diff --git a/src/protocol/commands.proto b/src/protocol/commands.proto
index d9ca8c819..6886d7682 100644
--- a/src/protocol/commands.proto
+++ b/src/protocol/commands.proto
@@ -543,7 +543,7 @@ message Capability {
       [default = NO_TEXT_DELETION_CAPABILITY];
 }
 
-// Next ID: 105
+// Next ID: 106
 // Bundles together some Android experiment flags so that they can be easily
 // retrieved throughout the native code.  These flags are generally specific to
 // the decoder, and are made available when the decoder is initialized.
@@ -646,6 +646,9 @@ message DecoderExperimentParams {
   // history rewriter wheh the target segment contains proper noun candidate.
   optional bool user_segment_history_rewriter_replace_proper_noun = 103
       [default = false];
+
+  // Apply inner segment boundary information to the single segment candidate.
+  optional bool apply_single_inner_segment_boundary = 105 [default = true];
 }
 
 // Clients' request to the server.
diff --git a/src/rewriter/user_segment_history_rewriter.cc b/src/rewriter/user_segment_history_rewriter.cc
index d54b3c57d..d38058c3d 100644
--- a/src/rewriter/user_segment_history_rewriter.cc
+++ b/src/rewriter/user_segment_history_rewriter.cc
@@ -740,11 +740,21 @@ bool UserSegmentHistoryRewriter::IsAvailable(const ConversionRequest &request,
 // Returns segments for learning.
 // Inner segments boundary will be expanded.
 Segments UserSegmentHistoryRewriter::MakeLearningSegmentsFromInnerSegments(
-    const Segments &segments) {
+    const ConversionRequest &request, const Segments &segments) {
+  auto inner_segments_info_available = [&request](const Segment::Candidate &c) {
+    if (request.request()
+            .decoder_experiment_params()
+            .apply_single_inner_segment_boundary()) {
+      return !c.inner_segment_boundary.empty();
+    } else {
+      return c.inner_segment_boundary.size() > 1;
+    }
+  };
+
   Segments ret;
   for (const Segment &segment : segments) {
     const Segment::Candidate &candidate = segment.candidate(0);
-    if (candidate.inner_segment_boundary.empty()) {
+    if (!inner_segments_info_available(candidate)) {
       // No inner segment info
       Segment *seg = ret.add_segment();
       *seg = segment;
@@ -796,7 +806,7 @@ void UserSegmentHistoryRewriter::Finish(const ConversionRequest &request,
 
   const Segments target_segments =
       UseInnerSegments(request)
-          ? MakeLearningSegmentsFromInnerSegments(*segments)
+          ? MakeLearningSegmentsFromInnerSegments(request, *segments)
           : *segments;
   std::vector<Segments::RevertEntry> revert_entries;
   for (size_t i = target_segments.history_segments_size();
diff --git a/src/rewriter/user_segment_history_rewriter.h b/src/rewriter/user_segment_history_rewriter.h
index c9e3a0c98..6187bb064 100644
--- a/src/rewriter/user_segment_history_rewriter.h
+++ b/src/rewriter/user_segment_history_rewriter.h
@@ -90,7 +90,7 @@ class UserSegmentHistoryRewriter : public RewriterInterface {
   };
 
   static Segments MakeLearningSegmentsFromInnerSegments(
-      const Segments &segments);
+      const ConversionRequest &request, const Segments &segments);
 
   // Returns id for RevertEntry
   static uint16_t revert_id();
diff --git a/src/rewriter/user_segment_history_rewriter_test.cc b/src/rewriter/user_segment_history_rewriter_test.cc
index 4b331a4db..1262332fa 100644
--- a/src/rewriter/user_segment_history_rewriter_test.cc
+++ b/src/rewriter/user_segment_history_rewriter_test.cc
@@ -67,9 +67,9 @@ class UserSegmentHistoryRewriterTestPeer {
   UserSegmentHistoryRewriterTestPeer() = delete;
 
   static Segments MakeLearningSegmentsFromInnerSegments(
-      const Segments &segments) {
+      const ConversionRequest &request, const Segments &segments) {
     return UserSegmentHistoryRewriter::MakeLearningSegmentsFromInnerSegments(
-        segments);
+        request, segments);
   }
 };
 
@@ -1755,9 +1755,11 @@ TEST_F(UserSegmentHistoryRewriterTest, SupportInnerSegmentsOnLearning) {
         Segment::Candidate::RERANKED;
     segments.mutable_segment(0)->set_segment_type(Segment::FIXED_VALUE);
 
+    const ConversionRequest default_mobile_convreq = CreateConversionRequest();
     {
       const Segments learning_segments = UserSegmentHistoryRewriterTestPeer::
-          MakeLearningSegmentsFromInnerSegments(segments);
+          MakeLearningSegmentsFromInnerSegments(default_mobile_convreq,
+                                                segments);
       EXPECT_EQ(learning_segments.segments_size(), 3);
       EXPECT_EQ(learning_segments.segment(0).key(), "わたしの");
       EXPECT_EQ(learning_segments.segment(0).candidate(0).key, "わたしの");
@@ -1795,8 +1797,7 @@ TEST_F(UserSegmentHistoryRewriterTest, SupportInnerSegmentsOnLearning) {
                 Segment::FIXED_VALUE);
     }
 
-    const ConversionRequest convreq = CreateConversionRequest();
-    rewriter->Finish(convreq, &segments);
+    rewriter->Finish(default_mobile_convreq, &segments);
   }
 
   {
@@ -1823,9 +1824,11 @@ TEST_F(UserSegmentHistoryRewriterTest, SupportInnerSegmentsOnLearning) {
         Segment::Candidate::RERANKED;
     segments.mutable_segment(0)->set_segment_type(Segment::FIXED_VALUE);
 
+    const ConversionRequest default_mobile_convreq = CreateConversionRequest();
     {
       const Segments learning_segments = UserSegmentHistoryRewriterTestPeer::
-          MakeLearningSegmentsFromInnerSegments(segments);
+          MakeLearningSegmentsFromInnerSegments(default_mobile_convreq,
+                                                segments);
       EXPECT_EQ(learning_segments.segments_size(), 1);
       EXPECT_EQ(learning_segments.segment(0).key(), "わたしの");
       EXPECT_EQ(learning_segments.segment(0).candidate(0).key, "わたしの");
@@ -1839,52 +1842,7 @@ TEST_F(UserSegmentHistoryRewriterTest, SupportInnerSegmentsOnLearning) {
                 Segment::FIXED_VALUE);
     }
 
-    const ConversionRequest convreq = CreateConversionRequest();
-    rewriter->Finish(convreq, &segments);
-  }
-
-  {
-    // Inner segment boundary with size 1 may have better information.
-    segments.Clear();
-    InitSegments(&segments, 1, 2);
-    constexpr absl::string_view kKey = "わたしの";
-    constexpr absl::string_view kValue = "私の";
-    segments.mutable_segment(0)->set_key(kKey);
-    Segment::Candidate *candidate =
-        segments.mutable_segment(0)->mutable_candidate(1);
-
-    candidate->value = kValue;
-    candidate->content_value = kValue;
-    candidate->key = kKey;
-    candidate->content_key = kKey;
-    // "わたしの, 私の", "わたし, 私"
-    candidate->PushBackInnerSegmentBoundary(12, 6, 9, 3);
-    candidate->lid = 10;
-    candidate->rid = 10;
-
-    segments.mutable_segment(0)->move_candidate(1, 0);
-    segments.mutable_segment(0)->mutable_candidate(0)->attributes |=
-        Segment::Candidate::RERANKED;
-    segments.mutable_segment(0)->set_segment_type(Segment::FIXED_VALUE);
-
-    {
-      const Segments learning_segments = UserSegmentHistoryRewriterTestPeer::
-          MakeLearningSegmentsFromInnerSegments(segments);
-      EXPECT_EQ(learning_segments.segments_size(), 1);
-      EXPECT_EQ(learning_segments.segment(0).key(), "わたしの");
-      EXPECT_EQ(learning_segments.segment(0).candidate(0).key, "わたしの");
-      EXPECT_EQ(learning_segments.segment(0).candidate(0).value, "私の");
-      EXPECT_EQ(learning_segments.segment(0).candidate(0).content_key,
-                "わたし");
-      EXPECT_EQ(learning_segments.segment(0).candidate(0).content_value, "私");
-      EXPECT_EQ(learning_segments.segment(0).candidate(0).lid, 10);
-      EXPECT_EQ(learning_segments.segment(0).candidate(0).rid, 10);
-      EXPECT_EQ(learning_segments.segment(0).segment_type(),
-                Segment::FIXED_VALUE);
-    }
-
-    const ConversionRequest convreq = CreateConversionRequest();
-    rewriter->Finish(convreq, &segments);
+    rewriter->Finish(default_mobile_convreq, &segments);
   }
 
   {
@@ -1904,10 +1862,59 @@ TEST_F(UserSegmentHistoryRewriterTest, SupportInnerSegmentsOnLearning) {
     candidate->content_key = "なかの";
     candidate->content_key = "なかの";
 
-    const ConversionRequest convreq = CreateConversionRequest();
-    EXPECT_TRUE(rewriter->Rewrite(convreq, &segments));
+    const ConversionRequest default_mobile_convreq = CreateConversionRequest();
+    EXPECT_TRUE(rewriter->Rewrite(default_mobile_convreq, &segments));
     EXPECT_EQ(segments.segment(0).candidate(0).value, "中野");
   }
+
+  {
+    // Disable inner segment boundary for single segment
+    request_->mutable_decoder_experiment_params()
+        ->set_apply_single_inner_segment_boundary(false);
+
+    // Inner segment boundary with size 1 may have better information.
+    segments.Clear();
+    InitSegments(&segments, 1, 2);
+    constexpr absl::string_view kKey = "わたしの";
+    constexpr absl::string_view kValue = "私の";
+    segments.mutable_segment(0)->set_key(kKey);
+    Segment::Candidate *candidate =
+        segments.mutable_segment(0)->mutable_candidate(1);
+
+    candidate->value = kValue;
+    candidate->content_value = kValue;
+    candidate->key = kKey;
+    candidate->content_key = kKey;
+    // "わたしの, 私の", "わたし, 私"
+    candidate->PushBackInnerSegmentBoundary(12, 6, 9, 3);
+    candidate->lid = 10;
+    candidate->rid = 10;
+
+    segments.mutable_segment(0)->move_candidate(1, 0);
+    segments.mutable_segment(0)->mutable_candidate(0)->attributes |=
+        Segment::Candidate::RERANKED;
+    segments.mutable_segment(0)->set_segment_type(Segment::FIXED_VALUE);
+
+    const ConversionRequest convreq = CreateConversionRequest();
+    {
+      const Segments learning_segments = UserSegmentHistoryRewriterTestPeer::
+          MakeLearningSegmentsFromInnerSegments(convreq, segments);
+      EXPECT_EQ(learning_segments.segments_size(), 1);
+      EXPECT_EQ(learning_segments.segment(0).key(), "わたしの");
+      EXPECT_EQ(learning_segments.segment(0).candidate(0).key, "わたしの");
+      EXPECT_EQ(learning_segments.segment(0).candidate(0).value, "私の");
+      EXPECT_EQ(learning_segments.segment(0).candidate(0).content_key,
+                "わたしの");
+      EXPECT_EQ(learning_segments.segment(0).candidate(0).content_value,
+                "私の");
+      EXPECT_EQ(learning_segments.segment(0).candidate(0).lid, 10);
+      EXPECT_EQ(learning_segments.segment(0).candidate(0).rid, 10);
+      EXPECT_EQ(learning_segments.segment(0).segment_type(),
+                Segment::FIXED_VALUE);
+    }
+
+    rewriter->Finish(convreq, &segments);
+  }
 }
 
 TEST_F(UserSegmentHistoryRewriterTest, ReplaceableSingleKanji) {