A BIP draft proposes one shared policy format for Bitcoin co-signers that emulate covenants
Victoria Shinder1 min readA draft Bitcoin Improvement Proposal titled "Co-signer Spending Policies" was posted for feedback on the Delving Bitcoin forum on 10 October 2026 by Luke Carriere. It aims to standardise the policy a co-signer enforces, rather than the co-signer itself.
The background. A co-signer that only signs when some condition holds is an existing way to emulate covenants on Bitcoin today; the post cites Towns's 2021 description of the multisig version. Since then, the author notes, several designs — blinded co-signers, Chain Code Delegation, predicate blind signatures, bonded co-signers — and products such as Liquidium and Lendasat have each defined their own policy format. The result: a wallet built for one co-signer or oracle cannot work with another.
What the draft covers. One policy format with three verification modes — open, blinded and enclave — and conditions drawn either from the transaction itself or from external attestations. Co-signers must accept DLC oracle attestations, so existing oracles can serve as evidence sources without changes. Two rules are built in: anything that Script can enforce must be enforced in Script, and every policy must keep a spending path that needs no co-signer.
What is being asked. The author is not requesting a BIP number yet and wants to know whether this is the right layer to standardise. Open questions listed in the post: canonical JSON or TLV encoding; whether blinded verification can be specified now; whether the attestation format belongs here or in the DLC specifications; whether the output expression language is sized right; and whether the fallback path must be timelocked.
The draft is published in a separate GitHub repository linked from the post.
Source: Delving Bitcoin, "[BIP Draft] Co-signer Spending Policies" — https://delvingbitcoin.org/t/bip-draft-co-signer-spending-policies/2955