Parity Technologies published Polkadot SDK `polkadot-stable2609-rc1`. The release notes explicitly mark it as a pre-release for testing purposes and recommend waiting for the official release when a stable production build is required.
According to the notes, the transition from stable2606 to stable2609 includes 87 changes considered breaking under Rust SemVer because each raises the major version of at least one crate. That makes the RC particularly relevant to runtime, bridge and tooling teams that need to test compilation, API compatibility and integration behavior ahead of a stable release.
One specifically listed change is a Snowbridge fix that blocks an origin-spoofing attack vector in the V2 outbound queue converter. The release also attaches a complete `CHANGELOG.md` and machine-readable `changelog.json`, which makes dependency and compatibility analysis easier to automate.
For DOT, this is an SDK preparation signal rather than evidence that a new Polkadot mainnet runtime has already activated. A release candidate, a runtime-upgrade proposal and actual on-chain activation are separate stages and should be monitored separately.