diff --git a/backend-java/src/test/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinResultContractReplayTest.java b/backend-java/src/test/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinResultContractReplayTest.java
new file mode 100644
index 00000000..af972188
--- /dev/null
+++ b/backend-java/src/test/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinResultContractReplayTest.java
@@ -0,0 +1,102 @@
+package com.nanri.aiimage.modules.similarasin.service;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Assumptions;
+
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.charset.StandardCharsets;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.Statement;
+import java.time.Duration;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * task-203：/result 幂等契约回放（真实服务，env-gated）。
+ *
+ * 依赖运行中的应用与可写本地库（复现生产 schema）：设 CONTRACT_BASE_URL、CONTRACT_DB_URL、
+ * CONTRACT_DB_USER、CONTRACT_DB_PASSWORD 后启用；未设则跳过（保证 CI 全绿）。
+ * 流程：造 SIMILAR_ASIN RUNNING 任务 + 内联解析载荷 → GET parsed-payload 验证成功 →
+ * POST /result 同 submissionId/chunk 两次 → 断言两次 success:true 且 biz_task_chunk 只落 1 行（幂等）。
+ * done=true 封口/终态因需真实 LLM 流水线，不在本回放覆盖（见 commit 说明）。
+ */
+class SimilarAsinResultContractReplayTest {
+
+    private static final long TASK_ID = 9000001L;
+    private static final String SUBMISSION = "contract-replay-001";
+
+    @Test
+    void duplicateSubmitResultIsIdempotent() throws Exception {
+        String base = System.getenv("CONTRACT_BASE_URL");
+        String dbUrl = System.getenv("CONTRACT_DB_URL");
+        String dbUser = System.getenv("CONTRACT_DB_USER");
+        String dbPass = System.getenv("CONTRACT_DB_PASSWORD");
+        Assumptions.assumeTrue(base != null && dbUrl != null && dbUser != null,
+                "未设 CONTRACT_BASE_URL / CONTRACT_DB_*，跳过真实服务回放");
+
+        seedTask(dbUrl, dbUser, dbPass);
+        HttpClient client = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(10)).build();
+
+        // parsed-payload 成功返回全量载荷
+        HttpResponse<String> parsed = get(client, base + "/api/similar-asin/tasks/" + TASK_ID + "/parsed-payload?user_id=1");
+        assertEquals(200, parsed.statusCode());
+        assertTrue(parsed.body().contains("\"success\":true"), "parsed-payload 应 success:true: " + parsed.body());
+        assertTrue(parsed.body().contains("B0FAKETEST123"), "应含解析行数据");
+
+        // 同 submissionId/chunk 提交两次
+        String body = "{\"submissionId\":\"" + SUBMISSION + "\",\"chunkIndex\":0,\"chunkTotal\":1,\"done\":false,"
+                + "\"error\":null,\"groups\":[{\"name\":\"g\",\"items\":[{\"rowIndex\":1,\"asin\":\"B0FAKETEST123\","
+                + "\"status\":\"SUCCESS\"}]}]}";
+        HttpResponse<String> first = post(client, base + "/api/similar-asin/tasks/" + TASK_ID + "/result?user_id=1", body);
+        HttpResponse<String> second = post(client, base + "/api/similar-asin/tasks/" + TASK_ID + "/result?user_id=1", body);
+        assertEquals(200, first.statusCode());
+        assertEquals(200, second.statusCode());
+        assertTrue(first.body().contains("\"success\":true"), "首次提交应成功: " + first.body());
+        assertTrue(second.body().contains("\"success\":true"), "重复提交应幂等成功: " + second.body());
+
+        // 幂等：只落一份 chunk
+        assertEquals(1, countChunks(dbUrl, dbUser, dbPass, TASK_ID), "同 submissionId/chunk 应只落 1 行");
+    }
+
+    private static void seedTask(String dbUrl, String user, String pass) throws Exception {
+        String payload = "{\"aiPrompt\":\"<redacted>\",\"apiKey\":\"<redacted>\",\"imgSwitch\":false,"
+                + "\"categorySwitch\":false,\"sourceFiles\":[],\"headers\":[\"asin\",\"keyword\"],"
+                + "\"items\":[{\"rowIndex\":1,\"asin\":\"B0FAKETEST123\",\"keyword\":\"ring\"}],"
+                + "\"groups\":[],\"allItems\":[{\"rowIndex\":1,\"asin\":\"B0FAKETEST123\",\"keyword\":\"ring\"}]}";
+        try (Connection c = DriverManager.getConnection(dbUrl, user, pass);
+             Statement s = c.createStatement()) {
+            s.executeUpdate("INSERT INTO biz_file_task (id,task_no,module_type,task_mode,status,created_at,updated_at,user_id,owner_instance_id,result_json) "
+                    + "VALUES (" + TASK_ID + ",'REPLAY-" + TASK_ID + "','SIMILAR_ASIN','workbook','RUNNING',NOW(),NOW(),1,'local-smoke','"
+                    + payload.replace("'", "''") + "') ON DUPLICATE KEY UPDATE module_type='SIMILAR_ASIN',status='RUNNING',user_id=1,result_json=VALUES(result_json)");
+            s.executeUpdate("DELETE FROM biz_task_chunk WHERE task_id=" + TASK_ID);
+        }
+    }
+
+    private static int countChunks(String dbUrl, String user, String pass, long taskId) throws Exception {
+        try (Connection c = DriverManager.getConnection(dbUrl, user, pass);
+             Statement s = c.createStatement();
+             var rs = s.executeQuery("SELECT COUNT(*) FROM biz_task_chunk WHERE task_id=" + taskId)) {
+            rs.next();
+            return rs.getInt(1);
+        }
+    }
+
+    private static HttpResponse<String> get(HttpClient client, String url) throws Exception {
+        return client.send(HttpRequest.newBuilder(URI.create(url)).GET()
+                        .timeout(Duration.ofSeconds(15)).build(),
+                HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8));
+    }
+
+    private static HttpResponse<String> post(HttpClient client, String url, String body) throws Exception {
+        return client.send(HttpRequest.newBuilder(URI.create(url))
+                        .header("Content-Type", "application/json")
+                        .POST(HttpRequest.BodyPublishers.ofString(body, StandardCharsets.UTF_8))
+                        .timeout(Duration.ofSeconds(15)).build(),
+                HttpResponse.BodyHandlers.ofString(StandardCharsets.UTF_8));
+    }
+}