diff --git a/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts b/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
index 677ee37a3bc..c84dfdf5c1b 100644
--- a/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
+++ b/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
@@ -700,6 +700,7 @@ export class CopilotAgentSession extends Disposable {
 	private readonly _parentToolCallIdsByAgentId = new Map<string, string>();
 	/** Maps SDK root-agent turn ids to their owning host protocol turn ids. */
 	private readonly _hostTurnIdsBySdkTurnId = new Map<string, string>();
+	private _activeRootSdkTurnId: string | undefined;
 	private readonly _activeSubagentAgentIds = new Set<string>();
 	private readonly _unroutableSubagentToolCallIds = new Set<string>();
 	private readonly _autoApprovals = new Map<string, PermissionAutoApproval | null>();
@@ -1163,6 +1164,9 @@ export class CopilotAgentSession extends Disposable {
 			turn.messageCharLen = steering.message.text.length;
 			turn.markRunning();
 		}
+		if (this._activeRootSdkTurnId) {
+			this._hostTurnIdsBySdkTurnId.set(this._activeRootSdkTurnId, newTurnId);
+		}
 		return newTurnId;
 	}
 
@@ -5562,7 +5566,9 @@ export class CopilotAgentSession extends Disposable {
 		this._register(wrapper.onTurnStart(e => {
 			this._currentTurn.value?.markRunning();
 			this._logService.trace(`[Copilot:${sessionId}] Turn started: ${e.data.turnId}`);
+			this._resumeSubagentForEvent(e);
 			if (!e.agentId) {
+				this._activeRootSdkTurnId = e.data.turnId;
 				if (this._currentTurn.value) {
 					this._hostTurnIdsBySdkTurnId.set(e.data.turnId, this._currentTurn.value.id);
 				}
@@ -5605,6 +5611,9 @@ export class CopilotAgentSession extends Disposable {
 
 		this._register(wrapper.onTurnEnd(e => {
 			this._logService.trace(`[Copilot:${sessionId}] Turn ended: ${e.data.turnId}`);
+			if (!e.agentId && this._activeRootSdkTurnId === e.data.turnId) {
+				this._activeRootSdkTurnId = undefined;
+			}
 		}));
 
 		this._register(wrapper.onAbort(e => {
diff --git a/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts b/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
index 0d84d283e00..20c9e3b3184 100644
--- a/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
+++ b/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
@@ -5005,6 +5005,35 @@ suite('CopilotAgentSession', () => {
 			assert.strictEqual(steeringCompletions.length, 0, 'an aborted steering turn must not be completed');
 		});
 
+		test('maps model-call lifecycle events to a promoted steering turn', async () => {
+			const { session, mockSession, signals } = await createAgentSession(disposables);
+			session.resetTurnState('turn-original');
+			mockSession.fire('assistant.turn_start', { turnId: 'sdk-0' } as SessionEventPayload<'assistant.turn_start'>['data']);
+
+			await session.sendSteering({ id: 'steer-1', message: { text: 'focus on tests', origin: { kind: MessageKind.User } } });
+			mockSession.fire('user.message', {
+				content: 'focus on tests',
+				interactionId: 'interaction-steer',
+			} as SessionEventPayload<'user.message'>['data']);
+			const steeringTurnId = getActions(signals).find(a => a.type === ActionType.ChatTurnStarted)?.turnId;
+			assert.ok(steeringTurnId);
+
+			mockSession.fireRaw({
+				type: 'model.call_finished',
+				ephemeral: true,
+				id: 'model-call-steering',
+				data: {
+					turnId: 'sdk-0',
+					dispatchDurationMs: 250,
+					outcome: 'success',
+					containsBuiltInFileEditRequest: true,
+					editClassifierVersion: 1,
+				},
+			});
+
+			assert.strictEqual(signals.find(signal => signal.kind === 'model_call_finished')?.turnId, steeringTurnId);
+		});
+
 		test('does not signal cleanup when send fails', async () => {
 			const { session, mockSession, signals } = await createAgentSession(disposables);
 
@@ -5308,6 +5337,47 @@ suite('CopilotAgentSession', () => {
 			}]);
 		});
 
+		test('resumes a subagent on turn start before mapping model.call_finished', async () => {
+			const { session, mockSession, signals } = await createAgentSession(disposables);
+			session.resetTurnState('host-turn-1');
+			mockSession.fire('subagent.started', {
+				toolCallId: 'subagent-tool-call',
+				agentName: 'helper',
+				agentDisplayName: 'Helper',
+				agentDescription: 'Helps',
+			} as SessionEventPayload<'subagent.started'>['data'], { agentId: 'agent-1' });
+			mockSession.fire('subagent.completed', {
+				toolCallId: 'subagent-tool-call',
+				agentName: 'helper',
+				agentDisplayName: 'Helper',
+				durationMs: 1,
+				totalTokens: 0,
+				totalToolCalls: 0,
+			} as SessionEventPayload<'subagent.completed'>['data'], { agentId: 'agent-1' });
+
+			mockSession.fire('assistant.turn_start', { turnId: 'sdk-subagent-turn' }, { agentId: 'agent-1' });
+			mockSession.fireRaw({
+				type: 'model.call_finished',
+				ephemeral: true,
+				id: 'subagent-model-call',
+				agentId: 'agent-1',
+				data: {
+					turnId: 'sdk-subagent-turn',
+					dispatchDurationMs: 125,
+					outcome: 'error',
+					editClassifierVersion: 1,
+				},
+			});
+
+			assert.deepStrictEqual(signals.filter(signal => signal.kind === 'subagent_resumed' || signal.kind === 'model_call_finished').map(signal => ({
+				kind: signal.kind,
+				parentToolCallId: signal.kind === 'model_call_finished' ? signal.parentToolCallId : signal.toolCallId,
+			})), [
+				{ kind: 'subagent_resumed', parentToolCallId: 'subagent-tool-call' },
+				{ kind: 'model_call_finished', parentToolCallId: 'subagent-tool-call' },
+			]);
+		});
+
 		test('tool_start event is mapped for non-hidden tools', async () => {
 			const { mockSession, signals } = await createAgentSession(disposables);
 			mockSession.fire('tool.execution_start', {