diff --git a/test/Dockerfile b/test/Dockerfile
index 0658adf..8970515 100644
--- a/test/Dockerfile
+++ b/test/Dockerfile
@@ -12,7 +12,7 @@ ENV PYTHONDONTWRITEBYTECODE=1 \
 WORKDIR /app
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
-      ca-certificates \
+      ca-certificates nodejs \
     && rm -rf /var/lib/apt/lists/*
 
 COPY shared/requirements.txt ./requirements.txt
diff --git a/test/Dockerfile.unit b/test/Dockerfile.unit
index a2f8dfe..5e8098e 100644
--- a/test/Dockerfile.unit
+++ b/test/Dockerfile.unit
@@ -8,6 +8,10 @@ ENV PYTHONDONTWRITEBYTECODE=1 \
 
 WORKDIR /app
 
+# Node.js for sexp.js parity tests
+RUN apt-get update && apt-get install -y --no-install-recommends nodejs && \
+    rm -rf /var/lib/apt/lists/*
+
 # Install shared deps (includes pytest, pytest-asyncio)
 COPY shared/requirements.txt ./requirements-shared.txt
 RUN pip install --no-cache-dir -r requirements-shared.txt pytest-watch