What is app-lifecycle-state-machine?

An iOS app architecture that models the app lifecycle as a set of states, such as launching and being in the foreground, instead of placing most logic in one AppDelegate file.

Use it when designing or refactoring iOS lifecycle code, including service setup, dependency configuration, UI initialization, and resuming work after suspension.

It makes startup and active-app behavior more predictable and keeps related responsibilities organized.

app-lifecycle-state-machine — Cursor rule for Cursor by duckduckgo: An iOS app architecture that models the app lifecycle…

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 rules/duckduckgo/apple-browsers/app-lifecycle-state-machine

Clone the repo

git clone --depth 1 https://github.com/duckduckgo/apple-browsers

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/rules/duckduckgo/apple-browsers/app-lifecycle-state-machine.svg)](https://agentmods.dev/rules/duckduckgo/apple-browsers/app-lifecycle-state-machine)

Your own site

<a href="https://agentmods.dev/rules/duckduckgo/apple-browsers/app-lifecycle-state-machine"><img src="https://agentmods.dev/badge/rules/duckduckgo/apple-browsers/app-lifecycle-state-machine.svg" alt="Measured on agentmods" height="20"></a>

Per session 0 Nothing until a file matches its globs; then the whole rule loads.

When invoked 3,041 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.

Model	Per session	Once invoked
Fable 5	$0.00000	$0.03041
Opus 5	$0.00000	$0.01520
Sonnet 5	$0.00000	$0.00608
Haiku 4.5	$0.00000	$0.00304

Measured 3d ago against content hash 7b3bf3395599, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

app-lifecycle-state-machine 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.

.cursor/rules/app-lifecycle-state-machine.mdc · 572 lines

How it starts

The opening of the file, as written. The whole thing — 572 lines — stays where its author put it; the contents beside it link to each section on GitHub.

App Lifecycle State Machine Architecture

Overview

The DuckDuckGo browser has moved away from traditional AppDelegate-based lifecycle handling to a state machine architecture. While AppDelegate still exists, it has been significantly thinned out and now delegates responsibility to a structured state machine.

This approach ensures that lifecycle handling is predictable, organized, and easy to maintain.

Architecture Components

Three Core States

The architecture revolves around a state machine with three major states:

1. Launching (Transient State)

Associated with: application(_:didFinishLaunchingWithOptions:)
File: Launching.swift
Purpose: App's initial setup and dependency configuration
Responsibilities:
- Initialize all services and objects
- Configure dependencies
- Prepare UI components
- Create MainViewController and set as rootViewController

2. Foreground (Permanent State)

Associated with: applicationDidBecomeActive(_:)
File: Foreground.swift
Purpose: App is fully interactive and user can engage with UI
Responsibilities:
- Resume suspended work
- Handle user interactions
- Manage active UI state

3. Background (Permanent State)

Associated with: applicationDidEnterBackground(_:)
File: Background.swift
Purpose: App is not active and UI is not visible
Responsibilities:
- Suspend ongoing work that doesn't need background execution
- Prepare for potential termination
- Handle background tasks

State Machine Methods

Core Transition Methods

All states implement specific methods for handling transitions:

`onTransition()`

When: Called whenever the app enters that state from another state
Purpose: Setup or cleanup during state transitions
Available in: Foreground, Background

`willLeave()`

When: Called before transitioning away from current state
Purpose: Prepare for potential state change
Note: Transition may be cancelled, in which case didReturn() is called
Available in: Foreground, Background

Read the full file on GitHub · 572 lines

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.

3d ago First seen · 572 lines · 0 tokens per session scan A 7b3bf3395599

Subscribe to this mod's changes

app-lifecycle-state-machine is a cursor rule published in the GitHub repository duckduckgo/apple-browsers (251 stars, last pushed today), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 3,041 tokens. 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 2026-09-01.

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