EDGE FDE
AdvancedDurable On-Device AI Workflows
Survive app backgrounding and retries so long tasks finish without starting over.
Checkpoint and resume mini workflow engine for on-device agent work.
Write progress to disk. Restore a new LanguageModelSession. Do not claim the old session survived. iOS 27 and macOS 27 only.
Lessons
Key concepts
- Long jobs die from backgrounding, cancellation, and process death.
LanguageModelSessionlives in memory. The transcript is readable when it is not responding.- A checkpoint is a Codable record written after each successful step.
- Resume creates a new session and restores transcript data from disk.
Takeaways
- You can ship a mini workflow engine that checkpoints each step and resumes with a new session.
- You can write progress to disk before the next model call.
- You can tell stakeholders iOS background resume is best effort.
Agent briefs
Related courses
Run an agent with a state machine · Make several agents agree first · Talk to tools with MCP · Stop prompt attacks and leaks · Keep On-Device LLMs Alive on Real Phones