feat: add agent cost reporting

hub/src/agent/runner.ts

@@ -73,6 +73,8 @@ export interface RunResult {
   readonly status: RunStatus;
   readonly text: string;
   readonly usage: { inputTokens: number; outputTokens: number };
+  /** Provider- or gateway-reported cost for this run, in USD. */
+  readonly costUsd?: number | undefined;
   readonly numTurns: number;
   readonly sdkSessionId?: string | undefined;
   readonly error?: string;
@@ -123,6 +125,7 @@ export async function runAgent(req: RunRequest): Promise<RunResult> {
 
   let fullText = "";
   let usage = { inputTokens: 0, outputTokens: 0 };
+  let costUsd: number | undefined;
   let numTurns = 0;
   let sdkSessionId: string | undefined;
   let error: string | undefined;
@@ -248,6 +251,7 @@ export async function runAgent(req: RunRequest): Promise<RunResult> {
         case "result": {
           const result = message as SDKResultMessage;
           sdkSessionId = result.session_id;
+          costUsd = Number.isFinite(result.total_cost_usd) ? result.total_cost_usd : undefined;
           if (result.subtype !== "success") {
             error = `result_${result.subtype}`;
           }
@@ -261,6 +265,7 @@ export async function runAgent(req: RunRequest): Promise<RunResult> {
       status: error !== undefined ? "failed" : "completed",
       text: fullText,
       usage,
+      ...(costUsd !== undefined ? { costUsd } : {}),
       numTurns,
       sdkSessionId,
       ...(error !== undefined ? { error } : {}),
@@ -271,6 +276,7 @@ export async function runAgent(req: RunRequest): Promise<RunResult> {
       status: aborted ? "interrupted" : "failed",
       text: fullText,
       usage,
+      ...(costUsd !== undefined ? { costUsd } : {}),
       numTurns,
       sdkSessionId,
       ...(aborted ? {} : { error: e instanceof Error ? e.message : String(e) }),