diff --git a/src/env_dispatch.cpp b/src/env_dispatch.cpp
index 14799cf11..21259b645 100644
--- a/src/env_dispatch.cpp
+++ b/src/env_dispatch.cpp
@@ -214,6 +214,13 @@ static void handle_fish_history_change(const env_stack_t &vars) {
     reader_change_history(history_session_id(vars));
 }
 
+static void handle_fish_cursor_selection_mode_change(const env_stack_t &vars) {
+    auto mode = vars.get(L"fish_cursor_selection_mode");
+    reader_change_cursor_selection_mode(mode && mode->as_string() == L"inclusive"
+                                            ? cursor_selection_mode_t::inclusive
+                                            : cursor_selection_mode_t::exclusive);
+}
+
 void handle_autosuggestion_change(const env_stack_t &vars) {
     reader_set_autosuggestion_enabled(vars);
 }
@@ -327,6 +334,8 @@ static std::unique_ptr<const var_dispatch_table_t> create_dispatch_table() {
     var_dispatch_table->add(L"TZ", handle_tz_change);
     var_dispatch_table->add(L"fish_use_posix_spawn", handle_fish_use_posix_spawn_change);
     var_dispatch_table->add(L"fish_trace", handle_fish_trace);
+    var_dispatch_table->add(L"fish_cursor_selection_mode",
+                            handle_fish_cursor_selection_mode_change);
 
     // This std::move is required to avoid a build error on old versions of libc++ (#5801),
     // but it causes a different warning under newer versions of GCC (observed under GCC 9.3.0,
diff --git a/src/reader.cpp b/src/reader.cpp
index ff84b2b96..9c271deb6 100644
--- a/src/reader.cpp
+++ b/src/reader.cpp
@@ -681,6 +681,9 @@ class reader_data_t : public std::enable_shared_from_this<reader_data_t> {
     /// The history search.
     reader_history_search_t history_search{};
 
+    /// The cursor selection mode.
+    cursor_selection_mode_t cursor_selection_mode{cursor_selection_mode_t::exclusive};
+
     /// The selection data. If this is not none, then we have an active selection.
     maybe_t<selection_data_t> selection{};
 
@@ -780,8 +783,6 @@ class reader_data_t : public std::enable_shared_from_this<reader_data_t> {
           inputter(*parser_ref, conf.in),
           history(std::move(hist)) {}
 
-    /// Whether the selection should always include the character after the cursor.
-    bool select_char_after_cursor();
     void update_buff_pos(editable_line_t *el, maybe_t<size_t> new_pos = none_t());
 
     void kill(editable_line_t *el, size_t begin_idx, size_t length, int mode, int newv);
@@ -1048,11 +1049,6 @@ wcstring combine_command_and_autosuggestion(const wcstring &cmdline,
     return full_line;
 }
 
-bool reader_data_t::select_char_after_cursor() {
-    auto val = vars().get(L"fish_cursor_selection_mode");
-    return !val || val->as_string() == L"inclusive";
-}
-
 /// Update the cursor position.
 void reader_data_t::update_buff_pos(editable_line_t *el, maybe_t<size_t> new_pos) {
     if (new_pos) {
@@ -1062,10 +1058,12 @@ void reader_data_t::update_buff_pos(editable_line_t *el, maybe_t<size_t> new_pos
     if (el == &command_line && selection.has_value()) {
         if (selection->begin <= buff_pos) {
             selection->start = selection->begin;
-            selection->stop = buff_pos + (select_char_after_cursor() ? 1 : 0);
+            selection->stop =
+                buff_pos + (cursor_selection_mode == cursor_selection_mode_t::inclusive ? 1 : 0);
         } else {
             selection->start = buff_pos;
-            selection->stop = selection->begin + (select_char_after_cursor() ? 1 : 0);
+            selection->stop = selection->begin +
+                              (cursor_selection_mode == cursor_selection_mode_t::inclusive ? 1 : 0);
         }
     }
 }
@@ -2677,6 +2675,14 @@ void reader_change_history(const wcstring &name) {
     }
 }
 
+void reader_change_cursor_selection_mode(cursor_selection_mode_t selection_mode) {
+    // We don't need to _change_ if we're not initialized yet.
+    reader_data_t *data = current_data_or_null();
+    if (data) {
+        data->cursor_selection_mode = selection_mode;
+    }
+}
+
 static bool check_autosuggestion_enabled(const env_stack_t &vars) {
     if (auto val = vars.get(L"fish_autosuggestion_enabled")) {
         return val->as_string() != L"0";
@@ -3971,7 +3977,8 @@ void reader_data_t::handle_readline_command(readline_cmd_t c, readline_loop_stat
             size_t pos = command_line.position();
             selection->begin = pos;
             selection->start = pos;
-            selection->stop = pos + (select_char_after_cursor() ? 1 : 0);
+            selection->stop =
+                pos + (cursor_selection_mode == cursor_selection_mode_t::inclusive ? 1 : 0);
             break;
         }
 
diff --git a/src/reader.h b/src/reader.h
index d80634208..e8ef270b4 100644
--- a/src/reader.h
+++ b/src/reader.h
@@ -149,6 +149,18 @@ void restore_term_mode();
 /// Change the history file for the current command reading context.
 void reader_change_history(const wcstring &name);
 
+/// Strategy for determining how the selection behaves.
+enum class cursor_selection_mode_t : uint8_t {
+    /// The character at/after the cursor is excluded.
+    /// This is most useful with a line cursor shape.
+    exclusive,
+    /// The character at/after the cursor is included.
+    /// This is most useful with a block or underscore cursor shape.
+    inclusive,
+};
+
+void reader_change_cursor_selection_mode(cursor_selection_mode_t selection_mode);
+
 /// Enable or disable autosuggestions based on the associated variable.
 void reader_set_autosuggestion_enabled(const env_stack_t &vars);