diff --git a/app/game-engine/test/playAuditDecisionCost.integration.test.ts b/app/game-engine/test/playAuditDecisionCost.integration.test.ts
index e04a0ffc..91026408 100644
--- a/app/game-engine/test/playAuditDecisionCost.integration.test.ts
+++ b/app/game-engine/test/playAuditDecisionCost.integration.test.ts
@@ -1,7 +1,7 @@
 import { writeFile } from 'node:fs/promises';
 import { performance } from 'node:perf_hooks';
 import { afterAll, beforeAll, describe, expect, it } from 'vitest';
-import { createGamePostgresConnector, type GamePrismaClient } from '@sammo-ts/infra';
+import { createGamePostgresConnector, type GamePrisma, type GamePrismaClient } from '@sammo-ts/infra';
 import { persistAuditDecisions } from '../src/playAudit/decisionPersistence.js';
 import { buildAuditDecisionFixture } from './fixtures/playAuditDecision.js';
 
@@ -9,12 +9,26 @@ const databaseUrl = process.env.PLAY_AUDIT_COST_DATABASE_URL;
 describe.skipIf(!databaseUrl)('decision storage cost probe', () => {
     let db: GamePrismaClient;
     let close: () => Promise<void>;
+    let recording = false;
+    let statements: Record<string, number> = {};
     beforeAll(async () => {
         if (new URL(databaseUrl!).searchParams.get('schema') !== 'play_audit_cost_decision_fixture')
             throw new Error('Dedicated audit cost fixture required');
-        const connector = createGamePostgresConnector({ url: databaseUrl!, maxConnections: 1 });
+        const connector = createGamePostgresConnector({
+            url: databaseUrl!,
+            maxConnections: 1,
+            log: [{ emit: 'event', level: 'query' }],
+        });
         await connector.connect();
         db = connector.prisma;
+        // connector의 반환 타입은 log generic을 지운다. 위에서 활성화한 event만 구독한다.
+        const observedDb = db as GamePrismaClient<GamePrisma.PrismaClientOptions, 'query'>;
+        observedDb.$on('query', (event) => {
+            if (!recording) return;
+            // 원문 SQL/params는 보존하거나 출력하지 않고 명령 종류만 집계한다.
+            const command = event.query.trim().split(/\s+/, 1)[0]!.toUpperCase();
+            statements[command] = (statements[command] ?? 0) + 1;
+        });
         close = () => connector.disconnect();
         await db.playAuditDecisionChunk.deleteMany();
         await db.playAuditDecision.deleteMany();
@@ -27,9 +41,19 @@ describe.skipIf(!databaseUrl)('decision storage cost probe', () => {
             return { ...decision, tick: decision.tick + index };
         });
         const payloadBytes = Buffer.byteLength(JSON.stringify(decisions));
+        statements = {};
+        recording = true;
         const start = performance.now();
-        await db.$transaction((tx) => persistAuditDecisions(tx, decisions), { timeout: 30_000 });
+        try {
+            await db.$transaction((tx) => persistAuditDecisions(tx, decisions), { timeout: 30_000 });
+        } finally {
+            recording = false;
+        }
         const writeMs = performance.now() - start;
+        const writeStatements = { ...statements };
+        // 200결정: header1 + chunk3, 나머지1결정: header1 + chunk1. hash 조회는 batch당1.
+        expect(writeStatements.INSERT).toBe(6);
+        expect(writeStatements.SELECT).toBe(2);
         expect(await db.playAuditDecision.count()).toBe(201);
         expect(await db.playAuditDecisionChunk.count()).toBe(603);
         const [storage] = await db.$queryRaw<
@@ -75,7 +99,7 @@ describe.skipIf(!databaseUrl)('decision storage cost probe', () => {
         `;
         const metrics = {
             scope: 'synthetic 201 decisions, 302 steps each; isolated schema, warm local reads',
-            limitations: 'Not production p95; no gameplay baseline, SQL count, WAL or retained heap measurement. Repetitive synthetic steps compress well. Relation allocation can retain space from previous runs.',
+            limitations: 'Not production p95; no gameplay baseline, WAL or retained heap measurement. SQL counts cover only the persistence transaction. Repetitive synthetic steps compress well. Relation allocation can retain space from previous runs.',
             decisions: 201,
             steps: Number(storage!.steps),
             chunks: 603,
@@ -89,6 +113,7 @@ describe.skipIf(!databaseUrl)('decision storage cost probe', () => {
                 totalBytes: Number(row.totalBytes),
             })),
             writeMs,
+            writeStatements,
             samples: timings.length,
             readP50Ms: timings[14],
             readP95Ms: timings[28],
diff --git a/docs/design/play-audit-implementation.md b/docs/design/play-audit-implementation.md
index 7e955e83..935f635b 100644
--- a/docs/design/play-audit-implementation.md
+++ b/docs/design/play-audit-implementation.md
@@ -29,7 +29,12 @@ p50/p95와 EXPLAIN ANALYZE BUFFERS를 `/tmp/play-audit-decision-cost.json`에 
 2026-09-16 격리 PG 결과는 JSON12,271,836B, header행101,304B/chunk행666,924B,
 저장677.56ms, 목록51건 p50 0.76ms/p95 1.01ms였다. 월별 장수 index scan으로51행을
 읽었다. 반복 RNG 합성 fixture는 압축률이 높으므로 평균 운영 trace 크기의 근거가 아니다.
-SQL 왕복·WAL·retained heap, 실제 scenario 계측 전후와 전체 COST gate는 여전히 남는다.
+추가 query event 계측에서는 동일201결정의 저장에 INSERT6회(헤더2/chunk4),
+SELECT2회(hash 확인), COMMIT1회가 관측됐다. BEGIN 등 driver 내부 통신은 event에
+나타나지 않으므로 네트워크 왕복 전체로 해석하지 않는다. test는 INSERT/SELECT 수를
+assert하며 SQL/params 원문은 저장하지 않는다. 관측60,702단계마다 SQL을 쓰지 않고 batch당
+저장·hash 조회를 확인한 범위다. WAL·retained heap, 실제 scenario 계측 전후와 전체
+COST gate는 여전히 남는다.
 
 
 ### 정책·외교 사건의 요청 처리 상태