Sync: oversized domains ride Blossom blobs — plus a coinos-hosted server.

2026-09-10T06:06:35Z

A wallet with deep Ark coins had a 633KB ark sync domain against the relay's 40KB budget: the publish silently failed forever, the slot stayed stale, and every boot retried. Relays can't carry it (64KB event cap) and neither can NIP-44 (64KB plaintext), so a domain over budget now goes to Blossom (nostr blob storage, BUD-01/02/06/11/12): sealed into an envelope ("CSB1" + xchacha20poly1305 under an HKDF of the wallet's NIP-44 self-key), uploaded to the configured servers, and the kind-30078 event carries only { blob: { sha256, size, servers } }. Readers resolve pointers from their own outbox copy first, else from the pointer's servers plus the configured list, hash-verified. Small domains are unchanged. The outbox uploads before it publishes (upload/delete authorizations are kind-24242 events signed at enqueue time, so delivery after logout still holds no key), keeps a local copy for recovery, and deletes superseded blobs once the replacement is acknowledged. Servers: Settings → Nostr → Sync storage (any Blossom server; a typed list is kept), else the user's BUD-03 list (kind 10063) with the coinos server as mirror, else blossom.coinos.io. blossom/server.js is that default: a Bun Blossom server that stores ONLY these envelopes (magic check → 415 for anything else), serves every blob as an octet-stream attachment with nosniff, requires signed auth for upload/list/delete, and enforces per-blob size, per-key quota (oldest evicted), rate limits, a disk cap and unused-blob expiry — it cannot serve as a file host. tools/sync-blob-test.js spawns it and covers the policy, the outbox flow and a fresh device resolving a pointer. Co-Authored-By: Claude Fable 5.1 Claude-Session: https://claude.ai/code/session_01Nw1Dijik1tLVKRM1WkU7xE

coinosv3.git/blossom/compose-blossom.yml, branch master

Sync: oversized domains ride Blossom blobs — plus a coinos-hosted server.