diff --git a/bin/el/src/main.rs b/bin/el/src/main.rs
index 483e3ff..74eb298 100644
--- a/bin/el/src/main.rs
+++ b/bin/el/src/main.rs
@@ -5738,6 +5738,109 @@ fn dispatch_builtin(
             BuiltinResult::NotBuiltin
         }
 
+        // ── List helpers (append / set / concat) ──────────────────────────────
+        "list_append" => {
+            // list_append(list, item) -> [item, ...]
+            let item = stack.pop().unwrap_or(Value::Nil);
+            let list = match stack.pop().unwrap_or(Value::List(vec![])) { Value::List(l) => l, _ => vec![] };
+            let mut new_list = list;
+            new_list.push(item);
+            stack.push(Value::List(new_list)); BuiltinResult::Handled
+        }
+        "list_set" => {
+            // list_set(list, idx, value) -> new list with item at idx replaced
+            let value = stack.pop().unwrap_or(Value::Nil);
+            let idx = match stack.pop().unwrap_or(Value::Int(0)) { Value::Int(i) => i, _ => 0 };
+            let list = match stack.pop().unwrap_or(Value::List(vec![])) { Value::List(l) => l, _ => vec![] };
+            let mut new_list = list;
+            if idx >= 0 && (idx as usize) < new_list.len() {
+                new_list[idx as usize] = value;
+            }
+            stack.push(Value::List(new_list)); BuiltinResult::Handled
+        }
+        "list_concat" => {
+            // list_concat(a, b) -> combined list
+            let b = match stack.pop().unwrap_or(Value::List(vec![])) { Value::List(l) => l, _ => vec![] };
+            let a = match stack.pop().unwrap_or(Value::List(vec![])) { Value::List(l) => l, _ => vec![] };
+            let mut new_list = a;
+            new_list.extend(b);
+            stack.push(Value::List(new_list)); BuiltinResult::Handled
+        }
+        "list_slice" => {
+            // list_slice(list, start, end) -> sublist [start..end)
+            let end_idx = match stack.pop().unwrap_or(Value::Int(0)) { Value::Int(i) => i, _ => 0 };
+            let start_idx = match stack.pop().unwrap_or(Value::Int(0)) { Value::Int(i) => i, _ => 0 };
+            let list = match stack.pop().unwrap_or(Value::List(vec![])) { Value::List(l) => l, _ => vec![] };
+            let len = list.len() as i64;
+            let s = start_idx.max(0) as usize;
+            let e = end_idx.min(len) as usize;
+            let sliced = if s < e && s < list.len() { list[s..e.min(list.len())].to_vec() } else { vec![] };
+            stack.push(Value::List(sliced)); BuiltinResult::Handled
+        }
+        "list_reverse" => {
+            let list = match stack.pop().unwrap_or(Value::List(vec![])) { Value::List(l) => l, _ => vec![] };
+            let mut rev = list;
+            rev.reverse();
+            stack.push(Value::List(rev)); BuiltinResult::Handled
+        }
+        "list_contains" => {
+            // list_contains(list, item) -> Bool — string equality check
+            let item = match stack.pop().unwrap_or(Value::Nil) { Value::Str(s) => s, other => other.to_string() };
+            let list = match stack.pop().unwrap_or(Value::List(vec![])) { Value::List(l) => l, _ => vec![] };
+            let found = list.iter().any(|v| {
+                let vs = match v { Value::Str(s) => s.clone(), other => other.to_string() };
+                vs == item
+            });
+            stack.push(Value::Bool(found)); BuiltinResult::Handled
+        }
+
+        // ── String character mutation ──────────────────────────────────────────
+        "str_set_char" => {
+            // str_set_char(s, idx, ch) -> new string with ch at position idx
+            let ch = match stack.pop().unwrap_or(Value::Str(String::new())) { Value::Str(s) => s, _ => String::new() };
+            let idx = match stack.pop().unwrap_or(Value::Int(0)) { Value::Int(i) => i, _ => 0 };
+            let s = match stack.pop().unwrap_or(Value::Str(String::new())) { Value::Str(s) => s, _ => String::new() };
+            let ch_char = ch.chars().next().unwrap_or(' ');
+            let mut chars: Vec<char> = s.chars().collect();
+            if idx >= 0 && (idx as usize) < chars.len() {
+                chars[idx as usize] = ch_char;
+            }
+            stack.push(Value::Str(chars.into_iter().collect())); BuiltinResult::Handled
+        }
+
+        // ── Shell execution ───────────────────────────────────────────────────
+        "shell_exec" => {
+            // shell_exec(cmd: String) -> String — execute shell command, return stdout+stderr
+            let cmd = match stack.pop().unwrap_or(Value::Nil) { Value::Str(s) => s, _ => String::new() };
+            let output = std::process::Command::new("sh")
+                .arg("-c")
+                .arg(&cmd)
+                .output();
+            let result = match output {
+                Ok(o) => {
+                    let stdout = String::from_utf8_lossy(&o.stdout).to_string();
+                    let stderr = String::from_utf8_lossy(&o.stderr).to_string();
+                    if stdout.is_empty() { stderr } else { stdout }
+                }
+                Err(e) => format!("error: {}", e),
+            };
+            stack.push(Value::Str(result)); BuiltinResult::Handled
+        }
+
+        // ── TTY write (raw ANSI output without newline) ───────────────────────
+        "native_tty_write" => {
+            let s = match stack.pop().unwrap_or(Value::Nil) { Value::Str(s) => s, other => other.to_string() };
+            use std::io::Write;
+            print!("{}", s);
+            let _ = std::io::stdout().flush();
+            stack.push(Value::Nil); BuiltinResult::Handled
+        }
+        "native_tty_size" => {
+            // Returns "cols,rows" string
+            let (cols, rows) = term_size();
+            stack.push(Value::Str(format!("{},{}", cols, rows))); BuiltinResult::Handled
+        }
+
         // ── Stack aliases ─────────────────────────────────────────────────────
         "stack_push" => {
             let item = stack.pop().unwrap_or(Value::Nil);
@@ -6448,10 +6551,16 @@ fn is_builtin(name: &str) -> bool {
         | "str_pad_left" | "str_pad_right" | "format_float" | "str_format"
         // List additions
         | "list_push" | "list_pop" | "list_pop_front" | "list_peek_last" | "list_range"
-        | "list_new" | "list_empty"
+        | "list_new" | "list_empty" | "list_append" | "list_set" | "list_concat"
+        | "list_slice" | "list_reverse" | "list_contains"
         | "stack_push" | "stack_pop" | "stack_peek" | "stack_new"
         | "queue_enqueue" | "queue_dequeue" | "queue_peek" | "queue_new"
         | "list_map" | "list_filter" | "list_reduce" | "fn_ref"
+        // String character mutation
+        | "str_set_char"
+        // Shell and TTY
+        | "shell_exec" | "native_tty_write" | "native_tty_size"
+        | "native_tty_read"  // reserved for future raw key input
         // Time
         | "time_now_utc" | "time_to_parts" | "time_from_parts" | "time_format" | "time_parse"
         | "time_add" | "time_diff" | "time_start_of" | "time_tz_offset" | "time_to_tz"