diff --git a/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts b/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
index 038485bda79a1..d7b3effeb5126 100644
--- a/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
+++ b/src/vs/platform/agentHost/node/copilot/copilotAgentSession.ts
@@ -3990,6 +3990,20 @@ export class CopilotAgentSession extends Disposable {
 
 		this._register(wrapper.onToolPartialResult(e => {
 			this._logService.trace(`[Copilot:${sessionId}] Tool partial result: ${e.data.toolCallId} (${e.data.partialOutput.length} chars)`);
+			const tracked = this._activeToolCalls.get(e.data.toolCallId);
+			if (!tracked || !isShellTool(tracked.toolName)) {
+				return;
+			}
+			// TODO: Use terminal-specific AHP content once live shell output is modeled separately from terminalComplete.preview.
+			this._emitAction({
+				type: ActionType.ChatToolCallContentChanged,
+				turnId: this._turnId,
+				toolCallId: e.data.toolCallId,
+				content: [
+					...tracked.content.filter(content => content.type !== ToolResultContentType.Text),
+					{ type: ToolResultContentType.Text, text: e.data.partialOutput },
+				],
+			}, tracked.parentToolCallId);
 		}));
 
 		this._register(wrapper.onToolProgress(e => {
diff --git a/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts b/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
index 2e2e222eb7bbd..ce918cbcac958 100644
--- a/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
+++ b/src/vs/platform/agentHost/test/node/copilotAgentSession.test.ts
@@ -2867,6 +2867,82 @@ suite('CopilotAgentSession', () => {
 			assert.strictEqual((toolStart.action as ChatToolCallStartAction).intention, 'List files in the repo root');
 		});
 
+		test('tool partial results stream cumulative output as running content', async () => {
+			const { session, mockSession, signals, waitForSignal } = await createAgentSession(disposables);
+			session.resetTurnState('turn-stream');
+
+			mockSession.fire('tool.execution_start', {
+				toolCallId: 'tc-stream',
+				toolName: 'bash',
+				arguments: { command: 'print ticks', description: 'Print ticks' },
+			} as SessionEventPayload<'tool.execution_start'>['data']);
+			mockSession.fire('tool.execution_partial_result', {
+				toolCallId: 'tc-stream',
+				partialOutput: 'tick 1\n',
+			} as SessionEventPayload<'tool.execution_partial_result'>['data']);
+			mockSession.fire('tool.execution_partial_result', {
+				toolCallId: 'tc-stream',
+				partialOutput: 'tick 1\ntick 2\n',
+			} as SessionEventPayload<'tool.execution_partial_result'>['data']);
+			mockSession.fire('tool.execution_complete', {
+				toolCallId: 'tc-stream',
+				success: true,
+				result: { content: 'tick 1\ntick 2\n' },
+			} as SessionEventPayload<'tool.execution_complete'>['data']);
+			await waitForSignal(signal => isAction(signal, ActionType.ChatToolCallComplete));
+
+			assert.deepStrictEqual(getActions(signals)
+				.filter(action => action.type === ActionType.ChatToolCallContentChanged)
+				.map(action => ({
+					turnId: action.turnId,
+					toolCallId: action.toolCallId,
+					content: action.content,
+				})), [
+				{
+					turnId: 'turn-stream',
+					toolCallId: 'tc-stream',
+					content: [{ type: ToolResultContentType.Text, text: 'tick 1\n' }],
+				},
+				{
+					turnId: 'turn-stream',
+					toolCallId: 'tc-stream',
+					content: [{ type: ToolResultContentType.Text, text: 'tick 1\ntick 2\n' }],
+				},
+			]);
+			const completed = getActions(signals).find(action => action.type === ActionType.ChatToolCallComplete) as ChatToolCallCompleteAction;
+			assert.deepStrictEqual(completed.result.content, [
+				{ type: ToolResultContentType.Text, text: 'tick 1\ntick 2\n' },
+			]);
+		});
+
+		test('tool partial results for untracked tools are ignored', async () => {
+			const { mockSession, signals } = await createAgentSession(disposables);
+
+			mockSession.fire('tool.execution_partial_result', {
+				toolCallId: 'tc-untracked',
+				partialOutput: 'orphaned output',
+			} as SessionEventPayload<'tool.execution_partial_result'>['data']);
+
+			assert.deepStrictEqual(getActions(signals), []);
+		});
+
+		test('tool partial results for tracked non-shell tools are ignored', async () => {
+			const { mockSession, signals } = await createAgentSession(disposables);
+
+			mockSession.fire('tool.execution_start', {
+				toolCallId: 'tc-non-shell',
+				toolName: 'grep',
+				arguments: { pattern: 'needle' },
+			} as SessionEventPayload<'tool.execution_start'>['data']);
+			mockSession.fire('tool.execution_partial_result', {
+				toolCallId: 'tc-non-shell',
+				partialOutput: 'unexpected partial output',
+			} as SessionEventPayload<'tool.execution_partial_result'>['data']);
+
+			assert.deepStrictEqual(getActions(signals)
+				.filter(action => action.type === ActionType.ChatToolCallContentChanged), []);
+		});
+
 		test('live tool_start strips redundant cd prefix matching workingDirectory', async () => {
 			const wd = URI.file('/repo/project');
 			const { mockSession, signals } = await createAgentSession(disposables, { workingDirectory: wd });