diff --git a/4ed_file_view.cpp b/4ed_file_view.cpp
index 6e3fe123..09461b68 100644
--- a/4ed_file_view.cpp
+++ b/4ed_file_view.cpp
@@ -2517,7 +2517,9 @@ file_do_single_edit(Mem_Options *mem, Editing_File *file,
         if (old_data) general_memory_free(general, old_data);
     }
 
+#if BUFFER_EXPERIMENT_SCALPEL == 3
     buffer_rope_check(&file->buffer, part->base + part->pos, scratch_size);
+#endif
     
 #if BUFFER_EXPERIMENT_SCALPEL == 2
     buffer_mugab_check(&file->buffer);
diff --git a/buffer/4coder_buffer_abstract.cpp b/buffer/4coder_buffer_abstract.cpp
index a7174603..998c50cd 100644
--- a/buffer/4coder_buffer_abstract.cpp
+++ b/buffer/4coder_buffer_abstract.cpp
@@ -546,8 +546,7 @@ buffer_measure_starts_end:
 #endif
 
 internal_4tech int
-buffer_measure_starts_widths(Buffer_Measure_Starts *state, Buffer_Type *buffer,
-                             float *advance_data){
+buffer_measure_starts_widths(Buffer_Measure_Starts *state, Buffer_Type *buffer, float *advance_data){
     Buffer_Stringify_Type loop;
     int *start_ptr, *start_end;
     float *width_ptr;
diff --git a/buffer/4coder_multi_gap_buffer.cpp b/buffer/4coder_multi_gap_buffer.cpp
index ea91001a..3b385d6b 100644
--- a/buffer/4coder_multi_gap_buffer.cpp
+++ b/buffer/4coder_multi_gap_buffer.cpp
@@ -542,7 +542,8 @@ buffer_replace_range(Multi_Gap_Buffer *buffer, int start, int end, char *str, in
                     }
                     else{
                         middle_size = 0;
-                        assert_4tech(head_size + tail_size >= len);
+                        head_size = len - tail_size;
+                        assert_4tech(head_size + gap->size1 <= fixed_width_buffer_size);
                     }
                 }
                 else{
@@ -585,7 +586,7 @@ buffer_replace_range(Multi_Gap_Buffer *buffer, int start, int end, char *str, in
                 mem_pos += tail_size;
                 assert_4tech(mem_pos == len);
                 debug_4tech(local_start_pos += gap->size1 + gap->size2);
-                assert_4tech(local_start_pos == buffer->size);
+                //assert_4tech(local_start_pos == buffer->size);
 
                 buffer->chunk_count += required_empty_buffers;
 
diff --git a/buffer/4coder_test_abstract.cpp b/buffer/4coder_test_abstract.cpp
index 39801040..671ab18b 100644
--- a/buffer/4coder_test_abstract.cpp
+++ b/buffer/4coder_test_abstract.cpp
@@ -63,5 +63,80 @@ measure_starts_widths(Buffer_Type *buffer, float *font_widths){
     buffer->widths_count = state.count;
 }
 
+void
+edit(Buffer_Type *buffer, int start, int end, char *word, int len,
+     float *advance_data, void *scratch, int scratch_size){
+    int shift_amount, request_amount;
+    
+    for (;buffer_replace_range(buffer, start, end, word, len, &shift_amount,
+                               scratch, scratch_size, &request_amount);){
+        void *new_data = 0;
+        if (request_amount > 0) new_data = malloc(request_amount);
+        void *old_data = buffer_edit_provide_memory(buffer, new_data, request_amount);
+        if (old_data) free(old_data);
+    }
+    
+    int line_start = buffer_get_line_index(buffer, start);
+    int line_end = buffer_get_line_index(buffer, end);
+    int replaced_line_count = line_end - line_start;
+    int new_line_count = buffer_count_newlines(buffer, start, start+len);
+    int line_shift =  new_line_count - replaced_line_count;
+
+    {
+        assert_4tech(buffer->line_starts);
+        int count = buffer->line_count;
+        if (count + line_shift > buffer->line_max){
+            int new_max = round_up_4tech(buffer->line_max + line_shift, 1 << 10);
+            int *new_lines = (int*)malloc(sizeof(int)*new_max);
+            memcpy_4tech(new_lines, buffer->line_starts, sizeof(int)*count);
+            free(buffer->line_starts);
+
+            buffer->line_starts = new_lines;
+            buffer->line_max = new_max;
+        }
+        
+        buffer_remeasure_starts(buffer, line_start, line_end, line_shift, shift_amount);
+    }
+
+    {
+        assert_4tech(buffer->line_widths);
+        if (buffer->line_count > buffer->widths_max){
+            int new_max = round_up_4tech(buffer->line_max, 1 << 10);
+            float *new_widths = (float*)malloc(sizeof(float)*new_max);
+            memcpy_4tech(new_widths, buffer->line_widths, sizeof(float)*buffer->widths_count);
+            free(buffer->line_widths);
+            
+            buffer->line_widths = new_widths;
+            buffer->widths_max = new_max;
+        }
+
+        buffer_remeasure_widths(buffer, advance_data, line_start, line_end, line_shift);
+    }
+}
+
+void
+insert_bottom(Buffer_Type *buffer, char *word, int len, float *advance_data, void *scratch, int scratch_size){
+    int size;
+    size = buffer_size(buffer);
+    edit(buffer, size, size, word, len, advance_data, scratch, scratch_size);
+}
+
+void
+insert_top(Buffer_Type *buffer, char *word, int len, float *advance_data, void *scratch, int scratch_size){
+    edit(buffer, 0, 0, word, len, advance_data, scratch, scratch_size);
+}
+
+void
+delete_bottom(Buffer_Type *buffer, int len, float *advance_data, void *scratch, int scratch_size){
+    int size;
+    size = buffer_size(buffer);
+    edit(buffer, size - len, size, 0, 0, advance_data, scratch, scratch_size);
+}
+
+void
+delete_top(Buffer_Type *buffer, int len, float *advance_data, void *scratch, int scratch_size){
+    edit(buffer, 0, len, 0, 0, advance_data, scratch, scratch_size);
+}
+
 // BOTTOM
 
diff --git a/buffer/4coder_test_main.cpp b/buffer/4coder_test_main.cpp
index 9c41399e..c46093ad 100644
--- a/buffer/4coder_test_main.cpp
+++ b/buffer/4coder_test_main.cpp
@@ -928,6 +928,45 @@ full_cursor_xy_test(Stats_Log *log, Buffer_Set *buffers, float x, float y, int r
     log_sample_set(log, litstr("full-cursor-seek"), stats_out, machine.samples, machine.count);
 }
 
+void
+word_seek_test(Stats_Log *log, Buffer_Set *buffers, int test_repitions,
+               int incremental_position, char *word, int len,
+               void *scratch, int scratch_size, Record_Statistics *stats_out){
+    Sample_Machine machine;
+    machine = begin_machine(test_repitions, &scratch, &scratch_size);
+    assert_4tech(scratch_size >= len);
+    
+    int pos, pos2, old_pos;
+    old_pos = 0;
+    
+    for (int i = 0; i < machine.count; ++i){
+        start(&machine);
+        pos = buffer_find_string(&buffers->buffer, old_pos, word, len, (char*)scratch);
+        machine.samples[i].buffer = stop(&machine);
+        
+        start(&machine);
+        pos2 = buffer_find_string(&buffers->gap_buffer, old_pos, word, len, (char*)scratch);
+        machine.samples[i].gap_buffer = stop(&machine);
+        assert_4tech(pos2 == pos);
+        
+        start(&machine);
+        pos2 = buffer_find_string(&buffers->multi_gap_buffer, old_pos, word, len, (char*)scratch);
+        machine.samples[i].multi_gap_buffer = stop(&machine);
+        assert_4tech(pos2 == pos);
+        
+        start(&machine);
+        pos2 = buffer_find_string(&buffers->rope_buffer, old_pos, word, len, (char*)scratch);
+        machine.samples[i].rope_buffer = stop(&machine);
+        assert_4tech(pos2 == pos);
+        
+        if (incremental_position) old_pos = pos;
+    }
+    
+    end_machine(&machine, stats_out, __FUNCTION__);
+    
+    log_sample_set(log, litstr("word-seek"), stats_out, machine.samples, machine.count);
+}
+
 void
 stream_check_test(Buffer_Set *buffers, void *scratch, int scratch_size){
     int i, page_size, size;
@@ -983,6 +1022,200 @@ stream_check_test(Buffer_Set *buffers, void *scratch, int scratch_size){
     }
 }
 
+void
+insert_bottom_test(Stats_Log *log, Buffer_Set *buffers, int test_repitions, float *advance_data,
+                int edit_count, void *scratch, int scratch_size, Record_Statistics *stats_out){
+    Sample_Machine machine;
+    machine = begin_machine(test_repitions, &scratch, &scratch_size);
+    
+    char word[] = "stuff";
+    int word_len = sizeof(word) - 1;
+    
+    int i, j;
+    for (i = 0; i < test_repitions; ++i){
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_bottom(&buffers->buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_bottom(&buffers->gap_buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_bottom(&buffers->multi_gap_buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].multi_gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_bottom(&buffers->rope_buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].rope_buffer = stop(&machine);
+
+        if (i == 0){
+            stream_check_test(buffers, scratch, scratch_size);
+        }
+    }
+    
+    end_machine(&machine, stats_out, __FUNCTION__);
+
+    log_sample_set(log, litstr("insert-bottom"), stats_out, machine.samples, machine.count);
+}
+
+void
+insert_top_test(Stats_Log *log, Buffer_Set *buffers, int test_repitions, float *advance_data,
+                int edit_count, void *scratch, int scratch_size, Record_Statistics *stats_out){
+    Sample_Machine machine;
+    machine = begin_machine(test_repitions, &scratch, &scratch_size);
+    
+    char word[] = "stuff";
+    int word_len = sizeof(word) - 1;
+    
+    int i, j;
+    for (i = 0; i < test_repitions; ++i){
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_top(&buffers->buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_top(&buffers->gap_buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_top(&buffers->multi_gap_buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].multi_gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            insert_top(&buffers->rope_buffer, word, word_len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].rope_buffer = stop(&machine);
+
+        if (i == 0){
+            stream_check_test(buffers, scratch, scratch_size);
+        }
+    }
+    
+    end_machine(&machine, stats_out, __FUNCTION__);
+
+    log_sample_set(log, litstr("insert-top"), stats_out, machine.samples, machine.count);
+}
+
+void
+delete_bottom_test(Stats_Log *log, Buffer_Set *buffers, int test_repitions, float *advance_data,
+                   int edit_count, void *scratch, int scratch_size, Record_Statistics *stats_out){
+    Sample_Machine machine;
+    machine = begin_machine(test_repitions, &scratch, &scratch_size);
+
+    int len = 5;
+    
+    int i, j;
+    for (i = 0; i < test_repitions; ++i){
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_bottom(&buffers->buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_bottom(&buffers->gap_buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_bottom(&buffers->multi_gap_buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].multi_gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_bottom(&buffers->rope_buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].rope_buffer = stop(&machine);
+
+        if (i == 0){
+            stream_check_test(buffers, scratch, scratch_size);
+        }
+    }
+    
+    end_machine(&machine, stats_out, __FUNCTION__);
+
+    log_sample_set(log, litstr("delete-bottom"), stats_out, machine.samples, machine.count);
+}
+
+void
+delete_top_test(Stats_Log *log, Buffer_Set *buffers, int test_repitions, float *advance_data,
+                int edit_count, void *scratch, int scratch_size, Record_Statistics *stats_out){
+    Sample_Machine machine;
+    machine = begin_machine(test_repitions, &scratch, &scratch_size);
+
+    int len = 5;
+    
+    int i, j;
+    for (i = 0; i < test_repitions; ++i){
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_top(&buffers->buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_top(&buffers->gap_buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_top(&buffers->multi_gap_buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].multi_gap_buffer = stop(&machine);
+        
+        start(&machine);
+        for (j = 0; j < edit_count; ++j){
+            delete_top(&buffers->rope_buffer, len,
+                       advance_data, scratch, scratch_size);
+        }
+        machine.samples[i].rope_buffer = stop(&machine);
+
+        if (i == 0){
+            stream_check_test(buffers, scratch, scratch_size);
+        }
+    }
+    
+    end_machine(&machine, stats_out, __FUNCTION__);
+
+    log_sample_set(log, litstr("delete-top"), stats_out, machine.samples, machine.count);
+}
+
 void
 measure_check_test(Buffer_Set *buffers){
     int count;
@@ -1137,6 +1370,41 @@ int main(int argc, char **argv){
     }
     log_end_section(&log);
     
+    log_begin_section(&log, litstr("word-seek"));
+    {
+        Record_Statistics word_seek;
+
+        {
+            char word[] = "not-going-to-find-this";
+            int word_len = sizeof(word) - 1;
+            
+            word_seek_test(&log, &buffers, 25, 0, word, word_len, scratch, scratch_size, &word_seek);
+
+        }
+
+        {
+            char word[] = "return";
+            int word_len = sizeof(word) - 1;
+            
+            word_seek_test(&log, &buffers, 25, 1, word, word_len, scratch, scratch_size, &word_seek);
+        
+            printf("average normal word seek:\n");
+            print_record(word_seek.expected);
+            printf("\n");
+        }
+    }
+    log_end_section(&log);
+    
+    log_begin_section(&log, litstr("one-hundred-single-edits"));
+    {
+        Record_Statistics edits;
+        insert_bottom_test(&log, &buffers, 25, widths_data, 100, scratch, scratch_size, &edits);
+        insert_top_test(&log, &buffers, 25, widths_data, 100, scratch, scratch_size, &edits);
+        delete_bottom_test(&log, &buffers, 25, widths_data, 100, scratch, scratch_size, &edits);
+        delete_top_test(&log, &buffers, 25, widths_data, 100, scratch, scratch_size, &edits);
+    }
+    log_end_section(&log);
+    
     log_finish(&log);
     
     return(0);