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Senior macOS Extension Developer (Contractor)
techholding • Mexico, Remote
No Relocation
Posted: February 26, 2026
Job Description
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
Additional Content
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