Release Notes: v4.2.1 → v4.3.0-rc.1

Date: 2026-05-15
Range: v4.2.1..v4.3.0-rc.1 (2026-05-07 → 2026-05-15)
Commits: 225 non-merge commits

Full migration instructions for every breaking change below live in docs/docs-developers/docs/resources/migration_notes.md.

Summary

v4.3.0-rc.1 is the first release candidate of the v4.3 line, cut after the v4.2.x series stabilized on the Alpha network. The release rolls up roughly 225 commits backported to v4-next since v4.2.1 and is primarily focused on PXE / wallet-side improvements, kv-store on SQLite-wasm, and Aztec.nr / TXE ergonomics. Beyond the two breaking changes listed below, the release is dominated by bug fixes, refactors that improve sync performance, and tooling improvements.

Breaking Changes

• aztec init / aztec new counter template (#22751): aztec init / aztec new now scaffold a counter template instead of the previous default. Any tooling or docs that relied on the prior scaffold contents must be updated.

• Shared protocol-circuit utilities in the history module (refactor! cherry-pick 8f805bb8d3): The aztec-nr history module now consumes shared protocol-circuit utilities. Direct consumers of internal history-module helpers must adapt — see migration notes.

Highlights

PXE / Wallet

• New opt-in SQLite kv-store backend (#22658, #22759, #23089, #23231): A new SQLite-on-WASM-over-OPFS implementation of the PXE / wallet kv-store ships alongside the existing LMDB and IndexedDB backends, with a page-level-encrypted variant for stricter browser environments. The new backend is opt-in at wallet construction time; existing PXE stores continue to work unchanged on LMDB / IndexedDB. SQLite is expected to become the recommended default in v5, with IndexedDB deprecated thereafter.
• Cross-contract utility call hooks and auth (#23007, #23064, #22822): PXE gains execution hooks for authorizing cross-contract utility calls, and TXE supports authorizing them in Noir tests. Nested utility-function calls are now supported end-to-end.
• Sync performance (#23129, #23131, #23123, #23130, #23100, #23088, #23048, #22988, #22525): A series of refactors batches nullifier sync across scopes, batches log RPC calls, prefetches updated class-id hints per contract, short-circuits block-header lookups at the anchor block, and parallelizes per-scope contract syncs.
• Tag-as-sender optimization (#23239): Faster get_next_app_tag_as_sender lookups.
• wallet-sdk heartbeat (#22948): Wallet SDK now emits a heartbeat for liveness signalling.

Aztec.nr / TXE

• TXE oracle versioning (#23285, #23289): TXE gains oracle versioning for the test environment and basic gas settings, mirroring production behavior more closely.
• Initial handshake registry contract (#22854): New handshake registry contract with non-interactive handshake function for offchain message delivery.
• call_self utility stubs (#22885): Aztec.nr utility functions gain call_self stubs for cleaner self-invocation patterns.
• Serializability assertions (#22877): Aztec.nr now asserts that contract function return types and parameters are serializable, catching a common compile-time class of bugs.
• Offchain delivered private transfer (#22574): Example/infra for offchain-delivered private transfers.
• Oxide upstream merge (#22979): Oxide aztec-nr changes upstreamed.

CLI / aztec-up

• aztec dep version check (#21245): Asserts the aztec-nr dependency version matches the CLI version.
• Multi-crate scaffolding (#21007, #20681, #20723, #20729): aztec new and aztec init now create a 2-crate workspace, warn if the contract crate has tests, and auto-recompile when aztec test is run.
• Contract version stamping (#22550): Contract artifacts now stamp the aztec version they were compiled against.
• aztec profile gates --json (#22860): JSON output for aztec profile gates.

Docs

• Node JSON-RPC API reference auto-generated (commit de6e69f8fa): The node JSON-RPC API reference is now generated from the TypeScript source.
• Aztec.nr API reference discoverability (#22861): Aztec.nr API reference docs are more discoverable in the sidebar.
• Nethermind / FPC docs (#22541 and 2511d876d7): FPC docs applied to developer versioned docs; Nethermind FPC docs added.
• Alpha Network privacy/limitations page (#22515).

Notable Bug Fixes

• Dropped tagging indices no longer crash PXE on sync (#23044).
• sendMessagesAs cross-contract utility-call sync (#23225): PXE now syncs the target contract before a cross-contract utility call.
• Anchor-header threading (cherry-pick of #22679): Backport of anchor-header threading in PXE simulation paths.
• Origin/contract address mismatch detected (#22637): PXE throws on origin/contract address mismatch during simulation rather than silently producing wrong results.
• Race conditions in block-stream event handling (#22635): PXE now serializes block-stream event handling.
• Private event store rollback (#22615): Guarded against in-flight jobs during rollback.
• setSenderForTags scope correctness (#22672): Restricted to the current call (F-564).
• registerSender wipe race (#22623): Wipes are now queued to avoid racing in-flight jobs.
• aztec-up PATH leak (#22709): Bundled binaries no longer leak node_modules/.bin onto PATH.
• ABI argument-encoder validation (#22529): Missing ABI validation in argument encoder added.

Full list in CHANGELOG.md.

Upgrade notes

• The breaking changes above are documented under the ## 4.3.0-rc.1 section of docs/docs-developers/docs/resources/migration_notes.md.

All Changes

See CHANGELOG.md for the complete list of 162 categorized commits (BREAKING / Features / Bug Fixes / Documentation / Miscellaneous).