WTXID-based transaction relay

The five-minute read

One action, walked through

1. Open BIP 339 and read the status line before the examples.
2. Write down the rule in one sentence. A fair version of that sentence is: Two changes to the p2p protocol to support transaction relay based on the BIP 141 wtxid of a transaction, rather than its txid.
3. Name the object that changes: MUST, WTXID.
4. Ask what an old client, an old contract, or an offline counterparty does. If the document is silent, the silence is part of the design.

The argument, unpacked

What has to be true

• You are implementing BIP 339 at the status the text itself states: Deployed.
• The object that has to change is MUST, WTXID. A neighbouring document with a similar name is not this one.
• Measurements of delay in one year do not travel with the specification.

What happened after the paper

The source marks this deployed. That is a statement about the text, not a promise that every wallet or node has shipped it. Later documents can narrow, replace, or ignore this one. Cite the number you mean.

What to check before you use the idea

• Which message does WTXID-based transaction relay add, and which old peer must still be answered?
• What does a node do when the short form fails and the full object is required?
• Which names are normative: MUST, WTXID?

Terms

BIP 339

The public text titled WTXID-based transaction relay.

Deployed

The document's own label for how finished the text is. It is not a market fact.

The problem the paper names

A node that cannot fetch, filter, or relay the data it is supposed to validate is not a peer of the network the paper describes.

What the design proposes

• Two changes to the p2p protocol to support transaction relay based on the BIP 141 wtxid of a transaction, rather than its txid.
• Historically, the inv messages sent on the Bitcoin peer-to-peer network to announce transactions refer to transactions by their txid, which is a hash of the transaction that does not include the witness (see BIP 141).
• This has been the case even since Segregated Witness (BIP 141/143/144) has been adopted by the network.

How the mechanism is specified

• Taken from the specification, the next constraint is: Historically, the inv messages sent on the Bitcoin peer-to-peer network to announce transactions refer to transactions by their txid, which is a hash of the transaction that does not include the witness (see BIP 141).
• Locate MUST, WTXID in BIP 339 and apply it to one transaction or call.
• Then check the failure the class of rule always has: a node that did not upgrade, a reverted call, a replayed signature, or a peer that does not speak the message.

What this page does not treat as proven

• A peer protocol is not a consensus rule. A peer can disconnect. A block is still valid or not on its own.
• Measurements of delay in one year do not travel with the specification.
• The source marks this deployed. That is a statement about the text, not a promise that every wallet or node has shipped it.

Why a venture studio still reads it

Use BIP 339 when a pitch says 'WTXID-based transaction relay' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.