diff --git a/playbooks/deploy-fish-cpp.yaml b/playbooks/deploy-fish-cpp.yaml
index 72832fb..8c50aaf 100644
--- a/playbooks/deploy-fish-cpp.yaml
+++ b/playbooks/deploy-fish-cpp.yaml
@@ -115,14 +115,20 @@ verify:
     changed_when: "false"
 
   - name: /v1/tts returns a real WAV (POST with text body)
+    # `set -e` so curl/file/grep failures actually propagate. The
+    # previous version put `rm -f` as the last command, which always
+    # exits 0 — masking real failures (verify reported OK even when
+    # nothing was running on host_port). Trap-based cleanup runs the
+    # rm even on failure.
     shell: |
+      set -e
       out=$(mktemp --suffix=.wav)
+      trap 'rm -f "$out"' EXIT
       curl -sf -X POST http://localhost:{{ host_port }}/v1/tts \
         -H 'Content-Type: application/json' \
         -d '{"text":"Verify."}' \
         -o "$out" --max-time 60
       file -b "$out" | grep -q '^RIFF.*WAVE'
-      rm -f "$out"
     changed_when: "false"
 
   - name: Container is running
diff --git a/stacks/fish-cpp/Dockerfile b/stacks/fish-cpp/Dockerfile
index 9bb88a1..f8d1007 100644
--- a/stacks/fish-cpp/Dockerfile
+++ b/stacks/fish-cpp/Dockerfile
@@ -26,7 +26,15 @@ RUN git clone --recurse-submodules https://github.com/rodrigomatta/s2.cpp.git \
     && git submodule update --init --recursive
 
 WORKDIR /src/s2.cpp
+# CUDA Driver API symbols (cuMemSetAccess, cuDeviceGet, etc.) live in
+# libcuda.so which the NVIDIA driver provides at RUNTIME via --gpus
+# mount. At build time there's no GPU, so we use the stubs library
+# at /usr/local/cuda/lib64/stubs/ which provides the symbols for
+# linking but is NOT runnable. The runtime image uses the real
+# driver-provided libcuda.so via NVIDIA's container runtime.
+ENV LIBRARY_PATH=/usr/local/cuda/lib64/stubs:${LIBRARY_PATH}
 RUN cmake -G Ninja -B build -DCMAKE_BUILD_TYPE=Release -DS2_CUDA=ON \
+      -DCMAKE_LIBRARY_PATH=/usr/local/cuda/lib64/stubs \
     && cmake --build build --parallel $(nproc) --target s2
 
 # ── Stage 2: runtime — slim image with the binary + python shim ────────