Monero is moving closer to another major privacy-development milestone, with the third beta stressnet for Full-Chain Membership Proofs, known as FCMP++, and the CARROT addressing protocol scheduled to go live on October 5, 2026. The announcement marks another stage in testing a proposed redesign of Monero’s transaction privacy system. Unlike the network’s current ring-signature model, FCMP++ is designed to prove that a transaction spends a valid output somewhere within the eligible output set across the blockchain without revealing which specific output is being spent.
Monero’s official documentation describes the system as a privacy upgrade intended to replace ring signatures with full-chain membership proofs.
FCMP++ Moves From Rings of 16 to the Full Chain
The central change proposed by FCMP++ is the size of the anonymity set. Monero’s current transaction design uses ring signatures in which the real input is hidden among a group of decoys. FCMP++ takes a fundamentally different approach by allowing each input to prove membership in the entire eligible set of outputs on the blockchain. Monero’s documentation explains that the proof does not reveal which particular output is the real one, while the project’s stressnet materials describe the potential anonymity set as encompassing more than 150 million historical outputs. This is considerably different from the current ring structure and is one of the reasons the upgrade requires extensive testing before any mainnet deployment.
The third beta stressnet is therefore more than a routine software test. Stressnets give developers and community participants an environment where the proposed system can be subjected to unusual transaction loads, implementation problems and adversarial testing without putting the production Monero network at risk. Monero Research Lab meetings throughout 2026 have specifically tracked FCMP++ development, including programming tasks, audits, integration work and the version-three stressnet launch checklist. The project’s GitHub milestone currently shows FCMP++ hard-fork work still in progress, underscoring that the technology has not yet become a completed mainnet feature.
CARROT is being developed alongside FCMP++ as part of the broader privacy architecture. Research documentation identifies CARROT as a CryptoNote-compatible addressing scheme that introduces additional forward-secrecy improvements, while the official Monero roadmap lists both FCMP++ and CARROT among the project’s active development efforts. This means the October stressnet is testing interconnected pieces of a wider redesign rather than simply increasing the number of decoys used in ordinary Monero transactions.
Testing Matters Before a Monero Network Upgrade
The development process also illustrates why the October 5 date should not be treated as a confirmed mainnet activation date. Monero’s own repository currently lists the FCMP++ hard-fork milestone as incomplete, with open work remaining around integration and related components. The project’s development model relies on testing, code review and staged deployment before consensus-changing software reaches the production network. Monero’s repository specifically describes its master branch as a staging environment and recommends using tagged releases for production stability.
The latest stressnet will give developers another opportunity to identify problems under realistic conditions. The quoted developer update says the code is ready for the targeted October 5 fork and that binaries are expected within a day, while proposed changes include a 10 MB initial penalty-free zone to avoid a warm-up period and allow earlier transaction volumes to resume. Those details concern the testing environment rather than a finalized change to Monero’s live network. They show the degree of operational experimentation taking place before FCMP++ can be considered ready for a production deployment.
Related: Monero Bulletproofs Explained: What the Latest Research Update Means for XMR
For XMR users, the significance of the development lies in what FCMP++ could eventually change about transaction privacy. The proposed system would move Monero from relatively small, fixed anonymity sets toward proofs covering the eligible output history of the chain. It could also provide a foundation for additional capabilities, including transaction chaining and optional outgoing view keys, according to Monero’s FCMP++ documentation. These are still development-stage capabilities, however, rather than features users should assume are already active on mainnet.
The October 5 stressnet therefore represents another test rather than the final destination. Monero developers have been working through FCMP++ integration, CARROT, audits and stress testing throughout 2026, and the project’s public development trackers show that work remains. If the third stressnet performs as expected, it would provide another data point toward a future network upgrade, but additional testing and review will determine when the technology is ready for production. For now, the confirmed milestone is the October 5 launch of the third FCMP++ and CARROT beta stressnet, giving developers and the wider Monero community another environment in which to test one of the project’s most significant proposed privacy changes.
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