Bitcoin BLAKE2b froze miners' rewards for 45 days. What it means in practice

On 21 September 2026, a change was merged into the Bitcoin Knots repository that prohibited miners on the Bitcoin BLAKE2b (BTCB2) chain from spending mined coins for roughly a month and a half. We examine exactly what happened, what the word coinbase has to do with it, where to follow developments and why it is practically impossible to calculate BTCB2 mining profitability today. What BTCB2 is and how it is mined is described in a separate article, BTCB2 (Bitcoin BLAKE2b).

What changed

The rule came via pull request #419 in the Bitcoin Knots repository, titled Long coinbase maturity. Luke Dashjr opened it on 15 September, and it was finally merged on 21 September 2026.

The essence: the maturity of coinbase transactions was raised from the standard 100 confirmations to 6,480. At a ten-minute block interval, that corresponds to approximately 45 days.

The rule applies to blocks 973,440 to 979,920, so it is declared as temporary. It is a consensus check, not a wallet setting: an attempt to spend a coinbase at a depth of 6,479 blocks is rejected by the node with the error bad-txns-premature-spend-of-coinbase, while at a depth of 6,480 it goes through.

Headlines like “the network is delaying transactions” are misleading. Ordinary transfers between wallets work as before. Only block rewards are frozen – that is, precisely the coins miners receive.

What coinbase has to do with it

The term has nothing to do with the US exchange of the same name. The exchange's name came later – and was taken from this very technical term.

A coinbase transaction is the first transaction in every block – the one through which new coins are created.

Every ordinary transaction takes coins from someone's address and moves them to another: it has an input and an output. But where do coins come from at the start, if every spend requires a previous one? There has to be a point where they are created out of nothing.

That point is the coinbase. When a miner finds a block, they themselves write the first transaction into it – the only one in the whole network that has no input. It spends nothing; it mints: it creates the block reward and sends it to the miner's address. The network rules allow exactly one such transaction per block and strictly limit its amount.

Hence the link with mining: the coinbase is the actual payout for the block found. When a pool writes that the miner's address goes into the block's coinbase, it literally means the reward is written inside the block itself and exists from the moment the block is created.

Why the coinbase is kept immature at all

The 100-confirmation restriction has existed in Bitcoin from the very beginning and was not created to punish anyone.

The reason is chain reorganisations. A newly found block can be cancelled: if another miner publishes a competing block at the same height and a longer chain grows on it, your block becomes an orphan. Its reward then ceases to exist. How blocks and the chain work is explained in our article Blockchain.

Imagine the miner managed to spend this reward straight away. After the reorganisation, it disappears, along with the whole tree of transactions that stemmed from it: the payment to an exchange, the withdrawal from it, the purchase from a third party. A chain of innocent people loses money because of a reorganisation they had nothing to do with.

That is why coins from a coinbase must not be used until enough blocks have been built on top of them that cancellation is practically impossible. One hundred confirmations is roughly 16 hours, which covers any realistic reorganisation with a large margin.

How the new rule differs

The mechanism is the same, only the number is different: instead of 100 confirmations it is 6,480 – instead of sixteen hours, forty-five days.

And that is the key to understanding the dispute around this change. 6,480 confirmations are not needed against reorganisations – one hundred fully cover that task. An existing protective mechanism has been stretched roughly sixty-five-fold and now does something other than what it was intended for.

Formally, it is defensible: the rule already existed; it has merely been tightened. In practice, though, an old tool has found a new use that has nothing to do with chain security.

The official reason

According to Dashjr, it is the first step of a three-phase plan aimed at curbing the concentration of hashpower in large pools. The release notes also include a reproach towards some operators: they perform computations “blindly”, without validating legitimate transactions.

The logic is that if a reward cannot be cashed in immediately, it is less worthwhile for a large pool to rent hashpower for quick revenue.

An alternative interpretation: it's about the price

The official explanation sounds convincing until you look at the state of the market. We have a different hypothesis and consider it at least as likely.

As of the date of this article, the coin was trading between 270 and 315 dollars on a handful of platforms. Neither CoinGecko nor CoinMarketCap listed it – neither under the ticker BTCB2 nor under XBT. Liquidity is negligible. In such a situation, every miner who sells rewards immediately after receiving them pushes the price down far more strongly than in a normal market – almost nobody is buying on the other side.

Freezing rewards for 45 days removes the entire flow of freshly mined coins from the market. The price stops falling, the chart looks more stable, the project livelier. That is exactly the effect of the measure, regardless of the declared goal.

We stress: there is no direct confirmation of this version in the documentation or in the developers' statements. It is an interpretation based on the outcome, not on intent.

Why profitability can't be calculated now

The usual payback calculation rests on a simple model: so much hashrate gives so many coins a day, the coins are worth so much, minus electricity – and you have the payback period. With BTCB2, three links in this chain are breaking at once.

First: the freeze horizon is not known. The figure of 6,480 is labelled as provisional. The fork's code notes that it has already changed between release candidates, and the discussion also includes a variant of a whole year. So while your coins are maturing, the rule may get stricter. Moreover, Dashjr himself called this the first of three steps, and what the second and third will be has not been published.

Second: it is not clear at what price to calculate. If the coin cannot be sold for a month and a half, there is no point in calculating revenue at today's rate. You will be selling at the price in 45 days, and in such a thin market anything can happen in that time – in either direction.

Third: liquidity at the moment of unfreezing is not known. When all miners' rewards for a month and a half unlock at once, a pent-up supply overhang will appear on exchanges. A scenario is possible in which the coins are formally unfrozen but the volume can't be sold at the expected price.

The practical conclusion: a BTCB2 payback calculation today is not a calculation but a bet. It only makes sense in scenario form: what if unfreezing comes in 45 days and the price holds; what if the period is extended to a year; what if the price halves before you can sell. If the economics only work in the first scenario, the risk is too high.

What BTCB2 is mined on

The chain uses BLAKE2b – the same algorithm for which ASIC miners were made for Siacoin. Goldshell's and iBeLink's Sia-family machines are therefore suitable. SHA-256 miners (Antminer S19, S21, Whatsminer) will connect to the pool, but all shares will be rejected – the algorithm doesn't match.

All the models listed are air-cooled. With a 45-day freeze, the daily income that calculators show for these machines should be taken as coins credited, not as income.

If you look at the hardware soberly, two approaches make sense. Either take the most efficient by J/TH – with a long freeze, you pay for electricity the whole time and only receive the revenue afterwards. Or start with the smallest model, such as the SC Lite, go through the whole cycle from share to sale on an exchange with minimal risk, and only then decide on scale.

Where to follow developments

Knots Fork Observer – a passive observer that compares blocks according to the old and new maturity rules. It states that enforcement of long maturity began with block 973,440 and that block 973,540 became the first point where the activation coinbase could have been spent under the old rules. The service points out that it only observes and does not validate proof-of-work, scripts or Merkle trees.

mempool.guide – the main chain explorer. The block hash links in B2Pool's found-blocks table lead to it. This is where you track the current height, from which you can calculate how much remains until block 979,920.

Pull request #419 in the Bitcoin Knots repository – the primary source with the check code and the developers' discussion.

B2Pool blocks page – the pool shows the height, reward, effort and number of confirmations for each block found, and explicitly states that coinbase maturity is a chain rule, not pool policy.

awesome-bitcoin-blake on GitHub – a catalogue of nodes, wallets, pools and explorers. With such a young network, services come and go, so the list is worth bookmarking.

What a miner should do now

Watch block 979,920 – as it approaches, it will become clear whether the rule ends or is extended. Plan your finances as if the coins might stay frozen longer than declared. And don't confuse already matured coins with future payouts: what is in your wallet and can be spent is free; only what has not yet collected 6,480 confirmations is frozen.

A general rule for a network like this: check the current state yourself – with pools, in the explorer, in the repository – not from an article written on a particular day. Including this one.

This material was prepared on 24 September 2026. Hardware specifications and coin prices correspond to the date of publication. Nothing in this text is investment advice.

What next

• BTCB2 (Bitcoin BLAKE2b) – what this coin is and how it is mined.
• Miners for BTCB2 and Siacoin – an overview of machines for the Blake2b-Sia algorithm.