Monero's Next Privacy Upgrade: FCMP++ Enters Another Round of Testing

 **On September 25 2026**, Monero developer j-berman released version 3.0 of the FCMP++ and Carrot beta stressnet, with a testnet hard fork planned for October 5 at block 3,102,800.[¹](https://monero.observer/fcmp%2B%2B-carrot-beta-stressnet-v3.0-released/) The developers are asking for as many testers as possible who can put the new code through real-world testing, find problems, and report them before a potential launch. Due to incompatibility with previous beta stressnet server versions, anyone who wishes to participate must start with a fresh sync or use an existing testnet database. ### What is FCMP++?  FCMP++ stands for Full-Chain Membership Proofs++. In plain English, it is a proposed replacement for Monero’s current ring signatures for hiding which output a transaction is spending. Right now, a Monero transaction uses a ring of 16 possible outputs. The real output is one of those 16, but an observer cannot tell which one. FCMP++ changes the idea completely: instead of proving “the output I spent is one of these 16,” the transaction proves that the output being spent belongs somewhere in the entire set of outputs on the Monero blockchain, without revealing which one. Monero’s own explanation describes this as moving from an immediate anonymity set of 16 to potentially the entire chain.[²](https://www.getmonero.org/pt-br/2024/04/27/fcmps.html) FCMP++ was developed as a version of Full-Chain Membership Proofs that doesn't require Monero to first migrate to the proposed Seraphis transaction/address system. The original proposal specifically aimed to make the privacy upgrade deployable without that migration. ### What FCMP++ actually changes for users of Montero Higher anonymous transactions aways for us all. We'd also be getting better protection against transaction tracing, because identifying the spent output becomes harder. No new actions will be required from the average user beyond updating their Monero software when the upgrade eventually reaches mainnet. Just one security patch update and you're done. This also means, because the privacy improvement happens underneath the wallet, users won't be required to amake any substantial changes, like to manually select larger rings or configure some new privacy setting. You can kiss that goodbye. All in all this making monero much safer and more secure to use while simultaneously making it easier to use. Montero is treating anonymity like bullets. Just can't get enough of it.  ### Transaction chaining Monero's output will now be allowed to be spent before the transaction that created it has even been confirmed. **Example**: If Alice sends Monero to Bob, Bob normally has to wait until that transaction is confirmed before spending the received output. FCMP++ changes that. Bob can construct and authorize a transaction spending that newly created output before Alice's transaction has been mined into a block. The child transaction can therefore be prepared before the parent transaction is confirmed. In short. Faster transactions. Monero's Research Lab specifically identifies this as "enabling payment-channel and atomic-swap designs that aren't practical under the current system."[³](https://beta.getmonero.org/resources/moneropedia/fcmp/) Even more so, Bob doesn't necessarily have to wait for Alice's transaction to confirm before creating the transaction that sends those funds onward. This is the kind of capability developers can build into things like payment channels and other Layer-2 protocols. A current Monero Research Lab project is already demonstrating FCMP++ integration with payment channels using chained transactions.[⁴](https://github.com/monero-project/research-lab/issues/129) ### Outgoing view keys You will now be able to let someone else see your outgoing transactions without giving them the ability to spend your money or have control over your wallet. This could be useful for things like accounting, auditing, or simply allowing someone to monitor where funds are going. Again, this is an optional feature to be used at your own discretion. ### Long-term privacy FCMP++ is designed to make it harder for anyone to work backward through old transactions and figure out which output was actually spent. The importance of this is so that information that looks harmless now cannot become much more useful later even if and when new data, better analysis, or additional transactions give an observer more pieces of the puzzle. ### What Is Carrot?  Carrot is the new transaction and address system being developed alongside FCMP++. It is designed to replace Monero's current transaction structure with a more flexible system that can take advantage of the new privacy features FCMP++ provides. For users, one of the important changes is more flexible ways to share wallet information without giving away control of the funds. Carrot also introduces changes to how addresses and keys work, giving wallets more options for things like selectively sharing transaction information. In other words, FCMP++ is the big change to how Monero hides the source of a transaction, while Carrot provides much of the new wallet and transaction structure around it. The two are being developed and tested together as part of the same larger upgrade. ### What is being tested? The current stressnet isn't only testing FCMP++ and Carrot. Version 3.0 also includes Hot-Cold wallet support, major improvements to transaction relay v2, RandomX v2 support, bug fixes from the previous stressnet, and the latest code from Monero's main development branch. All of this is being tested together before anything is considered for a mainnet launch. The developers want people actually using the network, creating transactions, running wallets and nodes, and reporting anything that goes wrong. This is still a testing network. The October 5 hard fork is a testnet milestone, not a mainnet launch date. There is currently no announced date for FCMP++ and Carrot to reach Monero's mainnet. ### Where things stand now As of the end of September, the FCMP++ hard-fork milestone is about 71% complete, with several remaining pieces still marked as in progress or pending review. The Monero development tracker currently shows FCMP++ consensus verification, FCMP++ proof verification, Carrot components, wallet work, and other supporting changes still being worked through. The September 30 Monero Research Lab meeting included FCMP++ programming tasks, code reviews, audits, the network upgrade schedule, and the beta stressnet launch checklist. A substantial amount of the work is already in the codebase, while the remaining pieces are being reviewed, tested, and audited before the upgrade can move forward. Conclusion Monero has spent years building privacy into the parts of a transaction that most people never see. FCMP++ has taken that work way much further. Users won't need to start learning a new cryptographic system or changing the way we use Monero. The underlying system has become harder to trace while opening the door to things that weren't practical before. We're still a ways from seeing this on mainnet, but the pieces are no longer theoretical. Developers are writing the code, testers are putting it through hell, and the remaining work is being reviewed and audited. If it makes it through all of that, Monero won't just have bigger anonymity sets, it will also have a different foundation underneath the money we already use. - @yayogerardo reporting, Writer, researcher, analyst, anarchist, autonomist, Humanoid 🃏™️  --- ### Find Me [Substack](https://yayogerardo.substack.com/) --- ### Services [Independent Research & Investigation Services](https://beblurt.com/@yayogerardo/independent-research-investigation-services-1789635522839) *** ### Support the work with The Worlds Most Private Currency — Monero(XMR). **XMR Adress:** > 86fXjLUF7W9SwGSjTtsbqq4t1LKzzypEZa1t77S5c68WF3yK9SmEfzPTtRyjUhDSk9Zn7p1ahFJT4PcKW8MN4h3QRpjx2Q5 LTC: > M8T9nY7orvpJHzJLj1UmoJTJ5j2gxNPAMc _{Posted via [HiveSuite](https://hivesuite.app/@muhshrooms/monero-s-next-privacy-upgrade-fcmp-enters-anoth-ffsz9nut)}