feat: show root orchestration cost tally for subtasks

When viewing a subtask spawned by an orchestrator, the TaskHeader now
displays the full orchestration cost (aggregated across all tasks in the
orchestration) alongside the current task cost. This gives users
visibility into total spend without having to navigate back to the
parent task.

Addresses #11928

webview-ui/src/components/chat/ChatView.tsx

@@ -505,7 +505,15 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
 				text: currentTaskItem.id,
 			})
 		}
-	}, [taskTs, currentTaskItem?.id, currentTaskItem?.childIds])
+		// When viewing a subtask, also request aggregated costs for the root orchestration task
+		const rootId = currentTaskItem?.rootTaskId
+		if (taskTs && rootId && rootId !== currentTaskItem?.id) {
+			vscode.postMessage({
+				type: "getTaskWithAggregatedCosts",
+				text: rootId,
+			})
+		}
+	}, [taskTs, currentTaskItem?.id, currentTaskItem?.childIds, currentTaskItem?.rootTaskId])
 
 	useEffect(() => {
 		if (isHidden) {
@@ -1563,6 +1571,13 @@ const ChatViewComponent: React.ForwardRefRenderFunction<ChatViewRef, ChatViewPro
 							)
 						}
 						parentTaskId={currentTaskItem?.parentTaskId}
+						rootOrchestrationCost={
+							currentTaskItem?.rootTaskId &&
+							currentTaskItem.rootTaskId !== currentTaskItem.id &&
+							aggregatedCostsMap.has(currentTaskItem.rootTaskId)
+								? aggregatedCostsMap.get(currentTaskItem.rootTaskId)!.totalCost
+								: undefined
+						}
 						costBreakdown={
 							currentTaskItem?.id && aggregatedCostsMap.has(currentTaskItem.id)
 								? getCostBreakdownIfNeeded(aggregatedCostsMap.get(currentTaskItem.id)!, {

webview-ui/src/components/chat/TaskHeader.tsx

@@ -36,6 +36,7 @@ export interface TaskHeaderProps {
 	aggregatedCost?: number
 	hasSubtasks?: boolean
 	parentTaskId?: string
+	rootOrchestrationCost?: number
 	costBreakdown?: string
 	contextTokens: number
 	buttonsDisabled: boolean
@@ -53,6 +54,7 @@ const TaskHeader = ({
 	aggregatedCost,
 	hasSubtasks,
 	parentTaskId,
+	rootOrchestrationCost,
 	costBreakdown,
 	contextTokens,
 	buttonsDisabled,
@@ -315,6 +317,25 @@ const TaskHeader = ({
 									</StandardTooltip>
 								</>
 							)}
+							{typeof rootOrchestrationCost === "number" && rootOrchestrationCost > 0 && (
+								<>
+									<span>·</span>
+									<StandardTooltip
+										content={
+											<div>
+												{t("chat:costs.orchestrationTotal", {
+													cost: rootOrchestrationCost.toFixed(2),
+												})}
+											</div>
+										}
+										side="top"
+										sideOffset={8}>
+										<span className="text-vscode-descriptionForeground">
+											{t("chat:costs.orchestrationLabel")}: ${rootOrchestrationCost.toFixed(2)}
+										</span>
+									</StandardTooltip>
+								</>
+							)}
 						</div>
 					</div>
 				)}
@@ -447,6 +468,28 @@ const TaskHeader = ({
 										</tr>
 									)}
 
+									{typeof rootOrchestrationCost === "number" && rootOrchestrationCost > 0 && (
+										<tr>
+											<th className="font-medium text-left align-top w-1 whitespace-nowrap pr-3 h-[24px]">
+												{t("chat:costs.orchestrationLabel")}
+											</th>
+											<td className="font-light align-top">
+												<StandardTooltip
+													content={
+														<div>
+															{t("chat:costs.orchestrationTotal", {
+																cost: rootOrchestrationCost.toFixed(2),
+															})}
+														</div>
+													}
+													side="top"
+													sideOffset={8}>
+													<span>${rootOrchestrationCost.toFixed(2)}</span>
+												</StandardTooltip>
+											</td>
+										</tr>
+									)}
+
 									{/* Size display */}
 									{!!currentTaskItem?.size && currentTaskItem.size > 0 && (
 										<tr>

webview-ui/src/components/chat/__tests__/TaskHeader.spec.tsx

@@ -470,4 +470,26 @@ describe("TaskHeader", () => {
 			expect(screen.getByText("0%")).toBeInTheDocument()
 		})
 	})
+
+	describe("Root orchestration cost", () => {
+		it("should display orchestration cost when rootOrchestrationCost is provided and > 0", () => {
+			renderTaskHeader({ rootOrchestrationCost: 1.5 })
+			expect(screen.getByText("chat:costs.orchestrationLabel: $1.50")).toBeInTheDocument()
+		})
+
+		it("should not display orchestration cost when rootOrchestrationCost is undefined", () => {
+			renderTaskHeader({ rootOrchestrationCost: undefined })
+			expect(screen.queryByText(/chat:costs.orchestrationLabel/)).not.toBeInTheDocument()
+		})
+
+		it("should not display orchestration cost when rootOrchestrationCost is 0", () => {
+			renderTaskHeader({ rootOrchestrationCost: 0 })
+			expect(screen.queryByText(/chat:costs.orchestrationLabel/)).not.toBeInTheDocument()
+		})
+
+		it("should display orchestration cost tooltip with correct text", () => {
+			renderTaskHeader({ rootOrchestrationCost: 2.75 })
+			expect(screen.getByText("chat:costs.orchestrationLabel: $2.75")).toBeInTheDocument()
+		})
+	})
 })

webview-ui/src/i18n/locales/en/chat.json

@@ -389,7 +389,9 @@
 	"costs": {
 		"totalWithSubtasks": "Total Cost (including subtasks): ${{cost}}",
 		"total": "Total Cost: ${{cost}}",
-		"includesSubtasks": "Includes subtask costs"
+		"includesSubtasks": "Includes subtask costs",
+		"orchestrationLabel": "Orchestration",
+		"orchestrationTotal": "Full orchestration cost (all tasks): ${{cost}}"
 	},
 	"codeblock": {
 		"tooltips": {