offshoot (data plane)

offshoot is the copy-on-write layer cellp uses to fork and promote application data between versions. It is not something Worker authors configure in wrangler.jsonc.

What it does for you

Operation	Meaning
Branch	Child version gets D1/KV/R2/Queue state derived from a parent version’s bucket
Promote	Production cutover updates data-plane pointers as part of the promote saga
Export / import	Root versions can seed D1 from SQLite files via the orchestrator + celld

cellp runs offshoot as a CLI integration next to celld. The Dashboard and your Worker never talk to offshoot directly.

What you configure instead

• Parent version — parent_version_id on POST /versions
• Artifacts and seeds — upload bundle + optional D1 seed for root deploys (Platform data)
• Storage — private S3 (RustFS in self-hosted stacks) holds artifacts, per-version celld blobs, and offshoot objects

Mental model

version A (parent)  ──branch──►  version B (child preview)
       │                              │
       └── S3 prefix + offshoot ──────┘  copy-on-write, not a full copy

For binding-level behavior and the parent/child matrix, see Data fork.

Technical storage tiers and RustFS notes for operators: Self-hosting · Limits.