appkit-interop

Guidance for connecting a macOS app’s SwiftUI interface to AppKit, Apple’s older macOS user-interface framework, when SwiftUI lacks a needed desktop behavior.

In plain words
What is it for?
Use it for wrapping AppKit views or view controllers, accessing windows and menus, showing panels, controlling focus, and handling other native macOS behavior.
Why use it?
It helps choose the smallest connection between the two frameworks and keeps ownership of app state clear.

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/robinebers/openusage/appkit-interop
Any agent
npx skills add robinebers/openusage --skill appkit-interop
Clone the repo
git clone --depth 1 https://github.com/robinebers/openusage

Made for: Claude Code, Codex.

Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 630 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 $0.00064 $0.00630
Opus 5 $0.00032 $0.00315
Sonnet 5 $0.00013 $0.00126
Haiku 4.5 $0.00006 $0.00063

Measured 3d ago against content hash 2021ce39bec3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

appkit-interop 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 3d 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.

Origin

Copies of this mod

3 near-identical copies found in the catalogue:

.agents/skills/appkit-interop/SKILL.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AppKit Interop

Quick Start

Use this skill when SwiftUI is close but not quite enough for native macOS behavior. Keep the bridge as small and explicit as possible. SwiftUI should usually remain the source of truth, while AppKit handles the imperative edge.

Choose The Smallest Bridge

  • Use pure SwiftUI when the required behavior already exists in scenes, toolbars, commands, inspectors, or standard controls.
  • Use NSViewRepresentable when you need a specific AppKit view with lightweight lifecycle needs.
  • Use NSViewControllerRepresentable when you need controller lifecycle, delegation, or presentation coordination.
  • Use direct AppKit window or app hooks when you need NSWindow, responder-chain, menu validation, panels, or app-level behavior.

Workflow

  1. Name the capability gap precisely.

    • Window behavior
    • Text system behavior
    • Menu validation
    • Drag and drop
    • File open/save panels
    • First responder control
  2. Pick the smallest boundary that solves it.

    • Avoid porting a whole screen to AppKit when one wrapped control or coordinator would do.
  3. Keep ownership explicit.

    • SwiftUI owns value state, selection, and observable models.
    • AppKit objects stay inside the representable, coordinator, or bridge object.
  4. Expose a narrow interface back to SwiftUI.

    • Bindings for editable state
    • Small callbacks for events
    • Focused bridge services only when necessary
  5. Validate lifecycle assumptions.

    • SwiftUI may recreate representables.
    • Coordinators exist to hold delegate and target-action glue, not as a second app architecture.

References

  • references/representables.md: choosing between view and view-controller wrappers, plus coordinator patterns.
  • references/window-panels.md: window access, utility windows, and open/save panels.
  • references/responder-menus.md: first responder, command routing, and menu validation.
  • references/drag-drop-pasteboard.md: pasteboard, file URLs, and desktop drag/drop edges.

Read the full file on GitHub · 69 lines

Files

What ships with it

4 files 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. 3d ago First seen · 69 lines · 64 tokens per session scan A 2021ce39bec3

Subscribe to this mod's changes

appkit-interop is a skill published in the GitHub repository robinebers/openusage (3,975 stars, last pushed yesterday), licensed MIT. It adds 64 tokens to every session and 630 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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