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WFN QUICK BRIEF · UNDER 1 MIN
The short version
MODE 2 OF 2
What the format changes
BIP 370 defines version 2 of the partially signed Bitcoin transaction format. Instead of relying on a fixed global unsigned transaction, it puts data for inputs and outputs into their respective maps and adds global fields for counts and transaction version. Modifiable flags describe whether collaborators may add inputs or outputs. BIP 370 · PSBT version 2 ↗
Follow a collaborative build
Suppose two participants plan to contribute inputs to a transaction. The coordinator can create an incomplete PSBT v2 and gather inputs and outputs in stages. Before signing, each party can reconstruct the proposed transaction and check which amounts are paid, where change goes and which sighash policy applies. A flag describing a permitted edit does not make every existing signature survive the edit.
Test the handoff
Use the same version across coordinator, signers and hardware wallets. Compare the decoded transaction at each handoff, verify locktime and sequences, and test unsupported PSBT versions explicitly. Inspect the final output addresses, fee and signature coverage before broadcast.
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01 · VERIFIED RECORD
What the format changes
BIP 370 defines version 2 of the partially signed Bitcoin transaction format. Instead of relying on a fixed global unsigned transaction, it puts data for inputs and outputs into their respective maps and adds global fields for counts and transaction version. Modifiable flags describe whether collaborators may add inputs or outputs. BIP 370 · PSBT version 2 ↗
02 · WFN EDITORIAL ANALYSIS
Follow a collaborative build
Suppose two participants plan to contribute inputs to a transaction. The coordinator can create an incomplete PSBT v2 and gather inputs and outputs in stages. Before signing, each party can reconstruct the proposed transaction and check which amounts are paid, where change goes and which sighash policy applies. A flag describing a permitted edit does not make every existing signature survive the edit.
03 · REVIEW POINTS
Test the handoff
Use the same version across coordinator, signers and hardware wallets. Compare the decoded transaction at each handoff, verify locktime and sequences, and test unsupported PSBT versions explicitly. Inspect the final output addresses, fee and signature coverage before broadcast.
Original WFN vector illustrationWFN · 9 November 2026
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Editorial noteSource-based explanation with original WFN analysis. Historical records retain their dates; numerical examples are illustrative. The original vector illustration is conceptual and is not documentary evidence.
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Primary-source explainer
Primary-source explainer
Primary record / reference periodBIP 370 · PSBT version 2
