diff --git a/.blueprint/manifest.yaml b/.blueprint/manifest.yaml
index cfe193a..3b14ddb 100644
--- a/.blueprint/manifest.yaml
+++ b/.blueprint/manifest.yaml
@@ -494,7 +494,7 @@ modules:
     area: infra
     status: done
     progress: 100
-    updated: 2026-09-26
+    updated: 2026-10-02
     note: "R1–R11 的合成路径和真实 Codex CLI 客户端试点已验证；真实用户凭证迁移、正式版 UI 与生产链路未验证，未启动第二个日常 Tauri 实例。"
     position: [3000, 950]
 
diff --git a/.blueprint/modules/project-resource-broker.md b/.blueprint/modules/project-resource-broker.md
index 7920f91..1151b32 100644
--- a/.blueprint/modules/project-resource-broker.md
+++ b/.blueprint/modules/project-resource-broker.md
@@ -68,6 +68,16 @@ progress: 100
 
 ## 任务拆解
 
+### ✅ R12 — 修复并行测试偶发失败：Credential Manager 串行化 + 模拟 Gitea 阻塞读
+- status: done
+- complexity: S
+- files: src-tauri/src/credential_store.rs, src-tauri/src/mcp_server.rs
+- depends: R3, R10
+- acceptance: "agent_verify: [cargo test] 全量并行连续 30 次 → 0 失败（修复前基线 10 次失败 3 次：R10 scoped_mcp_create_pull_request_uses_synthetic_credential 的 readiness=needs_repair、scoped_dev_variable_http_pilot 的「凭证引用缺失」；仅修凭据后 30 次仍有 1 次 R10 模拟 Gitea read_line WouldBlock）。"
+- verification: "2026-10-02：修复后全量并行 cargo test 连续 30 次 0 失败（247 passed、5 ignored）；仅凭据串行化的中间版本 30 次中凭据类失败为 0。"
+- unverified: "跨进程并发（如 tauri dev 实例与 cargo test 同时写凭据）不受进程内锁保护；历史失败可能在本机 Credential Manager 残留无权限合成条目，非 diag 前缀的未逐条清理。"
+- root_cause: "①同进程并发 CredWriteW/CredDeleteW 丢更新——写入成功后立即读回 NOT_FOUND、删除成功的条目被并发写回（8 线程压力实验复现；诊断日志证实无跨测试删除）；②Windows 上 nonblocking listener accept 出的 socket 继承 nonblocking，set_read_timeout 不生效，客户端请求晚到即 WouldBlock（commands/gitea.rs 已有同款修复，mcp_server 两处 mock 遗漏）。"
+
 ### ✅ R11 — 隔离真实客户端试点宿主
 - status: done
 - complexity: M
diff --git a/src-tauri/src/credential_store.rs b/src-tauri/src/credential_store.rs
index a46e428..7db4597 100644
--- a/src-tauri/src/credential_store.rs
+++ b/src-tauri/src/credential_store.rs
@@ -328,6 +328,17 @@ mod windows_store {
     const CRED_MAX_CREDENTIAL_BLOB_SIZE: usize = 5 * 512;
     const ERROR_NOT_FOUND: i32 = 1168;
 
+    /// 同进程内并发 CredWrite/CredDelete 实测会丢更新：写入成功后立即读回 NOT_FOUND，
+    /// 删除成功的条目又被并发写回（2026-10-02 并行 cargo test 偶发 needs_repair 的根因）。
+    /// 所有 Credential Manager 调用经此锁串行；跨进程并发不在此保护范围内。
+    static CREDENTIAL_MANAGER_LOCK: std::sync::Mutex<()> = std::sync::Mutex::new(());
+
+    fn serialized() -> std::sync::MutexGuard<'static, ()> {
+        CREDENTIAL_MANAGER_LOCK
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+    }
+
     #[repr(C)]
     struct FileTime {
         low: u32,
@@ -402,7 +413,10 @@ mod windows_store {
             target_alias: null_mut(),
             user_name: null_mut(),
         };
-        let ok = unsafe { CredWriteW(&credential, 0) };
+        let ok = {
+            let _guard = serialized();
+            unsafe { CredWriteW(&credential, 0) }
+        };
         blob.fill(0);
         if ok == 0 {
             Err("Credential Manager 写入失败".into())
@@ -414,6 +428,7 @@ mod windows_store {
     pub fn get(reference: &str) -> Result<Option<Vec<u8>>, String> {
         let target = target(reference)?;
         let mut raw = null_mut();
+        let _guard = serialized();
         let ok = unsafe { CredReadW(target.as_ptr(), CRED_TYPE_GENERIC, 0, &mut raw) };
         if ok == 0 {
             let error = std::io::Error::last_os_error();
@@ -450,6 +465,7 @@ mod windows_store {
 
     pub fn delete(reference: &str) -> Result<(), String> {
         let target = target(reference)?;
+        let _guard = serialized();
         let ok = unsafe { CredDeleteW(target.as_ptr(), CRED_TYPE_GENERIC, 0) };
         if ok != 0 {
             return Ok(());
diff --git a/src-tauri/src/mcp_server.rs b/src-tauri/src/mcp_server.rs
index ad4e572..955caff 100644
--- a/src-tauri/src/mcp_server.rs
+++ b/src-tauri/src/mcp_server.rs
@@ -1045,6 +1045,8 @@ mod tests {
                     Err(error) => panic!("模拟 Gitea 未收到请求: {error}"),
                 }
             };
+            // Windows 上从 nonblocking listener 接受的 socket 也可能保持 nonblocking。
+            stream.set_nonblocking(false).unwrap();
             stream
                 .set_read_timeout(Some(std::time::Duration::from_secs(3)))
                 .unwrap();
@@ -1217,6 +1219,8 @@ mod tests {
                     Err(error) => panic!("5 分钟内未收到客户端的模拟 PR 请求: {error}"),
                 }
             };
+            // Windows 上从 nonblocking listener 接受的 socket 也可能保持 nonblocking。
+            stream.set_nonblocking(false).unwrap();
             stream
                 .set_read_timeout(Some(std::time::Duration::from_secs(5)))
                 .unwrap();