View wraps on macOS Terminal.app despite calculating widths

[amoeba]

Describe the bug

The code sample below shows what might be a bug which is that, only on macOS Terminal.app, trying to render a View to the full-width of the terminal causes wrapping which breaks what I'm trying to achieve. All other terminals (including iTerm, kitty, Alacritty) render as expected.

I may be using the APIs incorrectly or not using an API I should be.

Setup

Please complete the following information along with version numbers, if applicable.

• OS: macOS 15
• Shell: zsh, fish
• Terminal Emulator: Terminal.app
• Terminal Multiplexer: None

To Reproduce
Steps to reproduce the behavior:

1. Create a go package and go run the source

Source Code

package main

import (
	"fmt"
	"strings"
	"time"

	"github.com/charmbracelet/bubbles/progress"
	"github.com/charmbracelet/bubbles/spinner"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

type model struct {
	n        int
	current  int
	spinner  spinner.Model
	progress progress.Model
	done     bool
	width    int
}

type tickMsg struct{}

func newModel() model {
	s := spinner.New()
	s.Spinner = spinner.Dot
	p := progress.New()

	return model{
		n:        10,
		spinner:  s,
		progress: p,
		width:    80,
	}
}

func (m model) Init() tea.Cmd {
	return tea.Batch(m.spinner.Tick, tick())
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.KeyMsg:
		return m, tea.Quit
	case tea.WindowSizeMsg:
		m.width = msg.Width
		return m, nil
	case tickMsg:
		if m.current >= m.n {
			m.done = true
			return m, tea.Quit
		}

		m.current++
		percent := float64(m.current) / float64(m.n)
		cmd := m.progress.SetPercent(percent)

		return m, tea.Batch(cmd, tick())
	default:
		var cmds []tea.Cmd

		var cmd tea.Cmd
		m.spinner, cmd = m.spinner.Update(msg)
		cmds = append(cmds, cmd)

		progressModel, cmd := m.progress.Update(msg)
		m.progress = progressModel.(progress.Model)
		cmds = append(cmds, cmd)

		return m, tea.Batch(cmds...)
	}
}

func (m model) View() string {
	if m.done || m.current >= m.n {
		return ""
	}

	status := fmt.Sprintf("%s Running... ", m.spinner.View())

	progressBarWidth := m.width / 2
	m.progress.Width = progressBarWidth
	progressBar := m.progress.View()

	statusWidth := lipgloss.Width(status)
	progressWidth := lipgloss.Width(progressBar)
	gapWidth := m.width - statusWidth - progressWidth

	// This is what we want to call
	gap := strings.Repeat(" ", gapWidth)

	// This is what we have to call on macOS Terminal.app
	// gap := strings.Repeat(" ", gapWidth - 1)

	return status + gap + progressBar
}

func tick() tea.Cmd {
	return tea.Tick(300*time.Millisecond, func(time.Time) tea.Msg {
		return tickMsg{}
	})
}

func main() {
	if _, err := tea.NewProgram(newModel()).Run(); err != nil {
		fmt.Printf("Error: %v\n", err)
	}
}

Expected behavior

I expect to be able to do my width calculation like shown in the source code snippet and to see rendering like what's shown in the iTerm 2 GIF.

Screenshots

Here's Terminal.app, showing that the line wraps which makes the rendering look wonky:

Here's iTerm2, showing the desired behavior:

[aymanbagabas]

Thank you, @amoeba, for reporting this one. I think this is a bug in the existing v1 renderer, and we're on it!

This, however, is fixed in the new faster and performance cell-based renderer in v2. You could switch to our v2 stack by updating your imports and using the latest changes from our v2-exp branches.

go get github.com/charmbracelet/lipgloss/v2@v2-exp
go get github.com/charmbracelet/bubbles/v2@v2-exp
go get github.com/charmbracelet/bubbletea/v2@v2-exp

[aymanbagabas]

I've opened #1472 to fix this issue. We will push a new v1 release soon so stay tuned!

While testing your example, I noticed a small issue with how the progress width is being calculated. Since model is being used as value receiver, mutating the progress model should happen in the Update rather than the View. Here's a diff that moves that logic to Update as well as remove the need to recalculate the progress width.

I hope this helps 🙂

--- _bug1471/a.go	2025-08-15 18:24:41
+++ _bug1471/b.go	2025-08-15 18:24:07
@@ -45,6 +45,8 @@
 		return m, tea.Quit
 	case tea.WindowSizeMsg:
 		m.width = msg.Width
+		progressBarWidth := m.width / 2
+		m.progress.Width = progressBarWidth
 		return m, nil
 	case tickMsg:
 		if m.current >= m.n {
@@ -79,13 +81,10 @@
 
 	status := fmt.Sprintf("%s Running... ", m.spinner.View())
 
-	progressBarWidth := m.width / 2
-	m.progress.Width = progressBarWidth
 	progressBar := m.progress.View()
 
 	statusWidth := lipgloss.Width(status)
-	progressWidth := lipgloss.Width(progressBar)
-	gapWidth := m.width - statusWidth - progressWidth
+	gapWidth := m.width - statusWidth - m.progress.Width
 
 	// This is what we want to call
 	gap := strings.Repeat(" ", gapWidth)

[amoeba]

Thanks for the options and the note @aymanbagabas. That patch makes sense. I can also confirm the v2 package fixes the issue.