ui-features

A guide for building interface features in a sidecar application, including dialogs, keyboard shortcuts, mouse interaction, scrolling, tabs, and resizable panes.

In plain words
What is it for?
Use it when adding or changing modals, shortcuts, mouse regions, pills, tabs, scrolling, pane resizing, or related user-interface tests.
Why use it?
It gives consistent rules for input handling and layout so new controls do not overlap, break navigation, or duplicate shared interface elements.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/marcus/sidecar/ui-features
Any agent
npx skills add marcus/sidecar --skill ui-features
Clone the repo
git clone --depth 1 https://github.com/marcus/sidecar

Made for: Claude Code, Codex.

Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,786 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00061 $0.03786
Opus 5 $0.00030 $0.01893
Sonnet 5 $0.00012 $0.00757
Haiku 4.5 $0.00006 $0.00379

Measured 2d ago against content hash 8d0dfe43acc2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

ui-features scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/ui-features/SKILL.md · 402 lines

How it starts

The opening of the file, as written. The whole thing — 402 lines — stays where its author put it; the contents beside it link to each section on GitHub.

UI Feature Implementation

Single entry point for sidecar UI work. All new modals must use internal/modal. For complete keyboard shortcut listings, see references/keyboard-shortcuts-reference.md.

Quick Checklist

  • Modals: use internal/modal, render with ui.OverlayModal, avoid manual hit region math
  • Pills/chips/tabs: use styles.RenderPillWithStyle; auto-fallback when nerdFontsEnabled is false
  • Keyboard: Commands + FocusContext + bindings must match; names short; priorities set
  • Mouse: rebuild hit regions on each render; add general regions first, specific last
  • Rendering: keep output within View width/height to avoid header/footer overlap. Use contentHeight := height - headerLines - footerLines
  • Testing: verify keyboard, mouse, hover, scrolling, and footer hints
  • Plugins must NOT render their own footer -- the app renders a unified footer from Commands()

Modals (internal/modal)

All new modals must use internal/modal. See docs/guides/deprecated/declarative-modal-guide.md for the full API.

Create a modal

m := modal.New("Delete Worktree?",
    modal.WithWidth(58),
    modal.WithVariant(modal.VariantDanger),
    modal.WithPrimaryAction("delete"),
).
    AddSection(modal.Text("Name: " + wt.Name)).
    AddSection(modal.Spacer()).
    AddSection(modal.Buttons(
        modal.Btn(" Delete ", "delete", modal.BtnDanger()),
        modal.Btn(" Cancel ", "cancel"),
    ))

Render in View

func (p *Plugin) renderDeleteView(width, height int) string {
    background := p.renderListView(width, height)
    rendered := p.deleteModal.Render(width, height, p.mouseHandler)
    return ui.OverlayModal(background, rendered, width, height)
}

Handle input in Update

case tea.KeyMsg:
    action, cmd := p.deleteModal.HandleKey(msg)
    if action != "" {
        return p.handleModalAction(action)
    }
    return p, cmd

case tea.MouseMsg:
    action := p.deleteModal.HandleMouse(msg, p.mouseHandler)
    if action != "" {
        return p.handleModalAction(action)
    }
    return p, nil

Read the full file on GitHub · 402 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 402 lines · 61 tokens per session scan A 8d0dfe43acc2

Subscribe to this mod's changes

ui-features is a skill published in the GitHub repository marcus/sidecar (1,049 stars, last pushed 2d ago), licensed MIT. It adds 61 tokens to every session and 3,786 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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