fix(statusline): reserve a fixed 5 columns instead of 20% of width

.claude/skills/running-tend/SKILL.md

@@ -288,6 +288,27 @@ git grep -niE "claude|codex"
 
 Check the latest IDs at <https://docs.anthropic.com/en/docs/about-claude/models> and <https://developers.openai.com/codex/models>. The recommended commit-message commands should use the most recent fastest model from each vendor (Haiku for Anthropic, the smallest current Codex variant for OpenAI).
 
+## Weekly Maintenance: Agent App Integration Surfaces
+
+Worktrunk ships a plugin for each agent CLI it integrates with, and those CLIs
+change their integration surfaces without notice. Each week, scan the upstream
+changelogs and flag changes that affect what Worktrunk consumes or produces.
+
+| App | Source to check | Integration surface |
+|-----|-----------------|---------------------|
+| Claude Code | `gh api repos/anthropics/claude-code/contents/CHANGELOG.md -H 'Accept: application/vnd.github.raw'`, plus `curl -sL https://code.claude.com/docs/en/statusline.md` for the statusline JSON schema | statusline stdin JSON, `WorktreeCreate`/`WorktreeRemove` hooks, plugin marketplace, `/wt-switch-create` |
+| Codex | `gh release list -R openai/codex -L 10` | plugin marketplace |
+| Gemini CLI | `gh release list -R google-gemini/gemini-cli -L 10` | native extension loading |
+| OpenCode | `gh release list -R sst/opencode -L 10` | plugins API in `~/.config/opencode/plugins/` |
+
+What to flag:
+
+- **New statusline JSON fields** — `src/commands/statusline.rs` parses `workspace.current_dir`, `model.display_name`, and `context_window.used_percentage`. A newly added field (rate limits, session cost, PR review state) may be worth surfacing in `wt list statusline`.
+- **Renamed or removed hook events** — `WorktreeCreate`/`WorktreeRemove` route agent worktree creation through `wt`; a renamed event silently disables isolation rather than erroring.
+- **Changed plugin install mechanisms** — `wt config plugins {claude,codex,opencode} install` and the Gemini extension manifest break if the marketplace or plugins-directory contract changes.
+
+Don't open a PR speculatively. File one issue per relevant change, linking the upstream entry and noting what Worktrunk would need to do. If nothing changed, say so and move on.
+
 ## README Date Check
 
 The README blockquote opens with a month+year (e.g., "**April 2026**"). During daily

src/styling/mod.rs

@@ -104,8 +104,8 @@ pub fn terminal_width() -> usize {
 /// stdout, and stderr — so [`terminal_width`] always falls through to its
 /// `usize::MAX` sentinel, and the statusline output would overflow the bar.
 /// As a last resort, this walks up to 10 parent processes looking for a TTY
-/// and asks `stty size` for its dimensions, reserving 20% for Claude Code's
-/// own UI messages.
+/// and asks `stty size` for its dimensions, reserving 5 columns for Claude
+/// Code's own UI messages.
 ///
 /// Every other caller should use [`terminal_width`] — the parent-TTY walk is
 /// a statusline-specific workaround, not a general fallback.
@@ -131,10 +131,7 @@ fn statusline_width_fallback(base: usize) -> usize {
 ///
 /// This is a fallback for subprocesses (like Claude Code hooks) that don't have
 /// direct TTY access. Walks up to 10 parent processes looking for one with a TTY,
-/// then queries that TTY's size.
-///
-/// Returns 80% of the detected width to reserve space for Claude Code's UI messages
-/// (like "Approaching context limit").
+/// then queries that TTY's size via `stty` and [`statusline_width_from_stty_size`].
 #[cfg(unix)]
 fn detect_parent_tty_width() -> Option<usize> {
     use crate::shell_exec::Cmd;
@@ -160,14 +157,7 @@ fn detect_parent_tty_width() -> Option<usize> {
                 .run()
                 .ok()?;
 
-            let cols = String::from_utf8_lossy(&size.stdout)
-                .split_whitespace()
-                .nth(1)?
-                .parse::<usize>()
-                .ok()?;
-
-            // Reserve 20% for Claude Code UI messages
-            return Some(cols * 80 / 100);
+            return statusline_width_from_stty_size(&String::from_utf8_lossy(&size.stdout));
         }
 
         if ppid == "1" || ppid == "0" {
@@ -179,6 +169,17 @@ fn detect_parent_tty_width() -> Option<usize> {
     None
 }
 
+/// Convert `stty size` output (`"<rows> <cols>"`) into a statusline width.
+///
+/// Reserves 5 columns for Claude Code's UI messages (like "Approaching
+/// context limit"). Returns `None` when the output has no parseable column
+/// count.
+#[cfg(unix)]
+fn statusline_width_from_stty_size(stty_size: &str) -> Option<usize> {
+    let cols = stty_size.split_whitespace().nth(1)?.parse::<usize>().ok()?;
+    Some(cols.saturating_sub(5))
+}
+
 /// Calculate visual width of a string, ignoring ANSI escape codes
 ///
 /// Uses unicode-width for proper handling of wide characters (CJK, emoji).
@@ -232,6 +233,21 @@ mod tests {
         assert!(width > 0);
     }
 
+    #[cfg(unix)]
+    #[test]
+    fn statusline_width_from_stty_size_reserves_five_columns() {
+        // `stty size` prints "<rows> <cols>"; the column count loses 5 to
+        // Claude Code's UI chrome.
+        assert_eq!(statusline_width_from_stty_size("24 200"), Some(195));
+        assert_eq!(statusline_width_from_stty_size("24 80"), Some(75));
+        // Saturates rather than underflowing on a terminal narrower than 5.
+        assert_eq!(statusline_width_from_stty_size("24 3"), Some(0));
+        // No parseable column count.
+        assert_eq!(statusline_width_from_stty_size(""), None);
+        assert_eq!(statusline_width_from_stty_size("24"), None);
+        assert_eq!(statusline_width_from_stty_size("24 wide"), None);
+    }
+
     #[test]
     fn test_toml_formatting() {
         let toml_content = r#"worktree-path = "../{{ repo }}.{{ branch }}"