Bitcoin has reached block 961,632, triggering the long-awaited mandatory signaling period for BIP-110, a controversial proposal designed to temporarily curb non-financial data from being embedded on the network.

The proposal entered the signaling phase at around 19:35 UTC on Saturday, with support from miners seldom exceeding 2.5%, a long way short of the 55% mark required.

Prominent Bitcoin voices such as Strategy chairman Michael Saylor and Blockstream CEO Adam Back have also voiced their opposition to the proposal.

Its supporters, however, are pushing BIP-110 as a user-activated soft fork (UASF), meaning it would rely on node operators, not miners, to force the rule change. Users would update their node software to reject any block from miners that fails to signal support for BIP-110, effectively attempting to coerce miners into line or cut them off entirely.

BIP-110’s proponents maintain there is an historic precedent for this outlook in the 2017 activation of SegWit via BIP-148, which enabled the separation of digital signatures from transaction data and was accepted by users not having the required support from miners.

For the time being, the immediate effect of users adopting BIP-110 will be that they reject the network that almost the entire mining sector is building. This could lead to a period in which there are two competing Bitcoin networks: the dominant mainnet, backed by the vast majority of hash power and institutional capital, and a minority chain populated exclusively by BIP-110 enforcing nodes.

The breakaway chain could then, in theory, grow in prominence as more node operators come onboard thereby forcing the mining sector’s hand or it could simply grind to a halt due to lack of support.

The signaling window is set to last until Bitcoin reaches 965,664, expected in about four weeks’ time.