Soma

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ADR-0004: Extract a dedicated blob CAS crate (historical soma-vdfs naming) ​

Context ​

Soma’s “blob CAS” implementation used to be duplicated in the daemon and bot binaries. It is now shared via soma-vdfs:

  • soma_vdfs::fs::FsBlobStore (backend/crates/vdfs/src/fs.rs)

Meanwhile, the peer runtime (backend/crates/peer/src/lib.rs) defines the BlobProvider boundary and the /soma/blob/1 protocol types. This makes it harder to:

  • reuse the CAS implementation in other projects,
  • keep hashing/layout rules consistent across binaries,
  • evolve the blob protocol without touching multiple unrelated crates.

Decision ​

Create (and use) a dedicated crate for the minimal blob CAS surface (blob CAS + fetch-by-CID primitives), and make soma-peer depend on it.

The crate will intentionally stay narrow (no virtual filesystem mapping).

Consequences ​

Positive:

  • One canonical CID + layout implementation shared by daemon/bot (and other projects).
  • Cleaner boundaries: soma-peer focuses on libp2p wiring; the historical soma-vdfs crate focuses on CAS rules.
  • Reduced duplication and drift.

Negative / follow-ups:

  • Requires a small refactor to move BlobProvider and blob protocol types out of soma-peer.
  • May need a short compatibility phase while consumers migrate.