diff --git a/src/rime/lever/deployment_tasks.cc b/src/rime/lever/deployment_tasks.cc
index 5e2e6d9d5..639db48ac 100644
--- a/src/rime/lever/deployment_tasks.cc
+++ b/src/rime/lever/deployment_tasks.cc
@@ -4,6 +4,7 @@
 //
 // 2011-12-10 GONG Chen <chen.sst@gmail.com>
 //
+#include <algorithm>
 #include <boost/algorithm/string.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/uuid/random_generator.hpp>
@@ -30,6 +31,51 @@ namespace fs = boost::filesystem;
 
 namespace rime {
 
+DetectModifications::DetectModifications(TaskInitializer arg) {
+  try {
+    data_dirs_ = boost::any_cast<vector<string>>(arg);
+  }
+  catch (const boost::bad_any_cast&) {
+    LOG(ERROR) << "DetectModifications: invalid arguments.";
+  }
+}
+
+bool DetectModifications::Run(Deployer* deployer) {
+  time_t last_modified = 0;
+  try {
+    for (auto dir : data_dirs_) {
+      fs::path p = fs::canonical(dir);
+      last_modified = (std::max)(last_modified, fs::last_write_time(p));
+      if (fs::is_directory(p)) {
+        for (fs::directory_iterator iter(p), end; iter != end; ++iter) {
+          fs::path entry(iter->path());
+          if (fs::is_regular_file(fs::canonical(entry)) &&
+              entry.extension().string() == ".yaml" &&
+              entry.filename().string() != "user.yaml") {
+            last_modified =
+                (std::max)(last_modified, fs::last_write_time(entry));
+          }
+        }
+      }
+    }
+  } catch(const fs::filesystem_error& ex) {
+    LOG(ERROR) << "Error reading file information: " << ex.what();
+    return true;
+  }
+
+  // TODO: store as 64-bit number to avoid the year 2038 problem
+  int last_build_time = 0;
+  {
+    the<Config> user_config(Config::Require("config")->Create("user"));
+    user_config->GetInt("var/last_build_time", &last_build_time);
+  }
+  if (last_modified > (time_t)last_build_time) {
+    LOG(INFO) << "modifications detected. workspace needs update.";
+    return true;
+  }
+  return false;
+}
+
 bool InstallationUpdate::Run(Deployer* deployer) {
   LOG(INFO) << "updating rime installation info.";
   fs::path shared_data_path(deployer->shared_data_dir);
@@ -188,6 +234,11 @@ bool WorkspaceUpdate::Run(Deployer* deployer) {
   }
   LOG(INFO) << "finished updating schemas: "
             << success << " success, " << failure << " failure.";
+
+  the<Config> user_config(Config::Require("config")->Create("user"));
+  // TODO: store as 64-bit number to avoid the year 2038 problem
+  user_config->SetInt("var/last_build_time", (int)time(NULL));
+
   return failure == 0;
 }
 
@@ -263,6 +314,7 @@ bool SchemaUpdate::Run(Deployer* deployer) {
     LOG(INFO) << "patched copy of schema '" << schema_id
               << "' is moved to trash";
   }
+  // TODO: compile the config file if needs update
 
   string dict_name;
   if (!config->GetString("translator/dictionary", &dict_name)) {
@@ -281,6 +333,7 @@ bool SchemaUpdate::Run(Deployer* deployer) {
   if (verbose_) {
     dict_compiler.set_options(DictCompiler::kRebuild | DictCompiler::kDump);
   }
+  // TODO: use compiled schema instead of the YAML file alone
   if (!dict_compiler.Compile(schema_file_)) {
     LOG(ERROR) << "dictionary '" << dict_name << "' failed to compile.";
     return false;
@@ -317,6 +370,7 @@ bool ConfigFileUpdate::Run(Deployer* deployer) {
                           trash)) {
     LOG(INFO) << "patched copy of '" << file_name_ << "' is moved to trash.";
   }
+  // TODO: compile the config file if needs update
   return true;
 }
 
diff --git a/src/rime/lever/deployment_tasks.h b/src/rime/lever/deployment_tasks.h
index d742be68f..66a9815f0 100644
--- a/src/rime/lever/deployment_tasks.h
+++ b/src/rime/lever/deployment_tasks.h
@@ -7,11 +7,23 @@
 #ifndef RIME_DEPLOYMENT_TASKS_H_
 #define RIME_DEPLOYMENT_TASKS_H_
 
+#include <rime/common.h>
 #include <rime/deployer.h>
 
 namespace rime {
 
-// initialize/update installation.yaml, default.yaml
+// detects changes in either user configuration or upgraded shared data
+class DetectModifications : public DeploymentTask {
+ public:
+  DetectModifications(TaskInitializer arg = TaskInitializer());
+  // Unlike other tasks, its return value indicates whether modifications
+  // has been detected and workspace needs update.
+  bool Run(Deployer* deployer);
+ protected:
+  vector<string> data_dirs_;
+};
+
+// initialize/update installation.yaml
 class InstallationUpdate : public DeploymentTask {
  public:
   InstallationUpdate(TaskInitializer arg = TaskInitializer()) {}
diff --git a/src/rime/lever/levers_module.cc b/src/rime/lever/levers_module.cc
index e49d9bebf..e5ad1f2d9 100644
--- a/src/rime/lever/levers_module.cc
+++ b/src/rime/lever/levers_module.cc
@@ -24,6 +24,7 @@ static void rime_levers_initialize() {
   Registry& r = Registry::instance();
 
   // deployment tools
+  r.Register("detect_modifications", new Component<DetectModifications>);
   r.Register("installation_update", new Component<InstallationUpdate>);
   r.Register("workspace_update", new Component<WorkspaceUpdate>);
   r.Register("schema_update", new Component<SchemaUpdate>);
diff --git a/src/rime_api.cc b/src/rime_api.cc
index 8322040f6..02271b25e 100644
--- a/src/rime_api.cc
+++ b/src/rime_api.cc
@@ -105,8 +105,9 @@ RIME_API Bool RimeStartMaintenance(Bool full_check) {
   }
   if (!full_check) {
     TaskInitializer args{
-        make_pair<string, string>("default.yaml", "config_version")};
-    if (!deployer.RunTask("config_file_update", args)) {
+      vector<string>{deployer.user_data_dir, deployer.shared_data_dir}
+    };
+    if (!deployer.RunTask("detect_modifications", args)) {
       return False;
     }
     LOG(INFO) << "changes detected; starting maintenance.";