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Bitcoin’s two most recognizable cypherpunks are fighting. Adam Back and Peter Todd are publicly at odds over whether Bitcoin’s 21 million supply cap should ever change — and the argument is getting ugly.
Todd’s position is pretty clear: once all Bitcoin is mined, around 2140, miners won’t earn block subsidies anymore. They’ll rely entirely on transaction fees. And Todd thinks that’s a problem. Fee revenue is volatile. On slow days, it could drop sharply. On busy days, it spikes. That kind of unpredictability, he argues, could push miners toward a dangerous behavior — re-mining old high-fee blocks instead of extending the chain forward. If that happens, the blockchain’s integrity breaks down. So Todd wants a permanent block reward baked in, even after the last satoshi is mined. He points to Monero’s model, where a small perpetual reward keeps miners paid while the inflation rate drifts toward zero over time. His broader theory leans on lost coins: new issuance could simply replace coins that are permanently inaccessible, keeping the effective supply roughly stable. His views got fresh attention after the Bitcoin++ conference put his talk on the subject front and center.
Back isn’t buying it.
Back Calls It a Misleading Narrative
Adam Back’s objection isn’t just technical — it’s political. He thinks Todd’s framing is misleading, and he’s drawing direct parallels to BIP-110, a soft fork proposal in 2026 that aimed to filter non-payment data from blocks. BIP-110 had early support. Then it collapsed, with barely any miner backing. Back’s point: if a relatively modest soft fork couldn’t survive, a supply cap change faces basically zero chance. The resistance would be enormous. And the narrative around it, he thinks, is dangerous precisely because it sounds reasonable at first glance.
Commentator Trey Sellers has made a similar point — that any attempt to touch the supply schedule would probably die the same death as BIP-110. Michael Saylor has also weighed in, raising concerns about what bending consensus rules would do to Bitcoin’s protocol neutrality. Saylor’s worry isn’t just about inflation. It’s about what it means if Bitcoin’s foundational rules become negotiable.
Former Ripple CTO David Schwartz has also joined the broader conversation, though where exactly he stands isn’t entirely clear from what’s been said publicly. Bitcoin Knots developers have separately flagged what they’re calling ongoing network vulnerabilities — a claim that adds another layer of noise to an already messy debate. No details on specifics there.
Hard Fork Math Makes This Nearly Impossible
Here’s the thing about actually changing the supply cap: it can’t happen through a soft fork. A soft fork only needs miner cooperation. Altering the 21 million limit would require a hard fork — meaning every Bitcoin holder would need to agree. Not most. Not a supermajority. Every holder, effectively. That’s not a political challenge. It’s closer to a logistical impossibility given how fragmented and global Bitcoin’s ownership base is.
Soft forks are already hard. BIP-110 proved that. A hard fork to change the supply cap would be orders of magnitude harder, and probably orders of magnitude more divisive. The community knows it. That’s maybe why the debate, for all its noise, hasn’t produced any concrete proposal with real traction.
And there’s no deadline forcing anyone’s hand. The block subsidy doesn’t hit zero until around 2140. That’s well over a century away. So the urgency Todd feels is theoretical, and the resistance Back is mounting is preemptive. Both sides are essentially arguing about a problem that won’t become concrete for generations.
That doesn’t make the debate pointless. Miner incentives matter now, not just in 2140. The economics of Bitcoin mining are already shifting as halvings continue to cut the subsidy roughly every four years. Transaction fees have grown as a share of miner revenue, but they’re still volatile and unpredictable. Whether fees alone can sustain the network’s security long-term is a genuinely open question — one the industry hasn’t resolved, and probably won’t until it has to.
Todd’s camp thinks waiting is reckless. Back’s camp thinks changing the cap is even more reckless. Neither side is blinking.
What’s probably true is that the 21 million cap is, at this point, close to untouchable — not because it’s technically impossible to change, but because the social consensus around it is one of Bitcoin’s most durable features. Breaking that consensus would require a crisis far bigger than anything currently on the table.
No such crisis exists yet. The subsidy keeps halving. Miners keep mining. And Back and Todd keep arguing.
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Frequently Asked Questions
What does Peter Todd propose for Bitcoin after all coins are mined?
Todd wants a permanent block reward to keep paying miners after the final Bitcoin is mined around 2140, citing Monero’s model of a small perpetual reward where the inflation rate trends toward zero.
Why does Adam Back oppose changing Bitcoin’s supply cap?
Back calls Todd’s framing misleading and warns it would face massive resistance, drawing parallels to BIP-110, a 2026 soft fork that collapsed with minimal miner support despite early backing.
Why It Matters
The debate over Bitcoin's 21 million supply cap is significant as it addresses fundamental questions about the cryptocurrency's long-term sustainability and economic model. Disagreements among prominent developers like Adam Back and Peter Todd highlight the broader tensions within the Bitcoin community regarding the potential need for monetary policy adjustments in response to changing market dynamics. As the Bitcoin ecosystem evolves, the resolution of this debate could have profound implications for miner incentives, transaction fee structures, and ultimately, the stability and value of the Bitcoin network.
