diff --git a/core/file_server/FileDiscoveryOptions.cpp b/core/file_server/FileDiscoveryOptions.cpp
index 632a2cb2bd..5340167601 100644
--- a/core/file_server/FileDiscoveryOptions.cpp
+++ b/core/file_server/FileDiscoveryOptions.cpp
@@ -214,6 +214,23 @@ bool FileDiscoveryOptions::Init(const Json::Value& config,
         mBasePathInfos.push_back(std::move(pathInfo));
     }
 
+    bool isNas = false;
+    if (!GetOptionalBoolParam(config, "IsNas", isNas, errorMsg)) {
+        PARAM_WARNING_DEFAULT(ctx.GetLogger(),
+                              ctx.GetAlarm(),
+                              errorMsg,
+                              isNas,
+                              pluginType,
+                              ctx.GetConfigName(),
+                              ctx.GetProjectName(),
+                              ctx.GetLogstoreName(),
+                              ctx.GetRegion());
+    }
+    mIsNas = isNas;
+    if (isNas) {
+        mMaxDirSearchDepth = 0;
+    }
+
     // PreservedDirDepth
     if (!GetOptionalIntParam(config, "PreservedDirDepth", mPreservedDirDepth, errorMsg)) {
         PARAM_WARNING_DEFAULT(ctx.GetLogger(),
diff --git a/core/file_server/FileDiscoveryOptions.h b/core/file_server/FileDiscoveryOptions.h
index 5a66e86dc3..749ad0e84e 100644
--- a/core/file_server/FileDiscoveryOptions.h
+++ b/core/file_server/FileDiscoveryOptions.h
@@ -112,6 +112,7 @@ class FileDiscoveryOptions {
     int64_t GetLastContainerUpdateTime() const { return mLastContainerUpdateTime; }
     void SetLastContainerUpdateTime(int64_t time) { mLastContainerUpdateTime = time; }
 
+    bool IsNas() const { return mIsNas; }
 
     std::vector<std::string> mFilePaths;
     int32_t mMaxDirSearchDepth = 0;
@@ -121,6 +122,7 @@ class FileDiscoveryOptions {
     std::vector<std::string> mExcludeDirs;
     bool mAllowingCollectingFilesInRootDir = false;
     bool mAllowingIncludedByMultiConfigs = false;
+    bool mIsNas = false;
 
 private:
     void ParseWildcardPath(BasePathInfo& pathInfo);
diff --git a/core/file_server/reader/LogFileReader.cpp b/core/file_server/reader/LogFileReader.cpp
index 4a378b2549..f5bddec28b 100644
--- a/core/file_server/reader/LogFileReader.cpp
+++ b/core/file_server/reader/LogFileReader.cpp
@@ -33,8 +33,11 @@
 
 #include "boost/filesystem.hpp"
 #include "boost/regex.hpp"
+#include "json/json.h"
 #include "rapidjson/document.h"
 
+#include "collection_pipeline/CollectionPipeline.h"
+
 #include "app_config/AppConfig.h"
 #include "application/Application.h"
 #include "collection_pipeline/queue/ExactlyOnceQueueManager.h"
@@ -78,6 +81,9 @@ DEFINE_FLAG_INT32(max_fix_pos_bytes, "", 128 * 1024);
 DEFINE_FLAG_INT32(force_release_deleted_file_fd_timeout,
                   "force release fd if file is deleted after specified seconds, no matter read to end or not",
                   -1);
+DEFINE_FLAG_INT32(nas_read_stable_interval_ms,
+                  "NAS mode: refresh readable size interval in ms (align with NFS FileAttr cache T 1s~60s), default 1000",
+                  1000);
 #if defined(_MSC_VER)
 // On Windows, if Chinese config base path is used, the log path will be converted to GBK,
 // so the __tag__.__path__ have to be converted back to UTF8 to avoid bad display.
@@ -118,6 +124,9 @@ LogFileReader* LogFileReader::CreateLogFileReader(const string& hostLogPathDir,
     }
 
     if (reader) {
+        if (discoveryConfig.first) {
+            reader->SetNasMode(discoveryConfig.first->IsNas());
+        }
         if (forceFromBeginning) {
             reader->SetReadFromBeginning();
         }
@@ -256,6 +265,41 @@ void LogFileReader::SetMetrics() {
     mSourceReadOffsetBytes = mMetricsRecordRef->GetIntGauge(METRIC_PLUGIN_SOURCE_READ_OFFSET_BYTES);
 }
 
+bool LogFileReader::PrepareNasRead(bool isFlushTimeout) {
+    if (!mIsNasMode || isFlushTimeout || !mLogFileOp.IsOpen()) {
+        return true;
+    }
+    fsutil::PathStat statBuf;
+    if (mLogFileOp.Stat(statBuf) != 0) {
+        return true;
+    }
+    const int64_t curSize = statBuf.GetFileSize();
+    const uint64_t nowMs = GetCurrentTimeInMilliSeconds();
+    const bool shouldUpdateBoundary = (mNasLastBoundaryTimeMs == 0)
+                                      || (nowMs - mNasLastBoundaryTimeMs
+                                          >= static_cast<uint64_t>(INT32_FLAG(nas_read_stable_interval_ms)));
+    if (shouldUpdateBoundary) {
+        bool isDeleted = false;
+        CloseFilePtr(isDeleted);
+        if (isDeleted || !UpdateFilePtr()) {
+            return false;
+        }
+        mNasLastBoundaryTimeMs = nowMs;
+        mNasSizeAtLastSecondBoundary = curSize;
+    }
+    if (mNasSizeAtLastSecondBoundary < 0) {
+        mNasSizeAtLastSecondBoundary = std::min(curSize, mLastFilePos > 0 ? mLastFilePos : 0);
+    }
+    int64_t readableSize;
+    if (mNasSizeAtLastSecondBoundary < mLastFilePos) {
+        readableSize = mLastFilePos;
+    } else {
+        readableSize = std::min(mLastFileSize, mNasSizeAtLastSecondBoundary);
+    }
+    SetExpectedFileSize(readableSize);
+    return true;
+}
+
 void LogFileReader::DumpMetaToMem(bool checkConfigFlag, int32_t idxInReaderArray) {
     if (checkConfigFlag) {
         size_t index = mHostLogPath.rfind(PATH_SEPARATOR);
@@ -993,6 +1037,9 @@ bool LogFileReader::ReadLog(LogBuffer& logBuffer, const Event* event, bool isSta
             return false;
         }
     }
+    if (!PrepareNasRead(event != nullptr && event->IsReaderFlushTimeout())) {
+        return false;
+    }
     bool moreData = GetRawData(logBuffer, mLastFileSize, tryRollback, isStaticFile);
     if (!logBuffer.rawBuffer.empty()) {
         if (mEOOption) {
diff --git a/core/file_server/reader/LogFileReader.h b/core/file_server/reader/LogFileReader.h
index bedded7656..a0d01a2215 100644
--- a/core/file_server/reader/LogFileReader.h
+++ b/core/file_server/reader/LogFileReader.h
@@ -279,6 +279,7 @@ class LogFileReader {
         mLastFilePos = pos;
     }
     void SetExpectedFileSize(int64_t size) { mExpectedFileSize = size; }
+    void SetNasMode(bool isNas) { mIsNasMode = isNas; }
     void
     InitReader(bool tailExisted = false, FileReadPolicy policy = BACKWARD_TO_FIXED_POS, uint32_t eoConcurrency = 0);
 
@@ -486,6 +487,8 @@ class LogFileReader {
     }
     void ResolveHostLogPath();
 
+    // NAS mode: compute stable size and call SetExpectedFileSize(stableSize); no out param.
+    bool PrepareNasRead(bool isFlushTimeout);
     // std::string mRegion;
     // std::string mCategory;
     // std::string mConfigName;
@@ -578,6 +581,11 @@ class LogFileReader {
     IntGaugePtr mSourceSizeBytes;
     IntGaugePtr mSourceReadOffsetBytes;
 
+    // NAS mode: read up to "file size from 1s ago", update every 1s (reopen + refresh boundary size).
+    bool mIsNasMode = false;
+    uint64_t mNasLastBoundaryTimeMs = 0;   // last time we updated readable size; 0 = not yet
+    int64_t mNasSizeAtLastSecondBoundary = -1; // file size at last boundary (readable limit)
+
 private:
     bool mHasReadContainerBom = false;
     void checkContainerType(LogFileOperator& op);