maui threading-async.instructions.md

Development guidance for handling background work and user-interface updates in .NET MAUI apps, which run on multiple platforms.

In plain words
What is it for?
Updating UI controls on the correct thread, managing asynchronous handlers, cancelling stale work, preventing race conditions, and applying Android, iOS, and Windows-specific checks.
Why use it?
It helps prevent interface crashes, outdated results, uncancelled work, and conflicts between concurrent operations.

Instructions file for GitHub Copilot

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 instructions/dotnet/maui/threading-async
Clone the repo
git clone --depth 1 https://github.com/dotnet/maui

Made for: GitHub Copilot.

Per session 373 This file is loaded in full into every session.
When invoked 373 The same file — it is already loaded in full.
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 $0.00373 $0.00373
Opus 5 $0.00187 $0.00187
Sonnet 5 $0.00075 $0.00075
Haiku 4.5 $0.00037 $0.00037

Measured yesterday against content hash 6eab7df92cc8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

maui threading-async.instructions.md 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 yesterday.

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.

.github/instructions/threading-async.instructions.md · 35 lines

What it actually says

Threading and Async Patterns

UI Thread Dispatch

  • Platform view modifications MUST happen on the UI thread
  • Android: platformView.Post(() => { }) or Looper.MainLooper for thread checks
  • iOS/MacCatalyst: MainThread.BeginInvokeOnMainThread() or DispatchQueue.MainQueue
  • Windows: DispatcherQueue.TryEnqueue() — be aware of COM threading apartment model

Async Handler Operations

  • Use .FireAndForget(handler) for async work in mapper methods — never bare async void
  • After await, verify the handler is still connected (VirtualView != null) before applying results
  • Thread CancellationToken through long-running operations and check at appropriate yield points

Race Condition Prevention

  • Concurrent access to shared state must use lock, Interlocked, or immutable patterns
  • Image loading and other async pipelines must cancel in-flight operations when the source changes
  • Guard against stale callbacks — platform callbacks may fire after DisconnectHandler

Platform-Specific Patterns

  • Android: API-level checks use Build.VERSION.SdkInt comparison, not version string parsing
  • iOS: Use System.OperatingSystem.IsIOSVersionAtLeast() for linker-friendly runtime checks
  • Windows: WinUI version checks may be needed for features in specific Windows App SDK versions
  • Use System.OperatingSystem APIs over RuntimeInformation — they are trimmer/AOT-friendly
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. yesterday First seen · 35 lines · 373 tokens per session scan A 6eab7df92cc8

Subscribe to this mod's changes

maui threading-async.instructions.md is an instructions file published in the GitHub repository dotnet/maui (23,317 stars, last pushed yesterday), licensed MIT. It adds 373 tokens to every session, about $0.0019 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.