fix(core): keep agent usage rounds cumulative

packages/core/src/agents/runtime/agent-core.ts

@@ -1207,7 +1207,7 @@ export class AgentCore {
 
         // Update token usage if available
         if (lastUsage) {
-          this.recordTokenUsage(lastUsage, turnCounter, roundStreamStart);
+          this.recordTokenUsage(lastUsage, cumulativeRounds, roundStreamStart);
         }
 
         if (functionCalls.length > 0) {

packages/core/src/agents/runtime/agent-headless.test.ts

@@ -51,6 +51,7 @@ import {
   type AgentStreamTextEvent,
   type AgentToolCallEvent,
   type AgentToolResultEvent,
+  type AgentUsageEvent,
 } from './agent-events.js';
 import type {
   ModelConfig,
@@ -661,6 +662,42 @@ describe('subagent.ts', () => {
         expect(scope.getExecutionSummary()).toMatchObject({ rounds: 2 });
       });
 
+      it('should keep usage rounds unique across finishing input segments', async () => {
+        const { config } = await createMockConfig();
+        mockSendMessageStream.mockImplementation(async () =>
+          (async function* () {
+            yield {
+              type: 'chunk',
+              value: {
+                candidates: [{ content: { parts: [{ text: 'Done.' }] } }],
+                usageMetadata: { totalTokenCount: 1 },
+              },
+            };
+          })(),
+        );
+
+        const scope = await AgentHeadless.create(
+          'test-agent',
+          config,
+          { systemPrompt: 'You are a test agent.' },
+          defaultModelConfig,
+          defaultRunConfig,
+        );
+        const usageRounds: number[] = [];
+        scope
+          .getEventEmitter()
+          .on(AgentEventType.USAGE_METADATA, (event: AgentUsageEvent) => {
+            usageRounds.push(event.round);
+          });
+
+        await scope.execute(new ContextState());
+        await scope.executeExternalInputs(['late correction'], undefined, {
+          resetStats: false,
+        });
+
+        expect(usageRounds).toEqual([1, 2]);
+      });
+
       it('should preserve statistics for continuation work in the same logical turn', async () => {
         const { config } = await createMockConfig();
         mockSendMessageStream.mockImplementation(