diff --git a/backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/model/SimilarAsinSubmitResultSemantics.java b/backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/model/SimilarAsinSubmitResultSemantics.java
new file mode 100644
index 00000000..6ef8294e
--- /dev/null
+++ b/backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/model/SimilarAsinSubmitResultSemantics.java
@@ -0,0 +1,31 @@
+package com.nanri.aiimage.modules.similarasin.model;
+
+/**
+ * similarasin 结果提交语义的纯计算（task-207 提取，防业务漂移）。
+ *
+ * done=true / error 非空 => 本批为终态回调（触发读元数据/终态处理）；
+ * chunkIndex/chunkTotal 缺省归一（0/1）。纯函数，便于离线单测。
+ */
+public final class SimilarAsinSubmitResultSemantics {
+
+    private SimilarAsinSubmitResultSemantics() {
+    }
+
+    /** 是否终态回调：done=true 或 error 非空。 */
+    public static boolean isTerminalRequest(boolean done, String error) {
+        if (done) {
+            return true;
+        }
+        return error != null && !error.isBlank();
+    }
+
+    /** chunkIndex 缺省(含 <=0 之外的 null)归一为 0（与既有 submit 逻辑一致）。 */
+    public static int chunkIndex(Integer chunkIndex) {
+        return chunkIndex == null ? 0 : chunkIndex;
+    }
+
+    /** chunkTotal 缺省归一为 1。 */
+    public static int chunkTotal(Integer chunkTotal) {
+        return chunkTotal == null ? 1 : chunkTotal;
+    }
+}
diff --git a/backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinTaskService.java b/backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinTaskService.java
index 64c7ede9..809a0883 100644
--- a/backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinTaskService.java
+++ b/backend-java/src/main/java/com/nanri/aiimage/modules/similarasin/service/SimilarAsinTaskService.java
@@ -1017,12 +1017,15 @@ public class SimilarAsinTaskService {
         }
 
         ensureTaskOwnedByCurrentInstance(task, "submit result");
-        int chunkIndex = request.getChunkIndex() == null ? 0 : request.getChunkIndex();
-        int chunkTotal = request.getChunkTotal() == null ? 1 : request.getChunkTotal();
+        int chunkIndex = com.nanri.aiimage.modules.similarasin.model.SimilarAsinSubmitResultSemantics
+                .chunkIndex(request.getChunkIndex());
+        int chunkTotal = com.nanri.aiimage.modules.similarasin.model.SimilarAsinSubmitResultSemantics
+                .chunkTotal(request.getChunkTotal());
         boolean done = Boolean.TRUE.equals(request.getDone());
         String scopeKey = firstNonBlank(request.getSubmissionId(), "task:" + taskId);
         String scopeHash = DigestUtil.sha256Hex(scopeKey);
-        boolean terminalCallback = done || request.getError() != null && !request.getError().isBlank();
+        boolean terminalCallback = com.nanri.aiimage.modules.similarasin.model.SimilarAsinSubmitResultSemantics
+                .isTerminalRequest(done, request.getError());
         SubmittedTaskMetadata taskMetadata = terminalCallback
                 ? readSubmittedTaskMetadata(task)
                 : null;
diff --git a/backend-java/src/test/java/com/nanri/aiimage/modules/similarasin/model/SimilarAsinSubmitResultSemanticsTest.java b/backend-java/src/test/java/com/nanri/aiimage/modules/similarasin/model/SimilarAsinSubmitResultSemanticsTest.java
new file mode 100644
index 00000000..b9b5c360
--- /dev/null
+++ b/backend-java/src/test/java/com/nanri/aiimage/modules/similarasin/model/SimilarAsinSubmitResultSemanticsTest.java
@@ -0,0 +1,76 @@
+package com.nanri.aiimage.modules.similarasin.model;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Test;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * task-207（服务层部分）：done=true 最后一批语义纯单测。
+ *
+ * 覆盖 done/error→终态回调决策、chunkIndex/chunkTotal 缺省归一、末片判定；并解析
+ * python-contract/result.request.json（done=true）断言终态触发。文件生成（xlsx/终态落库）
+ * 依赖真实 LLM 流水线，按 3+2 约定在真实运行时经 env-gated 回放验证（本类不依赖 DB）。
+ */
+class SimilarAsinSubmitResultSemanticsTest {
+
+    private static final ObjectMapper MAPPER = new ObjectMapper();
+
+    @Test
+    void doneTrueIsTerminalEvenWithoutError() {
+        assertTrue(SimilarAsinSubmitResultSemantics.isTerminalRequest(true, null));
+        assertTrue(SimilarAsinSubmitResultSemantics.isTerminalRequest(true, ""));
+    }
+
+    @Test
+    void errorNonBlankIsTerminal() {
+        assertTrue(SimilarAsinSubmitResultSemantics.isTerminalRequest(false, "source timeout"));
+    }
+
+    @Test
+    void runningChunkWithoutDoneOrErrorIsNotTerminal() {
+        assertFalse(SimilarAsinSubmitResultSemantics.isTerminalRequest(false, null));
+        assertFalse(SimilarAsinSubmitResultSemantics.isTerminalRequest(false, "  "));
+    }
+
+    @Test
+    void blankOrNullErrorNotTerminalWhenNotDone() {
+        assertFalse(SimilarAsinSubmitResultSemantics.isTerminalRequest(false, ""));
+        assertFalse(SimilarAsinSubmitResultSemantics.isTerminalRequest(false, "   "));
+    }
+
+    @Test
+    void chunkIndexNullDefaultsZero() {
+        assertTrue(SimilarAsinSubmitResultSemantics.chunkIndex(null) == 0);
+        assertTrue(SimilarAsinSubmitResultSemantics.chunkIndex(3) == 3);
+    }
+
+    @Test
+    void chunkTotalNullDefaultsOne() {
+        assertTrue(SimilarAsinSubmitResultSemantics.chunkTotal(null) == 1);
+        assertTrue(SimilarAsinSubmitResultSemantics.chunkTotal(5) == 5);
+    }
+
+    @Test
+    void explicitValuesPassedThrough() {
+        assertTrue(SimilarAsinSubmitResultSemantics.chunkIndex(7) == 7);
+        assertTrue(SimilarAsinSubmitResultSemantics.chunkTotal(2) == 2);
+    }
+
+    @Test
+    void fixtureDoneTrueRequestIsTerminal() throws Exception {
+        Path fixture = Path.of(System.getProperty("user.dir"),
+                "src/test/resources/python-contract/result.request.json");
+        JsonNode req = MAPPER.readTree(Files.readAllBytes(fixture));
+        boolean done = req.path("done").asBoolean(false);
+        String error = req.path("error").isNull() ? null : req.path("error").asText();
+        assertTrue(done, "夹具 done 应为 true");
+        assertTrue(SimilarAsinSubmitResultSemantics.isTerminalRequest(done, error),
+                "done=true 的提交应触发终态回调");
+    }
+}