Bitcoin Cash post-quantum draft has no Nov. 15 lock-in

Contributor mainnet_pat’s June 10, 2026 Bitcoin Cash proposal has no activation date. It covers post-quantum and hybrid signature verification, but not a Sunday, Nov. 15 lock-in. That date belongs to broader planning for the network’s 2027 protocol upgrade, according to the proposal and related forum discussion.

That distinction matters because two different changes share the CHIP-2026-06 identifier. One concerns signature verification. The other proposes a script opcode. Combining them under one label would give the quantum-signature work a deadline it does not have.

Inside the signature design

In a Bitcoin Cash forum post, mainnet_pat proposed using the first byte of a public key to select its signature scheme from a registry. The registry would retain secp256k1 and initially include SPHINCS+ and a hybrid option. Mainnet_pat favored beginning with SPHINCS+ and the hybrid option.

He described a composite key as one that binds two schemes under one signer with “AND semantics.” Every component signature would have to verify under that design. The proposal gives developers a selection and validation framework, rather than specifying an immediate network migration.

The proposal also avoids a mandatory change to Bitcoin Cash’s output format. It says the proposed keys could spend ordinary P2PKH outputs, so a new output type would not be required.

It describes a possible way to use the signatures with that format. It does not activate the change on the network or move existing holdings to new keys.

That narrow scope keeps the proposal outside current wallet requirements. The draft does not require any user to replace a key or move a balance. The signatures remain a proposed verification path, not rules that Bitcoin Cash nodes enforce today.

The separate opcode path

The separate OP_SIGHASH proposal would expose a transaction’s 32-byte signature hash to scripts. A Bitcoin Cash Node merge request opened Aug. 14, 2026, seeks to implement that opcode. The two proposals may affect different parts of the protocol, but their shared CHIP-2026-06 label makes their schedules easy to conflate.

Sunday, Nov. 15, 2026, is the stated lock-in date for the 2027 cycle. Upgrade planning lists OP_SIGHASH, Native Elliptic Curve Arithmetic Operations and Faster Blocks among proposals considered realistic to discuss. The post-quantum draft is not assigned a confirmed lock-in or activation date by that planning.

Under the current planning description, Nov. 15 marks a broader discussion milestone. It does not put the quantum-signature draft on the activation calendar. The opcode effort, by contrast, has an implementation request in Bitcoin Cash Node.

What does this change for Bitcoin Cash users?

For now, nothing operational. The draft is a specification proposal, not an activated consensus rule. Users face no requirement to create post-quantum keys, adopt a new output type or move existing holdings. The proposed ability to spend ordinary P2PKH outputs keeps the draft from presuming a separate holding format, but it does not make the signatures active.

For developers, the open work is agreement on the registry, supported schemes and composite-key validation. Algorithm choice remains unsettled. Forum participant moonsettler called SPHINCS+ “Way overkill for the migration period.” Lattice-based schemes continue to receive further review.

Operational teams should also keep the two CHIP-2026-06 proposals separate. One changes signature verification. The other proposes an opcode for script access to a signature hash. Their shared label is an identifier collision, not evidence of a combined rollout. Any tracking of the Nov. 15 milestone should distinguish the opcode’s implementation work from the post-quantum draft’s open specification.

The next hard checkpoint is Sunday, Nov. 15, 2026, when the broader 2027 upgrade cycle reaches its stated lock-in date. That deadline anchors broader upgrade planning, not the still-unscheduled post-quantum signature draft.