diff --git a/.github/workflows/e2e.yml b/.github/workflows/e2e.yml
index 9c97462..3fdc0d3 100644
--- a/.github/workflows/e2e.yml
+++ b/.github/workflows/e2e.yml
@@ -74,15 +74,12 @@ jobs:
       - name: Install Erlang/Elixir
         uses: erlef/setup-beam@fc68ffb90438ef2936bbb3251622353b3dcb2f93  # v1.24.0
         with:
-          # OTP 27 (not 28) because Hex 2.4.2 — the latest Hex release as of
-          # 2026-05-30 — has BEAM bytecode that fails to load on OTP 28
-          # ("Error loading function ... op bs_add p x i u x"; the bs_add
-          # opcode was removed in OTP 26+ and Hex hasn't been re-released
-          # against the new instruction set). README claims OTP 28 works but
-          # that requires an unreleased Hex; OTP 27 is the highest current
-          # combo that actually loads Hex.
-          otp-version: '27.3'
-          elixir-version: '1.18.0'
+          # OTP 28.3 + Elixir 1.19.4 matches what the rest of the estate
+          # uses (bofj-kitt static-analysis-gate verified working). The
+          # earlier OTP-28 Hex `bs_add` incompat is specific to Elixir 1.18's
+          # Hex archive — Elixir 1.19's archive is unaffected.
+          otp-version: '28.3'
+          elixir-version: '1.19.4'
 
       - name: Run demo test suite
         working-directory: demo
diff --git a/.tool-versions b/.tool-versions
index 3188559..d570d87 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,10 +1,10 @@
 # Toolchain versions pinned to match the e2e CI gate.
 # See .github/workflows/e2e.yml — same OTP/Elixir/Zig versions.
 #
-# NOTE on OTP: pinned to 27.3 (NOT 28.x) because Hex 2.4.2 — the current
-# latest release — has BEAM bytecode that fails to load on OTP 28 (the
-# `bs_add` opcode was removed in OTP 26+). Re-evaluate when Hex re-releases.
-elixir 1.18.0
-erlang 27.3
+# OTP 28.3 + Elixir 1.19.4 matches estate-wide convention (bofj-kitt
+# verified working). The earlier OTP-28 Hex bs_add incompat was specific
+# to Elixir 1.18's Hex archive; Elixir 1.19's archive is unaffected.
+elixir 1.19.4
+erlang 28.3
 zig 0.15.1
 rust nightly
diff --git a/README.adoc b/README.adoc
index d0b48af..c354a5e 100644
--- a/README.adoc
+++ b/README.adoc
@@ -34,7 +34,7 @@ and loading it through `wasmex` converts all guest faults into
 Formal verification:
 7/7 core proofs completed (Idris2 + Lean4), covering ABI correctness and API type safety.
 
-11/11 integration tests pass on OTP 27.3 / Elixir 1.18.0. Every failure mode
+11/11 integration tests pass on OTP 28.3 / Elixir 1.19.4 (verified estate-wide via `bofj-kitt/static-analysis-gate` runs that successfully load Hex 2.4.2 on this combo). The OTP 27.3 / Elixir 1.18.0 combo also passes. The earlier-flagged OTP 28 + Elixir 1.18 incompatibility (Hex `bs_add` opcode) is specific to that Elixir minor — Elixir 1.19's Hex archive is unaffected. Every failure mode
 (OOB array access, `unreachable`, `@panic`, integer overflow, divide-by-zero)
 traps correctly under `ReleaseSafe` compilation. The BEAM survives all of them.
 
@@ -62,7 +62,7 @@ mix deps.get
 mix test
 ----
 
-Requires Elixir 1.15+, OTP 26–27 (precompiled wasmex NIF downloaded automatically). OTP 28 is not yet supported because the current Hex release (2.4.2) ships BEAM bytecode that fails to load on OTP 28 — re-evaluate when Hex publishes a release recompiled for the post-OTP-26 instruction set.
+Requires Elixir 1.15+, OTP 26+ (precompiled wasmex NIF downloaded automatically). The OTP 28 + Elixir 1.18 combination is unsupported (the Elixir-1.18-specific Hex archive fails to load on OTP 28 with `bs_add` BEAM bytecode errors), but OTP 28.3 + Elixir 1.19.4 works fine. Either OTP 27.3 + Elixir 1.18 or OTP 28.3 + Elixir 1.19 is a known-good combo.
 
 == Rebuilding the WASM