BIP174: Specify PSBT_IN_PREVIOUS_TXID serialization order #2001

1. 
   Shadouts commented at 7:04 pm on October 9, 2025: contributor

   This change updates descriptions for the PSBT_IN_PREVIOUS_TXID field to specify serialization order.

   It was not straightforward the order with which to store the txid in a psbt. It’s not clearly specified in the spec, and there are not many resources or parsers to aid in debugging PSBTv2. I found the BIP370 test vector “Case: PSBTv0 but with PSBT_IN_PREVIOUS_TXID.” seems to imply that the order of this txid value in PSBT_IN_PREVIOUS_TXID should match network serialization order.

   I’m torn on if “little endian” is the correct phrase to use here in conjunction with “txid”. I usually think of a “txid” as the big endian, human-presented order of a txn hash, but maybe it’s okay to use interchangeably.

2. specify PSBT_IN_PREVIOUS_TXID serialization order 8b74cf054e
3. murchandamus renamed this:
   Specify PSBT_IN_PREVIOUS_TXID serialization order
   BIP174: Specify PSBT_IN_PREVIOUS_TXID serialization order
   on Oct 9, 2025
4. murchandamus added the label Proposed BIP modification on Oct 9, 2025
5. murchandamus added the label Pending acceptance on Oct 9, 2025
6. 
   murchandamus commented at 9:54 pm on October 9, 2025: contributor

   cc: @achow101

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Shadouts murchandamus

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Proposed BIP modification Pending acceptance