Align prefix parsing, smart-select characters

crates/agent_ui/src/terminal_thread_metadata_store.rs

@@ -93,7 +93,7 @@ pub(crate) fn terminal_title_without_prefix(title: &str) -> &str {
         .unwrap_or(title)
 }
 
-fn terminal_title_prefix(title: &str) -> Option<&str> {
+pub fn terminal_title_prefix(title: &str) -> Option<&str> {
     let mut prefix_byte_len = 0;
     let mut saw_prefix_character = false;
     let mut saw_whitespace_after_prefix = false;

crates/sidebar/Cargo.toml

@@ -44,6 +44,7 @@ telemetry.workspace = true
 theme.workspace = true
 theme_settings.workspace = true
 ui.workspace = true
+unicode-segmentation.workspace = true
 util.workspace = true
 workspace.workspace = true
 zed_actions.workspace = true

crates/sidebar/src/sidebar.rs

@@ -5,7 +5,7 @@ use action_log::DiffStats;
 use agent_client_protocol::schema as acp;
 use agent_settings::AgentSettings;
 use agent_ui::terminal_thread_metadata_store::{
-    TerminalThreadMetadata, TerminalThreadMetadataStore,
+    TerminalThreadMetadata, TerminalThreadMetadataStore, terminal_title_prefix,
 };
 use agent_ui::thread_metadata_store::{
     ThreadMetadata, ThreadMetadataStore, WorktreePaths, worktree_info_from_thread_paths,
@@ -55,6 +55,7 @@ use ui::{
     Scrollbars, Tab, ThreadItem, ThreadItemWorktreeInfo, TintColor, Tooltip, WithScrollbar,
     prelude::*, render_modifiers,
 };
+use unicode_segmentation::UnicodeSegmentation as _;
 use util::ResultExt as _;
 use util::path_list::PathList;
 use workspace::{
@@ -226,37 +227,77 @@ impl ThreadEntryWorkspace {
     }
 }
 
-/// If the title begins with a non-letter, non-whitespace character (such as a
-/// leading emoji or symbol the user prefixed their title with), splits that
-/// character out so it can be displayed in place of the entry's icon
+/// If the title begins with a decorative prefix (such as a leading emoji,
+/// spinner glyph, or symbol the agent prefixed the title with), splits that
+/// prefix off so a single representative glyph can be displayed in place of the
+/// entry's icon.
 fn split_leading_icon_char(
     title: &SharedString,
     highlight_positions: &[usize],
 ) -> Option<(SharedString, SharedString, Vec<usize>)> {
-    let first_char = title.chars().next()?;
-    if first_char.is_alphabetic() || first_char.is_whitespace() {
-        return None;
-    }
+    let prefix = terminal_title_prefix(title)?;
+    let icon_char = pick_icon_glyph(prefix)?;
 
-    let trimmed_title = title[first_char.len_utf8()..].trim_start();
+    let stripped_len = prefix.len();
+    let trimmed_title = &title[stripped_len..];
     if trimmed_title.is_empty() {
         return None;
     }
 
-    let stripped_len = title.len() - trimmed_title.len();
     let adjusted_positions = highlight_positions
         .iter()
         .filter(|&&position| position >= stripped_len)
         .map(|&position| position - stripped_len)
         .collect();
 
     Some((
-        first_char.to_string().into(),
+        icon_char,
         trimmed_title.to_string().into(),
         adjusted_positions,
     ))
 }
 
+/// Picks a single glyph to render as the icon from a detected title prefix.
+///
+/// We only ever show one glyph, so this makes a best effort to choose a
+/// meaningful one by glancing at the leading characters of the prefix:
+/// runs of `.` are condensed into a single ellipsis, surrounding ASCII brackets
+/// are stripped (so `[!]` yields `!`), and a leading run of the same character
+/// is collapsed (so `>>>` yields `>`). The result is the first grapheme cluster
+/// of whatever remains, keeping multi-codepoint emoji intact.
+fn pick_icon_glyph(prefix: &str) -> Option<SharedString> {
+    let prefix = prefix.trim();
+    if prefix.is_empty() {
+        return None;
+    }
+
+    // Condense a leading run of dots (`...`) into a single ellipsis.
+    if prefix.starts_with("..") {
+        return Some("\u{2026}".into());
+    }
+
+    // Strip a single pair of surrounding ASCII brackets, e.g. `[!]` -> `!`.
+    let unwrapped = match prefix.chars().next() {
+        Some('[') => prefix.strip_prefix('[').and_then(|s| s.strip_suffix(']')),
+        Some('(') => prefix.strip_prefix('(').and_then(|s| s.strip_suffix(')')),
+        Some('{') => prefix.strip_prefix('{').and_then(|s| s.strip_suffix('}')),
+        Some('<') => prefix.strip_prefix('<').and_then(|s| s.strip_suffix('>')),
+        _ => None,
+    };
+    let prefix = unwrapped
+        .map(str::trim)
+        .filter(|s| !s.is_empty())
+        .unwrap_or(prefix);
+
+    // Take the first grapheme cluster so multi-codepoint emoji stay intact.
+    let first_grapheme = prefix.graphemes(true).next()?;
+    if first_grapheme.trim().is_empty() {
+        return None;
+    }
+
+    Some(first_grapheme.to_string().into())
+}
+
 fn draft_display_label_for_thread_metadata(
     metadata: &ThreadMetadata,
     workspace: &ThreadEntryWorkspace,

crates/sidebar/src/sidebar_tests.rs

@@ -14733,26 +14733,48 @@ async fn test_cmd_click_project_header_returns_to_last_active_linked_worktree_wo
 
 #[test]
 fn test_split_leading_icon_char() {
-    // A leading symbol is pulled out and trimmed from the title.
+    // A leading symbol set off by whitespace is pulled out and trimmed from the
+    // title.
     let (icon, title, positions) =
         split_leading_icon_char(&"✳ Implement separate config".into(), &[]).unwrap();
     assert_eq!(icon.as_ref(), "✳");
     assert_eq!(title.as_ref(), "Implement separate config");
     assert_eq!(positions, Vec::<usize>::new());
 
-    // No leading symbol when the title starts with a letter.
+    // No prefix when the title starts with a letter.
     assert!(split_leading_icon_char(&"Implement separate config".into(), &[]).is_none());
 
-    // Whitespace is not treated as an icon character.
+    // Leading whitespace is not treated as a prefix.
     assert!(split_leading_icon_char(&" leading space".into(), &[]).is_none());
 
-    // Numbers are non-letters, so they are treated as icon characters.
-    let (icon, title, _) = split_leading_icon_char(&"1 first".into(), &[]).unwrap();
-    assert_eq!(icon.as_ref(), "1");
-    assert_eq!(title.as_ref(), "first");
+    // An alphanumeric prefix such as a version marker is not treated as an icon.
+    assert!(split_leading_icon_char(&"v1 Running".into(), &[]).is_none());
+    assert!(split_leading_icon_char(&"1 first".into(), &[]).is_none());
 
-    // A title consisting only of a symbol is left untouched.
+    // A title consisting only of a symbol (no whitespace separator) is left
+    // untouched.
     assert!(split_leading_icon_char(&"✳".into(), &[]).is_none());
+    assert!(split_leading_icon_char(&"✳Thinking".into(), &[]).is_none());
+
+    // A run of the same symbol collapses to a single glyph.
+    let (icon, title, _) = split_leading_icon_char(&">>> Thinking".into(), &[]).unwrap();
+    assert_eq!(icon.as_ref(), ">");
+    assert_eq!(title.as_ref(), "Thinking");
+
+    // Surrounding ASCII brackets are stripped so the inner glyph is used.
+    let (icon, title, _) = split_leading_icon_char(&"[!] codex waiting".into(), &[]).unwrap();
+    assert_eq!(icon.as_ref(), "!");
+    assert_eq!(title.as_ref(), "codex waiting");
+
+    // A run of dots is condensed into an ellipsis.
+    let (icon, title, _) = split_leading_icon_char(&"... working".into(), &[]).unwrap();
+    assert_eq!(icon.as_ref(), "\u{2026}");
+    assert_eq!(title.as_ref(), "working");
+
+    // Multi-codepoint emoji are kept intact rather than sliced mid-cluster.
+    let (icon, title, _) = split_leading_icon_char(&"🇺🇸 flag".into(), &[]).unwrap();
+    assert_eq!(icon.as_ref(), "🇺🇸");
+    assert_eq!(title.as_ref(), "flag");
 
     // Highlight positions are shifted to account for the stripped prefix, and
     // positions that fall inside the stripped prefix are dropped.