Announcing Aleo Stack v4.4.0

Our team is happy to announce a new version of the Aleo Stack, which includes the node implementation snarkOS and the programming language Leo. These applications are built on top of the developer-friendly snarkVM and Aleo SDK libraries. Aleo is an open source cryptocurrency through which developers can deploy cryptographically secure dApps.

Most notably, this release unlocks using block timestamps in Aleo smart contracts. A number of stability improvements have made their way into the nodes. Costs can now be estimated using Authorizations instead of Executions, making it easier for wallets to determine fees. \

If you want to try it out, you can build from source today or download the mainnet release from Github November 25th. Find the current release schedule at: https://provablehq.github.io/.

Please report any issues you might come across!

What's new in snarkOS v4.4.0

Consensus change: ConsensusVersion V12

A consensus change will occur at the following times:

Canary - ~9AM PT November 14th, 2025
Testnet - ~9AM PT November 21st, 2025
Mainnet - ~9AM PT December 2nd, 2025

The exact block heights will be encoded in the snarkVM library at release.

ATTENTION: Validators that do not upgrade in time will be at risk of forking and require manual intervention. Clients that do not upgrade will be at risk of halting until an upgrade occurs.

New operand: block.timestamp

This PR added a new block.timestamp operand that can be used in finalize. This adds to the existing block.height operand for accessing block state, and allows for richer smart contract logic on the Aleo chain.

Improvements for node operators

Further improvements worth mentioning include:

Logging has been improved to allow for better debugging of potential consensus or operational issues.
Bootstrap validator peering has been stabilized, lowering the risk of DoS attacks
A new BLOCK_LAG histogram metric to track the validator's system time with the block timestamp of the latest processed block. This is tracked in milliseconds..
This PR introduces a --trusted_peers_only flag, while deprecating --allow_external_peers and --rotate_external_peers. The new flag can be used by a node to sync with just the peers passed explicitly via --validators and --peers.
Reduced erroneous reporting of stale transmissions

What’s new in Leo v3.4.0

Empty arrays and empty loop

Arrays of size 0 and loops over empty ranges are now supported in Leo. While these constructs do not produce any instructions in the compiled Aleo bytecode, they enable more generic or pattern-based programming styles in Leo, especially when writing code that abstracts over sizes, iterates conditionally, or uses compile-time parameters. For example:

Stability improvements

Improved identifier validation in Leo, resulting in clearer and more precise error messages, especially when Leo identifiers conflict with reserved Aleo identifiers.
Fixed an issue where local const values failed to compile correctly when used in loop ranges.
Resolved a crash in the common subexpression elimination optimization pass that occurred for certain patterns of function calls.

Library and tooling updates

snarkVM v4.4.0

snarkVM is a zkVM library. It powers the Aleo network and most of the software used to interact with it. The following contains some of the most relevant changes which were introduced:

Support was added to compute a fee based on an Authorization instead of an Execution: execution_cost_for_authorization
execution_cost_v* functions have been made private and are no longer accessible, use execution_cost instead
The tracing feature has been removed from snarkvm-ledger-store