diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 34bc9fea..4107f615 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -92,6 +92,14 @@ jobs:
       - name: Build
         shell: bash
         run: |
+          # Release binaries target x86-64-v3 (AVX2/FMA/BMI — Intel Haswell/2013+,
+          # AMD Zen+; lets LLVM autovectorise wider than baseline SSE2). Dev/CI
+          # builds stay on the baseline for compatibility and fast compiles.
+          # aarch64 is excluded: the flag is invalid there, and ARM64 already
+          # has NEON in its baseline.
+          if [[ "${{ matrix.target }}" == x86_64-* ]]; then
+            export RUSTFLAGS="-C target-cpu=x86-64-v3"
+          fi
           args=(--release --locked --target ${{ matrix.target }} -p app -p route-editor -p vehicle-editor)
           if [ "${{ matrix.dlss }}" = "true" ]; then
             # Linux: libvulkan-dev puts the headers under /usr/include. Windows
diff --git a/README.md b/README.md
index 61e5988a..6755d086 100644
--- a/README.md
+++ b/README.md
@@ -72,7 +72,7 @@ For a faster edit-compile-run loop, add `--features dev` to any of the four bina
 (`app`, `route-editor`, `vehicle-editor`, `signal-editor`). It links Bevy as a shared library, which cuts the
 relink after a code change. The first build with the flag recompiles Bevy, and the resulting
 binary needs the Bevy DLL next to it — so use it for development only, never for a release.
-Builds also use the toolchain's own `rust-lld` linker on Windows (see `.cargo/config.toml`), dependencies compile at `opt-level = 3` while the workspace itself stays at `1`, and `--release` adds thin LTO with a single codegen unit.
+Builds also use the toolchain's own `rust-lld` linker on Windows (see `.cargo/config.toml`), dependencies compile at `opt-level = 3` while the workspace itself stays at `1`, and `--release` adds thin LTO with a single codegen unit. Release binaries for `x86_64` additionally build with `-C target-cpu=x86-64-v3` (see `.github/workflows/release.yml`) — needs an Intel/AMD CPU from ~2013+ (Haswell/Zen+); for a local release-equivalent build set `RUSTFLAGS="-C target-cpu=x86-64-v3"` yourself.
 
 On Linux the four programs run natively on **Wayland**: winit picks Wayland whenever `WAYLAND_DISPLAY` or `WAYLAND_SOCKET` is set and falls back to X11 (or XWayland) otherwise.