Senior macOS Extension Developer (Contractor)
About us:
Working at Tech Holding isn't just a job, it's an opportunity to be a part of something bigger. We are a full-service consulting firm that was founded on the premise of delivering predictable outcomes and high-quality solutions to our clients. Our founders and team members have industry experience and have held senior positions in a wide variety of companies – from emerging startups to large Fortune 50 firms – and we have taken our combined experiences and developed a unique approach that is supported by the principles of deep expertise, integrity, transparency, and dependability.
The Role
We are looking for a Senior macOS systems engineer with deep expertise in file system extensions and kernel-adjacent frameworks. You will be responsible for building and maintaining a production-grade sync or virtual drive client on macOS, one that users depend on every day. This is a technically demanding role suited to an engineer who has shipped real software in this space and understands the nuances of Apple's extension model from entitlements to on-demand resource management.
Key Responsibilities:
- Design, implement, and maintain macOS File Provider extensions using NSFileProviderExtension and related APIs
- Item enumeration, working set management, and placeholder lifecycle
- On-demand downloading and eviction of file content
- Conflict detection and resolution strategies
- Integrate and maintain macFUSE-based virtual file systems
- Implement low-level FUSE operations: read, write, getattr, readdir, open, release
- Handle partial byte-range reads for large file streaming scenarios
- Manage macOS System Extension lifecycle including code signing, notarization, entitlements, and sandboxing requirements
- Build and maintain XPC services for secure inter-process communication between the extension and host app
- Write idiomatic Swift using modern concurrency patterns (async/await, actors, structured concurrency)
- Diagnose and resolve complex, hard-to-reproduce issues at the intersection of the kernel, file system, and user space
- Collaborate with product and backend teams to define sync protocols and surface reliable UX
Required Skills:
- 5+ years of macOS development experience, with a focus on system-level or framework-level work
- Strong hands-on experience with the FileProvider framework
- NSFileProviderExtension, NSFileProviderItem, and domain management
- Item enumeration, on-demand download, and working set eviction
- Conflict resolution and syncing state machines
- Practical experience with macFUSE
- Implementing core FUSE operations: read, write, getattr, open, readdir
- Handling partial byte-range reads
- Debugging kernel panics and FUSE-layer failures
- Deep understanding of macOS System Extensions
- Code signing and notarization workflows
- Entitlement management and capability provisioning
- Sandbox constraints and their impact on file system access
- Proficiency with Swift async/await and XPC services for IPC
- Has shipped a production macOS sync client, cloud drive, backup tool, or similar, that real users depend on
Nice-to-have Skills:
- Experience with network file system protocols (WebDAV, SMB, NFS) at the application layer
- Familiarity with FSEvents for file system monitoring
- Prior experience with Endpoint Security or Network Extension frameworks
- Contributions to open-source macOS tooling or FUSE projects
- Background in cloud storage, backup, or enterprise file management products
- Familiarity with TestFlight distribution and enterprise MDM deployment of system extensions
What we offer:
- Fully remote engagement across MX.
- Opportunity to work on high-impact client systems with real operational ownership.
Employment type:
- Contract
Tech Holding is proud to be an Equal Opportunity Employer and is committed to fostering a diverse and inclusive workplace. We welcome applicants from all backgrounds and experiences, and we consider qualified applicants without regard to race, color, religion, gender, sexual orientation, gender identity, national origin, disability, veteran status, or any other legally protected characteristic. If you require accommodation in the application process, please contact our HR