Monero Privacy Upgrade Progresses as FCMP++ Moves Closer to Production

• Monero released FCMP++ and CARROT alpha stressnet v1.5 to cut memory use and improve node sync performance.
• FCMP++ aims to expand the anonymity set per input from 16 to as high as 100,000,000 outputs across the chain.

Monero’s planned privacy upgrade is advancing as developers continue testing Full-Chain Membership Proofs (FCMP++) alongside the CARROT integration. Monero said development is progressing well, citing the release of a new alpha stressnet software version and ongoing preparation for a beta stressnet, as well as audits related to CARROT.

FCMP++ is designed to replace Monero’s current ring signature model with a new proof system that expands the anonymity set for each transaction input. Under the existing structure, a spend is proven within a limited set of outputs. FCMP++ aims to prove that a spent output is any output on the blockchain. 

Monero said this approach would move each input from an immediate anonymity set of 16 to as high as 100,000,000, addressing privacy risks tied to smaller anonymity pools.

The latest milestone includes the pre-release of FCMP++ and CARROT alpha stressnet v1.5, published under version v0.19.0.0-alpha.1.5. The release is intended to improve stability during testing, with developers stating it mitigates out-of-memory failures and introduces multiple performance upgrades. 

Changes focus on reducing the memory footprint of FCMP++ verification, improving multithreaded synchronization, and adjusting how nodes download blocks during sync based on real-time performance.

Monero’s Alpha Stressnet v1.5 Improves FCMP++ Verification and Sync Performance

In the release notes, v1.5 also contains changes to avoid chain downloading overload, fix sync state problems with transaction pools filled, and improve connection stability when networks are synchronized.

Developers also introduced optimizations that speed up verification by changing when certain data points are decompressed and by adjusting proof calculations.

Wallet-related updates were also included to support stressnet testing. These changes fix false positives when receiving CARROT transactions. They also improve input selection rules when building a transaction. In addition, the wallet now excludes zero-amount CARROT outputs from some transfer reports. Developers also addressed rare cases where key image tracking could trigger unexpected double-spend errors.

The stressnet itself was created as a public testing environment and hard forked from the existing Monero testnet on October 3, 2025, at block 2,847,330. It is intended to give developers and community testers a live network to evaluate the combined FCMP++ and CARROT integration before rollout steps are considered.

Developers of the privacy-focused network have warned that the stressnet is still alpha software and may contain bugs. They also noted that some features are not yet supported, including hardware wallets, multisig, watch-only wallets, transaction proofs, and a block explorer. 

The development team has encouraged testers to report issues in detail to help improve readiness ahead of the planned beta phase and audit work.

Monero price is at $565, dipping 11% in the past 24 hours, the highest drop among the top 100 coins, with a 24-hour trading volume of $286.2 million at the time of writing.