Bun.file and OS-level File Locking Interoperability

Concurrent I/O and System Lock Consistency

Bun's Bun.file() API provides a high-performance interface for file system operations, leveraging Zig for optimized memory layout and minimized kernel-to-heap copying. While this provides significant throughput advantages over standard Node.js compatibility layers, the behavior of concurrent write operations across different operating systems remains a point of uncertainty.

When multiple asynchronous operations attempt to write to the same file handle or path, the runtime must interface with varying OS-level locking mechanisms. There is a potential discrepancy in how Linux and macOS handle these locks during high-concurrency I/O bursts, which could lead to inconsistent file states or race conditions.

• Target Runtime: Bun (latest stable)
• Operation: Concurrent Bun.file().write() calls
• Environment: Cross-platform (Linux vs. macOS)

Does Bun implement a unified locking abstraction to ensure write consistency across different operating systems, or does it rely entirely on the underlying system's native file locking behavior? How does the runtime handle lock contention when multiple asynchronous writes overlap?