diff --git a/debian/libva-v4l2-request-fourier/build-deb.sh b/debian/libva-v4l2-request-fourier/build-deb.sh
index 9d15f1d77..79ae918c9 100755
--- a/debian/libva-v4l2-request-fourier/build-deb.sh
+++ b/debian/libva-v4l2-request-fourier/build-deb.sh
@@ -16,7 +16,7 @@ set -euo pipefail
 # on 'p' (rpi-hevc-dec).
 UPSTREAM_COMMIT=c332d34643be29e88012e30878d2fbeb255b20ab
 PKGVER=1.0.0+r378+gc332d34
-PKGREL=1
+PKGREL=2  # rebuild against pinned trixie libva-dev (2.22) for __vaDriverInit_1_22 ABI
 
 HERE=$(dirname "$(readlink -f "$0")")
 
@@ -27,6 +27,47 @@ work=$(mktemp -d)
 trap "rm -rf $work" EXIT
 
 cd "$work"
+
+# ---------------------------------------------------------------------------
+# Pin libva ABI to Debian trixie's version (libva 2.22.0 -> VA-API 1.22).
+#
+# Without this, when the CI runner is Arch (libva 2.23.0 currently) the
+# driver compiles in __vaDriverInit_1_23 from Arch's <va/va.h> — but the
+# Debian trixie libva runtime on the install target looks up
+# __vaDriverInit_1_22 and the dlsym() returns NULL.  libva then reports
+# "has no function __vaDriverInit_1_0" (its fallback search name) and
+# vaInitialize() fails with -1.
+#
+# The driver itself doesn't link against libva.so — only the symbol NAME
+# matters, and the name is computed at compile time from VA_MAJOR /
+# VA_MINOR macros in <va/va.h>.  So all we have to do is point pkg-config
+# at trixie's libva-dev headers; the link step still resolves -lva
+# against the runner's libva (any version is fine — it's just for the
+# linker to be happy, the result has no NEEDED entry for libva).
+# ---------------------------------------------------------------------------
+LIBVA_TRIXIE_VER="2.22.0-3"
+TRIXIE_SYSROOT="$work/trixie-sysroot"
+mkdir -p "$TRIXIE_SYSROOT"
+for pkg in libva-dev libva2 libva-drm2; do
+    curl -sSLfo "$work/${pkg}.deb" \
+        "https://deb.debian.org/debian/pool/main/libv/libva/${pkg}_${LIBVA_TRIXIE_VER}_arm64.deb"
+    dpkg-deb -x "$work/${pkg}.deb" "$TRIXIE_SYSROOT"
+done
+
+# Rewrite the prefix in the .pc files so pkg-config returns -I/-L pointing
+# inside the sysroot (Debian's pkg-config files default to /usr).
+for pc in "$TRIXIE_SYSROOT"/usr/lib/aarch64-linux-gnu/pkgconfig/libva*.pc; do
+    sed -i "s|^prefix=/usr|prefix=$TRIXIE_SYSROOT/usr|" "$pc"
+done
+
+# Symlink libva.so -> libva.so.2 inside the sysroot so the linker can
+# resolve `-lva` against trixie's shipped runtime (no -dev symlink in
+# the libva2 .deb).  Same for libva-drm.
+ln -sf libva.so.2     "$TRIXIE_SYSROOT/usr/lib/aarch64-linux-gnu/libva.so"
+ln -sf libva-drm.so.2 "$TRIXIE_SYSROOT/usr/lib/aarch64-linux-gnu/libva-drm.so"
+
+export PKG_CONFIG_PATH="$TRIXIE_SYSROOT/usr/lib/aarch64-linux-gnu/pkgconfig:${PKG_CONFIG_PATH:-}"
+
 curl -sSLfo libva-fourier.tar.gz \
     "https://git.reauktion.de/marfrit/libva-v4l2-request-fourier/archive/${UPSTREAM_COMMIT}.tar.gz"
 tar xzf libva-fourier.tar.gz
@@ -40,6 +81,17 @@ meson setup build \
     -Db_lto=false
 meson compile -C build
 
+# Sanity check: the produced .so MUST export __vaDriverInit_1_22 (not 1_23).
+# Fail loud if it doesn't — otherwise the .deb installs but refuses to load
+# on trixie and the bug is invisible until someone runs vainfo.
+SO=$(find build -name 'v4l2_request_drv_video.so' | head -1)
+if ! nm -D --defined-only "$SO" | grep -q '__vaDriverInit_1_22'; then
+    echo "FATAL: built driver does not export __vaDriverInit_1_22"
+    nm -D --defined-only "$SO" | grep -i vadriverinit || true
+    exit 1
+fi
+echo "ABI check: $SO exports __vaDriverInit_1_22 (matches trixie libva 2.22)"
+
 ROOT="$work/pkgroot"
 DESTDIR="$ROOT" meson install -C build
 
diff --git a/debian/libva-v4l2-request-fourier/debian/changelog b/debian/libva-v4l2-request-fourier/debian/changelog
index a22e9236b..81201b0f9 100644
--- a/debian/libva-v4l2-request-fourier/debian/changelog
+++ b/debian/libva-v4l2-request-fourier/debian/changelog
@@ -1,3 +1,21 @@
+libva-v4l2-request-fourier (1.0.0+r378+gc332d34-2) bookworm trixie; urgency=medium
+
+  * Rebuild against pinned Debian trixie libva-dev (2.22.0-3) so the
+    driver exports __vaDriverInit_1_22 — the symbol trixie's libva
+    runtime looks up.  Previous -1 build used the CI runner's Arch
+    libva (2.23.0) and exported __vaDriverInit_1_23, which trixie's
+    loader cannot bind: vaInitialize() returns -1 ("has no function
+    __vaDriverInit_1_0") and ffmpeg -hwaccel vaapi fails on startup.
+  * No source change; pure build-env fix.  build-deb.sh now downloads
+    libva-dev / libva2 / libva-drm2 from Debian's archive, extracts
+    to a sysroot, and uses PKG_CONFIG_PATH to make pkg-config return
+    trixie headers regardless of what's installed on the runner.
+  * Hard sanity check: build fails if the resulting .so doesn't
+    export __vaDriverInit_1_22 (preempts the silent install-then-
+    refuse-to-load failure mode).
+
+ -- Markus Fritsche <mfritsche@reauktion.de>  Wed, 20 May 2026 18:00:00 +0000
+
 libva-v4l2-request-fourier (1.0.0+r378+gc332d34-1) bookworm trixie; urgency=medium
 
   * Bump to c332d34 — LIBVA-1 per-codec dispatch close.  Pi 5 mixed