# Tree nodes: bulk Merkle summaries vs itemized chain seals

The main Verae chain stores **hash + time + block + certificate**. A Zap that timestamps one document writes that document’s SHA-256 as its own seal.

A **batch** of many documents is different: middleware builds a Merkle tree of the item hashes, seals **only the Merkle root** on the chain, and writes each **leaf proof** to external tree-node NATS archives. A later lookup of a member hash will **miss** on the central chain unless the Zap also queries tree nodes.

```text
Zapier  HTTPS  zappier-edge  HTTPS  middleware
                                      |
                         Merkle root  |  verae.archive.put kind=tree
                         (chain seal) |  (leaf proof, sharded)
                                      v
                               tree-node-east/west/central
                               bloom miss = silence
                                      ^
              hash lookup includeTree |  verae.archive.query
                                      |  kinds=["tree"]
                              aggregator merges proof + root seal
```

## When to use which Zapier search

| Search | Hits |
|--------|------|
| Find Timestamp by SHA256 | Hash was registered as its own chain seal |
| Find Hash (tree nodes + central chain) | Chain first, then `includeTree=true` broadcast |

## Receipt shape for a bulk leaf

```json
{
  "sha256": "<leaf>",
  "exists": true,
  "itemizedOnMainChain": false,
  "merkleRoot": "<root sealed on chain>",
  "proofOk": true,
  "receipts": [
    { "kind": "seal", "of": "merkleRoot", "sha256": "<root>", "certificate": "…" },
    { "kind": "tree-leaf", "archiveId": "tree-node-east", "proof": […], "leafIndex": 1 }
  ]
}
```

Validate this path in the simulator (`packages/verae-zapier-simulator`) before pushing the Zapier app.