feat: add usage cost reporting

src/gateway/protocol/schema.ts

@@ -325,6 +325,9 @@ export const SessionsPatchParamsSchema = Type.Object(
     thinkingLevel: Type.Optional(Type.Union([NonEmptyString, Type.Null()])),
     verboseLevel: Type.Optional(Type.Union([NonEmptyString, Type.Null()])),
     reasoningLevel: Type.Optional(Type.Union([NonEmptyString, Type.Null()])),
+    responseUsage: Type.Optional(
+      Type.Union([Type.Literal("on"), Type.Literal("off"), Type.Null()]),
+    ),
     elevatedLevel: Type.Optional(Type.Union([NonEmptyString, Type.Null()])),
     model: Type.Optional(Type.Union([NonEmptyString, Type.Null()])),
     spawnedBy: Type.Optional(Type.Union([NonEmptyString, Type.Null()])),

src/gateway/server-methods/sessions.ts

@@ -19,6 +19,7 @@ import { normalizeGroupActivation } from "../../auto-reply/group-activation.js";
 import {
   normalizeReasoningLevel,
   normalizeThinkLevel,
+  normalizeUsageDisplay,
   normalizeVerboseLevel,
 } from "../../auto-reply/thinking.js";
 import { loadConfig } from "../../config/config.js";
@@ -234,6 +235,28 @@ export const sessionsHandlers: GatewayRequestHandlers = {
       }
     }
 
+    if ("responseUsage" in p) {
+      const raw = p.responseUsage;
+      if (raw === null) {
+        delete next.responseUsage;
+      } else if (raw !== undefined) {
+        const normalized = normalizeUsageDisplay(String(raw));
+        if (!normalized) {
+          respond(
+            false,
+            undefined,
+            errorShape(
+              ErrorCodes.INVALID_REQUEST,
+              'invalid responseUsage (use "on"|"off")',
+            ),
+          );
+          return;
+        }
+        if (normalized === "off") delete next.responseUsage;
+        else next.responseUsage = normalized;
+      }
+    }
+
     if ("model" in p) {
       const raw = p.model;
       if (raw === null) {
@@ -394,6 +417,7 @@ export const sessionsHandlers: GatewayRequestHandlers = {
       thinkingLevel: entry?.thinkingLevel,
       verboseLevel: entry?.verboseLevel,
       reasoningLevel: entry?.reasoningLevel,
+      responseUsage: entry?.responseUsage,
       model: entry?.model,
       contextTokens: entry?.contextTokens,
       sendPolicy: entry?.sendPolicy,

src/gateway/session-utils.ts

@@ -51,6 +51,8 @@ export type GatewaySessionRow = {
   inputTokens?: number;
   outputTokens?: number;
   totalTokens?: number;
+  responseUsage?: "on" | "off";
+  modelProvider?: string;
   model?: string;
   contextTokens?: number;
   lastProvider?: SessionEntry["lastProvider"];
@@ -503,6 +505,8 @@ export function listSessionsFromStore(params: {
         inputTokens: entry?.inputTokens,
         outputTokens: entry?.outputTokens,
         totalTokens: total,
+        responseUsage: entry?.responseUsage,
+        modelProvider: entry?.modelProvider,
         model: entry?.model,
         contextTokens: entry?.contextTokens,
         lastProvider: entry?.lastProvider,