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tr() Output Script Descriptors

BIP 386. Pieter Wuille.

BIP 386, tr() Output Script Descriptors. This document specifies tr() output script descriptors.

Status in the source: Deployed. A reading of the public specification, not a copy of it and not a certification.

tr() Output Script Descriptors is worth reading for the rule it actually adds: This document specifies tr() output script descriptors.

The five-minute read

The rule

This document specifies tr() output script descriptors.

What was already failing

A signature that does not commit to what the user saw can be replayed into a different spend, a different chain, or a different message.

What the number does not mean

The source marks this deployed. That is a statement about the text, not a promise that every wallet or node has shipped it.

What a builder should be able to point at

An implementation either constrains P2TR or it is a different design.

One action, walked through

  1. Open BIP 386 and read the status line before the examples.
  2. Write down the rule in one sentence. A fair version of that sentence is: This document specifies tr() output script descriptors.
  3. Name the object that changes: P2TR.
  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 the text is allowed to settle

Bitcoin Improvement Proposal 386 can settle the shape of tr() Output Script Descriptors. It cannot settle whether a later client, a later fork, or a later wallet still does this.

What this page will not pretend

There is no benchmark, no adoption number, and no claim that the mechanism is safe outside the assumptions written in the source.

What has to be true

  • You are implementing BIP 386 at the status the text itself states: Deployed.
  • The object that has to change is P2TR. A neighbouring document with a similar name is not this one.
  • Wallet support is not the same as consensus validity.

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

  • What is covered by the signed bytes in tr() Output Script Descriptors?
  • Can the same signature be replayed on another chain, account, or message?
  • Which primitive does the text require: P2TR?

Terms

BIP 386
The public text titled tr() Output Script Descriptors.
Deployed
The document's own label for how finished the text is. It is not a market fact.

The problem the paper names

A signature that does not commit to what the user saw can be replayed into a different spend, a different chain, or a different message.

What the design proposes

  • This document specifies tr() output script descriptors.
  • tr() descriptors take a key and optionally a tree of scripts and produces a P2TR output script.
  • Taproot added one additional standard output script format: P2TR.

How the mechanism is specified

  • Taken from the specification, the next constraint is: tr() descriptors take a key and optionally a tree of scripts and produces a P2TR output script.
  • Locate P2TR in BIP 386 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 signature scheme is not a privacy system. It hides the signer only if the protocol says so.
  • Wallet support is not the same as consensus validity.
  • 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 386 when a pitch says 'tr() Output Script Descriptors' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.

This is Blockchain Lab's reading of a public design paper. It is not the paper, not a copy of it, and not an offer of tokens, equity, custody or a partnership. Later network behaviour can diverge from the text. Nothing here is investment, legal or technical advice.

Research status: Design paper. Last reviewed: 1 October 2026. This is a reading of a public paper, not investment, legal or security advice.