--- a/src/misc/wasm/web-pre.js
+++ b/src/misc/wasm/web-pre.js
@@ -169,6 +169,7 @@
   // The host application persists manuscripts. Give each embedded editor
   // its own transient preferences and skip the standalone home lock.
   if (Module['tmEmbedded']) {
+    ENV['TEXMACS_TESSERA_EDITOR'] = '1';
     FS.mkdirTree ('/home/web/.TeXmacs');
     return;
   }
--- a/src/src/Edit/Interface/edit_interface.cpp
+++ b/src/src/Edit/Interface/edit_interface.cpp
@@ -1328,6 +1328,18 @@
     invalidate (ncr->x1, ncr->y1, ncr->x2, ncr->y2);
     copy_always= rectangles (ncr, copy_always);
     oc= copy (cu);
+
+    path slots[2];
+    rectangle bounds[2];
+    empty_fraction_targets (slots, bounds);
+    rectangles targets;
+    for (int i= 0; i < 2; i++)
+      if (!is_nil (slots[i])) targets= rectangles (bounds[i], targets);
+    if (targets != fraction_targets || (env_change & THE_FOCUS)) {
+      invalidate (thicken (fraction_targets, zpixel, zpixel));
+      invalidate (thicken (targets, zpixel, zpixel));
+      fraction_targets= targets;
+    }
    
     // set hot spot in the gui
     send_cursor (this, (SI) floor (cu->ox * magf),
--- a/src/src/Edit/Interface/edit_interface.hpp
+++ b/src/src/Edit/Interface/edit_interface.hpp
@@ -83,6 +83,7 @@
   rectangle     last_extents;
   rectangles    env_rects;
   rectangles    foc_rects;
+  rectangles    fraction_targets;
   rectangles    sem_rects;
   bool          sem_correct;
   cursor        oc;
@@ -142,6 +143,7 @@
   void draw_context (renderer ren, rectangle r);
   void draw_env (renderer ren);
   void draw_cursor (renderer ren);
+  void empty_fraction_targets (path* slots, rectangle* bounds);
   bool user_cursor_shape (int i, font& fn, string& name, SI& x1, SI& y1,
                           SI& x2, SI& y2, SI& fw, SI& fh);
   void invalidate_user_cursor (int i);
--- a/src/src/Edit/Interface/edit_mouse.cpp
+++ b/src/src/Edit/Interface/edit_mouse.cpp
@@ -17,6 +17,7 @@
 #include "drd_mode.hpp"
 #include "message.hpp"
 #include "window.hpp"
+#include "sys_utils.hpp"

   // These are tm-defined in graphics-utils.scm (looks like they shouldn't)
 #define ShiftMask     256
@@ -152,8 +153,59 @@
 }

 void
+edit_interface_rep::empty_fraction_targets (path* slots, rectangle* bounds) {
+  static const bool tessera_editor= get_env ("TEXMACS_TESSERA_EDITOR") == "1";
+  if (!tessera_editor || !got_focus || full_screen || is_nil (eb)) return;
+
+  // Offer targets for the innermost fraction containing the caret.
+  for (path p= path_up (tp); rp <= p; p= path_up (p)) {
+    tree t= subtree (et, p);
+    if (is_compound (t) && N(t) == 2 &&
+        (is_func (t, FRAC) || is_compound (t, "tfrac") ||
+         is_compound (t, "dfrac") || is_compound (t, "frac*") ||
+         is_compound (t, "cfrac"))) {
+      if (t[0] != "" && t[1] != "") return;
+      cursor num= eb->find_check_cursor (start (et, p * 0));
+      cursor den= eb->find_check_cursor (start (et, p * 1));
+      if (!num->valid || !den->valid) return;
+      SI split= (num->oy + num->y1 + den->oy + den->y2) / 2;
+      SI half_width= 8 * zpixel;
+      for (int i= 0; i < 2; i++) {
+        if (t[i] != "") continue;
+        cursor c= i == 0 ? num : den;
+        SI bottom= c->oy + c->y1 - 2*zpixel;
+        SI top= c->oy + c->y2 + 2*zpixel;
+        if (i == 0) bottom= max (bottom, split + zpixel);
+        else top= min (top, split - zpixel);
+        if (bottom >= top) continue;
+        bounds[i]= rectangle (c->ox - half_width, bottom,
+                              c->ox + half_width, top);
+        slots[i]= p * i * 0;
+      }
+      return;
+    }
+    if (p == rp) break;
+  }
+}
+
+void
 edit_interface_rep::mouse_select (SI x, SI y, int mods, bool drag) {
   if (mouse_message ("select" , x, y)) return;
+  if (!drag && (mods & (ShiftMask | ControlMask | Mod1Mask | Mod2Mask)) == 0) {
+    path slots[2];
+    rectangle bounds[2];
+    empty_fraction_targets (slots, bounds);
+    for (int i= 0; i < 2; i++) {
+      rectangle r= bounds[i];
+      if (!is_nil (slots[i]) && r->x1 <= x && x <= r->x2 &&
+          r->y1 <= y && y <= r->y2) {
+        go_to (slots[i]);
+        set_selection (tp, tp);
+        notify_change (THE_SELECTION);
+        return;
+      }
+    }
+  }
   if (!is_nil (mouse_ids) && (mods & (ShiftMask+Mod2Mask)) == 0 && !drag) {
     call ("link-follow-ids", object (mouse_ids), object ("click"));
     disable_double_clicks ();
--- a/src/src/Edit/Interface/edit_repaint.cpp
+++ b/src/src/Edit/Interface/edit_repaint.cpp
@@ -13,6 +13,7 @@
 #include "message.hpp"
 #include "analyze.hpp"
 #include "gui.hpp" // for gui_interrupted
+#include "sys_utils.hpp"

 extern int nr_painted;
 extern void clear_pattern_rectangles (renderer ren, rectangle m, rectangles l);
@@ -81,6 +82,10 @@
       }
       ren->draw_rectangles (sem_rects);
     }
+    if (!is_nil (fraction_targets)) {
+      ren->set_pencil (pencil (rgb_color (99, 139, 121, 190), ren->pixel));
+      ren->draw_selection (fraction_targets);
+    }
   }
 }

@@ -90,6 +95,15 @@
       !temp_invalid_cursor && (got_focus || full_screen)) {
     cursor cu= get_cursor();
     if (!inside_active_graphics ()) {
+      static const bool tessera_editor=
+        get_env ("TEXMACS_TESSERA_EDITOR") == "1";
+      if (tessera_editor) {
+        SI x1= cu->ox + (SI) (cu->y1 * cu->slope);
+        SI x2= cu->ox + (SI) (cu->y2 * cu->slope);
+        ren->set_pencil (pencil (rgb_color (24, 68, 57), 2*zpixel));
+        ren->line (x1, cu->oy + cu->y1, x2, cu->oy + cu->y2);
+        return;
+      }
       SI dw= 0;
       if (tremble_count > 3) dw= min (tremble_count - 3, 25) * pixel;
       cu->y1 -= 2*zpixel + dw; cu->y2 += 2*zpixel + dw;
--- a/src/src/Typeset/Boxes/Basic/text_boxes.cpp
+++ b/src/src/Typeset/Boxes/Basic/text_boxes.cpp
@@ -13,6 +13,7 @@
 #include "font.hpp"
 #include "Boxes/construct.hpp"
 #include "analyze.hpp"
+#include "sys_utils.hpp"

 /******************************************************************************
 * Text boxes
@@ -321,7 +322,9 @@
     if (l == N(str)) cu->ox += xk->right;
     STACK_DELETE_ARRAY (xpos);
   }
-  if (l != 0) {
+  static const bool tessera_editor= get_env ("TEXMACS_TESSERA_EDITOR") == "1";
+  if (tessera_editor) fn->get_extents ("Hg", ex);
+  else if (l != 0) {
     int k= l;
     tm_char_backwards (str, k);
     fn->get_extents (str (k, l), ex);