fix(cli): fallback to plain prompt on VTE terminals with broken emoji width (#8385)

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Signed-off-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: Douwe Osinga <douwe@squareup.com>

crates/goose-cli/src/session/input.rs

@@ -400,9 +400,23 @@ fn parse_plan_command(input: String) -> Option<InputResult> {
 }
 
 fn get_input_prompt_string() -> String {
+    if is_vte_with_broken_emoji_width() {
+        return "> ".to_string();
+    }
     "🪿 ".to_string()
 }
 
+/// VTE < 0.70 renders 🪿 as 1 cell while unicode-width counts 2, causing cursor offset.
+fn is_vte_with_broken_emoji_width() -> bool {
+    let Ok(vte_version) = std::env::var("VTE_VERSION") else {
+        return false;
+    };
+    let Ok(version) = vte_version.parse::<u32>() else {
+        return true;
+    };
+    version < 7000
+}
+
 fn print_help() {
     let newline_key = get_newline_key().to_ascii_uppercase();
     let modes = GooseMode::VARIANTS.join(", ");