Encore has developed "crackling," a cross-platform tool that enables engineers to run backend build environments locally on macOS and Linux using native hypervisors instead of remote shared servers.

Key Points

• Crackling replaces a complex remote build system that relied on shared Linux hosts, SSH, and manual Docker-to-block-device image conversions.
• The tool uses Firecracker on Linux and Apple’s Virtualization.framework (VZ) on macOS to boot OCI images as lightweight virtual machines.
• A unified Rust-based agent communicates with the host via vsock, providing consistent shell, execution, and file-copying capabilities across both platforms.
• The system handles kernel unwrapping and root filesystem generation in userspace, allowing it to boot Linux images natively on Apple Silicon.
• By moving the build environment to local hardware, developers can now use standard debugging tools and breakpoints directly within their build pipeline.

Why it Matters

This transition eliminates the latency and friction of remote development, allowing engineers to iterate on backend infrastructure as easily as application code. By unifying the build environment across different operating systems, Encore improves developer productivity and ensures that local testing environments accurately mirror production deployments.