diff --git a/RELEASES.md b/RELEASES.md
index eed762f2..bb95511b 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -10,7 +10,28 @@ Full auto-generated changelog: `CHANGELOG.md` · Releases: https://github.com/so
 
 ---
 
-## v8.0.0 — release candidate (`8.0.0-rc.8` published 2026-06-30 on npm tag `rc`)
+## v8.0.0 — release candidate (`8.0.0-rc.9` published 2026-07-01 on npm tag `rc`)
+
+> **rc.9 changes (2026-07-01):**
+> - **Whole-brain auto-upgrade is now a coordinated, observable LOCK — supersedes rc.8's no-freeze
+>   approach.** When a large brain's derived-index format changes (7.x→8.0), the native provider
+>   rebuilds the indexes from the canonical records **in place** while Brainy **blocks and queues**
+>   reads and writes — so no operation ever touches a half-built index. This is a clean *blocking
+>   upgrade to a known-good state* (vs rc.8's online background swap): unknown/halfway states are
+>   more dangerous than a bounded wait. Small brains still rebuild inline on open. New surface, all
+>   additive: a typed, exported, retryable **`MigrationInProgressError`** (catch it → HTTP 503 +
+>   `Retry-After`); `getIndexStatus()` gains **`migrating` + `migration`** progress (never gated —
+>   the readiness-probe signal); a **`migrationWaitTimeoutMs`** config (default 30 s — it bounds the
+>   *caller's wait*, NOT the rebuild, which is unbounded); `health()` / `checkHealth()` report the
+>   upgrade without blocking. No effect without a native provider.
+> - **Faster vector search (open-core).** The JS distance functions are rewritten from `reduce` to
+>   allocation-free loops — **~6× cosine, ~1.4× euclidean** (MEASURED, `tests/benchmarks/distance-microbench.mjs`,
+>   384-dim, median of 41). Numerically identical → recall unchanged.
+> - **Runtime floor + Bun.** Engines are now **Node ≥22 / Bun ≥1.1** (fixes a Node-24 `EBADENGINE`);
+>   compiler target ES2023 with DOM dropped from the type lib (8.0 is Node/Bun/Deno-only, no browser
+>   path). **Bun is recommended as a runtime** (`bun add` / `bun run`); the single-binary
+>   `bun build --compile` is not a supported target (native addon can't embed + a Bun 1.3.10 codegen
+>   regression). `.d.ts` stays TS-5.x-parseable.
 
 > **rc.8 additions (2026-06-30) — additive, no breaking change:**
 > - **No-freeze (online) whole-brain auto-upgrade.** When a derived-index format changes, a large