08-15T23:40:11.841Z","changesets":[{"label":"All Changes","changeKind":"session","uriTemplate":"copilotcli:/${uuid_1}/changeset/session","description":"Show all changes made in this session"},{"label":"This Turn","changeKind":"turn","uriTemplate":"copilotcli:/${uuid_1}/changeset/turn/{turnId}","description":"Show changes made in this turn"}]}]}'
+    response:
+      content: filtered
+      stopReason: end_turn
diff --git a/src/vs/platform/agentHost/test/node/e2e/coverage/summary.json b/src/vs/platform/agentHost/test/node/e2e/coverage/summary.json
index 6863ae43bd48b4..f247d9952b854f 100644
--- a/src/vs/platform/agentHost/test/node/e2e/coverage/summary.json
+++ b/src/vs/platform/agentHost/test/node/e2e/coverage/summary.json
@@ -15,31 +15,31 @@
 	},
 	"total": {
 		"statements": {
-			"covered": 86322,
-			"total": 113954,
-			"percentage": 75.75
+			"covered": 86462,
+			"total": 114066,
+			"percentage": 75.79
 		},
 		"branches": {
-			"covered": 9917,
-			"total": 14872,
-			"percentage": 66.68
+			"covered": 10023,
+			"total": 14969,
+			"percentage": 66.95
 		},
 		"functions": {
-			"covered": 3230,
-			"total": 4520,
-			"percentage": 71.46
+			"covered": 3239,
+			"total": 4529,
+			"percentage": 71.51
 		},
 		"lines": {
-			"covered": 86322,
-			"total": 113954,
-			"percentage": 75.75
+			"covered": 86462,
+			"total": 114066,
+			"percentage": 75.79
 		}
 	},
 	"files": {
 		"src/vs/platform/agentHost/common/agent.ts": {
 			"statements": {
-				"covered": 1149,
-				"total": 1159,
+				"covered": 1152,
+				"total": 1162,
 				"percentage": 99.13
 			},
 			"branches": {
@@ -53,8 +53,8 @@
 				"percentage": 83.33
 			},
 			"lines": {
-				"covered": 1149,
-				"total": 1159,
+				"covered": 1152,
+				"total": 1162,
 				"percentage": 99.13
 			}
 		},
@@ -725,9 +725,9 @@
 				"percentage": 80.07
 			},
 			"branches": {
-				"covered": 25,
-				"total": 35,
-				"percentage": 71.42
+				"covered": 29,
+				"total": 39,
+				"percentage": 74.35
 			},
 			"functions": {
 				"covered": 11,
@@ -769,9 +769,9 @@
 				"percentage": 86.48
 			},
 			"branches": {
-				"covered": 48,
-				"total": 60,
-				"percentage": 80
+				"covered": 49,
+				"total": 61,
+				"percentage": 80.32
 			},
 			"functions": {
 				"covered": 19,
@@ -1292,14 +1292,14 @@
 		},
 		"src/vs/platform/agentHost/common/openSessionLink.ts": {
 			"statements": {
-				"covered": 116,
+				"covered": 117,
 				"total": 151,
-				"percentage": 76.82
+				"percentage": 77.48
 			},
 			"branches": {
-				"covered": 12,
-				"total": 24,
-				"percentage": 50
+				"covered": 15,
+				"total": 25,
+				"percentage": 60
 			},
 			"functions": {
 				"covered": 4,
@@ -1307,9 +1307,9 @@
 				"percentage": 40
 			},
 			"lines": {
-				"covered": 116,
+				"covered": 117,
 				"total": 151,
-				"percentage": 76.82
+				"percentage": 77.48
 			}
 		},
 		"src/vs/platform/agentHost/common/otel/agentHostOTelService.ts": {
@@ -1341,9 +1341,9 @@
 				"percentage": 74.22
 			},
 			"branches": {
-				"covered": 39,
-				"total": 50,
-				"percentage": 78
+				"covered": 44,
+				"total": 52,
+				"percentage": 84.61
 			},
 			"functions": {
 				"covered": 21,
@@ -1759,9 +1759,9 @@
 				"percentage": 71.19
 			},
 			"branches": {
-				"covered": 62,
-				"total": 89,
-				"percentage": 69.66
+				"covered": 61,
+				"total": 88,
+				"percentage": 69.31
 			},
 			"functions": {
 				"covered": 6,
@@ -2172,14 +2172,14 @@
 		},
 		"src/vs/platform/agentHost/common/state/sessionState.ts": {
 			"statements": {
-				"covered": 1401,
+				"covered": 1403,
 				"total": 1848,
-				"percentage": 75.81
+				"percentage": 75.91
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 			"branches": {
-				"covered": 160,
-				"total": 232,
-				"percentage": 68.96
+				"covered": 162,
+				"total": 233,
+				"percentage": 69.52
 			},
 			"functions": {
 				"covered": 58,
@@ -2187,9 +2187,9 @@
 				"percentage": 68.23
 			},
 			"lines": {
-				"covered": 1401,
+				"covered": 1403,
 				"total": 1848,
-				"percentage": 75.81
+				"percentage": 75.91
 			}
 		},
 		"src/vs/platform/agentHost/common/state/sessionWorkingDirectories.ts": {
@@ -2331,9 +2331,9 @@
 				"percentage": 91.66
 			},
 			"branches": {
-				"covered": 44,
-				"total": 60,
-				"percentage": 73.33
+				"covered": 45,
+				"total": 61,
+				"percentage": 73.77
 			},
 			"functions": {
 				"covered": 17,
@@ -2458,14 +2458,14 @@
 		},
 		"src/vs/platform/agentHost/node/agentHostChangesetOperationService.ts": {
 			"statements": {
-				"covered": 265,
+				"covered": 264,
 				"total": 296,
-				"percentage": 89.52
+				"percentage": 89.18
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 			"branches": {
-				"covered": 53,
-				"total": 69,
-				"percentage": 76.81
+				"covered": 51,
+				"total": 68,
+				"percentage": 75
 			},
 			"functions": {
 				"covered": 13,
@@ -2473,21 +2473,21 @@
 				"percentage": 100
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 			"lines": {
-				"covered": 265,
+				"covered": 264,
 				"total": 296,
-				"percentage": 89.52
+				"percentage": 89.18
 			}
 		},
 		"src/vs/platform/agentHost/node/agentHostChangesetService.ts": {
 			"statements": {
-				"covered": 1229,
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-				"percentage": 74.66
+				"percentage": 74.54
 			},
 			"branches": {
-				"covered": 185,
-				"total": 258,
-				"percentage": 71.7
+				"covered": 180,
+				"total": 254,
+				"percentage": 70.86
 			},
 			"functions": {
 				"covered": 56,
@@ -2495,9 +2495,9 @@
 				"percentage": 80
 			},
 			"lines": {
-				"covered": 1229,
+				"covered": 1227,
 				"total": 1646,
-				"percentage": 74.66
+				"percentage": 74.54
 			}
 		},
 		"src/vs/platform/agentHost/node/agentHostChangesetStateCache.ts": {
@@ -2573,9 +2573,9 @@
 				"percentage": 94.44
 			},
 			"branches": {
-				"covered": 41,
+				"covered": 43,
 				"total": 52,
-				"percentage": 78.84
+				"percentage": 82.69
 			},
 			"functions": {
 				"covered": 6,
@@ -2700,14 +2700,14 @@
 		},
 		"src/vs/platform/agentHost/node/agentHostCustomizationEnablementService.ts": {
 			"statements": {
-				"covered": 558,
+				"covered": 554,
 				"total": 723,
-				"percentage": 77.17
+				"percentage": 76.62
 			},
 			"branches": {
-				"covered": 100,
-				"total": 143,
-				"percentage": 69.93
+				"covered": 92,
+				"total": 137,
+				"percentage": 67.15
 			},
 			"functions": {
 				"covered": 41,
@@ -2715,9 +2715,9 @@
 				"percentage": 87.23
 			},
 			"lines": {
-				"covered": 558,
+				"covered": 554,
 				"total": 723,
-				"percentage": 77.17
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 			}
 		},
 		"src/vs/platform/agentHost/node/agentHostDatabase.ts": {
@@ -2788,24 +2788,24 @@
 		},
 		"src/vs/platform/agentHost/node/agentHostFileCompletionProvider.ts": {
 			"statements": {
-				"covered": 247,
+				"covered": 277,
 				"total": 317,
-				"percentage": 77.91
+				"percentage": 87.38
 			},
 			"branches": {
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-				"total": 57,
-				"percentage": 63.15
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+				"percentage": 78.94
 			},
 			"functions": {
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-				"percentage": 88.88
+				"percentage": 100
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 			"lines": {
-				"covered": 247,
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 				"total": 317,
-				"percentage": 77.91
+				"percentage": 87.38
 			}
 		},
 		"src/vs/platform/agentHost/node/agentHostFileCompletionUtils.ts": {
@@ -2832,14 +2832,14 @@
 		},
 		"src/vs/platform/agentHost/node/agentHostFileMonitorService.ts": {
 			"statements": {
-				"covered": 165,
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-				"percentage": 89.18
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 			"branches": {
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-				"percentage": 65.71
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 			},
 			"functions": {
 				"covered": 14,
@@ -2847,9 +2847,9 @@
 				"percentage": 100
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 			"lines": {
-				"covered": 165,
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-				"percentage": 89.18
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 			}
 		},
 		"src/vs/platform/agentHost/node/agentHostGitHubEndpointService.ts": {
@@ -2903,9 +2903,9 @@
 				"percentage": 70.35
 			},
 			"branches": {
-				"covered": 263,
-				"total": 371,
-				"percentage": 70.88
+				"covered": 267,
+				"total": 375,
+				"percentage": 71.2
 			},
 			"functions": {
 				"covered": 61,
@@ -2920,14 +2920,14 @@
 		},
 		"src/vs/platform/agentHost/node/agentHostGitStateService.ts": {
 			"statements": {
-				"covered": 232,
+				"covered": 233,
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-				"percentage": 54.71
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 			"branches": {
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-				"total": 88,
-				"percentage": 71.59
+				"covered": 66,
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 			"functions": {
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@@ -2935,9 +2935,9 @@
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-				"covered": 232,
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 		"src/vs/platform/agentHost/node/agentHostHeadlessTerminal.ts": {
@@ -3057,9 +3057,9 @@
 				"percentage": 81
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 			"branches": {
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-				"percentage": 75
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 			"functions": {
 				"covered": 5,
@@ -3140,9 +3140,9 @@
 		},
 		"src/vs/platform/agentHost/node/agentHostProxyResolver.ts": {
 			"statements": {
-				"covered": 123,
-				"total": 167,
-				"percentage": 73.65
+				"covered": 131,
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 			},
 			"branches": {
 				"covered": 15,
@@ -3155,9 +3155,9 @@
 				"percentage": 46.42
 			},
 			"lines": {
-				"covered": 123,
-				"total": 167,
-				"percentage": 73.65
+				"covered": 131,
+				"total": 179,
+				"percentage": 73.18
 			}
 		},
 		"src/vs/platform/agentHost/node/agentHostPullRequestOperationHandler.ts": {
@@ -3470,14 +3470,14 @@
 		},
 		"src/vs/platform/agentHost/node/agentHostStateManager.ts": {
 			"statements": {
-				"covered": 1638,
+				"covered": 1636,
 				"total": 1776,
-				"percentage": 92.22
+				"percentage": 92.11
 			},
 			"branches": {
-				"covered": 263,
-				"total": 310,
-				"percentage": 84.83
+				"covered": 257,
+				"total": 305,
+				"percentage": 84.26
 			},
 			"functions": {
 				"covered": 70,
@@ -3485,9 +3485,9 @@
 				"percentage": 89.74
 			},
 			"lines": {
-				"covered": 1638,
+				"covered": 1636,
 				"total": 1776,
-				"percentage": 92.22
+				"percentage": 92.11
 			}
 		},
 		"src/vs/platform/agentHost/node/agentHostStorageService.ts": {
@@ -3607,9 +3607,9 @@
 				"percentage": 90.83
 			},
 			"branches": {
-				"covered": 119,
-				"total": 148,
-				"percentage": 80.4
+				"covered": 120,
+				"total": 149,
+				"percentage": 80.53
 			},
 			"functions": {
 				"covered": 35,
@@ -3695,9 +3695,9 @@
 				"percentage": 71.12
 			},
 			"branches": {
-				"covered": 15,
-				"total": 30,
-				"percentage": 50
+				"covered": 16,
+				"total": 31,
+				"percentage": 51.61
 			},
 			"functions": {
 				"covered": 5,
@@ -3800,24 +3800,24 @@
 		},
 		"src/vs/platform/agentHost/node/agentService.ts": {
 			"statements": {
-				"covered": 4438,
-				"total": 5740,
-				"percentage": 77.31
+				"covered": 4465,
+				"total": 5780,
+				"percentage": 77.24
 			},
 			"branches": {
-				"covered": 772,
-				"total": 1153,
-				"percentage": 66.95
+				"covered": 790,
+				"total": 1176,
+				"percentage": 67.17
 			},
 			"functions": {
-				"covered": 188,
-				"total": 228,
-				"percentage": 82.45
+				"covered": 193,
+				"total": 234,
+				"percentage": 82.47
 			},
 			"lines": {
-				"covered": 4438,
-				"total": 5740,
-				"percentage": 77.31
+				"covered": 4465,
+				"total": 5780,
+				"percentage": 77.24
 			}
 		},
 		"src/vs/platform/agentHost/node/agentSessionRegistry.ts": {
@@ -3959,9 +3959,9 @@
 				"percentage": 81.02
 			},
 			"branches": {
-				"covered": 211,
-				"total": 319,
-				"percentage": 66.14
+				"covered": 212,
+				"total": 320,
+				"percentage": 66.25
 			},
 			"functions": {
 				"covered": 95,
@@ -4949,9 +4949,9 @@
 				"percentage": 66.14
 			},
 			"branches": {
-				"covered": 411,
+				"covered": 410,
 				"total": 767,
-				"percentage": 53.58
+				"percentage": 53.45
 			},
 			"functions": {
 				"covered": 168,
@@ -5582,46 +5582,46 @@
 		},
 		"src/vs/platform/agentHost/node/copilot/copilotAgent.ts": {
 			"statements": {
-				"covered": 4365,
-				"total": 5802,
-				"percentage": 75.23
+				"covered": 4394,
+				"total": 5846,
+				"percentage": 75.16
 			},
 			"branches": {
-				"covered": 716,
-				"total": 1102,
-				"percentage": 64.97
+				"covered": 723,
+				"total": 1116,
+				"percentage": 64.78
 			},
 			"functions": {
-				"covered": 245,
-				"total": 300,
-				"percentage": 81.66
+				"covered": 247,
+				"total": 302,
+				"percentage": 81.78
 			},
 			"lines": {
-				"covered": 4365,
-				"total": 5802,
-				"percentage": 75.23
+				"covered": 4394,
+				"total": 5846,
+				"percentage": 75.16
 			}
 		},
 		"src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts": {
 			"statements": {
-				"covered": 4128,
-				"total": 5537,
-				"percentage": 74.55
+				"covered": 4137,
+				"total": 5550,
+				"percentage": 74.54
 			},
 			"branches": {
 				"covered": 740,
-				"total": 1074,
-				"percentage": 68.9
+				"total": 1077,
+				"percentage": 68.7
 			},
 			"functions": {
-				"covered": 174,
-				"total": 215,
-				"percentage": 80.93
+				"covered": 175,
+				"total": 216,
+				"percentage": 81.01
 			},
 			"lines": {
-				"covered": 4128,
-				"total": 5537,
-				"percentage": 74.55
+				"covered": 4137,
+				"total": 5550,
+				"percentage": 74.54
 			}
 		},
 		"src/vs/platform/agentHost/node/copilot/copilotAttachmentUtils.ts": {
@@ -5983,9 +5983,9 @@
 				"percentage": 80.34
 			},
 			"branches": {
-				"covered": 164,
-				"total": 277,
-				"percentage": 59.2
+				"covered": 165,
+				"total": 278,
+				"percentage": 59.35
 			},
 			"functions": {
 				"covered": 27,
@@ -6379,9 +6379,9 @@
 				"percentage": 100
 			},
 			"branches": {
-				"covered": 14,
-				"total": 15,
-				"percentage": 93.33
+				"covered": 17,
+				"total": 18,
+				"percentage": 94.44
 			},
 			"functions": {
 				"covered": 5,
@@ -6462,14 +6462,14 @@
 		},
 		"src/vs/platform/agentHost/node/protocolServerHandler.ts": {
 			"statements": {
-				"covered": 1603,
+				"covered": 1627,
 				"total": 1830,
-				"percentage": 87.59
+				"percentage": 88.9
 			},
 			"branches": {
-				"covered": 303,
-				"total": 380,
-				"percentage": 79.73
+				"covered": 328,
+				"total": 398,
+				"percentage": 82.41
 			},
 			"functions": {
 				"covered": 77,
@@ -6477,9 +6477,9 @@
 				"percentage": 87.5
 			},
 			"lines": {
-				"covered": 1603,
+				"covered": 1627,
 				"total": 1830,
-				"percentage": 87.59
+				"percentage": 88.9
 			}
 		},
 		"src/vs/platform/agentHost/node/serverUrls.ts": {
@@ -6528,14 +6528,14 @@
 		},
 		"src/vs/platform/agentHost/node/sessionDatabase.ts": {
 			"statements": {
-				"covered": 736,
+				"covered": 738,
 				"total": 882,
-				"percentage": 83.44
+				"percentage": 83.67
 			},
 			"branches": {
-				"covered": 107,
-				"total": 134,
-				"percentage": 79.85
+				"covered": 113,
+				"total": 139,
+				"percentage": 81.29
 			},
 			"functions": {
 				"covered": 39,
@@ -6543,9 +6543,9 @@
 				"percentage": 72.22
 			},
 			"lines": {
-				"covered": 736,
+				"covered": 738,
 				"total": 882,
-				"percentage": 83.44
+				"percentage": 83.67
 			}
 		},
 		"src/vs/platform/agentHost/node/sessionDiffAggregator.ts": {
@@ -6731,9 +6731,9 @@
 				"percentage": 86.46
 			},
 			"branches": {
-				"covered": 58,
-				"total": 103,
-				"percentage": 56.31
+				"covered": 64,
+				"total": 109,
+				"percentage": 58.71
 			},
 			"functions": {
 				"covered": 27,
@@ -6753,9 +6753,9 @@
 				"percentage": 83.24
 			},
 			"branches": {
-				"covered": 47,
+				"covered": 48,
 				"total": 56,
-				"percentage": 83.92
+				"percentage": 85.71
 			},
 			"functions": {
 				"covered": 8,
@@ -6858,14 +6858,14 @@
 		},
 		"src/vs/platform/agentHost/node/shared/fileEditTracker.ts": {
 			"statements": {
-				"covered": 237,
+				"covered": 239,
 				"total": 253,
-				"percentage": 93.67
+				"percentage": 94.46
 			},
 			"branches": {
 				"covered": 36,
-				"total": 43,
-				"percentage": 83.72
+				"total": 42,
+				"percentage": 85.71
 			},
 			"functions": {
 				"covered": 7,
@@ -6873,9 +6873,9 @@
 				"percentage": 100
 			},
 			"lines": {
-				"covered": 237,
+				"covered": 239,
 				"total": 253,
-				"percentage": 93.67
+				"percentage": 94.46
 			}
 		},
 		"src/vs/platform/agentHost/node/shared/loopbackProxyServer.ts": {
@@ -6902,14 +6902,14 @@
 		},
 		"src/vs/platform/agentHost/node/shared/mcpCustomizationController.ts": {
 			"statements": {
-				"covered": 459,
+				"covered": 464,
 				"total": 556,
-				"percentage": 82.55
+				"percentage": 83.45
 			},
 			"branches": {
-				"covered": 83,
+				"covered": 85,
 				"total": 103,
-				"percentage": 80.58
+				"percentage": 82.52
 			},
 			"functions": {
 				"covered": 25,
@@ -6917,9 +6917,9 @@
 				"percentage": 80.64
 			},
 			"lines": {
-				"covered": 459,
+				"covered": 464,
 				"total": 556,
-				"percentage": 82.55
+				"percentage": 83.45
 			}
 		},
 		"src/vs/platform/agentHost/node/shared/persistSessionMetadata.ts": {
@@ -6990,14 +6990,14 @@
 		},
 		"src/vs/platform/agentHost/node/shared/sessionServerTools.ts": {
 			"statements": {
-				"covered": 1033,
+				"covered": 1038,
 				"total": 1258,
-				"percentage": 82.11
+				"percentage": 82.51
 			},
 			"branches": {
-				"covered": 149,
-				"total": 241,
-				"percentage": 61.82
+				"covered": 155,
+				"total": 243,
+				"percentage": 63.78
 			},
 			"functions": {
 				"covered": 48,
@@ -7005,9 +7005,9 @@
 				"percentage": 82.75
 			},
 			"lines": {
-				"covered": 1033,
+				"covered": 1038,
 				"total": 1258,
-				"percentage": 82.11
+				"percentage": 82.51
 			}
 		},
 		"src/vs/platform/agentHost/node/shared/shellCommandExecution.ts": {
diff --git a/src/vs/platform/agentHost/test/node/e2e/harness/agentHostE2ETestHarness.ts b/src/vs/platform/agentHost/test/node/e2e/harness/agentHostE2ETestHarness.ts
index d78293568693f8..23b99e64a02b5c 100644
--- a/src/vs/platform/agentHost/test/node/e2e/harness/agentHostE2ETestHarness.ts
+++ b/src/vs/platform/agentHost/test/node/e2e/harness/agentHostE2ETestHarness.ts
@@ -511,15 +511,28 @@ export interface IDrivenTurnResult {
 }
 
 export async function driveTurnToCompletion(c: TestProtocolClient, session: string, turnId: string, text: string, clientSeq: number): Promise<IDrivenTurnResult> {
-	return driveTurn(c, session, turnId, clientSeq, () => dispatchTurn(c, session, turnId, text, clientSeq));
+	return driveTurn(c, buildDefaultChatUri(session), turnId, clientSeq, () => dispatchTurn(c, session, turnId, text, clientSeq));
+}
+
+export async function driveChatTurnToCompletion(c: TestProtocolClient, chat: string, turnId: string, text: string, clientSeq: number): Promise<IDrivenTurnResult> {
+	return driveTurn(c, chat, turnId, clientSeq, () => c.dispatch({
+		channel: chat,
+		clientSeq,
+		action: {
+			type: ActionType.ChatTurnStarted,
+			turnId,
+			startedAt: '2025-01-01T00:00:00.000Z',
+			message: { text, origin: { kind: MessageKind.User } },
+		},
+	}));
 }
 
 export async function driveTurnWithAttachmentsToCompletion(c: TestProtocolClient, session: string, turnId: string, text: string, attachments: readonly MessageAttachment[], clientSeq: number): Promise<IDrivenTurnResult> {
-	return driveTurn(c, session, turnId, clientSeq, () => dispatchTurnWithAttachments(c, session, turnId, text, attachments, clientSeq));
+	return driveTurn(c, buildDefaultChatUri(session), turnId, clientSeq, () => dispatchTurnWithAttachments(c, session, turnId, text, attachments, clientSeq));
 }
 
 export async function driveTurnWithModelToCompletion(c: TestProtocolClient, session: string, turnId: string, text: string, model: string, clientSeq: number): Promise<IDrivenTurnResult> {
-	return driveTurn(c, session, turnId, clientSeq, () => c.dispatch({
+	return driveTurn(c, buildDefaultChatUri(session), turnId, clientSeq, () => c.dispatch({
 		channel: buildDefaultChatUri(session),
 		clientSeq,
 		action: {
@@ -532,18 +545,17 @@ export async function driveTurnWithModelToCompletion(c: TestProtocolClient, sess
 }
 
 export async function driveTurnWithCancelledInputToCompletion(c: TestProtocolClient, session: string, turnId: string, text: string, clientSeq: number): Promise<IDrivenTurnResult> {
-	return driveTurn(c, session, turnId, clientSeq, () => dispatchTurn(c, session, turnId, text, clientSeq), ChatInputResponseKind.Cancel);
+	return driveTurn(c, buildDefaultChatUri(session), turnId, clientSeq, () => dispatchTurn(c, session, turnId, text, clientSeq), ChatInputResponseKind.Cancel);
 }
 
 export async function driveTurnWithAnswersToCompletion(c: TestProtocolClient, session: string, turnId: string, text: string, clientSeq: number, getAnswers: (request: ChatInputRequest) => Record<string, ChatInputAnswer>): Promise<IDrivenTurnResult> {
-	return driveTurn(c, session, turnId, clientSeq, () => dispatchTurn(c, session, turnId, text, clientSeq), ChatInputResponseKind.Accept, getAnswers);
+	return driveTurn(c, buildDefaultChatUri(session), turnId, clientSeq, () => dispatchTurn(c, session, turnId, text, clientSeq), ChatInputResponseKind.Accept, getAnswers);
 }
 
-async function driveTurn(c: TestProtocolClient, session: string, turnId: string, clientSeq: number, dispatch: () => void, inputResponse = ChatInputResponseKind.Accept, answerProvider = getAcceptedAnswers): Promise<IDrivenTurnResult> {
+async function driveTurn(c: TestProtocolClient, chat: string, turnId: string, clientSeq: number, dispatch: () => void, inputResponse = ChatInputResponseKind.Accept, answerProvider = getAcceptedAnswers): Promise<IDrivenTurnResult> {
 	c.clearReceived();
 	dispatch();
 
-	const chat = buildDefaultChatUri(session);
 	const seenNotifications = new Set<object>();
 	let nextClientSeq = clientSeq + 1;
 	let sawInputRequest = false;
@@ -578,7 +590,7 @@ async function driveTurn(c: TestProtocolClient, session: string, turnId: string,
 			if (!action.confirmed) {
 				sawPendingConfirmation = true;
 				c.dispatch({
-					channel: buildDefaultChatUri(session),
+					channel: chat,
 					clientSeq: nextClientSeq++,
 					action: {
 						type: ActionType.ChatToolCallConfirmed,
@@ -596,7 +608,7 @@ async function driveTurn(c: TestProtocolClient, session: string, turnId: string,
 			sawInputRequest = true;
 			const action = getActionEnvelope(notification).action as ChatInputRequestedAction;
 			c.dispatch({
-				channel: buildDefaultChatUri(session),
+				channel: chat,
 				clientSeq: nextClientSeq++,
 				action: {
 					type: ActionType.ChatInputCompleted,
diff --git a/src/vs/platform/agentHost/test/node/e2e/suites/clientFilesystemSuite.ts b/src/vs/platform/agentHost/test/node/e2e/suites/clientFilesystemSuite.ts
index 61bc4a5897f74f..04ad4697500c7f 100644
--- a/src/vs/platform/agentHost/test/node/e2e/suites/clientFilesystemSuite.ts
+++ b/src/vs/platform/agentHost/test/node/e2e/suites/clientFilesystemSuite.ts
@@ -129,6 +129,19 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		});
 	});
 
+	conformanceTest(context, 'resourceRequest accepts independent read and write access requests', async function () {
+		await initializeClient('resource-request-modes');
+		const root = createWorkspace('ahp-resource-request-modes-');
+		const uri = URI.file(root).toString();
+
+		const [read, write] = await Promise.all([
+			context.client.call('resourceRequest', { channel: ROOT_STATE_URI, uri, read: true }),
+			context.client.call('resourceRequest', { channel: ROOT_STATE_URI, uri, write: true }),
+		]);
+
+		assert.deepStrictEqual({ read, write }, { read: {}, write: {} });
+	});
+
 	conformanceTest(context, 'resourceList reports directory entries and their types', async function () {
 		await initializeClient('resource-list');
 		const root = createWorkspace('ahp-resource-list-');
@@ -157,6 +170,25 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.deepStrictEqual(result.entries, []);
 	});
 
+	conformanceTest(context, 'resourceRead preserves UTF-8 text and reports its content type', async function () {
+		await initializeClient('resource-read-unicode');
+		const root = createWorkspace('ahp-resource-read-unicode-');
+		const text = 'snowman \u2603 and smile \u{1F600}';
+		writeFileSync(join(root, 'unicode.txt'), text);
+
+		const result = await context.client.call<ResourceReadResult>('resourceRead', {
+			channel: ROOT_STATE_URI,
+			uri: fileUri(root, 'unicode.txt'),
+			encoding: ContentEncoding.Utf8,
+		});
+
+		assert.deepStrictEqual(result, {
+			data: text,
+			encoding: ContentEncoding.Utf8,
+			contentType: 'text/plain',
+		});
+	});
+
 	conformanceTest(context, 'resourceWrite truncates an existing file by default', async function () {
 		await initializeClient('resource-write-default-truncate');
 		const root = createWorkspace('ahp-resource-write-default-truncate-');
@@ -168,6 +200,37 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(readFileSync(join(root, 'replace.txt'), 'utf8'), 'short');
 	});
 
+	conformanceTest(context, 'resourceWrite creates an empty file from empty content', async function () {
+		await initializeClient('resource-write-empty');
+		const root = createWorkspace('ahp-resource-write-empty-');
+		const file = fileUri(root, 'empty.txt');
+
+		await writeText(file, '');
+
+		assert.deepStrictEqual({
+			exists: existsSync(join(root, 'empty.txt')),
+			content: readFileSync(join(root, 'empty.txt'), 'utf8'),
+		}, {
+			exists: true,
+			content: '',
+		});
+	});
+
+	conformanceTest(context, 'resourceWrite preserves arbitrary base64 bytes', async function () {
+		await initializeClient('resource-write-binary');
+		const root = createWorkspace('ahp-resource-write-binary-');
+		const bytes = Buffer.from([0, 1, 2, 127, 128, 254, 255]);
+
+		await context.client.call('resourceWrite', {
+			channel: ROOT_STATE_URI,
+			uri: fileUri(root, 'bytes.bin'),
+			data: bytes.toString('base64'),
+			encoding: ContentEncoding.Base64,
+		});
+
+		assert.deepStrictEqual([...readFileSync(join(root, 'bytes.bin'))], [...bytes]);
+	});
+
 	conformanceTest(context, 'resourceDelete removes an empty directory without recursive mode', async function () {
 		await initializeClient('resource-delete-empty-directory');
 		const root = createWorkspace('ahp-resource-delete-empty-directory-');
@@ -293,6 +356,134 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		});
 	});
 
+	conformanceTest(context, 'equivalent resource watch descriptors produce equivalent snapshots', async function () {
+		await initializeClient('resource-watch-stable-channel');
+		const root = createWorkspace('ahp-resource-watch-stable-channel-');
+		const params = {
+			channel: ROOT_STATE_URI,
+			uri: URI.file(root).toString(),
+			recursive: true,
+			excludes: { items: ['**/*.tmp'] },
+		} as const;
+
+		const first = await context.client.call<CreateResourceWatchResult>('createResourceWatch', params);
+		const second = await context.client.call<CreateResourceWatchResult>('createResourceWatch', params);
+		const firstSubscription = await context.client.call<SubscribeResult>('subscribe', { channel: first.channel });
+		const secondSubscription = second.channel === first.channel
+			? firstSubscription
+			: await context.client.call<SubscribeResult>('subscribe', { channel: second.channel });
+
+		assert.deepStrictEqual(secondSubscription.snapshot?.state, firstSubscription.snapshot?.state);
+	});
+
+	conformanceTest(context, 'different resource watch descriptors produce different channels', async function () {
+		await initializeClient('resource-watch-distinct-channel');
+		const root = createWorkspace('ahp-resource-watch-distinct-channel-');
+		const rootUri = URI.file(root).toString();
+
+		const shallow = await context.client.call<CreateResourceWatchResult>('createResourceWatch', {
+			channel: ROOT_STATE_URI,
+			uri: rootUri,
+			recursive: false,
+		});
+		const recursive = await context.client.call<CreateResourceWatchResult>('createResourceWatch', {
+			channel: ROOT_STATE_URI,
+			uri: rootUri,
+			recursive: true,
+		});
+
+		assert.notStrictEqual(recursive.channel, shallow.channel);
+	});
+
+	conformanceTest(context, 'multiple clients can subscribe to the same resource watch', async function () {
+		await initializeClient('resource-watch-multi-client');
+		const root = createWorkspace('ahp-resource-watch-multi-client-');
+		const watch = await context.client.call<CreateResourceWatchResult>('createResourceWatch', {
+			channel: ROOT_STATE_URI,
+			uri: URI.file(root).toString(),
+			recursive: true,
+		});
+		const client = await context.connectClient();
+		try {
+			await client.call('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: [PROTOCOL_VERSION],
+				clientId: `resource-watch-multi-client-extra-${config.provider}`,
+			});
+			const [first, second] = await Promise.all([
+				context.client.call<SubscribeResult>('subscribe', { channel: watch.channel }),
+				client.call<SubscribeResult>('subscribe', { channel: watch.channel }),
+			]);
+
+			assert.deepStrictEqual(second.snapshot?.state, first.snapshot?.state);
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'resource watch subscribe snapshot identifies its channel and sequence', async function () {
+		await initializeClient('resource-watch-snapshot-identity');
+		const root = createWorkspace('ahp-resource-watch-snapshot-identity-');
+		const watch = await context.client.call<CreateResourceWatchResult>('createResourceWatch', {
+			channel: ROOT_STATE_URI,
+			uri: URI.file(root).toString(),
+			recursive: false,
+		});
+		const subscribed = await context.client.call<SubscribeResult>('subscribe', { channel: watch.channel });
+
+		assert.deepStrictEqual({
+			resource: subscribed.snapshot?.resource,
+			hasSequence: typeof subscribed.snapshot?.fromSeq === 'number',
+		}, {
+			resource: watch.channel,
+			hasSequence: true,
+		});
+	});
+
+	conformanceTest(context, 'resource watch can target a regular file', async function () {
+		await initializeClient('resource-watch-file');
+		const root = createWorkspace('ahp-resource-watch-file-');
+		const file = join(root, 'watched.txt');
+		writeFileSync(file, 'watched');
+		const fileUriValue = URI.file(file).toString();
+
+		const watch = await context.client.call<CreateResourceWatchResult>('createResourceWatch', {
+			channel: ROOT_STATE_URI,
+			uri: fileUriValue,
+		});
+		const subscribed = await context.client.call<SubscribeResult>('subscribe', { channel: watch.channel });
+
+		assert.deepStrictEqual(subscribed.snapshot?.state, {
+			root: fileUriValue,
+			recursive: false,
+		});
+	});
+
+	conformanceTest(context, 'resource watch defaults recursive mode to false', async function () {
+		await initializeClient('resource-watch-default-recursive');
+		const root = createWorkspace('ahp-resource-watch-default-recursive-');
+		const rootUri = URI.file(root).toString();
+
+		const watch = await context.client.call<CreateResourceWatchResult>('createResourceWatch', {
+			channel: ROOT_STATE_URI,
+			uri: rootUri,
+		});
+		const subscribed = await context.client.call<SubscribeResult>('subscribe', { channel: watch.channel });
+
+		assert.deepStrictEqual(subscribed.snapshot?.state, {
+			root: rootUri,
+			recursive: false,
+		});
+	});
+
+	conformanceTest(context, 'subscribing to a malformed resource watch channel is rejected', async function () {
+		await initializeClient('resource-watch-malformed');
+
+		await assert.rejects(context.client.call('subscribe', {
+			channel: 'ahp-resource-watch:/not-a-valid-descriptor',
+		}));
+	});
+
 	conformanceTest(context, 'creating a resource watch for a missing root is rejected', async function () {
 		await initializeClient('resource-watch-missing');
 		const root = createWorkspace('ahp-resource-watch-missing-');
@@ -348,6 +539,39 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(readFileSync(join(root, 'truncate.txt'), 'utf8'), 'PREFIX-NEW');
 	});
 
+	conformanceTest(context, 'resourceWrite insert positions count UTF-8 bytes', async function () {
+		await initializeClient('resource-insert-utf8');
+		const root = createWorkspace('ahp-resource-insert-utf8-');
+		const file = fileUri(root, 'insert-utf8.txt');
+		writeFileSync(join(root, 'insert-utf8.txt'), 'A\u{1F600}B');
+
+		await writeText(file, 'Z', { mode: ResourceWriteMode.Insert, position: 5 });
+
+		assert.strictEqual(readFileSync(join(root, 'insert-utf8.txt'), 'utf8'), 'A\u{1F600}ZB');
+	});
+
+	conformanceTest(context, 'resourceWrite append positions count UTF-8 bytes from EOF', async function () {
+		await initializeClient('resource-append-utf8');
+		const root = createWorkspace('ahp-resource-append-utf8-');
+		const file = fileUri(root, 'append-utf8.txt');
+		writeFileSync(join(root, 'append-utf8.txt'), 'A\u{1F600}B');
+
+		await writeText(file, 'Z', { mode: ResourceWriteMode.Append, position: 1 });
+
+		assert.strictEqual(readFileSync(join(root, 'append-utf8.txt'), 'utf8'), 'A\u{1F600}ZB');
+	});
+
+	conformanceTest(context, 'resourceWrite truncate positions count UTF-8 bytes', async function () {
+		await initializeClient('resource-truncate-utf8');
+		const root = createWorkspace('ahp-resource-truncate-utf8-');
+		const file = fileUri(root, 'truncate-utf8.txt');
+		writeFileSync(join(root, 'truncate-utf8.txt'), 'A\u{1F600}B');
+
+		await writeText(file, 'Z', { mode: ResourceWriteMode.Truncate, position: 5 });
+
+		assert.strictEqual(readFileSync(join(root, 'truncate-utf8.txt'), 'utf8'), 'A\u{1F600}Z');
+	});
+
 	conformanceTest(context, 'resourceWrite createOnly rejects an existing file', async function () {
 		await initializeClient('resource-create-only');
 		const root = createWorkspace('ahp-resource-create-only-');
@@ -358,6 +582,45 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(readFileSync(join(root, 'existing.txt'), 'utf8'), 'original');
 	});
 
+	conformanceTest(context, 'concurrent resourceWrite createOnly calls have a single winner', async function () {
+		await initializeClient('resource-create-only-concurrent');
+		const root = createWorkspace('ahp-resource-create-only-concurrent-');
+		const file = fileUri(root, 'winner.txt');
+
+		const results = await Promise.allSettled([
+			writeText(file, 'first', { createOnly: true }),
+			writeText(file, 'second', { createOnly: true }),
+		]);
+		const content = readFileSync(join(root, 'winner.txt'), 'utf8');
+		const rejected = results.find((result): result is PromiseRejectedResult => result.status === 'rejected');
+
+		assert.deepStrictEqual({
+			fulfilled: results.filter(result => result.status === 'fulfilled').length,
+			rejected: results.filter(result => result.status === 'rejected').length,
+			errorCode: rejected?.reason instanceof Error ? Reflect.get(rejected.reason, 'code') : undefined,
+			validContent: content === 'first' || content === 'second',
+		}, {
+			fulfilled: 1,
+			rejected: 1,
+			errorCode: AhpErrorCodes.AlreadyExists,
+			validContent: true,
+		});
+	});
+
+	conformanceTest(context, 'resourceList preserves Unicode entry names', async function () {
+		await initializeClient('resource-list-unicode');
+		const root = createWorkspace('ahp-resource-list-unicode-');
+		const name = 'smile-\u{1F600}.txt';
+		writeFileSync(join(root, name), 'unicode');
+
+		const result = await context.client.call<ResourceListResult>('resourceList', {
+			channel: ROOT_STATE_URI,
+			uri: URI.file(root).toString(),
+		});
+
+		assert.deepStrictEqual(result.entries, [{ name, type: ResourceType.File }]);
+	});
+
 	conformanceTest(context, 'resourceWrite ifMatch rejects a stale etag', async function () {
 		await initializeClient('resource-if-match');
 		const root = createWorkspace('ahp-resource-if-match-');
@@ -376,6 +639,88 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(readFileSync(join(root, 'etag.txt'), 'utf8'), 'first');
 	});
 
+	conformanceTest(context, 'resourceResolve returns a stable etag without mutation', async function () {
+		await initializeClient('resource-etag-stable');
+		const root = createWorkspace('ahp-resource-etag-stable-');
+		const file = fileUri(root, 'stable.txt');
+		writeFileSync(join(root, 'stable.txt'), 'stable');
+
+		const first = await context.client.call<ResourceResolveResult>('resourceResolve', { channel: ROOT_STATE_URI, uri: file });
+		const second = await context.client.call<ResourceResolveResult>('resourceResolve', { channel: ROOT_STATE_URI, uri: file });
+
+		assert.deepStrictEqual({
+			hasEtag: typeof first.etag === 'string',
+			stable: second.etag === first.etag,
+		}, {
+			hasEtag: true,
+			stable: true,
+		});
+	});
+
+	conformanceTest(context, 'resourceResolve changes the etag after content changes', async function () {
+		await initializeClient('resource-etag-change');
+		const root = createWorkspace('ahp-resource-etag-change-');
+		const file = fileUri(root, 'changing.txt');
+		writeFileSync(join(root, 'changing.txt'), 'before');
+		const before = await context.client.call<ResourceResolveResult>('resourceResolve', { channel: ROOT_STATE_URI, uri: file });
+
+		await writeText(file, 'after-with-a-different-size');
+		const after = await context.client.call<ResourceResolveResult>('resourceResolve', { channel: ROOT_STATE_URI, uri: file });
+
+		assert.deepStrictEqual({
+			hasEtags: typeof before.etag === 'string' && typeof after.etag === 'string',
+			changed: before.etag !== after.etag,
+		}, {
+			hasEtags: true,
+			changed: true,
+		});
+	});
+
+	conformanceTest(context, 'resourceWrite enforces ifMatch in append mode', async function () {
+		await initializeClient('resource-if-match-append');
+		const root = createWorkspace('ahp-resource-if-match-append-');
+		const file = fileUri(root, 'append.txt');
+		writeFileSync(join(root, 'append.txt'), 'before');
+		const resolved = await context.client.call<ResourceResolveResult>('resourceResolve', { channel: ROOT_STATE_URI, uri: file });
+		assert.ok(resolved.etag);
+		await writeText(file, 'changed');
+
+		await assert.rejects(
+			writeText(file, '-after', { mode: ResourceWriteMode.Append, ifMatch: resolved.etag }),
+			{ code: AhpErrorCodes.Conflict },
+		);
+
+		assert.strictEqual(readFileSync(join(root, 'append.txt'), 'utf8'), 'changed');
+	});
+
+	conformanceTest(context, 'concurrent ifMatch writes allow only one winner', async function () {
+		await initializeClient('resource-if-match-concurrent');
+		const root = createWorkspace('ahp-resource-if-match-concurrent-');
+		const file = fileUri(root, 'concurrent.txt');
+		writeFileSync(join(root, 'concurrent.txt'), 'seed');
+		const resolved = await context.client.call<ResourceResolveResult>('resourceResolve', { channel: ROOT_STATE_URI, uri: file });
+		assert.ok(resolved.etag);
+
+		const results = await Promise.allSettled([
+			writeText(file, 'first-winner', { ifMatch: resolved.etag }),
+			writeText(file, 'second-winner', { ifMatch: resolved.etag }),
+		]);
+		const content = readFileSync(join(root, 'concurrent.txt'), 'utf8');
+		const rejected = results.find((result): result is PromiseRejectedResult => result.status === 'rejected');
+
+		assert.deepStrictEqual({
+			fulfilled: results.filter(result => result.status === 'fulfilled').length,
+			rejected: results.filter(result => result.status === 'rejected').length,
+			errorCode: rejected?.reason instanceof Error ? Reflect.get(rejected.reason, 'code') : undefined,
+			validContent: content === 'first-winner' || content === 'second-winner',
+		}, {
+			fulfilled: 1,
+			rejected: 1,
+			errorCode: AhpErrorCodes.Conflict,
+			validContent: true,
+		});
+	});
+
 	conformanceTest(context, 'resourceCopy failIfExists preserves the destination', async function () {
 		await initializeClient('resource-copy-conflict');
 		const root = createWorkspace('ahp-resource-copy-conflict-');
@@ -391,6 +736,30 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(readFileSync(join(root, 'destination.txt'), 'utf8'), 'destination');
 	});
 
+	conformanceTest(context, 'resourceCopy failIfExists preserves both directory trees', async function () {
+		await initializeClient('resource-copy-directory-conflict');
+		const root = createWorkspace('ahp-resource-copy-directory-conflict-');
+		mkdirSync(join(root, 'source'));
+		mkdirSync(join(root, 'destination'));
+		writeFileSync(join(root, 'source', 'source.txt'), 'source');
+		writeFileSync(join(root, 'destination', 'destination.txt'), 'destination');
+
+		await assert.rejects(context.client.call('resourceCopy', {
+			channel: ROOT_STATE_URI,
+			source: fileUri(root, 'source'),
+			destination: fileUri(root, 'destination'),
+			failIfExists: true,
+		}), { code: AhpErrorCodes.AlreadyExists });
+
+		assert.deepStrictEqual({
+			source: readFileSync(join(root, 'source', 'source.txt'), 'utf8'),
+			destination: readFileSync(join(root, 'destination', 'destination.txt'), 'utf8'),
+		}, {
+			source: 'source',
+			destination: 'destination',
+		});
+	});
+
 	conformanceTest(context, 'resourceMove failIfExists preserves both files', async function () {
 		await initializeClient('resource-move-conflict');
 		const root = createWorkspace('ahp-resource-move-conflict-');
@@ -412,6 +781,30 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		});
 	});
 
+	conformanceTest(context, 'resourceMove failIfExists preserves both directory trees', async function () {
+		await initializeClient('resource-move-directory-conflict');
+		const root = createWorkspace('ahp-resource-move-directory-conflict-');
+		mkdirSync(join(root, 'source'));
+		mkdirSync(join(root, 'destination'));
+		writeFileSync(join(root, 'source', 'source.txt'), 'source');
+		writeFileSync(join(root, 'destination', 'destination.txt'), 'destination');
+
+		await assert.rejects(context.client.call('resourceMove', {
+			channel: ROOT_STATE_URI,
+			source: fileUri(root, 'source'),
+			destination: fileUri(root, 'destination'),
+			failIfExists: true,
+		}), { code: AhpErrorCodes.AlreadyExists });
+
+		assert.deepStrictEqual({
+			source: readFileSync(join(root, 'source', 'source.txt'), 'utf8'),
+			destination: readFileSync(join(root, 'destination', 'destination.txt'), 'utf8'),
+		}, {
+			source: 'source',
+			destination: 'destination',
+		});
+	});
+
 	conformanceTest(context, 'resourceMkdir rejects a path occupied by a file', async function () {
 		await initializeClient('resource-mkdir-file');
 		const root = createWorkspace('ahp-resource-mkdir-file-');
@@ -424,6 +817,57 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		}), { code: AhpErrorCodes.AlreadyExists });
 	});
 
+	conformanceTest(context, 'resourceMkdir creates missing parent directories', async function () {
+		await initializeClient('resource-mkdir-parents');
+		const root = createWorkspace('ahp-resource-mkdir-parents-');
+		const nested = join(root, 'one', 'two', 'three');
+
+		await context.client.call('resourceMkdir', {
+			channel: ROOT_STATE_URI,
+			uri: URI.file(nested).toString(),
+		});
+
+		assert.strictEqual(existsSync(nested), true);
+	});
+
+	conformanceTest(context, 'resourceResolve reports directory metadata', async function () {
+		await initializeClient('resource-resolve-directory');
+		const root = createWorkspace('ahp-resource-resolve-directory-');
+		const nested = join(root, 'directory');
+		mkdirSync(nested);
+
+		const result = await context.client.call<ResourceResolveResult>('resourceResolve', {
+			channel: ROOT_STATE_URI,
+			uri: URI.file(nested).toString(),
+		});
+
+		assert.deepStrictEqual({
+			uri: result.uri,
+			type: result.type,
+			hasMtime: typeof result.mtime === 'string',
+			hasCtime: typeof result.ctime === 'string',
+		}, {
+			uri: URI.file(nested).toString(),
+			type: ResourceType.Directory,
+			hasMtime: true,
+			hasCtime: true,
+		});
+	});
+
+	conformanceTest(context, 'resourceResolve reports binary size in bytes', async function () {
+		await initializeClient('resource-resolve-binary-size');
+		const root = createWorkspace('ahp-resource-resolve-binary-size-');
+		const bytes = Buffer.from([0, 255, 1, 254, 2]);
+		writeFileSync(join(root, 'size.bin'), bytes);
+
+		const result = await context.client.call<ResourceResolveResult>('resourceResolve', {
+			channel: ROOT_STATE_URI,
+			uri: fileUri(root, 'size.bin'),
+		});
+
+		assert.strictEqual(result.size, bytes.byteLength);
+	});
+
 	conformanceTest(context, 'resourceDelete recursively removes a directory tree', async function () {
 		await initializeClient('resource-delete-tree');
 		const root = createWorkspace('ahp-resource-delete-tree-');
@@ -440,6 +884,20 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(existsSync(tree), false);
 	});
 
+	conformanceTest(context, 'resourceDelete removes a regular file without recursive mode', async function () {
+		await initializeClient('resource-delete-file');
+		const root = createWorkspace('ahp-resource-delete-file-');
+		const file = join(root, 'delete.txt');
+		writeFileSync(file, 'delete');
+
+		await context.client.call('resourceDelete', {
+			channel: ROOT_STATE_URI,
+			uri: URI.file(file).toString(),
+		});
+
+		assert.strictEqual(existsSync(file), false);
+	});
+
 	conformanceTest(context, 'resourceWrite decodes base64 content', async function () {
 		await initializeClient('resource-base64');
 		const root = createWorkspace('ahp-resource-base64-');
@@ -633,6 +1091,21 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(readFileSync(join(root, 'destination', 'nested', 'file.txt'), 'utf8'), 'copied');
 	});
 
+	conformanceTest(context, 'resourceCopy preserves binary file bytes', async function () {
+		await initializeClient('resource-copy-binary');
+		const root = createWorkspace('ahp-resource-copy-binary-');
+		const bytes = Buffer.from([0, 255, 32, 128, 64]);
+		writeFileSync(join(root, 'source.bin'), bytes);
+
+		await context.client.call('resourceCopy', {
+			channel: ROOT_STATE_URI,
+			source: fileUri(root, 'source.bin'),
+			destination: fileUri(root, 'copy.bin'),
+		});
+
+		assert.deepStrictEqual([...readFileSync(join(root, 'copy.bin'))], [...bytes]);
+	});
+
 	conformanceTest(context, 'resourceCopy overwrites an existing destination by default', async function () {
 		await initializeClient('resource-copy-overwrite');
 		const root = createWorkspace('ahp-resource-copy-overwrite-');
@@ -648,6 +1121,29 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		assert.strictEqual(readFileSync(join(root, 'destination.txt'), 'utf8'), 'source');
 	});
 
+	conformanceTest(context, 'resourceCopy replaces an existing destination directory tree', async function () {
+		await initializeClient('resource-copy-directory-overwrite');
+		const root = createWorkspace('ahp-resource-copy-directory-overwrite-');
+		mkdirSync(join(root, 'source'));
+		mkdirSync(join(root, 'destination'));
+		writeFileSync(join(root, 'source', 'source.txt'), 'source');
+		writeFileSync(join(root, 'destination', 'stale.txt'), 'stale');
+
+		await context.client.call('resourceCopy', {
+			channel: ROOT_STATE_URI,
+			source: fileUri(root, 'source'),
+			destination: fileUri(root, 'destination'),
+		});
+
+		assert.deepStrictEqual({
+			source: readFileSync(join(root, 'destination', 'source.txt'), 'utf8'),
+			staleExists: existsSync(join(root, 'destination', 'stale.txt')),
+		}, {
+			source: 'source',
+			staleExists: false,
+		});
+	});
+
 	conformanceTest(context, 'resourceCopy reports a missing source', async function () {
 		await initializeClient('resource-copy-missing');
 		const root = createWorkspace('ahp-resource-copy-missing-');
@@ -680,6 +1176,27 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		});
 	});
 
+	conformanceTest(context, 'resourceMove preserves binary file bytes', async function () {
+		await initializeClient('resource-move-binary');
+		const root = createWorkspace('ahp-resource-move-binary-');
+		const bytes = Buffer.from([0, 255, 32, 128, 64]);
+		writeFileSync(join(root, 'source.bin'), bytes);
+
+		await context.client.call('resourceMove', {
+			channel: ROOT_STATE_URI,
+			source: fileUri(root, 'source.bin'),
+			destination: fileUri(root, 'moved.bin'),
+		});
+
+		assert.deepStrictEqual({
+			sourceExists: existsSync(join(root, 'source.bin')),
+			bytes: [...readFileSync(join(root, 'moved.bin'))],
+		}, {
+			sourceExists: false,
+			bytes: [...bytes],
+		});
+	});
+
 	conformanceTest(context, 'resourceMove overwrites an existing destination by default', async function () {
 		await initializeClient('resource-move-overwrite');
 		const root = createWorkspace('ahp-resource-move-overwrite-');
@@ -701,6 +1218,31 @@ export function defineClientFilesystemTests(context: IAgentHostE2ETestContext):
 		});
 	});
 
+	conformanceTest(context, 'resourceMove replaces an existing destination directory tree', async function () {
+		await initializeClient('resource-move-directory-overwrite');
+		const root = createWorkspace('ahp-resource-move-directory-overwrite-');
+		mkdirSync(join(root, 'source'));
+		mkdirSync(join(root, 'destination'));
+		writeFileSync(join(root, 'source', 'source.txt'), 'source');
+		writeFileSync(join(root, 'destination', 'stale.txt'), 'stale');
+
+		await context.client.call('resourceMove', {
+			channel: ROOT_STATE_URI,
+			source: fileUri(root, 'source'),
+			destination: fileUri(root, 'destination'),
+		});
+
+		assert.deepStrictEqual({
+			sourceExists: existsSync(join(root, 'source')),
+			content: readFileSync(join(root, 'destination', 'source.txt'), 'utf8'),
+			staleExists: existsSync(join(root, 'destination', 'stale.txt')),
+		}, {
+			sourceExists: false,
+			content: 'source',
+			staleExists: false,
+		});
+	});
+
 	conformanceTest(context, 'resourceMove reports a missing source', async function () {
 		await initializeClient('resource-move-missing');
 		const root = createWorkspace('ahp-resource-move-missing-');
diff --git a/src/vs/platform/agentHost/test/node/e2e/suites/hostFeaturesSuite.ts b/src/vs/platform/agentHost/test/node/e2e/suites/hostFeaturesSuite.ts
index f4b5e406b2ac34..31d2d56054b94d 100644
--- a/src/vs/platform/agentHost/test/node/e2e/suites/hostFeaturesSuite.ts
+++ b/src/vs/platform/agentHost/test/node/e2e/suites/hostFeaturesSuite.ts
@@ -8,10 +8,11 @@ import { execSync } from 'child_process';
 import { mkdirSync, mkdtempSync, unlinkSync, writeFileSync } from 'fs';
 import { tmpdir } from 'os';
 import { join } from '../../../../../../base/common/path.js';
+import { basename } from '../../../../../../base/common/resources.js';
 import { URI } from '../../../../../../base/common/uri.js';
 import { CompletionItemKind, type CompletionsResult, type InitializeResult, type ResolveSessionConfigResult, type SessionConfigCompletionsResult, type SubscribeResult } from '../../../../common/state/protocol/commands.js';
 import { PROTOCOL_VERSION } from '../../../../common/state/protocol/version/registry.js';
-import { buildDefaultChatUri, ROOT_STATE_URI, ToolCallConfirmationReason, type TerminalState, type ToolResultContent } from '../../../../common/state/sessionState.js';
+import { buildDefaultChatUri, MessageAttachmentKind, ROOT_STATE_URI, ToolCallConfirmationReason, type TerminalState, type ToolResultContent } from '../../../../common/state/sessionState.js';
 import {
 	createRealSession,
 	dispatchTurn,
@@ -38,12 +39,12 @@ export function defineHostFeaturesTests(context: IAgentHostE2ETestContext): void
 		return createRealSession(context.client, config, `${prefix}-${config.provider}`, createdSessions, URI.file(workspace));
 	}
 
-	async function getCompletions(sessionUri: string, text: string): Promise<CompletionsResult> {
+	async function getCompletions(sessionUri: string, text: string, offset = text.length): Promise<CompletionsResult> {
 		return context.client.call<CompletionsResult>('completions', {
 			channel: buildDefaultChatUri(sessionUri),
 			kind: CompletionItemKind.UserMessage,
 			text,
-			offset: text.length,
+			offset,
 		});
 	}
 
@@ -115,6 +116,154 @@ export function defineHostFeaturesTests(context: IAgentHostE2ETestContext): void
 		assert.deepStrictEqual(result, { items: [] });
 	});
 
+	conformanceTest(context, 'workspace file completion replaces only the token before the cursor', async function () {
+		const workspace = createWorkspace('ahp-file-completion-range-');
+		writeFileSync(join(workspace, 'alpha.ts'), 'alpha');
+		const sessionUri = await createSession('file-completion-range', workspace);
+		const text = 'review @alp trailing';
+
+		const result = await getCompletions(sessionUri, text, 'review @alp'.length);
+
+		assert.deepStrictEqual(result.items.map(item => ({
+			insertText: item.insertText,
+			rangeStart: item.rangeStart,
+			rangeEnd: item.rangeEnd,
+		})), [{
+			insertText: '@alpha.ts',
+			rangeStart: 'review '.length,
+			rangeEnd: 'review @alp'.length,
+		}]);
+	});
+
+	conformanceTest(context, 'workspace file completion ignores embedded at signs', async function () {
+		const workspace = createWorkspace('ahp-file-completion-embedded-');
+		writeFileSync(join(workspace, 'example.txt'), 'example');
+		const sessionUri = await createSession('file-completion-embedded', workspace);
+
+		const result = await getCompletions(sessionUri, 'email@example');
+
+		assert.deepStrictEqual(result.items, []);
+	});
+
+	conformanceTest(context, 'workspace file completion accepts tab and newline delimiters', async function () {
+		const workspace = createWorkspace('ahp-file-completion-whitespace-');
+		writeFileSync(join(workspace, 'alpha.txt'), 'alpha');
+		const sessionUri = await createSession('file-completion-whitespace', workspace);
+
+		const [tab, newline] = await Promise.all([
+			getCompletions(sessionUri, 'review\t@alp'),
+			getCompletions(sessionUri, 'review\n#alp'),
+		]);
+
+		assert.deepStrictEqual({
+			tab: tab.items.map(item => item.insertText),
+			newline: newline.items.map(item => item.insertText),
+		}, {
+			tab: ['@alpha.txt'],
+			newline: ['#alpha.txt'],
+		});
+	});
+
+	conformanceTest(context, 'workspace file completion disambiguates duplicate basenames', async function () {
+		const workspace = createWorkspace('ahp-file-completion-duplicates-');
+		mkdirSync(join(workspace, 'one'));
+		mkdirSync(join(workspace, 'two'));
+		writeFileSync(join(workspace, 'one', 'same.ts'), 'one');
+		writeFileSync(join(workspace, 'two', 'same.ts'), 'two');
+		const sessionUri = await createSession('file-completion-duplicates', workspace);
+
+		const result = await getCompletions(sessionUri, '@same');
+
+		assert.deepStrictEqual(result.items.map(item => item.attachment?.label).sort(), [
+			`${basename(URI.file(workspace))} \u2022 one/same.ts`,
+			`${basename(URI.file(workspace))} \u2022 two/same.ts`,
+		]);
+	});
+
+	conformanceTest(context, 'workspace file completion matches nested relative paths', async function () {
+		const workspace = createWorkspace('ahp-file-completion-nested-');
+		mkdirSync(join(workspace, 'feature'));
+		writeFileSync(join(workspace, 'feature', 'target.ts'), 'nested');
+		writeFileSync(join(workspace, 'target.ts'), 'root');
+		const sessionUri = await createSession('file-completion-nested', workspace);
+
+		const result = await getCompletions(sessionUri, '@feature/target');
+
+		assert.deepStrictEqual(result.items.map(item => item.attachment?.type === MessageAttachmentKind.Resource ? item.attachment.uri : undefined), [
+			URI.file(join(workspace, 'feature', 'target.ts')).toString(),
+		]);
+	});
+
+	conformanceTest(context, 'workspace file completion caps an empty query at fifty results', async function () {
+		const workspace = createWorkspace('ahp-file-completion-limit-');
+		for (let index = 0; index < 60; index++) {
+			writeFileSync(join(workspace, `file-${String(index).padStart(2, '0')}.txt`), String(index));
+		}
+		const sessionUri = await createSession('file-completion-limit', workspace);
+
+		const result = await getCompletions(sessionUri, '@');
+
+		assert.strictEqual(result.items.length, 50);
+	});
+
+	conformanceTest(context, 'workspace file completion supports a trigger at the start of input', async function () {
+		const workspace = createWorkspace('ahp-file-completion-start-');
+		writeFileSync(join(workspace, 'alpha.ts'), 'alpha');
+		const sessionUri = await createSession('file-completion-start', workspace);
+
+		const result = await getCompletions(sessionUri, '#alp');
+
+		assert.deepStrictEqual(result.items.map(item => ({
+			insertText: item.insertText,
+			rangeStart: item.rangeStart,
+			rangeEnd: item.rangeEnd,
+		})), [{
+			insertText: '#alpha.ts',
+			rangeStart: 0,
+			rangeEnd: 4,
+		}]);
+	});
+
+	conformanceTest(context, 'workspace file completion ignores a token separated from the cursor', async function () {
+		const workspace = createWorkspace('ahp-file-completion-separated-');
+		writeFileSync(join(workspace, 'alpha.ts'), 'alpha');
+		const sessionUri = await createSession('file-completion-separated', workspace);
+
+		const result = await getCompletions(sessionUri, 'review @alpha later');
+
+		assert.deepStrictEqual(result.items, []);
+	});
+
+	conformanceTest(context, 'workspace file completion matches file names case-insensitively', async function () {
+		const workspace = createWorkspace('ahp-file-completion-case-');
+		writeFileSync(join(workspace, 'MixedCase.ts'), 'mixed');
+		const sessionUri = await createSession('file-completion-case', workspace);
+
+		const result = await getCompletions(sessionUri, '@mixedcase');
+
+		assert.deepStrictEqual(result.items.map(item => item.insertText), ['@MixedCase.ts']);
+	});
+
+	conformanceTest(context, 'workspace file completion fuzzy matches a basename', async function () {
+		const workspace = createWorkspace('ahp-file-completion-fuzzy-');
+		writeFileSync(join(workspace, 'agentHostCoverage.ts'), 'coverage');
+		const sessionUri = await createSession('file-completion-fuzzy', workspace);
+
+		const result = await getCompletions(sessionUri, '@agcov');
+
+		assert.deepStrictEqual(result.items.map(item => item.insertText), ['@agentHostCoverage.ts']);
+	});
+
+	conformanceTest(context, 'workspace file completion ignores a token after the cursor', async function () {
+		const workspace = createWorkspace('ahp-file-completion-offset-');
+		writeFileSync(join(workspace, 'alpha.ts'), 'alpha');
+		const sessionUri = await createSession('file-completion-offset', workspace);
+
+		const result = await getCompletions(sessionUri, 'prefix @alpha', 'prefix'.length);
+
+		assert.deepStrictEqual(result.items, []);
+	});
+
 	conformanceTest(context, 'rename completion appears after a locally renamed turn', async function () {
 
 		const sessionUri = await createSession('rename-completion');
diff --git a/src/vs/platform/agentHost/test/node/e2e/suites/protocolContractsSuite.ts b/src/vs/platform/agentHost/test/node/e2e/suites/protocolContractsSuite.ts
index 226e185858d352..b7139239892946 100644
--- a/src/vs/platform/agentHost/test/node/e2e/suites/protocolContractsSuite.ts
+++ b/src/vs/platform/agentHost/test/node/e2e/suites/protocolContractsSuite.ts
@@ -72,6 +72,18 @@ export function defineProtocolContractTests(context: IAgentHostE2ETestContext):
 		return client;
 	}
 
+	async function triggerServerActivity(client: TestProtocolClient, marker: string): Promise<void> {
+		await client.call('createSession', {
+			channel: `missing-provider:/${marker}`,
+			provider: 'missing-provider',
+		}).catch(() => undefined);
+		await client.call('ping', { channel: ROOT_STATE_URI });
+	}
+
+	function isOtlpExport(notification: { readonly method: string }): boolean {
+		return notification.method === 'otlp/exportLogs';
+	}
+
 	conformanceTest(context, 'ping answers while the connection is live', async function () {
 		// Liveness has no payload — the response itself is the signal, so the
 		// contract is that the call resolves rather than what it returns.
@@ -113,6 +125,193 @@ export function defineProtocolContractTests(context: IAgentHostE2ETestContext):
 		}
 	});
 
+	conformanceTest(context, 'initialize advertises the OTLP log channel template', async function () {
+		const client = await context.connectClient();
+		try {
+			const result = await client.call<InitializeResult>('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: [PROTOCOL_VERSION],
+				clientId: `otlp-capability-${config.provider}`,
+			});
+
+			assert.deepStrictEqual(result.telemetry, { logs: 'ahp-otlp://logs/{level}' });
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'initialize ignores an unknown OTLP log level', async function () {
+		const client = await context.connectClient();
+		try {
+			const result = await client.call<InitializeResult>('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: [PROTOCOL_VERSION],
+				clientId: `otlp-invalid-initial-${config.provider}`,
+				initialSubscriptions: ['ahp-otlp://logs/verbose'],
+			});
+			client.clearReceived();
+
+			await triggerServerActivity(client, 'otlp-invalid-initial');
+
+			assert.deepStrictEqual({
+				snapshots: result.snapshots,
+				receivedExports: client.receivedNotifications(isOtlpExport).length,
+			}, {
+				snapshots: [],
+				receivedExports: 0,
+			});
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'subscribe acknowledges an unknown OTLP log level without installing it', async function () {
+		const client = await initializeAdditionalClient('otlp-invalid-subscribe');
+		try {
+			const result = await client.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/verbose' });
+			client.clearReceived();
+
+			await triggerServerActivity(client, 'otlp-invalid-subscribe');
+
+			assert.deepStrictEqual({
+				result,
+				receivedExports: client.receivedNotifications(isOtlpExport).length,
+			}, {
+				result: {},
+				receivedExports: 0,
+			});
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'OTLP log subscriptions route exports on their canonical channel', async function () {
+		const client = await initializeAdditionalClient('otlp-canonical');
+		try {
+			await client.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/trace' });
+			const exported = client.waitForNotification(isOtlpExport, 30_000);
+
+			await triggerServerActivity(client, 'otlp-canonical');
+			const notification = await exported;
+
+			assert.strictEqual((notification.params as OtlpExportLogsParams).channel, 'ahp-otlp://logs/trace');
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'OTLP log delivery resumes after unsubscribe and resubscribe', async function () {
+		const client = await initializeAdditionalClient('otlp-resubscribe');
+		try {
+			await client.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/trace' });
+			client.notify('unsubscribe', { channel: 'ahp-otlp://logs/trace' });
+			await client.call('ping', { channel: ROOT_STATE_URI });
+			await client.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/trace' });
+			client.clearReceived();
+			const exported = client.waitForNotification(isOtlpExport, 30_000);
+
+			await triggerServerActivity(client, 'otlp-resubscribe');
+
+			assert.strictEqual((await exported).method, 'otlp/exportLogs');
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'unsubscribing from OTLP logs stops delivery', async function () {
+		const client = await initializeAdditionalClient('otlp-unsubscribe');
+		try {
+			await client.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/trace' });
+			client.notify('unsubscribe', { channel: 'ahp-otlp://logs/trace' });
+			await client.call('ping', { channel: ROOT_STATE_URI });
+			client.clearReceived();
+
+			await triggerServerActivity(client, 'otlp-unsubscribe');
+
+			assert.strictEqual(client.receivedNotifications(isOtlpExport).length, 0);
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'info-level OTLP subscriptions receive server activity', async function () {
+		const client = await initializeAdditionalClient('otlp-info-level');
+		try {
+			await client.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/info' });
+			const exported = client.waitForNotification(isOtlpExport, 30_000);
+
+			await triggerServerActivity(client, 'otlp-info-level');
+
+			assert.strictEqual((await exported).method, 'otlp/exportLogs');
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'fatal-level OTLP subscriptions filter ordinary server activity', async function () {
+		const client = await initializeAdditionalClient('otlp-fatal-level');
+		try {
+			await client.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/fatal' });
+			client.clearReceived();
+
+			await triggerServerActivity(client, 'otlp-fatal-level');
+
+			assert.strictEqual(client.receivedNotifications(isOtlpExport).length, 0);
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'OTLP logs fan out to every subscribed client', async function () {
+		const first = await initializeAdditionalClient('otlp-fanout-first');
+		const second = await initializeAdditionalClient('otlp-fanout-second');
+		try {
+			await second.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/trace' });
+			await first.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/trace' });
+			await Promise.all([
+				first.call('ping', { channel: ROOT_STATE_URI }),
+				second.call('ping', { channel: ROOT_STATE_URI }),
+			]);
+			first.clearReceived();
+			second.clearReceived();
+			const firstExport = first.waitForNotification(isOtlpExport, 30_000);
+			const secondExport = second.waitForNotification(isOtlpExport, 30_000);
+
+			await triggerServerActivity(first, 'otlp-fanout');
+
+			assert.deepStrictEqual([(await firstExport).method, (await secondExport).method], ['otlp/exportLogs', 'otlp/exportLogs']);
+		} finally {
+			first.close();
+			second.close();
+		}
+	});
+
+	conformanceTest(context, 'initialize installs an OTLP log subscription without a snapshot', async function () {
+		const client = await context.connectClient();
+		try {
+			const initialized = await client.call<InitializeResult>('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: [PROTOCOL_VERSION],
+				clientId: `otlp-initial-${config.provider}`,
+				initialSubscriptions: ['ahp-otlp://logs/trace'],
+			});
+			const exported = client.waitForNotification(n => n.method === 'otlp/exportLogs', 30_000);
+
+			await client.call('createSession', { channel: 'missing-provider:/otlp-initial', provider: 'missing-provider' }).catch(() => undefined);
+			const notification = await exported;
+
+			assert.deepStrictEqual({
+				snapshots: initialized.snapshots,
+				channel: (notification.params as OtlpExportLogsParams).channel,
+			}, {
+				snapshots: [],
+				channel: 'ahp-otlp://logs/trace',
+			});
+		} finally {
+			client.close();
+		}
+	});
+
 	conformanceTest(context, 'management diagnostics report providers and network endpoints', async function () {
 		const client = await context.connectClient();
 		try {
@@ -232,6 +431,69 @@ export function defineProtocolContractTests(context: IAgentHostE2ETestContext):
 		}
 	});
 
+	conformanceTest(context, 'initialize selects a supported fallback protocol version', async function () {
+		const client = await context.connectClient();
+		try {
+			const result = await client.call<InitializeResult>('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: ['999.0.0', PROTOCOL_VERSION],
+				clientId: `fallback-version-${config.provider}`,
+			});
+
+			assert.strictEqual(result.protocolVersion, PROTOCOL_VERSION);
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'initialize accepts informational client identity', async function () {
+		const client = await context.connectClient();
+		try {
+			const result = await client.call<InitializeResult>('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: [PROTOCOL_VERSION],
+				clientId: `client-info-${config.provider}`,
+				clientInfo: { name: 'agent-host-e2e', version: '1.2.3', title: 'Agent Host E2E' },
+			});
+
+			assert.strictEqual(result.protocolVersion, PROTOCOL_VERSION);
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'initialize accepts locale metadata', async function () {
+		const client = await context.connectClient();
+		try {
+			const result = await client.call<InitializeResult>('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: [PROTOCOL_VERSION],
+				clientId: `locale-${config.provider}`,
+				locale: 'ja-JP',
+			});
+
+			assert.strictEqual(result.protocolVersion, PROTOCOL_VERSION);
+		} finally {
+			client.close();
+		}
+	});
+
+	conformanceTest(context, 'initialize accepts declared client capabilities', async function () {
+		const client = await context.connectClient();
+		try {
+			const result = await client.call<InitializeResult>('initialize', {
+				channel: ROOT_STATE_URI,
+				protocolVersions: [PROTOCOL_VERSION],
+				clientId: `capabilities-${config.provider}`,
+				capabilities: { mcpApps: {} },
+			});
+
+			assert.strictEqual(result.protocolVersion, PROTOCOL_VERSION);
+		} finally {
+			client.close();
+		}
+	});
+
 	conformanceTest(context, 'initialize cannot be repeated after the handshake', async function () {
 		const client = await initializeAdditionalClient('repeat-initialize');
 		try {
@@ -670,6 +932,172 @@ export function defineProtocolContractTests(context: IAgentHostE2ETestContext):
 		}
 	});
 
+	conformanceTest(context, 'reconnect with no missed actions returns an empty replay', async function () {
+		const { sessionUri } = await createSession('reconnect-empty');
+		const chatUri = buildDefaultChatUri(sessionUri);
+		const droppedClientId = `reconnect-empty-${config.provider}`;
+		const { carried: seenThrough, revived } = await afterConnectionDrop(droppedClientId, async first => {
+			const subscribed = await first.call<SubscribeResult>('subscribe', { channel: chatUri });
+			return subscribed.snapshot!.fromSeq;
+		});
+
+		try {
+			const result = await revived.call<ReconnectResult>('reconnect', {
+				channel: ROOT_STATE_URI,
+				clientId: droppedClientId,
+				lastSeenServerSeq: seenThrough,
+				subscriptions: [chatUri],
+			});
+
+			assert.deepStrictEqual(result, { type: ReconnectResultType.Replay, actions: [], missing: [] });
+		} finally {
+			revived.close();
+		}
+	});
+
+	conformanceTest(context, 'reconnect excludes actions from channels the client did not restore', async function () {
+		const firstSession = await createSession('reconnect-filter-first');
+		const secondWorkspace = mkdtempSync(join(tmpdir(), 'ahp-reconnect-filter-second-'));
+		tempDirs.push(secondWorkspace);
+		const secondSessionUri = URI.from({ scheme: config.scheme, path: `/${generateUuid()}` }).toString();
+		await context.client.call('createSession', {
+			channel: secondSessionUri,
+			provider: config.provider,
+			workingDirectories: [URI.file(secondWorkspace).toString()],
+			config: { isolation: 'folder' },
+		});
+		createdSessions.push(secondSessionUri);
+		await context.client.call<SubscribeResult>('subscribe', { channel: secondSessionUri });
+		const firstChat = buildDefaultChatUri(firstSession.sessionUri);
+		const secondChat = buildDefaultChatUri(secondSessionUri);
+		await context.client.call<SubscribeResult>('subscribe', { channel: secondChat });
+		const droppedClientId = `reconnect-filter-${config.provider}`;
+
+		const { carried: seenThrough, revived } = await afterConnectionDrop(droppedClientId, async first => {
+			const subscribed = await first.call<SubscribeResult>('subscribe', { channel: firstChat });
+			return subscribed.snapshot!.fromSeq;
+		});
+
+		try {
+			await dispatchAndWaitOnShared(firstChat, { type: ActionType.ChatDraftChanged, draft: { text: 'included', origin: { kind: MessageKind.User } } });
+			await dispatchAndWaitOnShared(secondChat, { type: ActionType.ChatDraftChanged, draft: { text: 'excluded', origin: { kind: MessageKind.User } } });
+
+			const result = await revived.call<ReconnectResult>('reconnect', {
+				channel: ROOT_STATE_URI,
+				clientId: droppedClientId,
+				lastSeenServerSeq: seenThrough,
+				subscriptions: [firstChat],
+			});
+
+			assert.deepStrictEqual(result.type === ReconnectResultType.Replay
+				? result.actions.map(action => ({ channel: action.channel, type: action.action.type }))
+				: result.type, [{ channel: firstChat, type: ActionType.ChatDraftChanged }]);
+		} finally {
+			revived.close();
+		}
+	});
+
+	conformanceTest(context, 'reconnect restores an OTLP log subscription', async function () {
+		const droppedClientId = `reconnect-otlp-${config.provider}`;
+		const { carried: seenThrough, revived } = await afterConnectionDrop(droppedClientId, async first => {
+			const root = await first.call<SubscribeResult>('subscribe', { channel: ROOT_STATE_URI });
+			await first.call<SubscribeResult>('subscribe', { channel: 'ahp-otlp://logs/trace' });
+			return root.snapshot!.fromSeq;
+		});
+
+		try {
+			await revived.call<ReconnectResult>('reconnect', {
+				channel: ROOT_STATE_URI,
+				clientId: droppedClientId,
+				lastSeenServerSeq: seenThrough,
+				subscriptions: ['ahp-otlp://logs/trace'],
+			});
+			const exported = revived.waitForNotification(n => n.method === 'otlp/exportLogs', 30_000);
+
+			await context.client.call('createSession', { channel: 'missing-provider:/otlp-reconnect', provider: 'missing-provider' }).catch(() => undefined);
+
+			assert.strictEqual((await exported).method, 'otlp/exportLogs');
+		} finally {
+			revived.close();
+		}
+	});
+
+	conformanceTest(context, 'reconnect replays missed session and chat actions together', async function () {
+		const { sessionUri } = await createSession('reconnect-state-snapshots');
+		const chatUri = buildDefaultChatUri(sessionUri);
+		const droppedClientId = `reconnect-state-snapshots-${config.provider}`;
+		const { carried: seenThrough, revived } = await afterConnectionDrop(droppedClientId, async first => {
+			const session = await first.call<SubscribeResult>('subscribe', { channel: sessionUri });
+			const chat = await first.call<SubscribeResult>('subscribe', { channel: chatUri });
+			return Math.max(session.snapshot!.fromSeq, chat.snapshot!.fromSeq);
+		});
+
+		try {
+			await dispatchAndWaitOnShared(sessionUri, { type: ActionType.SessionTitleChanged, title: 'Replay Session' });
+			await dispatchAndWaitOnShared(chatUri, { type: ActionType.ChatDraftChanged, draft: { text: 'replay draft', origin: { kind: MessageKind.User } } });
+
+			const result = await revived.call<ReconnectResult>('reconnect', {
+				channel: ROOT_STATE_URI,
+				clientId: droppedClientId,
+				lastSeenServerSeq: seenThrough,
+				subscriptions: [sessionUri, chatUri],
+			});
+
+			assert.deepStrictEqual(result.type === ReconnectResultType.Replay
+				? result.actions.map(action => ({ channel: action.channel, type: action.action.type }))
+				: result.type, [
+				{ channel: sessionUri, type: ActionType.SessionTitleChanged },
+				{ channel: chatUri, type: ActionType.ChatDraftChanged },
+			]);
+		} finally {
+			revived.close();
+		}
+	});
+
+	conformanceTest(context, 'reconnected state subscriptions receive subsequent live actions', async function () {
+		const { sessionUri } = await createSession('reconnect-live');
+		const chatUri = buildDefaultChatUri(sessionUri);
+		const droppedClientId = `reconnect-live-${config.provider}`;
+		const { carried: seenThrough, revived } = await afterConnectionDrop(droppedClientId, async first => {
+			const session = await first.call<SubscribeResult>('subscribe', { channel: sessionUri });
+			const chat = await first.call<SubscribeResult>('subscribe', { channel: chatUri });
+			return Math.max(session.snapshot!.fromSeq, chat.snapshot!.fromSeq);
+		});
+
+		try {
+			await revived.call<ReconnectResult>('reconnect', {
+				channel: ROOT_STATE_URI,
+				clientId: droppedClientId,
+				lastSeenServerSeq: seenThrough,
+				subscriptions: [sessionUri, chatUri],
+			});
+			const sessionChanged = revived.waitForNotification(n =>
+				isActionNotification(n, 'session/titleChanged') && getActionEnvelope(n).channel === sessionUri,
+			);
+			const chatChanged = revived.waitForNotification(n =>
+				isActionNotification(n, 'chat/draftChanged') && getActionEnvelope(n).channel === chatUri,
+			);
+
+			context.client.dispatch({
+				channel: sessionUri,
+				clientSeq: nextClientSeq(),
+				action: { type: ActionType.SessionTitleChanged, title: 'Reconnected Live' },
+			});
+			context.client.dispatch({
+				channel: chatUri,
+				clientSeq: nextClientSeq(),
+				action: { type: ActionType.ChatDraftChanged, draft: { text: 'live', origin: { kind: MessageKind.User } } },
+			});
+
+			assert.deepStrictEqual([
+				getActionEnvelope(await sessionChanged).action.type,
+				getActionEnvelope(await chatChanged).action.type,
+			], [ActionType.SessionTitleChanged, ActionType.ChatDraftChanged]);
+		} finally {
+			revived.close();
+		}
+	});
+
 	conformanceTest(context, 'reconnect reports a subscription it cannot resume as missing', async function () {
 		const { sessionUri } = await createSession('reconnect-missing');
 		const chatUri = buildDefaultChatUri(sessionUri);
diff --git a/src/vs/platform/agentHost/test/node/e2e/suites/serverToolsSuite.ts b/src/vs/platform/agentHost/test/node/e2e/suites/serverToolsSuite.ts
index 117e3936255b7e..842631f16c3f59 100644
--- a/src/vs/platform/agentHost/test/node/e2e/suites/serverToolsSuite.ts
+++ b/src/vs/platform/agentHost/test/node/e2e/suites/serverToolsSuite.ts
@@ -25,7 +25,7 @@ import {
 	type SessionState,
 } from '../../../../common/state/sessionState.js';
 import { PROTOCOL_VERSION } from '../../../../common/state/protocol/version/registry.js';
-import { createRealSession, driveTurnToCompletion, resolveGitHubToken, textFromContent } from '../harness/agentHostE2ETestHarness.js';
+import { createRealSession, driveChatTurnToCompletion, driveTurnToCompletion, resolveGitHubToken, textFromContent } from '../harness/agentHostE2ETestHarness.js';
 import { summarizeAnthropicRequest } from '../harness/capiWireCodec.js';
 import { getActionEnvelope, isActionNotification } from '../../serverIntegrationTestHelpers.js';
 import type { IAgentHostE2ETestContext } from './e2eTestContext.js';
@@ -200,7 +200,7 @@ export function defineServerToolsTests(context: IAgentHostE2ETestContext): void
 		toolName: string,
 		options: { readonly success?: boolean; readonly result?: readonly RegExp[] } = {},
 	): Promise<{ readonly turn: Awaited<ReturnType<typeof driveTurnToCompletion>>; readonly tool: IObservedToolCall }> {
-		const turn = await driveTurnToCompletion(context.client, session.sessionUri, turnId, prompt, reserveClientSequenceBlock());
+		const turn = await driveChatTurnToCompletion(context.client, session.chatUri, turnId, prompt, reserveClientSequenceBlock());
 		const starts = context.client.receivedNotifications(n => isActionNotification(n, 'chat/toolCallStart'))
 			.map(n => ({ envelope: getActionEnvelope(n), action: getActionEnvelope(n).action as ChatToolCallStartAction }))
 			.filter(({ envelope, action }) => envelope.channel === session.chatUri && action.turnId === turnId && toolNameMatches(action.toolName, toolName));
@@ -498,6 +498,55 @@ export function defineServerToolsTests(context: IAgentHostE2ETestContext): void
 		assert.deepStrictEqual(result.sessions.find(item => item.session === archived.sessionUri)?.status?.split(',').sort(), ['archived', 'idle']);
 	});
 
+	serverToolTest('server tool: list_sessions hides archived sessions by default', async function () {
+		const session = await createSession('sessions-hide-archived');
+		const archived = await addSession('sessions-hide-archived-target', session.workspace);
+		await materializeSession(archived, 'turn-sessions-hide-archived-target', 'ARCHIVED_HIDDEN_READY');
+		await dispatchAndWait(archived.sessionUri, { type: ActionType.SessionIsArchivedChanged, isArchived: true });
+		context.client.clearReceived();
+
+		const { tool } = await driveServerTool(
+			session,
+			'turn-sessions-hide-archived',
+			`Call list_sessions exactly once with workspace "${session.workspace}", then reply exactly "listed".`,
+			SessionServerToolName.ListSessions,
+		);
+		const result = JSON.parse(tool.resultText) as { sessions: readonly { session: string }[] };
+
+		assert.deepStrictEqual({
+			includesActive: result.sessions.some(item => item.session === session.sessionUri),
+			includesArchived: result.sessions.some(item => item.session === archived.sessionUri),
+		}, {
+			includesActive: true,
+			includesArchived: false,
+		});
+	});
+
+	serverToolTest('server tool: list_sessions includeArchived returns active and archived sessions', async function () {
+		const session = await createSession('sessions-include-archived');
+		const archived = await addSession('sessions-include-archived-target', session.workspace);
+		await materializeSession(archived, 'turn-sessions-include-archived-target', 'ARCHIVED_INCLUDED_READY');
+		await dispatchAndWait(archived.sessionUri, { type: ActionType.SessionIsArchivedChanged, isArchived: true });
+		context.client.clearReceived();
+
+		const { tool } = await driveServerTool(
+			session,
+			'turn-sessions-include-archived',
+			`Call list_sessions exactly once with workspace "${session.workspace}" and includeArchived true, then reply exactly "listed".`,
+			SessionServerToolName.ListSessions,
+		);
+		const result = JSON.parse(tool.resultText) as { sessions: readonly { session: string }[] };
+		const returned = new Set(result.sessions.map(item => item.session));
+
+		assert.deepStrictEqual({
+			includesActive: returned.has(session.sessionUri),
+			includesArchived: returned.has(archived.sessionUri),
+		}, {
+			includesActive: true,
+			includesArchived: true,
+		});
+	});
+
 	serverToolTest('server tool: list_sessions status filter finds the invoking in-progress session', async function () {
 		const session = await createSession('sessions-status');
 		const { tool } = await driveServerTool(
@@ -513,6 +562,31 @@ export function defineServerToolsTests(context: IAgentHostE2ETestContext): void
 		}]);
 	});
 
+	serverToolTest('server tool: list_sessions status filter combines active and archived sessions', async function () {
+		const session = await createSession('sessions-status-combined');
+		const archived = await addSession('sessions-status-combined-target', session.workspace);
+		await materializeSession(archived, 'turn-sessions-status-combined-target', 'COMBINED_TARGET_READY');
+		await dispatchAndWait(archived.sessionUri, { type: ActionType.SessionIsArchivedChanged, isArchived: true });
+		context.client.clearReceived();
+
+		const { tool } = await driveServerTool(
+			session,
+			'turn-sessions-status-combined',
+			'Call list_sessions exactly once with status ["inProgress", "archived"], then reply exactly "filtered".',
+			SessionServerToolName.ListSessions,
+		);
+		const result = JSON.parse(tool.resultText) as { sessions: readonly { session: string }[] };
+		const returned = new Set(result.sessions.map(item => item.session));
+
+		assert.deepStrictEqual({
+			includesActive: returned.has(session.sessionUri),
+			includesArchived: returned.has(archived.sessionUri),
+		}, {
+			includesActive: true,
+			includesArchived: true,
+		});
+	});
+
 	serverToolTest('server tool: list_sessions unread filter returns the invoking unread session', async function () {
 		const session = await createSession('sessions-unread');
 		const { tool } = await driveServerTool(
@@ -540,6 +614,19 @@ export function defineServerToolsTests(context: IAgentHostE2ETestContext): void
 		assert.ok(result.sessions.some(item => item.session === session.sessionUri));
 	});
 
+	serverToolTest('server tool: list_sessions createdAfter excludes sessions before the boundary', async function () {
+		const session = await createSession('sessions-created-after-exclude');
+		const { tool } = await driveServerTool(
+			session,
+			'turn-sessions-created-after-exclude',
+			'Call list_sessions exactly once with createdAfter "2999-01-01T00:00:00Z", then reply exactly "filtered".',
+			SessionServerToolName.ListSessions,
+		);
+		const result = JSON.parse(tool.resultText) as { sessions: readonly { session: string }[] };
+
+		assert.strictEqual(result.sessions.some(item => item.session === session.sessionUri), false);
+	});
+
 	serverToolTest('server tool: list_sessions createdBefore excludes current sessions', async function () {
 		const session = await createSession('sessions-created-before');
 		const { tool } = await driveServerTool(
@@ -552,6 +639,19 @@ export function defineServerToolsTests(context: IAgentHostE2ETestContext): void
 		assert.strictEqual(result.sessions.some(item => item.session === session.sessionUri), false);
 	});
 
+	serverToolTest('server tool: list_sessions createdBefore accepts sessions before a future boundary', async function () {
+		const session = await createSession('sessions-created-before-include');
+		const { tool } = await driveServerTool(
+			session,
+			'turn-sessions-created-before-include',
+			'Call list_sessions exactly once with createdBefore "2999-01-01T00:00:00Z", then reply exactly "filtered".',
+			SessionServerToolName.ListSessions,
+		);
+		const result = JSON.parse(tool.resultText) as { sessions: readonly { session: string }[] };
+
+		assert.ok(result.sessions.some(item => item.session === session.sessionUri));
+	});
+
 	serverToolTest('server tool: create_chat defaults to the invoking session and starts its local prompt', async function () {
 		const session = await createSession('create-chat-default');
 		const before = new Set((await sessionState(session.sessionUri)).chats.map(chat => chat.resource));
@@ -609,6 +709,76 @@ export function defineServerToolsTests(context: IAgentHostE2ETestContext): void
 		});
 	});
 
+	serverToolTest('server tool: get_session_context accepts explicit summary detail', async function () {
+		const session = await createSession('context-explicit-summary', true);
+		await driveTurnToCompletion(context.client, session.sessionUri, 'turn-context-explicit-summary-seed', 'Reply exactly "SUMMARY_READY".', reserveClientSequenceBlock());
+		const { tool } = await driveServerTool(
+			session,
+			'turn-context-explicit-summary',
+			`Call get_session_context exactly once with session "${session.sessionUri}" and detail "summary", then reply exactly "read".`,
+			SessionServerToolName.GetSessionContext,
+		);
+		const result = JSON.parse(tool.resultText) as { detail: string; transcript: readonly { user?: string; assistant?: string }[] };
+
+		assert.deepStrictEqual({
+			detail: result.detail,
+			first: result.transcript[0],
+		}, {
+			detail: 'summary',
+			first: {
+				turn: 1,
+				state: 'complete',
+				user: 'Reply exactly "SUMMARY_READY".',
+				assistant: 'SUMMARY_READY',
+			},
+		});
+	});
+
+	serverToolTest('server tool: get_session_context accepts an open-session link', async function () {
+		const session = await createSession('context-link', true);
+		await driveTurnToCompletion(context.client, session.sessionUri, 'turn-context-link-seed', 'Reply exactly "LINK_READY".', reserveClientSequenceBlock());
+		const link = buildOpenSessionLinkUri(URI.parse(session.sessionUri));
+		const { tool } = await driveServerTool(
+			session,
+			'turn-context-link',
+			`Call get_session_context exactly once with session "${link}", then reply exactly "read".`,
+			SessionServerToolName.GetSessionContext,
+		);
+		const result = JSON.parse(tool.resultText) as { transcript: readonly { user?: string; assistant?: string }[] };
+
+		assert.deepStrictEqual(result.transcript[0], {
+			turn: 1,
+			state: 'complete',
+			user: 'Reply exactly "LINK_READY".',
+			assistant: 'LINK_READY',
+		});
+	});
+
+	serverToolTest('server tool: get_session_context digest includes completed response text', async function () {
+		const session = await createSession('context-digest', true);
+		await driveTurnToCompletion(context.client, session.sessionUri, 'turn-context-digest-seed', 'Reply exactly "DIGEST_READY".', reserveClientSequenceBlock());
+		const { tool } = await driveServerTool(
+			session,
+			'turn-context-digest',
+			`Call get_session_context exactly once with session "${session.sessionUri}" and detail "digest", then reply exactly "read".`,
+			SessionServerToolName.GetSessionContext,
+		);
+		const result = JSON.parse(tool.resultText) as { detail: string; transcript: readonly { user?: string; assistant?: string }[] };
+
+		assert.deepStrictEqual({
+			detail: result.detail,
+			first: result.transcript[0],
+		}, {
+			detail: 'digest',
+			first: {
+				turn: 1,
+				state: 'complete',
+				user: 'Reply exactly "DIGEST_READY".',
+				assistant: 'DIGEST_READY',
+			},
+		});
+	});
+
 	serverToolTest('server tool: get_session_context full includes prior server-tool input', async function () {
 		const session = await createSession('context-full', true);
 		await driveServerTool(
diff --git a/src/vs/platform/agentHost/test/node/e2e/suites/stateOperationsSuite.ts b/src/vs/platform/agentHost/test/node/e2e/suites/stateOperationsSuite.ts
index fb883481c6d447..50b05e209afd93 100644
--- a/src/vs/platform/agentHost/test/node/e2e/suites/stateOperationsSuite.ts
+++ b/src/vs/platform/agentHost/test/node/e2e/suites/stateOperationsSuite.ts
@@ -15,6 +15,7 @@ import type { SubscribeResult } from '../../../../common/state/protocol/commands
 import { TerminalClaimKind, type TerminalClaim } from '../../../../common/state/protocol/state.js';
 import {
 	buildDefaultChatUri,
+	MessageAttachmentKind,
 	MessageKind,
 	PendingMessageKind,
 	ROOT_STATE_URI,
@@ -149,6 +150,22 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		assert.strictEqual((await sessionState(sessionUri)).status & SessionStatus.IsArchived, 0);
 	});
 
+	conformanceTest(context, 'session read and archived flags compose independently', async function () {
+		const { sessionUri } = await createSession('status-compose');
+
+		await dispatchAndWait(sessionUri, 1, { type: ActionType.SessionIsReadChanged, isRead: true });
+		await dispatchAndWait(sessionUri, 2, { type: ActionType.SessionIsArchivedChanged, isArchived: true });
+		const state = await sessionState(sessionUri);
+
+		assert.deepStrictEqual({
+			isRead: (state.status & SessionStatus.IsRead) !== 0,
+			isArchived: (state.status & SessionStatus.IsArchived) !== 0,
+		}, {
+			isRead: true,
+			isArchived: true,
+		});
+	});
+
 	conformanceTest(context, 'session config changes merge with existing values', async function () {
 		const { sessionUri } = await createSession('config-merge');
 		const before = await sessionState(sessionUri);
@@ -178,6 +195,22 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		});
 	});
 
+	conformanceTest(context, 'empty session config replacement clears previous values', async function () {
+		const { sessionUri } = await createSession('config-clear');
+		await dispatchAndWait(sessionUri, 1, {
+			type: ActionType.SessionConfigChanged,
+			config: { [SessionConfigKey.AutoApprove]: 'assisted' },
+		});
+
+		await dispatchAndWait(sessionUri, 2, {
+			type: ActionType.SessionConfigChanged,
+			config: {},
+			replace: true,
+		});
+
+		assert.deepStrictEqual((await sessionState(sessionUri)).config?.values, {});
+	});
+
 	conformanceTest(context, 'active client set adds a session participant', async function () {
 		const { sessionUri, clientId } = await createSession('active-client-add');
 
@@ -193,6 +226,30 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		}]);
 	});
 
+	conformanceTest(context, 'active client tools retain their protocol schemas', async function () {
+		const { sessionUri, clientId } = await createSession('active-client-tools');
+		const tools = [{
+			name: 'coverage_echo',
+			description: 'Echoes a value',
+			inputSchema: {
+				type: 'object' as const,
+				properties: { value: { type: 'string' } },
+				required: ['value'],
+			},
+		}];
+
+		await dispatchAndWait(sessionUri, 1, {
+			type: ActionType.SessionActiveClientSet,
+			activeClient: { clientId, displayName: 'Tool Client', tools },
+		});
+
+		assert.deepStrictEqual((await sessionState(sessionUri)).activeClients, [{
+			clientId,
+			displayName: 'Tool Client',
+			tools,
+		}]);
+	});
+
 	conformanceTest(context, 'active client set replaces an existing participant', async function () {
 		const { sessionUri, clientId } = await createSession('active-client-update');
 		await dispatchAndWait(sessionUri, 1, {
@@ -208,6 +265,40 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		assert.deepStrictEqual((await sessionState(sessionUri)).activeClients.map(client => client.displayName), ['After']);
 	});
 
+	conformanceTest(context, 'two active clients remain independently addressable', async function () {
+		const { sessionUri, clientId } = await createSession('active-client-multiple');
+
+		await dispatchAndWait(sessionUri, 1, {
+			type: ActionType.SessionActiveClientSet,
+			activeClient: { clientId, displayName: 'First', tools: [] },
+		});
+		await dispatchAndWait(sessionUri, 2, {
+			type: ActionType.SessionActiveClientSet,
+			activeClient: { clientId: 'second-client', displayName: 'Second', tools: [] },
+		});
+
+		assert.deepStrictEqual((await sessionState(sessionUri)).activeClients.map(client => client.clientId).sort(), [
+			clientId,
+			'second-client',
+		].sort());
+	});
+
+	conformanceTest(context, 'removing one active client preserves its sibling', async function () {
+		const { sessionUri, clientId } = await createSession('active-client-remove-one');
+		await dispatchAndWait(sessionUri, 1, {
+			type: ActionType.SessionActiveClientSet,
+			activeClient: { clientId, displayName: 'First', tools: [] },
+		});
+		await dispatchAndWait(sessionUri, 2, {
+			type: ActionType.SessionActiveClientSet,
+			activeClient: { clientId: 'second-client', displayName: 'Second', tools: [] },
+		});
+
+		await dispatchAndWait(sessionUri, 3, { type: ActionType.SessionActiveClientRemoved, clientId });
+
+		assert.deepStrictEqual((await sessionState(sessionUri)).activeClients.map(client => client.clientId), ['second-client']);
+	});
+
 	conformanceTest(context, 'active client removal removes the session participant', async function () {
 		const { sessionUri, clientId } = await createSession('active-client-remove');
 		await dispatchAndWait(sessionUri, 1, {
@@ -229,6 +320,35 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		assert.deepStrictEqual((await chatState(chatUri)).draft, draft);
 	});
 
+	conformanceTest(context, 'draft change preserves resource attachments', async function () {
+		const { chatUri, workspace } = await createSession('draft-attachment');
+		const draft: Message = {
+			...userMessage('review this'),
+			attachments: [{
+				type: MessageAttachmentKind.Resource,
+				uri: URI.file(join(workspace, 'draft.ts')).toString(),
+				label: 'draft.ts',
+				displayKind: 'document',
+			}],
+		};
+
+		await dispatchAndWait(chatUri, 1, { type: ActionType.ChatDraftChanged, draft });
+
+		assert.deepStrictEqual((await chatState(chatUri)).draft, draft);
+	});
+
+	conformanceTest(context, 'draft change preserves the selected model', async function () {
+		const { chatUri } = await createSession('draft-model');
+		const draft: Message = {
+			...userMessage('model draft'),
+			model: { id: 'coverage-model' },
+		};
+
+		await dispatchAndWait(chatUri, 1, { type: ActionType.ChatDraftChanged, draft });
+
+		assert.deepStrictEqual((await chatState(chatUri)).draft, draft);
+	});
+
 	conformanceTest(context, 'draft change replaces the previous message', async function () {
 		const { chatUri } = await createSession('draft-replace');
 		await dispatchAndWait(chatUri, 1, { type: ActionType.ChatDraftChanged, draft: userMessage('before') });
@@ -358,6 +478,36 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		});
 	});
 
+	conformanceTest(context, 'successive terminal resizes retain the latest dimensions', async function () {
+		await withTerminal('terminal-resize-latest', async ({ terminalUri }) => {
+			await dispatchAndWait(terminalUri, 1, { type: ActionType.TerminalResized, cols: 100, rows: 35 });
+			await dispatchAndWait(terminalUri, 2, { type: ActionType.TerminalResized, cols: 140, rows: 50 });
+
+			const state = await terminalState(terminalUri);
+			assert.deepStrictEqual({ cols: state.cols, rows: state.rows }, { cols: 140, rows: 50 });
+		});
+	});
+
+	conformanceTest(context, 'terminal claim transfer preserves dimensions and cwd', async function () {
+		await withTerminal('terminal-claim-metadata', async ({ sessionUri, terminalUri, workspace }) => {
+			await dispatchAndWait(terminalUri, 1, {
+				type: ActionType.TerminalClaimed,
+				claim: { kind: TerminalClaimKind.Session, session: sessionUri },
+			});
+
+			const state = await terminalState(terminalUri);
+			assert.deepStrictEqual({
+				cwd: state.cwd,
+				cols: state.cols,
+				rows: state.rows,
+			}, {
+				cwd: URI.file(workspace).fsPath,
+				cols: 90,
+				rows: 30,
+			});
+		});
+	});
+
 	conformanceTest(context, 'terminal title change is broadcast', async function () {
 		await withTerminal('terminal-title', async ({ terminalUri }) => {
 			context.client.clearReceived();
@@ -383,6 +533,35 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		});
 	});
 
+	conformanceTest(context, 'terminal claim can transfer back to the client', async function () {
+		await withTerminal('terminal-claim-return', async ({ sessionUri, terminalUri, clientId }) => {
+			await dispatchAndWait(terminalUri, 1, {
+				type: ActionType.TerminalClaimed,
+				claim: { kind: TerminalClaimKind.Session, session: sessionUri },
+			});
+			const clientClaim: TerminalClaim = { kind: TerminalClaimKind.Client, clientId };
+
+			await dispatchAndWait(terminalUri, 2, { type: ActionType.TerminalClaimed, claim: clientClaim });
+
+			assert.deepStrictEqual((await terminalState(terminalUri)).claim, clientClaim);
+		});
+	});
+
+	conformanceTest(context, 'session terminal claims preserve turn and tool identifiers', async function () {
+		await withTerminal('terminal-session-claim', async ({ sessionUri, terminalUri }) => {
+			const claim: TerminalClaim = {
+				kind: TerminalClaimKind.Session,
+				session: sessionUri,
+				turnId: 'turn-claim',
+				toolCallId: 'tool-claim',
+			};
+
+			await dispatchAndWait(terminalUri, 1, { type: ActionType.TerminalClaimed, claim });
+
+			assert.deepStrictEqual((await terminalState(terminalUri)).claim, claim);
+		});
+	});
+
 	conformanceTest(context, 'terminal input reaches the shell and produces output', async function () {
 		await withTerminal('terminal-input', async ({ terminalUri }) => {
 			context.client.clearReceived();
@@ -405,6 +584,27 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		});
 	});
 
+	conformanceTest(context, 'terminal input preserves Unicode output', async function () {
+		await withTerminal('terminal-unicode', async ({ terminalUri }) => {
+			context.client.clearReceived();
+			context.client.dispatch({
+				channel: terminalUri,
+				clientSeq: 1,
+				action: { type: ActionType.TerminalInput, data: 'node -e "console.log(\'SNOWMAN_\'+String.fromCodePoint(0x2603))"\r' },
+			});
+			let streamedOutput = '';
+			await context.client.waitForNotification(n => {
+				if (!isActionNotification(n, 'terminal/data') || getActionEnvelope(n).channel !== terminalUri) {
+					return false;
+				}
+				streamedOutput += (getActionEnvelope(n).action as { data: string }).data;
+				return streamedOutput.includes('SNOWMAN_\u2603');
+			}, 30_000);
+
+			assert.match(terminalText(await terminalState(terminalUri)), /SNOWMAN_\u2603/);
+		});
+	});
+
 	conformanceTest(context, 'clearing a terminal drops the scrollback the client already saw', async function () {
 		await withTerminal('terminal-clear', async ({ terminalUri }) => {
 			context.client.clearReceived();
@@ -444,6 +644,25 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		});
 	});
 
+	conformanceTest(context, 'clearing a terminal preserves dimensions and claim', async function () {
+		await withTerminal('terminal-clear-metadata', async ({ terminalUri, clientId }) => {
+			await dispatchAndWait(terminalUri, 1, { type: ActionType.TerminalResized, cols: 111, rows: 37 });
+
+			await dispatchAndWait(terminalUri, 2, { type: ActionType.TerminalCleared });
+
+			const state = await terminalState(terminalUri);
+			assert.deepStrictEqual({
+				cols: state.cols,
+				rows: state.rows,
+				claim: state.claim,
+			}, {
+				cols: 111,
+				rows: 37,
+				claim: { kind: TerminalClaimKind.Client, clientId },
+			});
+		});
+	});
+
 	conformanceTest(context, 'a terminal whose shell exits reports its exit code', async function () {
 		await withTerminal('terminal-exit', async ({ terminalUri }) => {
 			context.client.clearReceived();
@@ -517,6 +736,84 @@ export function defineStateOperationsTests(context: IAgentHostE2ETestContext): v
 		});
 	});
 
+	conformanceTest(context, 'root terminal metadata reflects title changes', async function () {
+		await withTerminal('terminal-root-title', async ({ terminalUri }) => {
+			await context.client.call<SubscribeResult>('subscribe', { channel: ROOT_STATE_URI });
+			context.client.clearReceived();
+			context.client.dispatch({
+				channel: terminalUri,
+				clientSeq: 1,
+				action: { type: ActionType.TerminalTitleChanged, title: 'Root Metadata Title' },
+			});
+
+			const changed = await context.client.waitForNotification(n => {
+				if (!isActionNotification(n, 'root/terminalsChanged')) {
+					return false;
+				}
+				const terminals = (getActionEnvelope(n).action as { terminals?: readonly { resource: string; title: string }[] }).terminals;
+				return terminals?.some(terminal => terminal.resource === terminalUri && terminal.title === 'Root Metadata Title') ?? false;
+			});
+
+			assert.ok(isActionNotification(changed, 'root/terminalsChanged'));
+		});
+	});
+
+	conformanceTest(context, 'root terminal metadata reflects claim transfers', async function () {
+		await withTerminal('terminal-root-claim', async ({ sessionUri, terminalUri }) => {
+			await context.client.call<SubscribeResult>('subscribe', { channel: ROOT_STATE_URI });
+			const claim: TerminalClaim = { kind: TerminalClaimKind.Session, session: sessionUri, turnId: 'turn-root-claim' };
+			context.client.clearReceived();
+			context.client.dispatch({
+				channel: terminalUri,
+				clientSeq: 1,
+				action: { type: ActionType.TerminalClaimed, claim },
+			});
+
+			const changed = await context.client.waitForNotification(n => {
+				if (!isActionNotification(n, 'root/terminalsChanged')) {
+					return false;
+				}
+				const terminals = (getActionEnvelope(n).action as { terminals?: readonly { resource: string; claim: TerminalClaim }[] }).terminals;
+				return terminals?.some(terminal =>
+					terminal.resource === terminalUri
+					&& terminal.claim.kind === TerminalClaimKind.Session
+					&& terminal.claim.session === claim.session
+					&& terminal.claim.turnId === claim.turnId,
+				) ?? false;
+			});
+
+			assert.ok(isActionNotification(changed, 'root/terminalsChanged'));
+		});
+	});
+
+	conformanceTest(context, 'an exited terminal remains discoverable with its exit code until disposal', async function () {
+		await withTerminal('terminal-root-exit', async ({ terminalUri }) => {
+			context.client.clearReceived();
+			context.client.dispatch({
+				channel: terminalUri,
+				clientSeq: 1,
+				action: { type: ActionType.TerminalInput, data: 'exit\r' },
+			});
+			const exited = await context.client.waitForNotification(n =>
+				isActionNotification(n, 'terminal/exited') && getActionEnvelope(n).channel === terminalUri,
+				30_000,
+			);
+			const exitCode = (getActionEnvelope(exited).action as { exitCode?: number }).exitCode;
+
+			const root = await context.client.call<SubscribeResult>('subscribe', { channel: ROOT_STATE_URI });
+			const terminal = (root.snapshot!.state as RootState).terminals?.find(terminal => terminal.resource === terminalUri);
+			assert.deepStrictEqual({
+				listed: terminal !== undefined,
+				reportedExitCode: typeof exitCode,
+				stateMatchesNotification: terminal?.exitCode === exitCode,
+			}, {
+				listed: true,
+				reportedExitCode: 'number',
+				stateMatchesNotification: true,
+			});
+		});
+	});
+
 	conformanceTest(context, 'disposeTerminal removes the terminal from root state', async function () {
 		const { terminalUri } = await createTerminal('terminal-dispose');
 
diff --git a/src/vs/platform/agentHost/test/node/historyRecordFixtures.test.ts b/src/vs/platform/agentHost/test/node/historyRecordFixtures.test.ts
index c2fd8cb7ed9a3d..0ceacf275c24e5 100644
--- a/src/vs/platform/agentHost/test/node/historyRecordFixtures.test.ts
+++ b/src/vs/platform/agentHost/test/node/historyRecordFixtures.test.ts
@@ -8,11 +8,11 @@ import { DisposableStore } from '../../../../base/common/lifecycle.js';
 import { URI } from '../../../../base/common/uri.js';
 import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../base/test/common/utils.js';
 import { AgentSession } from '../../common/agent.js';
-import { FileEditKind, MessageKind, ResponsePartKind, ToolResultContentType } from '../../common/state/sessionState.js';
+import { FileEditKind, MessageKind, ResponsePartKind, ToolResultContentType, buildChatUri } from '../../common/state/sessionState.js';
 import { SessionDatabase } from '../../node/sessionDatabase.js';
 import { parseSessionDbUri } from '../../common/sessionDbUri.js';
 import { mapSessionEventsToHistoryRecords } from './historyRecordFixtures.js';
-import { mapSessionEvents } from '../../node/copilot/mapSessionEvents.js';
+import { mapSessionEvents as mapSessionEventsWithRouting } from '../../node/copilot/mapSessionEvents.js';
 import { toSessionEvents, type ISessionEvent } from './copilotTestEvents.js';
 
 suite('mapSessionEventsToHistoryRecords', () => {
@@ -21,6 +21,10 @@ suite('mapSessionEventsToHistoryRecords', () => {
 	let db: SessionDatabase | undefined;
 	const session = AgentSession.uri('copilot', 'test-session');
 
+	function mapSessionEvents(session: URI, db: undefined, events: Parameters<typeof mapSessionEventsWithRouting>[2]) {
+		return mapSessionEventsWithRouting(session, db, events, URI.parse(buildChatUri(session, 'default')));
+	}
+
 	teardown(async () => {
 		disposables.clear();
 		await db?.close();
diff --git a/src/vs/platform/agentHost/test/node/mapSessionEvents.perf.test.ts b/src/vs/platform/agentHost/test/node/mapSessionEvents.perf.test.ts
index e81a0c9db4133d..b5190129134389 100644
--- a/src/vs/platform/agentHost/test/node/mapSessionEvents.perf.test.ts
+++ b/src/vs/platform/agentHost/test/node/mapSessionEvents.perf.test.ts
@@ -7,8 +7,10 @@ import assert from 'assert';
 import type { SessionEvent } from '@github/copilot-sdk';
 import { readFileSync } from 'fs';
 import { StopWatch } from '../../../../base/common/stopwatch.js';
+import { URI } from '../../../../base/common/uri.js';
 import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../base/test/common/utils.js';
 import { AgentSession } from '../../common/agent.js';
+import { buildChatUri } from '../../common/state/sessionState.js';
 import { mapSessionEvents } from '../../node/copilot/mapSessionEvents.js';
 
 interface BenchmarkResult {
@@ -66,7 +68,8 @@ async function runBenchmarkRound(path: string): Promise<BenchmarkResult> {
 	const parseMs = parse.elapsed();
 
 	const map = StopWatch.create();
-	const restored = await mapSessionEvents(AgentSession.uri('copilot', 'event-restoration-benchmark'), undefined, events);
+	const session = AgentSession.uri('copilot', 'event-restoration-benchmark');
+	const restored = await mapSessionEvents(session, undefined, events, URI.parse(buildChatUri(session, 'default')));
 	const mapMs = map.elapsed();
 
 	const serialize = StopWatch.create();
diff --git a/src/vs/platform/agentHost/test/node/mapSessionEvents.test.ts b/src/vs/platform/agentHost/test/node/mapSessionEvents.test.ts
index f71b5274c54ce0..121c976b296595 100644
--- a/src/vs/platform/agentHost/test/node/mapSessionEvents.test.ts
+++ b/src/vs/platform/agentHost/test/node/mapSessionEvents.test.ts
@@ -8,10 +8,14 @@ import { URI } from '../../../../base/common/uri.js';
 import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../base/test/common/utils.js';
 import { readToolCallMeta } from '../../common/meta/agentToolCallMeta.js';
 import { AgentSession } from '../../common/agent.js';
-import { MessageAttachmentKind, MessageKind, ResponsePartKind, ToolCallContributorKind, ToolCallStatus, ToolResultContentType, TurnState, type ResponsePart, type StringOrMarkdown, type ToolCallResponsePart, type ToolResultContent } from '../../common/state/sessionState.js';
-import { appendSdkToolResultContent, mapSessionEvents } from '../../node/copilot/mapSessionEvents.js';
+import { MessageAttachmentKind, MessageKind, ResponsePartKind, ToolCallContributorKind, ToolCallStatus, ToolResultContentType, TurnState, buildChatUri, type ResponsePart, type StringOrMarkdown, type ToolCallResponsePart, type ToolResultContent } from '../../common/state/sessionState.js';
+import { appendSdkToolResultContent, mapSessionEvents as mapSessionEventsWithRouting, type IMapSessionEventsOptions } from '../../node/copilot/mapSessionEvents.js';
 import { toSessionEvents, type ISessionEvent } from './copilotTestEvents.js';
 
+function mapSessionEvents(session: URI, db: undefined, events: Parameters<typeof mapSessionEventsWithRouting>[2], options: IMapSessionEventsOptions | undefined = undefined) {
+	return mapSessionEventsWithRouting(session, db, events, URI.parse(buildChatUri(session, 'default')), options);
+}
+
 suite('mapSessionEvents — history replay', () => {
 
 	ensureNoDisposablesAreLeakedInTestSuite();
@@ -141,7 +145,7 @@ suite('mapSessionEvents — history replay', () => {
 			{ type: 'tool.execution_complete', data: { toolCallId: 'tc-1', success: true } },
 		];
 
-		const { turns } = await mapSessionEvents(session, undefined, toSessionEvents(events), URI.file('/workspace'));
+		const { turns } = await mapSessionEvents(session, undefined, toSessionEvents(events), { workingDirectory: URI.file('/workspace') });
 		const part = turns[0].responseParts.find(part => part.kind === ResponsePartKind.ToolCall) as ToolCallResponsePart | undefined;
 		assert.ok(part);
 		assert.deepStrictEqual({
@@ -198,7 +202,9 @@ suite('mapSessionEvents — history replay', () => {
 			},
 		];
 
-		const { turns } = await mapSessionEvents(session, undefined, toSessionEvents(events));
+		const chatUri = URI.parse(buildChatUri(session, 'restored-chat'));
+		const sdkConversationUri = URI.parse('copilot-sdk:/conversation-123');
+		const { turns } = await mapSessionEventsWithRouting(sdkConversationUri, undefined, toSessionEvents(events), chatUri);
 
 		const part = turns[0].responseParts[0] as ToolCallResponsePart;
 		assert.strictEqual(part.kind, ResponsePartKind.ToolCall);
@@ -215,7 +221,7 @@ suite('mapSessionEvents — history replay', () => {
 				mcpToolName: 'get_me',
 				ui: {
 					resourceUri: 'ui://github-mcp-server/get-me',
-					channel: 'mcp://copilot/test-session/GitHub',
+					channel: `mcp://copilot/${encodeURIComponent(chatUri.toString())}/GitHub`,
 				},
 			},
 		});
diff --git a/src/vs/platform/agentHost/test/node/shared/mcpCustomizationController.test.ts b/src/vs/platform/agentHost/test/node/shared/mcpCustomizationController.test.ts
index 92a2f4ae9c43cc..c56cf43c924a4b 100644
--- a/src/vs/platform/agentHost/test/node/shared/mcpCustomizationController.test.ts
+++ b/src/vs/platform/agentHost/test/node/shared/mcpCustomizationController.test.ts
@@ -5,15 +5,22 @@
 
 import assert from 'assert';
 import { DisposableStore } from '../../../../../base/common/lifecycle.js';
+import { URI } from '../../../../../base/common/uri.js';
 import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../base/test/common/utils.js';
 import { NullLogService } from '../../../../../platform/log/common/log.js';
 import { AgentSession } from '../../../common/agent.js';
 import { isCustomizationEnabled } from '../../../common/customizationEnablement.js';
 import { ActionType } from '../../../common/state/protocol/common/actions.js';
 import { CustomizationEnablementKind, CustomizationType, McpAuthRequiredReason, McpServerStatus, SessionStatus, type Customization, type CustomizationEnablement, type McpServerCustomization, type McpServerState, type PluginCustomization } from '../../../common/state/protocol/channels-session/state.js';
+import { buildChatUri } from '../../../common/state/sessionState.js';
 import type { SessionAction } from '../../../common/state/sessionActions.js';
 import { AgentHostStateManager } from '../../../node/agentHostStateManager.js';
-import { getEffectiveMcpServerCustomizations, McpCustomizationController, findMcpChildId, findMcpServerName, parseMcpChannelUri, type ISdkMcpServer } from '../../../node/shared/mcpCustomizationController.js';
+import { buildMcpChannel, getEffectiveMcpServerCustomizations, McpCustomizationController, findMcpChildId, findMcpServerName, parseMcpChannelUri, type ISdkMcpServer } from '../../../node/shared/mcpCustomizationController.js';
+
+const SESSION_URI = AgentSession.uri('copilot', 'session-1');
+const CHAT_URI = URI.parse(buildChatUri(SESSION_URI, 'chat-1'));
+const MCP_FS_CHANNEL = buildMcpChannel(CHAT_URI, 'fs');
+const MCP_SEARCH_CHANNEL = buildMcpChannel(CHAT_URI, 'search');
 
 function harness(store: Pick<DisposableStore, 'add'>, opts: {
 	customizations?: readonly Customization[];
@@ -23,7 +30,7 @@ function harness(store: Pick<DisposableStore, 'add'>, opts: {
 } = {}) {
 	const actions: SessionAction[] = [];
 	const stateManager = store.add(new AgentHostStateManager(new NullLogService()));
-	const sessionUri = AgentSession.uri('copilot', 'session-1');
+	const sessionUri = SESSION_URI;
 	const session = sessionUri.toString();
 	stateManager.createSession({
 		resource: session,
@@ -47,9 +54,7 @@ function harness(store: Pick<DisposableStore, 'add'>, opts: {
 		});
 	}
 	const controller = new McpCustomizationController({
-		providerId: 'copilot',
-		sessionId: 'session-1',
-		sessionUri,
+		chatUri: CHAT_URI,
 		emit: a => actions.push(a),
 		pluginMcpServerSources: opts.pluginMcpServerSources,
 		resolveEnablement: opts.resolveEnablement,
@@ -124,7 +129,7 @@ suite('McpCustomizationController', () => {
 				type: ActionType.SessionMcpServerStateChanged,
 				id: 'mcp-child:demo:fs',
 				state: { kind: McpServerStatus.Ready },
-				channel: 'mcp://copilot/session-1/fs',
+				channel: MCP_FS_CHANNEL,
 			},
 			{
 				type: ActionType.SessionMcpServerStateChanged,
@@ -136,7 +141,7 @@ suite('McpCustomizationController', () => {
 				type: ActionType.SessionMcpServerStateChanged,
 				id: 'mcp-child:demo:fs',
 				state: { kind: McpServerStatus.Ready },
-				channel: 'mcp://copilot/session-1/fs',
+				channel: MCP_FS_CHANNEL,
 			},
 		]);
 		assert.deepStrictEqual(controller.topLevelCustomizations(), []);
@@ -158,7 +163,7 @@ suite('McpCustomizationController', () => {
 					uri: expectedId,
 					name: 'search',
 					state: { kind: McpServerStatus.Ready },
-					channel: 'mcp://copilot/session-1/search',
+					channel: MCP_SEARCH_CHANNEL,
 					mcpApp: { capabilities: { serverTools: { listChanged: true }, serverResources: {}, sampling: {} } },
 				},
 			},
@@ -170,7 +175,7 @@ suite('McpCustomizationController', () => {
 				uri: expectedId,
 				name: 'search',
 				state: { kind: McpServerStatus.Ready },
-				channel: 'mcp://copilot/session-1/search',
+				channel: MCP_SEARCH_CHANNEL,
 				mcpApp: { capabilities: { serverTools: { listChanged: true }, serverResources: {}, sampling: {} } },
 			},
 		]);
@@ -278,7 +283,7 @@ suite('McpCustomizationController', () => {
 				type: ActionType.SessionMcpServerStateChanged,
 				id: 'mcp-child:demo:fs',
 				state: { kind: McpServerStatus.Ready },
-				channel: 'mcp://copilot/session-1/fs',
+				channel: MCP_FS_CHANNEL,
 			},
 			{
 				type: ActionType.SessionMcpServerStateChanged,
@@ -296,7 +301,7 @@ suite('McpCustomizationController', () => {
 		controller.applyOne(server('search', starting()));
 
 		assert.deepStrictEqual(controller.runtimeStates.get(), new Map([
-			['mcp-child:demo:fs', { state: { kind: McpServerStatus.Ready }, channel: 'mcp://copilot/session-1/fs' }],
+			['mcp-child:demo:fs', { state: { kind: McpServerStatus.Ready }, channel: MCP_FS_CHANNEL }],
 			['mcp-top-level:copilot:session-1:search', { state: { kind: McpServerStatus.Starting }, channel: undefined }],
 		]));
 		assert.strictEqual(controller.serverNameForCustomizationId('mcp-child:demo:fs'), 'fs');
@@ -395,25 +400,26 @@ suite('McpCustomizationController', () => {
 				type: ActionType.SessionMcpServerStateChanged,
 				id: 'mcp-child:demo:fs',
 				state: { kind: McpServerStatus.Ready },
-				channel: 'mcp://copilot/session-1/fs',
+				channel: MCP_FS_CHANNEL,
 			},
 		]);
 	});
 
 	test('parseMcpChannelUri round-trips the controller-minted channel URI', () => {
-		const channel = 'mcp://copilot/session-1/fs';
-		assert.deepStrictEqual(parseMcpChannelUri(channel), {
+		const route = parseMcpChannelUri(MCP_FS_CHANNEL);
+		assert.deepStrictEqual(route && { ...route, chatUri: route.chatUri.toString() }, {
 			providerId: 'copilot',
-			sessionId: 'session-1',
+			chatUri: CHAT_URI.toString(),
 			serverName: 'fs',
 		});
 	});
 
 	test('parseMcpChannelUri decodes URL-encoded path segments', () => {
-		const channel = 'mcp://copilot/session%2F1/my%20server';
-		assert.deepStrictEqual(parseMcpChannelUri(channel), {
+		const chatUri = URI.parse(buildChatUri(AgentSession.uri('copilot', 'session/1'), 'chat with spaces'));
+		const route = parseMcpChannelUri(buildMcpChannel(chatUri, 'my server'));
+		assert.deepStrictEqual(route && { ...route, chatUri: route.chatUri.toString() }, {
 			providerId: 'copilot',
-			sessionId: 'session/1',
+			chatUri: chatUri.toString(),
 			serverName: 'my server',
 		});
 	});
@@ -424,6 +430,7 @@ suite('McpCustomizationController', () => {
 		assert.strictEqual(parseMcpChannelUri('mcp:///session/server'), undefined);
 		assert.strictEqual(parseMcpChannelUri('mcp://copilot/session-only'), undefined);
 		assert.strictEqual(parseMcpChannelUri('mcp://copilot/session/'), undefined);
+		assert.strictEqual(parseMcpChannelUri(MCP_FS_CHANNEL.replace('mcp://copilot/', 'mcp://codex/')), undefined);
 		// Bad percent escapes must not throw — caller turns undefined
 		// into a clean Method not found, not an internal error.
 		assert.strictEqual(parseMcpChannelUri('mcp://copilot/bad%/server'), undefined);