diff --git a/src/builtins/commandline.rs b/src/builtins/commandline.rs
index d1d04cf05..39fed1cc2 100644
--- a/src/builtins/commandline.rs
+++ b/src/builtins/commandline.rs
@@ -60,6 +60,7 @@ enum TokenMode {
 /// \param buff the original command line buffer
 /// \param cursor_pos the position of the cursor in the command line
 fn replace_part(
+    parser: &Parser,
     range: Range<usize>,
     insert: &wstr,
     insert_mode: AppendMode,
@@ -94,9 +95,9 @@ fn replace_part(
 
     out.push_utfstr(&buff[range.end..]);
     if search_field_mode {
-        commandline_set_search_field(out, Some(out_pos));
+        commandline_set_search_field(parser, out, Some(out_pos));
     } else {
-        commandline_set_buffer(Some(out), Some(out_pos));
+        commandline_set_buffer(parser, Some(out), Some(out_pos));
     }
 }
 
@@ -547,7 +548,7 @@ pub fn commandline(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr])
                 }
                 line_offset + new_coord
             };
-            commandline_set_buffer(None, Some(new_pos));
+            commandline_set_buffer(parser, None, Some(new_pos));
         } else {
             streams.out.append(sprintf!(
                 "%d\n",
@@ -709,7 +710,7 @@ pub fn commandline(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr])
                     .saturating_add_signed(isize::try_from(new_pos).unwrap()),
                 current_buffer.len(),
             );
-            commandline_set_buffer(None, Some(new_pos));
+            commandline_set_buffer(parser, None, Some(new_pos));
         } else {
             streams
                 .out
@@ -731,6 +732,7 @@ pub fn commandline(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr])
         );
     } else if positional_args == 1 {
         replace_part(
+            parser,
             range,
             args[w.wopt_index],
             append_mode,
@@ -741,6 +743,7 @@ pub fn commandline(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr])
     } else {
         let sb = join_strings(&w.argv[w.wopt_index..], '\n');
         replace_part(
+            parser,
             range,
             &sb,
             append_mode,
diff --git a/src/builtins/read.rs b/src/builtins/read.rs
index 6d48d7f1d..24b7cb9f5 100644
--- a/src/builtins/read.rs
+++ b/src/builtins/read.rs
@@ -234,7 +234,12 @@ fn read_interactive(
 
     // Keep in-memory history only.
     reader_push(parser, L!(""), conf);
-    commandline_set_buffer(Some(commandline.to_owned()), None);
+    let _modifiable_commandline = parser.scope().readonly_commandline.then(|| {
+        parser.push_scope(|s| {
+            s.readonly_commandline = false;
+        })
+    });
+    commandline_set_buffer(parser, Some(commandline.to_owned()), None);
 
     let mline = {
         let _interactive = parser.push_scope(|s| s.is_interactive = true);
diff --git a/src/editable_line.rs b/src/editable_line.rs
index 1c69374a7..433ccf0b1 100644
--- a/src/editable_line.rs
+++ b/src/editable_line.rs
@@ -41,11 +41,7 @@ pub fn new(range: std::ops::Range<usize>, replacement: WString) -> Self {
 /// Currently exposed for testing only.
 pub fn apply_edit(target: &mut WString, colors: &mut Vec<HighlightSpec>, edit: &Edit) {
     let range = &edit.range;
-    if target.is_empty() {
-        *target = edit.replacement.clone();
-    } else {
-        target.replace_range(range.clone(), &edit.replacement);
-    }
+    target.replace_range(range.clone(), &edit.replacement);
 
     // Now do the same to highlighting.
     let last_color = edit
@@ -54,16 +50,10 @@ pub fn apply_edit(target: &mut WString, colors: &mut Vec<HighlightSpec>, edit: &
         .checked_sub(1)
         .map(|i| colors[i])
         .unwrap_or_default();
-    if colors.is_empty() {
-        *colors = std::iter::repeat(last_color)
-            .take(edit.replacement.len())
-            .collect();
-    } else {
-        colors.splice(
-            range.clone(),
-            std::iter::repeat(last_color).take(edit.replacement.len()),
-        );
-    }
+    colors.splice(
+        range.clone(),
+        std::iter::repeat(last_color).take(edit.replacement.len()),
+    );
 }
 
 /// The history of all edits to some command line.
@@ -195,11 +185,7 @@ pub fn push_edit(&mut self, mut edit: Edit, allow_coalesce: bool) {
                 .truncate(self.undo_history.edits_applied);
         }
         edit.cursor_position_before_edit = self.pending_position.take().unwrap_or(self.position());
-        edit.old = if self.text.is_empty() {
-            L!("").to_owned()
-        } else {
-            self.text[range.clone()].to_owned()
-        };
+        edit.old = self.text[range.clone()].to_owned();
         apply_edit(&mut self.text, &mut self.colors, &edit);
         self.set_position(cursor_position_after_edit(&edit));
         assert_eq!(
@@ -218,7 +204,7 @@ pub fn undo(&mut self) -> bool {
         let mut last_group_id = None;
         let position_before_undo = self.position();
         let end = self.undo_history.edits_applied;
-        while !self.undo_history.edits.is_empty() && self.undo_history.edits_applied != 0 {
+        while self.undo_history.edits_applied != 0 {
             let edit = &self.undo_history.edits[self.undo_history.edits_applied - 1];
             if did_undo
                 && edit
diff --git a/src/parser.rs b/src/parser.rs
index 4ab2a3b04..981856009 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -232,6 +232,9 @@ pub struct ScopedData {
     /// Whether we are currently interactive.
     pub is_interactive: bool,
 
+    /// Whether the command line is closed for modification from fish script.
+    pub readonly_commandline: bool,
+
     /// Whether to suppress fish_trace output. This occurs in the prompt, event handlers, and key
     /// bindings.
     pub suppress_fish_trace: bool,
@@ -253,6 +256,7 @@ fn default() -> Self {
             eval_level: -1,
             is_subshell: false,
             is_event: false,
+            readonly_commandline: false,
             is_interactive: false,
             suppress_fish_trace: false,
             read_limit: 0,
diff --git a/src/reader.rs b/src/reader.rs
index f07aab2ed..21d4122ae 100644
--- a/src/reader.rs
+++ b/src/reader.rs
@@ -983,6 +983,9 @@ pub fn reader_schedule_prompt_repaint() {
 }
 
 pub fn reader_execute_readline_cmd(parser: &Parser, ch: CharEvent) {
+    if parser.scope().readonly_commandline {
+        return;
+    }
     if let Some(data) = current_data() {
         let mut data = Reader { parser, data };
         let CharEvent::Readline(readline_cmd_evt) = &ch else {
@@ -1062,7 +1065,10 @@ pub fn commandline_get_state(sync: bool) -> CommandlineState {
 
 /// Set the command line text and position. This may be called on a background thread; the reader
 /// will pick it up when it is done executing.
-pub fn commandline_set_buffer(text: Option<WString>, cursor_pos: Option<usize>) {
+pub fn commandline_set_buffer(parser: &Parser, text: Option<WString>, cursor_pos: Option<usize>) {
+    if parser.scope().readonly_commandline {
+        return;
+    }
     {
         let mut state = commandline_state_snapshot();
         if let Some(text) = text {
@@ -1073,7 +1079,10 @@ pub fn commandline_set_buffer(text: Option<WString>, cursor_pos: Option<usize>)
     current_data().map(|data| data.apply_commandline_state_changes());
 }
 
-pub fn commandline_set_search_field(text: WString, cursor_pos: Option<usize>) {
+pub fn commandline_set_search_field(parser: &Parser, text: WString, cursor_pos: Option<usize>) {
+    if parser.scope().readonly_commandline {
+        return;
+    }
     {
         let mut state = commandline_state_snapshot();
         assert!(state.search_field.is_some());
@@ -5321,7 +5330,10 @@ fn expand_replacer(
     let mut cmd = escape(&repl.replacement);
     cmd.push(' ');
     cmd.push_utfstr(&escape(token));
-    let _not_interactive = parser.push_scope(|s| s.is_interactive = false);
+    let _not_interactive = parser.push_scope(|s| {
+        s.is_interactive = false;
+        s.readonly_commandline = true;
+    });
 
     let mut outputs = vec![];
     if exec_subshell(