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Content Addressable Streaming (CAS) is Tensorlake’s newer format for sandbox images and snapshots. A sandbox created from a CAS image or snapshot starts running before its contents have been downloaded from the underlying blob storage. The missing parts stream in the background at high throughput, while the memory and I/O requests the sandbox makes are served at high priority to keep their latency low. Images and snapshots are deduplicated, so only data that isn’t already cached locally is downloaded. The result is fast and consistent cold starts, with extra disk read latency only for a short time after creation. Sandboxes created from CAS images and snapshots run on Tensorlake’s next-generation dataplane, which enables live resize and nested virtualization. GPU sandboxes run on gVisor and use CAS images and snapshots too. CAS is opt-in. Pass --cas to tl sbx image create or tl sbx image import to build or import a CAS image. A sandbox booted or restored from a CAS image or snapshot takes its snapshots in CAS format too.

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Example: Launch a Sandbox from a CAS Image

The managed Tensorlake images are available in CAS form under the tensorlake/cas/ prefix:

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Build a CAS Image

Add --cas to tl sbx image create. Everything else works as described in Define, Build and Register an Image.
Dockerfile
A CAS build resolves the Dockerfile’s FROM references against the CAS catalog. A Tensorlake image named without the tensorlake/cas/ prefix is looked up as tensorlake/cas/<name>, so FROM tensorlake/ubuntu-minimal builds on tensorlake/cas/ubuntu-minimal, and the build fails if that CAS image doesn’t exist. Other references, such as ubuntu:24.04 or a private registry image, are pulled from their registry. Unlike default builds, CAS builds accept Dockerfile build args:

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Import a CAS Image

Add --cas to tl sbx image import to import a registry image as is:
--disk_mb sets the root disk size of sandboxes created from the image, as for any build or import. You can grow it further for an individual sandbox with --disk_mb on tl sbx create.

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See Also

Build and Import Images

The build and import workflow that --cas plugs into.

Live Resize

Change the CPUs, memory, and disk of a running CAS sandbox.

Nested Virtualization

Run QEMU/KVM virtual machines inside a CAS sandbox.