Terminology, sizing and limits

Glossary

Drop

One recorded artifact or Pact Seed. The singular of the protocol name. Identified by the input that revealed it.

Drops

The application protocol. Covers media-first artifacts and Drop Pacts.

Drops leaf

The Tapscript leaf that carries a Drop: five data pushes, four OP_DROPs and an OP_CHECKSIG.

Marker

The first push. A namespace, not a label. drops or drops-pact for this protocol.

Body

The fourth push. 1 to 256 opaque bytes, interpreted according to the declared content type.

Dropmark

The first ten hex characters of the body hash, uppercased. A short human label. Never an identity, because it is not unique.

Commit transaction

The transaction that creates the Taproot output committing to the script tree containing the Drops leaf. Reveals nothing.

Reveal transaction

The transaction that spends the commit output on the script path, putting the leaf and control block into the witness.

Control block

The third witness item: a leaf-version-and-parity byte, the 32-byte internal key, and up to 128 merkle path hashes.

Custody outpoint

The output currently holding the artifact. Output 0 of the reveal, then output 0 of each spending transaction.

Pact Seed

A 184-byte record that fixes an agreement's identity and the hashes of its ruleset, ABI, genesis state, policy and data-availability policy.

Enforcement floor

The Seed field stating how much of the agreement Bitcoin enforces alone: recorded, co-signed or template-enforced.

Pact Cell

A 176-byte descriptor carried in its own leaf, asserting a Pact's current state, policy and the transition that produced it.

Transition commitment

A tagged hash over the 245-byte transition preimage. Appears in the successor Cell and in the DPC1 anchor.

DPC1 anchor

A 38-byte OP_RETURN output marking a candidate Pact transition. Marks; does not prove.

Proof pack

The deterministic CBOR structure holding a transition's supporting evidence.

Projection

Anything derived from immutable records, such as custody. Rebuilt after a reorganisation rather than patched.

Finalized target

The height an indexer will persist up to: tip - (N - 1) for confirmation depth N.

OP_DROP

The neighbouring token protocol, marker bip110-op-drop. Also the Bitcoin Script opcode this carrier is named after.

Fee and size considerations

The leaf lives in the witness, so its bytes are discounted to one weight unit each instead of four. Virtual size is weight divided by four, so witness bytes cost roughly a quarter of what the same bytes would cost in an output script.

Leaf size arithmetic

leafBytes = (1 + markerLen)          # marker push
          + 1                        # OP_DROP
          + (1 + mimeLen)            # content type push
          + 1                        # OP_DROP
          + 33                       # 32-byte hash push
          + 1                        # OP_DROP
          + pushOverhead(bodyLen) + bodyLen
          + 1                        # OP_DROP
          + 33                       # 32-byte key push
          + 1                        # OP_CHECKSIG

pushOverhead(n) = 1 for n <= 75, 2 for 76..255, 3 for 256

Witness total assumes a 64-byte signature and a 33-byte control block, plus the witness item count and one compactSize length prefix per item. A leaf of 253 bytes or more needs a three-byte prefix rather than one, which is why the last row gains more than the body alone. Add 32 bytes to the control block for each merkle sibling, which is 8 vbytes each. Add the transaction's own base cost, roughly 42 to 60 vbytes for a one-input, one-output transaction, plus the commit transaction that funded it.