diff --git a/Source/Engine/Gramambular/Node.h b/Source/Engine/Gramambular/Node.h
index 89a74813..6e2bf45e 100644
--- a/Source/Engine/Gramambular/Node.h
+++ b/Source/Engine/Gramambular/Node.h
@@ -47,10 +47,12 @@ namespace Formosa {
             const vector<KeyValuePair>& candidates() const;
             void selectCandidateAtIndex(size_t inIndex = 0, bool inFix = true);
             void resetCandidate();
+            void selectFloatingCandidateAtIndex(size_t index, double score);
             
             const string& key() const;
             double score() const;
             const KeyValuePair currentKeyValue() const;
+            double highestUnigramScore() const;
             
         protected:
             const LanguageModel* m_LM;
@@ -175,6 +177,16 @@ namespace Formosa {
                 m_score = m_unigrams[0].score;
             }
         }
+
+        inline void Node::selectFloatingCandidateAtIndex(size_t index, double score) {
+            if (index >= m_unigrams.size()) {
+                m_selectedUnigramIndex = 0;
+            } else {
+                m_selectedUnigramIndex = index;
+            }
+            m_candidateFixed = false;
+            m_score = score;
+        }
         
         inline const string& Node::key() const
         {
@@ -185,6 +197,13 @@ namespace Formosa {
         {
             return m_score;
         }
+
+        inline double Node::highestUnigramScore() const {
+            if (m_unigrams.empty()) {
+                return 0.0;
+            }
+            return m_unigrams[0].score;
+        }
         
         inline const KeyValuePair Node::currentKeyValue() const
         {
diff --git a/Source/InputMethodController.h b/Source/InputMethodController.h
index 8741cbed..71437a00 100644
--- a/Source/InputMethodController.h
+++ b/Source/InputMethodController.h
@@ -37,6 +37,7 @@
 #import "Mandarin.h"
 #import "Gramambular.h"
 #import "FastLM.h"
+#import "UserOverrideModel.h"
 
 @interface McBopomofoInputMethodController : IMKInputController
 {
@@ -53,6 +54,9 @@
     // latest walked path (trellis) using the Viterbi algorithm
     std::vector<Formosa::Gramambular::NodeAnchor> _walkedNodes;
 
+    // user override model
+    McBopomofo::UserOverrideModel *_uom;
+
     // the latest composing buffer that is updated to the foreground app
     NSMutableString *_composingBuffer;
     NSInteger _latestReadingCursor;
diff --git a/Source/InputMethodController.mm b/Source/InputMethodController.mm
index 3b4ad001..b11e4609 100644
--- a/Source/InputMethodController.mm
+++ b/Source/InputMethodController.mm
@@ -114,6 +114,7 @@ static NSString *const kGraphVizOutputfile = @"/tmp/McBopomofo-visualization.dot
 // shared language model object that stores our phrase-term probability database
 FastLM gLanguageModel;
 FastLM gLanguageModelPlainBopomofo;
+McBopomofo::UserOverrideModel gUserOverrideModel(200, 60.0);
 
 // https://clang-analyzer.llvm.org/faq.html
 __attribute__((annotate("returns_localized_nsstring")))
@@ -176,6 +177,7 @@ public:
         // create the lattice builder
         _languageModel = &gLanguageModel;
         _builder = new BlockReadingBuilder(_languageModel);
+        _uom = &gUserOverrideModel;
 
         // each Mandarin syllable is separated by a hyphen
         _builder->setJoinSeparator("-");
@@ -659,6 +661,33 @@ public:
         // then walk the lattice
         [self popOverflowComposingTextAndWalk:client];
 
+        // get user override model suggestion
+        string overrideCandidate = _uom->suggest(_walkedNodes, _builder->cursorIndex(), [[NSDate date] timeIntervalSince1970]);
+        if (!overrideCandidate.empty()) {
+            size_t cursorIndex = [self actualCandidateCursorIndex];
+            vector<NodeAnchor> nodes = _builder->grid().nodesCrossingOrEndingAt(cursorIndex);
+
+            double highestScore = 0.0;
+            for (auto ni = nodes.begin(), ne = nodes.end(); ni != ne; ++ni) {
+                double score = ni->node->highestUnigramScore();
+                if (score > highestScore) {
+                    highestScore = score;
+                }
+            }
+            highestScore += 0.00001;
+
+            for (vector<NodeAnchor>::iterator ni = nodes.begin(), ne = nodes.end(); ni != ne; ++ni) {
+                const vector<KeyValuePair>& candidates = (*ni).node->candidates();
+                for (size_t i = 0, c = candidates.size(); i < c; ++i) {
+                    if (candidates[i].value == overrideCandidate) {
+                        // found our node
+                        const_cast<Node*>((*ni).node)->selectFloatingCandidateAtIndex(i, highestScore);
+                        break;
+                    }
+                }
+            }
+        }
+
         // then update the text
         _bpmfReadingBuffer->clear();
         [self updateClientComposingBuffer:client];
@@ -1373,6 +1402,7 @@ public:
 
     size_t cursorIndex = [self actualCandidateCursorIndex];
     _builder->grid().fixNodeSelectedCandidate(cursorIndex, selectedValue);
+    _uom->observe(_walkedNodes, cursorIndex, selectedValue, [[NSDate date] timeIntervalSince1970]);
 
     [_candidates removeAllObjects];