diff --git a/src/client/UsageIndicator.tsx b/src/client/UsageIndicator.tsx
index d84f8e2..d049c62 100644
--- a/src/client/UsageIndicator.tsx
+++ b/src/client/UsageIndicator.tsx
@@ -10,8 +10,10 @@ import { currencySymbol, useBalance } from './balance.ts'
 import { useDisplayCurrency } from './currency.ts'
 import { getUiCopy, useUiLocale } from './i18n.ts'
 import { resolveCost, usePricing } from './pricing-api.ts'
+import { useHistoryRounds } from './rounds/history.ts'
 import { useObservedRounds } from './rounds/observed.ts'
-import { useSessionNodes, type ChatNodesHook, type ConversationNode, type ConversationSnapshot } from './snapshot.ts'
+import { sumRoundCosts, type ChartRound } from './rounds/types.ts'
+import { snapshotNodes, type ConversationNode, type ConversationSnapshot } from './snapshot.ts'
 import type { ContextBreakdownData } from './diagnose/context.ts'
 import { UsagePanel } from './UsagePanel.tsx'
 
@@ -27,6 +29,15 @@ export interface DockUsageProps {
   input: unknown
 }
 
+/** 历史折叠的模型归因：0.1.2+ 的快照节点不带 provenance/requestConfig，用最后一轮校准（面板同口径）。 */
+function lastRoundModel(rounds: readonly ChartRound[]): string | undefined {
+  for (let i = rounds.length - 1; i >= 0; i--) {
+    const model = rounds[i].model
+    if (model !== null && model !== '') return model
+  }
+  return undefined
+}
+
 function deriveModel(nodes: readonly ConversationNode[]): string | undefined {
   for (let i = nodes.length - 1; i >= 0; i--) {
     const n = nodes[i]
@@ -83,14 +94,24 @@ export function UsageIndicator(props: DockUsageProps): JSX.Element | null {
   const totals = useProjection('tokenUsage') as TokenUsageBuckets | undefined
   const pressure = useProjection('contextPressure') as { pressureTokens?: number; projectedTokens?: number; contextWindow?: number } | undefined
   const breakdown = useProjection('contextBreakdown') as ContextBreakdownData | undefined
-  const nodes = useSessionNodes(useChat, useSession)
-  const model = useMemo(() => deriveModel(nodes), [nodes])
+  const nodes = useSession((s) => snapshotNodes(s))
+  const history = useHistoryRounds(sessionId)
+  const model = useMemo(() => deriveModel(nodes) ?? lastRoundModel(history.rounds), [nodes, history.rounds])
   const pricing = usePricing()
   const observedRounds = useObservedRounds(totals, nodes, pricing.table, currency)
   const { status: balanceStatus, data: balanceData, load: loadBalance } = useBalance(true)
 
   const hasTokens = totals !== undefined && (billedInputTokens(totals) > 0 || totals.outputTokens > 0)
-  const cost = totals !== undefined && pricing.table !== null ? resolveCost(pricing.table, totals, model, Date.now(), currency) : undefined
+  // 会话总计：优先「Σ 各轮成本」（每轮各自的时段与模型，与每轮徽章天然自洽）；
+  // 历史不可用时才退回「当前时段 × 会话总量」的估算。
+  const historyCost = useMemo(
+    () => (history.status === 'ok' ? sumRoundCosts(history.rounds, currency) : null),
+    [history.status, history.rounds, currency],
+  )
+  const estimate = totals !== undefined && pricing.table !== null ? resolveCost(pricing.table, totals, model, Date.now(), currency) : undefined
+  const cost = historyCost !== null
+    ? { total: historyCost.total, estimated: historyCost.estimated }
+    : estimate === undefined ? undefined : { total: estimate.split.total, estimated: estimate.estimated }
   const cacheHit = totals !== undefined ? cacheHitPercent(totals) : null
   const pressurePct = pressurePercent(pressure)
   const breakdownTotal = (breakdown?.systemTokens ?? 0) + (breakdown?.toolsTokens ?? 0) + (breakdown?.messageTokens ?? 0)
@@ -161,7 +182,7 @@ export function UsageIndicator(props: DockUsageProps): JSX.Element | null {
     parts.push({ key: 'output', text: `${copy.output} ${formatTokens(totals.outputTokens)}` })
     if (cacheHit !== null) parts.push({ key: 'cache', text: `${copy.cache} ${cacheHit}%` })
   }
-  if (cost !== undefined) parts.push({ key: 'cost', text: `${copy.cost} ${cost.estimated ? '≈' : ''}${formatMoney(cost.split.total, currency)}`, estimated: cost.estimated })
+  if (cost !== undefined) parts.push({ key: 'cost', text: `${copy.cost} ${cost.estimated ? '≈' : ''}${formatMoney(cost.total, currency)}`, estimated: cost.estimated })
   if (model !== undefined) parts.push({ key: 'model', text: model.replace(/^deepseek-/, '') })
 
   const balanceLabel = balanceStatus === 'loading' || (balanceStatus === 'ok' && balance === undefined)
diff --git a/src/client/UsagePanel.tsx b/src/client/UsagePanel.tsx
index bf0267d..44916b4 100644
--- a/src/client/UsagePanel.tsx
+++ b/src/client/UsagePanel.tsx
@@ -18,7 +18,7 @@ import { analyzeContext, type ContextBreakdownData } from './diagnose/context.ts
 import { getUiCopy, type UiLocale } from './i18n.ts'
 import { resolvePricing, usePricing } from './pricing-api.ts'
 import { useHistoryRounds } from './rounds/history.ts'
-import type { ChartRound } from './rounds/types.ts'
+import { sumRoundCosts, type ChartRound } from './rounds/types.ts'
 export interface ContextPressureView {
   pressureTokens?: number
   projectedTokens?: number
@@ -99,9 +99,11 @@ export function UsagePanel(props: UsagePanelProps): JSX.Element {
     if (pricing.table === null) return null
     return resolvePricing(pricing.table, effectiveModel)
   }, [pricing.table, effectiveModel])
-  // 面板汇总成本：按所选币种的官方刊例价、按高峰/空闲时段计费。时段取
-  // 「最近一轮历史的开始时刻」（更贴近实际发生时段；无历史时用当前时刻）。
+  // 面板汇总成本：优先「Σ 各轮成本」（每轮各自的时段与模型，与每轮徽章自洽）；
+  // 历史不可用时退回「会话总量 × 刊例价」，时段取最近一轮开始时刻（无历史用当前时刻）。
   const costSplitTotal = useMemo(() => {
+    const summed = historyRounds !== null ? sumRoundCosts(historyRounds, currency) : null
+    if (summed !== null) return summed
     if (costView === null) return null
     const last = historyRounds !== null && historyRounds.length > 0 ? historyRounds[historyRounds.length - 1] : null
     return costSplitAt(totals, costView.pricing, last?.startedAt ?? Date.now(), currency)
diff --git a/src/client/rounds/types.ts b/src/client/rounds/types.ts
index 37b06c7..97751b0 100644
--- a/src/client/rounds/types.ts
+++ b/src/client/rounds/types.ts
@@ -2,7 +2,7 @@
  * client 侧轮次数据形状：host `/usage` 的 wire 格式（权威历史）
  * 与本页观测增量共用同一 ChartRound 形状，图表只认这一个类型。
  */
-import type { CostSplit, TokenUsageBuckets } from '../../pricing/calc.ts'
+import type { CostCurrency, CostSplit, TokenUsageBuckets } from '../../pricing/calc.ts'
 import type { CompactionRecord } from '../../usage/compactions.ts'
 
 /** 每轮成本（来自 host 折叠，官方 CNY/USD 双币种各一份；观测增量路径为 null）。 */
@@ -45,3 +45,24 @@ export interface UsageResponse {
 }
 
 export type UsageStatus = 'idle' | 'loading' | 'ok' | 'error'
+
+/**
+ * Σ 各轮成本（权威历史口径：每轮各自的时段与模型），用于会话汇总——
+ * 与每轮徽章天然自洽。任一轮缺成本（观测增量路径）或无轮次时返回 null，调用方回退估算。
+ */
+export function sumRoundCosts(rounds: readonly ChartRound[], currency: CostCurrency): (CostSplit & { estimated: boolean }) | null {
+  if (rounds.length === 0) return null
+  const sum: CostSplit = { input: 0, cacheRead: 0, output: 0, total: 0 }
+  let estimated = false
+  for (const round of rounds) {
+    const cost = round.cost
+    if (cost === null) return null
+    const split = cost[currency]
+    sum.input += split.input
+    sum.cacheRead += split.cacheRead
+    sum.output += split.output
+    sum.total += split.total
+    estimated ||= cost.estimated
+  }
+  return { ...sum, estimated }
+}