release: v2.4.0

Version bump for photon-ring and photon-ring-derive to 2.4.0.
CHANGELOG [Unreleased] → [2.4.0] - 2026-03-19.
Updated version references in README and docs.

Highlights since v2.3.0:
- atomic-slots feature: formally sound seqlock via AtomicU64 stripes
- Multi-model audit: 17 findings fixed (MPMC ordering, derive soundness,
  Pipeline Drop/panic, backpressure livelock, safety comment accuracy)
- PREFETCHW on x86 publisher, WFE in recv() on ARM, dead rdtsc removed
- 3 research documents from constraint-anchored analysis
- MSRV CI job, derive auto-publish, test timeouts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: userFRM

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
+## [2.4.0] - 2026-03-19
 
 ### Performance
 - **PREFETCHW on x86 publisher write path:** Replaces `PREFETCHT0` (Shared

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "photon-ring"
-version = "2.3.0"
+version = "2.4.0"
 edition = "2021"
 rust-version = "1.94"
 description = "Ultra-low-latency SPMC/MPMC pub/sub using stamped ring buffers. Formally sound with atomic-slots feature. no_std compatible."
@@ -22,7 +22,7 @@ atomic-slots = []
 hashbrown = "0.16.1"
 spin = "0.10.0"
 libc = { version = "0.2.183", default-features = false, optional = true }
-photon-ring-derive = { version = "2.3.0", path = "photon-ring-derive", optional = true }
+photon-ring-derive = { version = "2.4.0", path = "photon-ring-derive", optional = true }
 
 [target.'cfg(any(target_os = "linux", target_os = "macos", target_os = "windows", target_os = "freebsd", target_os = "netbsd", target_os = "android"))'.dependencies]
 core_affinity2 = "0.15.4"

Cargo.toml

@@ -50,7 +50,7 @@ assert_eq!(s.try_recv(), Ok(100));
 
 ```toml
 [dependencies]
-photon-ring = "2.3.0"
+photon-ring = "2.4.0"
 ```
 
 Optional features:

README.md

@@ -167,5 +167,5 @@ one extra DMB barrier in the reader (~5-10ns).
 
 Users who need formal soundness can opt in via:
 ```toml
-photon-ring = { version = "2.3.0", features = ["atomic-slots"] }
+photon-ring = { version = "2.4.0", features = ["atomic-slots"] }
 ```

docs/discussion-seqlock-soundness-and-no_std.md

@@ -614,5 +614,5 @@ The impossibility proofs demonstrate that no other approach can achieve formal s
 ## Implementation Status
 
 Design 6 (ASCL / Atomic Stripe Compile-Time Layout) has been implemented as the
-`atomic-slots` feature in photon-ring v2.3.0. Benchmark results confirm the
+`atomic-slots` feature in photon-ring v2.4.0. Benchmark results confirm the
 zero-cost prediction on x86-64. See CHANGELOG.md for details.

docs/research-seqlock-alternatives.md

@@ -1,6 +1,6 @@
 [package]
 name = "photon-ring-derive"
-version = "2.3.0"
+version = "2.4.0"
 edition = "2021"
 description = "Derive macro for photon-ring's Pod trait"
 license = "Apache-2.0"