Anza released stable Agave 4.0 for Solana validators

Anza released Agave v4.0.0 on May 16, 2026, marking the validator client as a stable build suitable for Solana Testnet, Devnet and Mainnet Beta. The GitHub release was attached to commit `2a165e7`, whose signature GitHub displayed as verified.

That designation mattered because Agave is core infrastructure, not an optional application layered above Solana. Validator and RPC operators use the software to ingest transactions, replay blocks, maintain ledger data and expose network information. A stable major version therefore created a concrete migration point for organizations running production infrastructure, even though publication of the binary did not mean every operator had upgraded or every associated network feature had activated.

A deliberately breaking release

Agave 4.0 removed transaction ingestion over UDP, leaving QUIC as the supported path. Public TPU address configuration and related RPC methods consequently referred to QUIC ports rather than UDP ports. The release also eliminated several deprecated validator arguments, including the switches that had enabled or disabled the older TPU transport modes.

Those changes reduced the number of transport configurations the client had to support, but they also imposed an operational compatibility boundary. Operators carrying forward old command lines or network assumptions could not treat the upgrade as a drop-in binary replacement. The changelog further warned that the former `blockstore-processor` verification method was no longer supported and directed users toward the unified scheduler.

The release removed fallback support for multiple legacy blockstore formats. These included the older performance-sample representation, earlier transaction-metadata key formats, and prior `SlotMeta` and `Index` formats. That cleanup simplified the active code path, but it limited what Agave 4.0 could read from sufficiently old local ledger data. The project’s own compatibility policy, rather than a claim of universal backward compatibility, remained the appropriate boundary.

RPC and restart behavior changed

For RPC providers, `getSignaturesForAddress` was changed to return error code `-32020` when a supplied `before` or `until` signature could not be found. Earlier behavior could return a successful response containing an empty array. Indexers and applications therefore needed to distinguish a missing pagination anchor from a valid page with no results.

Agave 4.0 also added a client identifier to each node returned by `getClusterNodes` and introduced optional scheduler bindings through a local inter-process socket. On the validator side, a graceful exit saved bank state, supporting restarts from local state when snapshot generation was disabled. Snapshot archive unpacking used direct I/O by default, with an opt-out for filesystems that did not support the required operation.

The changelog also documented tighter handling of Linux capabilities used for high-performance XDP networking. A validator would exit when required capabilities were absent and drop permissions that its active configuration did not need. The significance was operational: performance work was arriving with explicit privilege controls rather than an assumption that validator processes should retain broad system permissions.

What the release did not establish

Contemporaneous technical analysis described Agave 4.0 as preparation for wider XDP adoption, faster replay, expanded cryptographic support and future Alpenglow-related changes. Several of those network capabilities were feature-gated. The May 16 release made compatible code available; it did not prove that a feature was active on Mainnet Beta, that validators representing a particular share of stake had installed it, or that Solana’s consensus mechanism had changed that day.

That distinction is central to interpreting protocol releases. Shipping client code, recommending operator adoption and activating network behavior are separate events with separate risks.

Later rollout record

Anza’s subsequently updated rollout schedule records May 18, 2026 as the delivery date for recommending general Mainnet Beta adoption and May 29, 2026 for the beginning of v4.0 feature activations. Those later milestones clarify the staged rollout but do not change the narrower May 16 event: publication of the stable Agave 4.0 client.