The Stellar Development Foundation announced the Bell upgrade, also known as Protocol 30, on October 20. The upgrade is scheduled for a mainnet vote on November 23, 2026, following a testnet vote on November 3. It contains three proposed changes: muxed contract addresses, post-quantum signature verification in smart contracts, and millisecond ledger timing.
Muxed Contract Addresses for Smart Accounts
Many exchanges, ramps, and custodial products on Stellar already use muxed accounts, which attach an ID to a single account so each customer receives a unique deposit address while funds land in one account. Smart accounts, which are smart contracts rather than keypairs and can set their own spending rules, previously lacked an equivalent feature. Businesses holding customer balances therefore needed one contract per customer.
CAP-84 addresses this gap by allowing a contract address to carry a 64-bit ID, written in a new format that starts with W. Jake Urban, Senior Engineering Manager at the Stellar Development Foundation, described the W as “an upside-down M.” He said a distinct type lets developers always know which address they handle. Developers must update SDKs and add the W variant to type checks.
Post-Quantum Signature Verification
Stellar secures accounts with Ed25519, secp256k1, and secp256r1 elliptic-curve signatures. A large enough quantum computer could break these in theory. No such machine is publicly known, but public keys remain visible on the ledger, and migrations take years.
CAP-87 lets smart contracts verify ML-DSA signatures, a standard NIST finalized in 2024. Verification needs far more computation than Ed25519, so Stellar Core performs it directly instead of contract code. This keeps calls cheap and allows testing against official vectors.
Within the Bell upgrade, this is the first onchain piece of the Quantum Preparedness Plan. Custom account contracts can now require a quantum-safe signature to spend. Network transaction signatures remain Ed25519 for now. A native post-quantum signer for classic accounts is planned for a later protocol change.
Millisecond Ledger Timing and Schedule
Stellar currently records ledger close times in whole seconds, so the network cannot target intervals shorter than one second. In September, Protocol 28 reduced mainnet close times from about 5.7 seconds to 5 seconds.
CAP-88 moves the ledger to a millisecond clock, allowing future protocol changes to target finer close times. Stellar Core developers are already testing faster closes on experimental branches. The ledger header format also changes, so tools reading ledger data need updated XDR definitions.
SDK users should upgrade before the votes. The previous closeTime field still reports whole seconds. Stellar Core v30.0.0 became available on October 16. The testnet vote occurs on November 3 at 1700 UTC. The mainnet vote follows on November 23 at the same time.
