diff -Nur -X../diff_ignore ../LT2_5/client/client_main.c ./client/client_main.c
--- ../LT2_5/client/client_main.c	2019-01-19 17:40:00.451899163 +0300
+++ ./client/client_main.c	2019-08-01 23:37:42.793397996 +0300
@@ -147,6 +147,7 @@
 bool auto_spawn = FALSE; /* TRUE = skip main menu, start local server */
 bool in_ggz = FALSE;
 enum announce_type announce;
+enum fc_tristate got_tech = TRI_MAYBE;
 
 struct civclient client;
 
@@ -875,6 +876,7 @@
     can_slide = FALSE;
     unit_focus_update();
     can_slide = TRUE;
+    got_tech = TRI_MAYBE; /* No way know if the player has just got a tech */
     set_client_page(PAGE_GAME);
     /* Find something sensible to display instead of the intro gfx. */
     center_on_something();
diff -Nur -X../diff_ignore ../LT2_5/client/client_main.h ./client/client_main.h
--- ../LT2_5/client/client_main.h	2019-01-19 17:40:00.451899163 +0300
+++ ./client/client_main.h	2019-08-01 23:37:42.885398827 +0300
@@ -37,7 +37,7 @@
  *                   to a server.  In this state, neither game nor ruleset
  *                   is in effect.
  * C_S_PREPARING:    Connected in pregame.  Game and ruleset are done.
- * C_S_RUNNING:      Connected ith game in progress.
+ * C_S_RUNNING:      Connected with game in progress.
  * C_S_OVER:         Connected with game over.
  */
 enum client_states { 
@@ -80,6 +80,7 @@
 extern bool auto_spawn;
 extern bool waiting_for_end_turn;
 extern bool in_ggz;
+extern enum fc_tristate got_tech;
 
 struct global_worklist_list;    /* Defined in global_worklist.[ch]. */
 
diff -Nur -X../diff_ignore ../LT2_5/client/gui-gtk-2.0/repodlgs.c ./client/gui-gtk-2.0/repodlgs.c
--- ../LT2_5/client/gui-gtk-2.0/repodlgs.c	2019-01-19 17:40:00.467904144 +0300
+++ ./client/gui-gtk-2.0/repodlgs.c	2019-08-02 23:19:36.421363530 +0300
@@ -74,6 +74,8 @@
   GtkProgressBar *progress_bar;
   GtkLabel *goal_label;
   GtkLayout *drawing_area;
+  GtkWidget *ch_now;
+  Tech_type_id target_tech; /* for ch_now dialog */
 };
 
 static GtkListStore *science_report_store_new(void);
@@ -105,6 +107,9 @@
 
 static struct science_report science_report = { NULL, };
 static bool science_report_no_combo_callback = FALSE;
+static void science_report_confirm_research(Tech_type_id tech);
+static void confirm_change_response(GtkWidget *w, gint response,
+                                    gpointer data);
 
 /* Those values must match the function science_report_store_new(). */
 enum science_report_columns {
@@ -187,6 +192,143 @@
   log_error("%s(): Tech %d not found in the combo.", __FUNCTION__, tech);
 }
 
+
+/************************************************************************//**
+  Handles changing research: if changing will have effect immediately,
+  asks to confirm and warns about bulb loss.
+****************************************************************************/
+static void science_report_confirm_research(Tech_type_id tech)
+{
+  struct player_research *research =
+    (client_has_player() ? player_research_get(client_player()) : NULL);;
+  GtkWidget *chpop;
+  int bulbs, loss;
+  int cost = base_total_bulbs_required(client_player(), tech, FALSE);
+  int min_cost = (int) (cost * min_leakage_ratio(client_player(), tech));
+  struct advance *vap = valid_advance_by_number(tech);
+  char buf[511];
+  struct option *tpo;
+  
+  fc_assert(NULL != vap);
+  fc_assert(0 != cost);
+  
+  bulbs = (tech == research->researching_saved)
+          ? research->bulbs_researching_saved
+          : research->bulbs_researched;
+  
+  /* In some cases you have more bulbs than your current tech costs... */
+  if (!(TRI_YES == got_tech) && (tech != research->researching_saved)) {
+    tpo = optset_option_by_name(server_optset, "techpenalty");
+    
+    if (!tpo) {
+      log_error("techpenalty server option unknown");
+      loss = 0;
+    } else {
+      loss = option_int_get(tpo) * bulbs / 100;
+    }
+  } else {
+    loss = 0;
+  }
+  fc_assert(bulbs >= loss);
+  if(!min_cost) {
+    min_cost = 1;
+  }
+  log_debug("Consider switching to %s with %d bulbs (%d|%d), %d losing, "
+            "%d..%d expecting to spend",
+            advance_rule_name(advance_by_number(tech)), bulbs,
+            research->bulbs_researching_saved, research->bulbs_researched,
+            loss, min_cost, cost);
+  
+  if ((TRI_NO == got_tech ? bulbs - loss : bulbs) >= min_cost) {
+    if (min_cost != cost) {
+      fc_snprintf(buf, sizeof(buf),
+                  PL_("(The cost might be down to %d bulb"
+                      " due to tech leakage.)\n",
+                      "(The cost might be down to %d bulbs"
+                      " due to tech leakage.)\n",
+                      min_cost),
+                  min_cost);
+    } else {
+      buf[0] = '\0';
+    }
+    if (loss > 0) {
+      if (TRI_NO == got_tech) {
+        cat_snprintf(buf, sizeof(buf),
+                     PL_("%d bulb will be lost.\n",
+                         "%d bulbs will be lost.\n", loss), loss);
+      } else {
+        cat_snprintf(buf, sizeof(buf),
+                     PL_("%d bulb may be lost "
+                         "if you have got no advance this turn.\n",
+                         "%d bulbs may be lost "
+                         "if you have got no advance this turn.\n", loss),
+                     loss);
+      }
+    }
+    
+    if ((TRI_MAYBE != got_tech) && (min_cost == cost)) {
+      cat_snprintf(buf, sizeof(buf),
+                   PL_("%d bulb will remain.\n",
+                       "%d bulbs will remain.\n", bulbs - cost - loss),
+                   bulbs - cost - loss);
+    } else {
+      int max_rem = (TRI_NO == got_tech 
+                     ? bulbs - min_cost - loss
+                     : bulbs - min_cost);
+      int min_rem = (TRI_YES == got_tech 
+                     ? bulbs - cost
+                     : bulbs - cost - loss);
+      cat_snprintf(buf, sizeof(buf),
+                   /* FIXME: in some languages does PL_ act good here? */
+                   PL_("%d to %d bulb will remain.\n",
+                       "%d to %d bulbs will remain.\n",
+                       max_rem),
+                   MAX(0, min_rem),
+                   max_rem
+                   );
+    }
+     
+    chpop = gtk_message_dialog_new(NULL,
+      GTK_DIALOG_DESTROY_WITH_PARENT,
+      GTK_MESSAGE_WARNING,
+      GTK_BUTTONS_OK_CANCEL,
+      PL_("Research %s for %d bulb?\n%s",
+          "Research %s for %d bulbs?\n%s", cost),
+      advance_name_translation(vap), cost, buf);
+    setup_dialog(chpop, gui_dialog_get_toplevel(science_report.shell));
+    
+    gtk_window_set_title(GTK_WINDOW(chpop),
+                         (bulbs - loss >= cost) ? _("Research now!")
+                         : _("Immediate research might happen!"));
+    gtk_window_set_position(GTK_WINDOW(chpop), GTK_WIN_POS_CENTER_ON_PARENT);
+    
+    science_report.ch_now = chpop;
+    science_report.target_tech = tech;
+    g_signal_connect(chpop, "response",
+         G_CALLBACK(confirm_change_response), &science_report);
+    
+    gtk_window_present(GTK_WINDOW(chpop));
+  } else {
+    dsend_packet_player_research(&client.conn, tech);
+  }
+}
+
+/**********************************************************************//**
+  User has responded to change research confirmation
+**************************************************************************/
+static void confirm_change_response(GtkWidget *w, gint response,
+                                    gpointer data)
+{
+  struct science_report *pdialog = data;
+
+  if (response == GTK_RESPONSE_OK) {
+    dsend_packet_player_research(&client.conn, pdialog->target_tech);
+  }
+  gtk_widget_destroy(w);
+  
+  pdialog->ch_now = NULL;
+}
+
 /****************************************************************************
   Change tech goal, research or open help dialog.
 ****************************************************************************/
@@ -209,7 +351,8 @@
       /* LMB: set research or research goal */
       switch (player_invention_state(client_player(), tech)) {
        case TECH_PREREQS_KNOWN:
-         dsend_packet_player_research(&client.conn, tech);
+         /* If we can research target tech immediately, popup a dialog */
+         science_report_confirm_research(tech);
          break;
        case TECH_UNKNOWN:
          dsend_packet_player_tech_goal(&client.conn, tech);
@@ -473,7 +616,7 @@
   if (gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(data))) {
     popup_help_dialog_typed(tech_name, HELP_TECH);
   } else if (can_client_issue_orders()) {
-    dsend_packet_player_research(&client.conn, tech);
+    science_report_confirm_research(tech);
   }
   /* Revert, or we will be not synchron with the server. */
   science_report_combo_set_active(combo, player_research_get
@@ -620,6 +763,8 @@
 
   science_report_update(preport);
   gui_dialog_show_all(preport->shell);
+  preport->ch_now = NULL;
+  preport->target_tech = A_LAST;
 
   /* This must be _after_ the dialog is drawn to really center it ... */
   science_report_redraw(preport);
@@ -632,6 +777,9 @@
 {
   fc_assert_ret(NULL != preport);
 
+  if (preport->ch_now) {
+    gtk_widget_destroy(preport->ch_now);
+  }
   gui_dialog_destroy(preport->shell);
   fc_assert(NULL == preport->shell);
 
diff -Nur -X../diff_ignore ../LT2_5/common/tech.c ./common/tech.c
--- ../LT2_5/common/tech.c	2019-01-19 17:40:00.511917844 +0300
+++ ./common/tech.c	2019-08-02 00:22:06.229454963 +0300
@@ -662,6 +662,63 @@
                                    FALSE);
 }
 
+/**********************************************************************//**
+  If leakage style is 2 or 3, it counts players that pplayer does not have
+  embassy to and returns how much cheaper the tech would be if they all
+  know it rather than if they all don't know
+**************************************************************************/
+double min_leakage_ratio(const struct player *pplayer,
+                         Tech_type_id tech)
+{
+  const struct player_research *presearch = player_research_get(pplayer);
+  fc_assert(presearch);
+  
+  switch (game.info.tech_leakage) {
+  case 0:
+  case 1:
+    return 1.0;
+    break;
+  case 2:
+  case 3:
+    {
+      int players = 0, players_with_tech = 0, players_obscure = 0;
+
+      players_iterate_alive(aplayer) {
+        if ((3 == game.info.tech_leakage) && is_barbarian(aplayer)) {
+          continue;
+        }
+        players++;
+        if (player_has_embassy(pplayer, aplayer)) {
+          if (A_FUTURE == tech
+              ? (player_research_get(aplayer)->future_tech
+                 > presearch->future_tech)
+              : TECH_KNOWN == player_invention_state(aplayer, tech)) {
+            players_with_tech++;
+          }
+        } else {
+          players_obscure++;
+        }
+        
+      } players_iterate_alive_end;
+
+      fc_assert_ret_val(0 < players, 1.0);
+      fc_assert(players >= players_with_tech + players_obscure);
+      
+      if (0 == players_obscure) {
+        return 1.0;
+      }
+      return (double) (players - players_with_tech - players_obscure)
+                      / (players - players_with_tech);
+    }
+    break;
+
+  default:
+    log_error("Invalid tech_leakage %d", game.info.tech_leakage);
+  }
+  
+  return 1.0;
+}
+
 /****************************************************************************
   Function to determine cost for technology.  The equation is determined
   from game.info.tech_cost_style and game.info.tech_leakage.
diff -Nur -X../diff_ignore ../LT2_5/common/tech.h ./common/tech.h
--- ../LT2_5/common/tech.h	2019-01-19 17:40:00.511917844 +0300
+++ ./common/tech.h	2019-08-01 23:37:42.929399224 +0300
@@ -225,6 +225,8 @@
 bool is_future_tech(Tech_type_id tech);
 
 void precalc_tech_data(void);
+double min_leakage_ratio(const struct player *pplayer,
+                         Tech_type_id tech);
 
 /* Initialization and iteration */
 void techs_init(void);