diff --git a/nix/npm-deps.hash b/nix/npm-deps.hash
index 5b4e50d81..fd8f7984d 100644
--- a/nix/npm-deps.hash
+++ b/nix/npm-deps.hash
@@ -1 +1 @@
-sha256-H18zIrryRN+tfQA68vfbWHNMN1mOxhO4PAWcZ4yuNSc=
+sha256-s1HwJgifRYWfnIVit2JVrJmFSyu8lL8TpX67I/33dQQ=
diff --git a/packages/app/src/components/composer.tsx b/packages/app/src/components/composer.tsx
index 1212e201c..c52330b36 100644
--- a/packages/app/src/components/composer.tsx
+++ b/packages/app/src/components/composer.tsx
@@ -177,6 +177,7 @@ function buildAgentStateSelector(serverId: string, agentId: string) {
       status: agent?.status ?? null,
       contextWindowMaxTokens: agent?.lastUsage?.contextWindowMaxTokens ?? null,
       contextWindowUsedTokens: agent?.lastUsage?.contextWindowUsedTokens ?? null,
+      totalCostUsd: agent?.lastUsage?.totalCostUsd ?? null,
     };
   };
 }
@@ -184,10 +185,15 @@ function buildAgentStateSelector(serverId: string, agentId: string) {
 function renderContextWindowMeterSlot(
   contextWindowMaxTokens: number | null,
   contextWindowUsedTokens: number | null,
+  totalCostUsd: number | null,
 ): ReactElement {
   const meter =
     contextWindowMaxTokens !== null && contextWindowUsedTokens !== null ? (
-      <ContextWindowMeter maxTokens={contextWindowMaxTokens} usedTokens={contextWindowUsedTokens} />
+      <ContextWindowMeter
+        maxTokens={contextWindowMaxTokens}
+        usedTokens={contextWindowUsedTokens}
+        totalCostUsd={totalCostUsd}
+      />
     ) : null;
   return <View style={styles.contextWindowMeterSlot}>{meter}</View>;
 }
@@ -1419,8 +1425,13 @@ export function Composer({
   );
 
   const beforeVoiceContent = useMemo(
-    () => renderContextWindowMeterSlot(contextWindowMaxTokens, contextWindowUsedTokens),
-    [contextWindowMaxTokens, contextWindowUsedTokens],
+    () =>
+      renderContextWindowMeterSlot(
+        contextWindowMaxTokens,
+        contextWindowUsedTokens,
+        agentState.totalCostUsd,
+      ),
+    [contextWindowMaxTokens, contextWindowUsedTokens, agentState.totalCostUsd],
   );
 
   const githubSearchQueryTrimmed = githubSearchQuery.trim();
diff --git a/packages/app/src/components/context-window-meter.tsx b/packages/app/src/components/context-window-meter.tsx
index 9e63f70a2..0b8da5ef5 100644
--- a/packages/app/src/components/context-window-meter.tsx
+++ b/packages/app/src/components/context-window-meter.tsx
@@ -6,6 +6,7 @@ import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip
 interface ContextWindowMeterProps {
   maxTokens: number;
   usedTokens: number;
+  totalCostUsd?: number | null;
 }
 
 const SVG_SIZE = 16;
@@ -43,6 +44,16 @@ function formatTokenCount(value: number): string {
   return Math.round(value).toString();
 }
 
+function formatSessionCost(value: number): string | null {
+  if (!Number.isFinite(value) || value <= 0) {
+    return null;
+  }
+  if (value < 0.01) {
+    return `$${value.toFixed(4)}`;
+  }
+  return `$${value.toFixed(2)}`;
+}
+
 function getMeterColors(
   percentage: number,
   theme: ReturnType<typeof useUnistyles>["theme"],
@@ -57,7 +68,11 @@ function getMeterColors(
   return { progress: theme.colors.foregroundMuted, track };
 }
 
-export function ContextWindowMeter({ maxTokens, usedTokens }: ContextWindowMeterProps) {
+export function ContextWindowMeter({
+  maxTokens,
+  usedTokens,
+  totalCostUsd,
+}: ContextWindowMeterProps) {
   const { theme } = useUnistyles();
   const percentage = getUsagePercentage(maxTokens, usedTokens);
 
@@ -69,6 +84,8 @@ export function ContextWindowMeter({ maxTokens, usedTokens }: ContextWindowMeter
   const roundedPercentage = Math.round(percentage);
   const dashOffset = CIRCUMFERENCE - (clampedPercentage / 100) * CIRCUMFERENCE;
   const colors = getMeterColors(clampedPercentage, theme);
+  const formattedSessionCost =
+    typeof totalCostUsd === "number" ? formatSessionCost(totalCostUsd) : null;
 
   return (
     <Tooltip delayDuration={0} enabledOnDesktop enabledOnMobile>
@@ -115,6 +132,9 @@ export function ContextWindowMeter({ maxTokens, usedTokens }: ContextWindowMeter
           <Text
             style={styles.tooltipDetail}
           >{`${formatTokenCount(usedTokens)} / ${formatTokenCount(maxTokens)} tokens`}</Text>
+          {formattedSessionCost ? (
+            <Text style={styles.tooltipDetail}>{`Session cost ${formattedSessionCost}`}</Text>
+          ) : null}
         </View>
       </TooltipContent>
     </Tooltip>
diff --git a/packages/server/src/server/agent/providers/opencode-agent.ts b/packages/server/src/server/agent/providers/opencode-agent.ts
index 436fcb14e..ca85cba57 100644
--- a/packages/server/src/server/agent/providers/opencode-agent.ts
+++ b/packages/server/src/server/agent/providers/opencode-agent.ts
@@ -424,6 +424,16 @@ function readPositiveFiniteNumber(value: unknown): number | undefined {
   return typeof value === "number" && Number.isFinite(value) && value > 0 ? value : undefined;
 }
 
+function maxFiniteNumber(left: number | undefined, right: number): number {
+  return left === undefined ? right : Math.max(left, right);
+}
+
+function assignUsageNumber(usage: AgentUsage, key: keyof AgentUsage, value: number | undefined) {
+  if (value !== undefined) {
+    usage[key] = value;
+  }
+}
+
 function buildOpenCodeModelLookupKey(providerId: string, modelId: string): string {
   return `${providerId}/${modelId}`;
 }
@@ -591,6 +601,7 @@ function mergeOpenCodeStepFinishUsage(
       };
     };
   },
+  options: { totalCostUsd?: number } = {},
 ): void {
   const inputTokens = readPositiveFiniteNumber(part.tokens?.input);
   const outputTokens = readPositiveFiniteNumber(part.tokens?.output);
@@ -605,20 +616,14 @@ function mergeOpenCodeStepFinishUsage(
     (cacheWriteTokens ?? 0);
   const cost = readPositiveFiniteNumber(part.cost);
 
-  if (inputTokens !== undefined) {
-    usage.inputTokens = inputTokens;
-  }
-  if (cacheReadTokens !== undefined) {
-    usage.cachedInputTokens = cacheReadTokens;
-  }
-  if (outputTokens !== undefined) {
-    usage.outputTokens = outputTokens;
-  }
+  assignUsageNumber(usage, "inputTokens", inputTokens);
+  assignUsageNumber(usage, "cachedInputTokens", cacheReadTokens);
+  assignUsageNumber(usage, "outputTokens", outputTokens);
   if (totalTokens > 0) {
     usage.contextWindowUsedTokens = totalTokens;
   }
   if (cost !== undefined) {
-    usage.totalCostUsd = (usage.totalCostUsd ?? 0) + cost;
+    usage.totalCostUsd = options.totalCostUsd ?? (usage.totalCostUsd ?? 0) + cost;
   }
 }
 
@@ -1348,6 +1353,7 @@ export interface OpenCodeEventTranslationState {
   cwd?: string;
   messageRoles: Map<string, OpenCodeMessageRole>;
   accumulatedUsage: AgentUsage;
+  sessionTotalCostUsd?: number;
   streamedPartKeys: Set<string>;
   emittedStructuredMessageIds: Set<string>;
   /** Tracks the type of each part by ID, learned from message.part.updated events. */
@@ -1932,7 +1938,13 @@ function appendOpenCodeSessionCreatedOrUpdated(
   state: OpenCodeEventTranslationState,
   events: AgentStreamEvent[],
 ): void {
+  const info = readOpenCodeRecord(event.properties.info);
   if (event.properties.info.id === state.sessionId) {
+    const sessionCost = readPositiveFiniteNumber(info?.cost);
+    if (sessionCost !== undefined) {
+      state.sessionTotalCostUsd = maxFiniteNumber(state.sessionTotalCostUsd, sessionCost);
+      state.accumulatedUsage.totalCostUsd = state.sessionTotalCostUsd;
+    }
     events.push({
       type: "thread_started",
       sessionId: state.sessionId,
@@ -1941,7 +1953,6 @@ function appendOpenCodeSessionCreatedOrUpdated(
     return;
   }
 
-  const info = readOpenCodeRecord(event.properties.info);
   const parentSessionId = readNonEmptyString(info?.parentID) ?? readNonEmptyString(info?.parentId);
   if (parentSessionId === state.sessionId) {
     appendOpenCodeSubAgentChildSessionLinked(event.properties.info.id, state, events);
@@ -2022,7 +2033,13 @@ function appendOpenCodeMessagePartUpdated(
     return;
   }
   if (part.type === "step-finish") {
-    mergeOpenCodeStepFinishUsage(state.accumulatedUsage, part);
+    const stepCost = readPositiveFiniteNumber(part.cost);
+    if (stepCost !== undefined) {
+      state.sessionTotalCostUsd = (state.sessionTotalCostUsd ?? 0) + stepCost;
+    }
+    mergeOpenCodeStepFinishUsage(state.accumulatedUsage, part, {
+      totalCostUsd: state.sessionTotalCostUsd,
+    });
     if (hasNormalizedOpenCodeUsage(state.accumulatedUsage)) {
       events.push({
         type: "usage_updated",
@@ -2300,6 +2317,7 @@ class OpenCodeAgentSession implements AgentSession {
   private abortController: AbortController | null = null;
   private pendingAbortPromise: Promise<void> | null = null;
   private accumulatedUsage: AgentUsage = {};
+  private sessionTotalCostUsd: number | undefined;
   private mcpConfigured = false;
   private mcpSetupPromise: Promise<void> | null = null;
   /** Tracks the role of each message by ID to distinguish user from assistant messages */
@@ -3198,6 +3216,7 @@ class OpenCodeAgentSession implements AgentSession {
       cwd: this.config.cwd,
       messageRoles: this.messageRoles,
       accumulatedUsage: this.accumulatedUsage,
+      sessionTotalCostUsd: this.sessionTotalCostUsd,
       streamedPartKeys: this.streamedPartKeys,
       emittedStructuredMessageIds: this.emittedStructuredMessageIds,
       partTypes: this.partTypes,
@@ -3214,6 +3233,12 @@ class OpenCodeAgentSession implements AgentSession {
     });
 
     const events: AgentStreamEvent[] = [];
+    if (typeof this.accumulatedUsage.totalCostUsd === "number") {
+      this.sessionTotalCostUsd = maxFiniteNumber(
+        this.sessionTotalCostUsd,
+        this.accumulatedUsage.totalCostUsd,
+      );
+    }
 
     for (const translatedEvent of translated) {
       if (translatedEvent.type === "permission_requested") {
diff --git a/packages/server/src/server/agent/providers/opencode/event-translator.test.ts b/packages/server/src/server/agent/providers/opencode/event-translator.test.ts
index daae7c51a..548a40f44 100644
--- a/packages/server/src/server/agent/providers/opencode/event-translator.test.ts
+++ b/packages/server/src/server/agent/providers/opencode/event-translator.test.ts
@@ -418,6 +418,72 @@ describe("translateOpenCodeEvent", () => {
     });
   });
 
+  it("reports totalCostUsd as cumulative session cost across turns", () => {
+    const state = createState();
+    state.accumulatedUsage.contextWindowMaxTokens = 400_000;
+    state.sessionTotalCostUsd = 0.5;
+
+    const events = translateOpenCodeEvent(
+      {
+        type: "message.part.updated",
+        properties: {
+          part: {
+            id: "step-finish-1",
+            sessionID: "session-1",
+            messageID: "message-usage-1",
+            type: "step-finish",
+            reason: "stop",
+            cost: 0.25,
+            tokens: {
+              total: 55_000,
+              input: 30_000,
+              output: 12_000,
+              reasoning: 10_000,
+              cache: {
+                read: 2_000,
+                write: 1_000,
+              },
+            },
+          },
+        },
+      },
+      state,
+    );
+
+    expect(events).toEqual([
+      {
+        type: "usage_updated",
+        provider: "opencode",
+        usage: expect.objectContaining({
+          totalCostUsd: 0.75,
+        }),
+      },
+    ]);
+    expect(state.sessionTotalCostUsd).toBe(0.75);
+    expect(state.accumulatedUsage.totalCostUsd).toBe(0.75);
+  });
+
+  it("seeds cumulative session cost from OpenCode session updates", () => {
+    const state = createState();
+
+    translateOpenCodeEvent(
+      {
+        type: "session.updated",
+        properties: {
+          sessionID: "session-1",
+          info: {
+            id: "session-1",
+            cost: 1.25,
+          },
+        },
+      } as Parameters<typeof translateOpenCodeEvent>[0],
+      state,
+    );
+
+    expect(state.sessionTotalCostUsd).toBe(1.25);
+    expect(state.accumulatedUsage.totalCostUsd).toBe(1.25);
+  });
+
   it("emits normalized todo timeline items from todo.updated", () => {
     const state = createState();