@buildtovalue/anchor-s3

S3 object-lock anchor adapter (Handoff 8): anchors the ledger chain head to a write-once object, implementing the AnchorAdapter contract from @buildtovalue/identity.

The host owns the S3 client (no network in the library)

You inject put/get; the library never talks to S3. Point put at an object-lock (WORM) bucket so anchors are immutable.

import { createS3Anchor } from '@buildtovalue/anchor-s3';

const anchor = createS3Anchor({
  async put(key, body) {
    return host.s3PutObject(key, body); // { versionId? }
  },
  async get(key) {
    return host.s3GetObject(key); // undefined when unreachable
  },
});

const receipt = await anchor.anchor({ hash: head.hash, seq: head.seq });
await anchor.verify(receipt, currentHashAtSeq); // 'anchored' | 'mismatch' | 'unavailable'

Derive the UI state from the result via deriveAnchorState in @buildtovalue/identity. Consumes only @buildtovalue/identity — pinned by tests/independence.test.ts. Zero runtime dependencies.