diff --git a/src/lib/availability/availability-service.ts b/src/lib/availability/availability-service.ts
index 4d5e6f0bd..386abd5d3 100644
--- a/src/lib/availability/availability-service.ts
+++ b/src/lib/availability/availability-service.ts
@@ -4,7 +4,7 @@
  * Simple two-tier status: success (green) or failure (red)
  */
 
-import { and, eq, inArray, isNull, type SQLWrapper, sql } from "drizzle-orm";
+import { and, eq, inArray, isNotNull, isNull, type SQLWrapper, sql } from "drizzle-orm";
 import { db } from "@/drizzle/db";
 import { messageRequest, providers } from "@/drizzle/schema";
 import type {
@@ -62,19 +62,12 @@ export class AvailabilityQueryValidationError extends Error {
 }
 
 /**
- * 当前版本把“已终态”收敛为 `statusCode` 已落库。
- *
- * 已知限制：在当前异步写入/丢 patch 的极端场景，或未来新增了 `durationMs` / `errorMessage`
- * 已落库、但 `statusCode` 仍为空且已稳定结束的写路径时，这些记录会被当前可用性统计排除。
- * 届时应引入独立的 finalized 谓词，而不是直接放宽为 `durationMs IS NOT NULL`。
+ * 可用性监控用 `statusCode IS NOT NULL` 作为终态边界。
+ * 请求过程中的中间状态可能已经有 providerChain/errorMessage 片段，但仍不能算入可用性，
+ * 否则会把 requesting 中的请求误判为失败。success-rate outcome 仅用于终态记录的分类。
  */
 function buildAvailabilityFinalizedCondition() {
-  return sql`fn_is_message_request_finalized(
-    ${messageRequest.blockedBy},
-    ${messageRequest.statusCode},
-    ${messageRequest.providerChain},
-    ${messageRequest.errorMessage}
-  )`;
+  return isNotNull(messageRequest.statusCode);
 }
 
 function assertValidDate(date: Date, fieldName: string): Date {
diff --git a/tests/unit/lib/availability-service.test.ts b/tests/unit/lib/availability-service.test.ts
index ac14b0013..582223f56 100644
--- a/tests/unit/lib/availability-service.test.ts
+++ b/tests/unit/lib/availability-service.test.ts
@@ -39,15 +39,45 @@ function normalizeSql(sqlObject: unknown): string {
   return sqlToString(sqlObject).replace(/\s+/g, " ").trim().toLowerCase();
 }
 
+function findCteBoundary(
+  queryText: string,
+  cteName: string
+): { cteStart: number; boundaryStart: number } | null {
+  // cteName 先经长度/格式校验，再生成 escapedName 参与受控测试正则构造。
+  if (queryText.length === 0 || cteName.length > 100 || !/^[a-z_][a-z0-9_]*$/i.test(cteName)) {
+    return null;
+  }
+
+  const escapedName = cteName.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+  const match = new RegExp(`(^|\\bwith\\s+|,\\s*)("?${escapedName}"?)\\s+as\\s*\\(`).exec(
+    queryText
+  );
+
+  if (!match?.[2]) {
+    return null;
+  }
+
+  return {
+    cteStart: match.index + match[1].length,
+    boundaryStart: match.index,
+  };
+}
+
 function extractFinalizedRequestsSql(queryText: string): string {
-  const start = queryText.indexOf("finalized_requests as");
-  const end = queryText.indexOf("provider_bucket_stats as");
+  const start = findCteBoundary(queryText, "finalized_requests");
+  const end = findCteBoundary(queryText, "provider_bucket_stats");
 
-  if (start === -1 || end === -1 || end <= start) {
-    throw new Error("Could not locate finalized_requests CTE in query text");
+  if (!start) {
+    throw new Error("finalized_requests CTE not found in query text");
+  }
+  if (!end) {
+    throw new Error("provider_bucket_stats CTE not found in query text");
+  }
+  if (end.boundaryStart <= start.cteStart) {
+    throw new Error("finalized_requests CTE appears after provider_bucket_stats CTE");
   }
 
-  return queryText.slice(start, end);
+  return queryText.slice(start.cteStart, end.boundaryStart);
 }
 
 describe("availability-service", () => {
@@ -309,7 +339,7 @@ describe("availability-service", () => {
 
     const queryText = normalizeSql(executeMock.mock.calls[0]?.[0]);
     const finalizedRequestsSql = extractFinalizedRequestsSql(queryText);
-    expect(finalizedRequestsSql).toContain("fn_is_message_request_finalized");
+    expect(finalizedRequestsSql).toContain('"status_code" is not null');
     expect(queryText).toContain("group by");
     expect(queryText).toContain("percentile_cont(0.95)");
     expect(queryText).toContain("row_number() over");
@@ -482,7 +512,7 @@ describe("availability-service", () => {
     const finalizedRequestsSql = extractFinalizedRequestsSql(
       normalizeSql(executeMock.mock.calls[0]?.[0])
     );
-    expect(finalizedRequestsSql).toContain("fn_is_message_request_finalized");
+    expect(finalizedRequestsSql).toContain('"status_code" is not null');
   });
 
   it("queryProviderAvailability 会保留 Gemini passthrough 终态(statusCode!=null 且 durationMs=null)", async () => {
@@ -515,6 +545,7 @@ describe("availability-service", () => {
     const finalizedRequestsSql = extractFinalizedRequestsSql(
       normalizeSql(executeMock.mock.calls[0]?.[0])
     );
+    expect(finalizedRequestsSql).toContain('"status_code" is not null');
     expect(finalizedRequestsSql).not.toMatch(/where .*duration_?ms.*is not null/);
   });
 
@@ -548,7 +579,7 @@ describe("availability-service", () => {
     const queryText = normalizeSql(executeMock.mock.calls[0]?.[0]);
     const finalizedRequestsSql = extractFinalizedRequestsSql(queryText);
 
-    expect(finalizedRequestsSql).toContain("fn_is_message_request_finalized");
+    expect(finalizedRequestsSql).toContain('"status_code" is not null');
     expect(queryText).toContain("fn_compute_message_request_success_rate_outcome");
     expect(queryText).toContain(`"successrateoutcome" = 'failure'`);
   });
@@ -717,7 +748,7 @@ describe("availability-service", () => {
     ]);
 
     const queryText = normalizeSql(executeMock.mock.calls[0]?.[0]);
-    expect(queryText).toContain("fn_is_message_request_finalized");
+    expect(queryText).toContain('"status_code" is not null');
     expect(queryText).toContain(">= now() - (15 * interval '1 minute')");
     expect(queryText).toContain("<= now()");
     expect(queryText).toContain("count(*) filter");