diff --git a/.gitignore b/.gitignore
index 14fc18f..7939616 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,6 +41,9 @@ docker-compose.override.yml
 # Notebook user data (tracked separately)
 notebooks/user/
 
+# LTspice install -- transferred to prod host via rsync, not tracked (~182MB)
+/ltspice/
+
 # Coverage
 htmlcov/
 .coverage
diff --git a/backend/Dockerfile b/backend/Dockerfile
index e5ecf8e..33fd7e4 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -1,11 +1,43 @@
 FROM ghcr.io/astral-sh/uv:python3.12-bookworm-slim AS base
 
-# System dependencies -- ngspice is required for simulation
-# NOTE: LTspice requires Wine + a Windows LTspice install, which is only
-# available on the dev host (not in this container). The backend gracefully
-# degrades -- LTspice engine returns UnsupportedEngineError in Docker.
+# System dependencies:
+#   ngspice  -- native SPICE engine
+#   wine     -- runs LTspice (a Windows x86-64 binary) in batch mode
+#   xvfb     -- headless X display; LTspice opens an X connection even with -b
+# The LTspice binaries themselves are NOT in the image -- they are mounted from
+# the host at /opt/ltspice-src (see docker-compose.prod.yml). Without that mount
+# the LTspice engine degrades gracefully and ngspice still works.
+# Debian's Wine (8.0) is too old for LTspice v26 -- it opens a GUI event loop
+# instead of running -b headless. Use WineHQ 11.10 to match the dev host, where
+# LTspice runs fine. i386 multiarch is required (Wine pulls 32-bit components
+# even for the x86-64 LTspice.exe). All four packages are pinned to the same
+# version because the WineHQ repo sometimes carries mismatched amd64/i386
+# versions, and the wine-devel metapackage demands an exact-version match.
+RUN dpkg --add-architecture i386 && \
+    apt-get update && \
+    apt-get install -y --no-install-recommends \
+        ngspice xvfb xauth wget gnupg ca-certificates && \
+    mkdir -pm755 /etc/apt/keyrings && \
+    wget -qO- https://dl.winehq.org/wine-builds/winehq.key | gpg --dearmor -o /etc/apt/keyrings/winehq-archive.key && \
+    wget -qNP /etc/apt/sources.list.d/ https://dl.winehq.org/wine-builds/debian/dists/bookworm/winehq-bookworm.sources && \
+    apt-get update && \
+    apt-get install -y --install-recommends \
+        winehq-devel=11.10~bookworm-1 wine-devel=11.10~bookworm-1 \
+        wine-devel-amd64=11.10~bookworm-1 wine-devel-i386=11.10~bookworm-1 && \
+    rm -rf /var/lib/apt/lists/*
+
+# WineHQ installs to /opt/wine-devel/bin; put it on PATH so `wine` resolves
+# (mcltspice's runner invokes the bare `wine` command).
+ENV PATH="/opt/wine-devel/bin:${PATH}"
+
+# LTspice v26 blocks on graphics init unless libGL/libEGL are loadable. The
+# slim image ships neither, so add Mesa software rendering (llvmpipe) -- Xvfb
+# has no GPU, so this is the fallback the dev host reaches via DRI3 anyway.
+# Separate layer to keep the heavy WineHQ layer cached.
 RUN apt-get update && \
-    apt-get install -y --no-install-recommends ngspice && \
+    apt-get install -y --no-install-recommends \
+        libgl1 libglx-mesa0 libgl1-mesa-dri libegl1 libegl-mesa0 \
+        libvulkan1 mesa-vulkan-drivers && \
     rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
@@ -21,7 +53,7 @@ FROM base AS dev
 # Install in editable mode (source mounted via docker-compose volume)
 RUN --mount=type=cache,target=/root/.cache/uv \
     --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
-    uv pip install --system -e ".[dev]"
+    uv pip install --system -e ".[dev,ltspice]"
 
 # Copy source for initial build (overridden by volume mount in dev)
 COPY src/ ./src/
@@ -40,20 +72,50 @@ ENV UV_COMPILE_BYTECODE=1
 # Install dependencies first (no source yet -- better caching)
 RUN --mount=type=cache,target=/root/.cache/uv \
     --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
-    uv pip install --system .
+    uv pip install --system ".[ltspice]"
 
 COPY src/ ./src/
 
 # Re-install with source to get the package registered
 RUN --mount=type=cache,target=/root/.cache/uv \
-    uv pip install --system .
+    uv pip install --system ".[ltspice]"
 
-# Run as non-root
+COPY docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
+RUN chmod +x /usr/local/bin/docker-entrypoint.sh
+
+# Run as non-root. /opt/ltspice is the writable LTSPICE_DIR (holds the Wine
+# prefix); /opt/ltspice-src is the read-only mountpoint for the host binaries.
 RUN useradd --create-home --shell /bin/bash spicebook && \
-    mkdir -p /app/notebooks/user /app/notebooks/examples && \
-    chown -R spicebook:spicebook /app/notebooks
+    mkdir -p /app/notebooks/user /app/notebooks/examples /opt/ltspice /opt/ltspice-src && \
+    chown -R spicebook:spicebook /app/notebooks /opt/ltspice
 USER spicebook
 
+# Build a fresh Wine prefix with this image's own Wine version (avoids the
+# version-mismatch hazard of shipping a prefix built by a different Wine).
+# LTspice batch mode needs no Mono/Gecko, so disable them to skip the download.
+ENV WINEARCH=win64 \
+    WINEPREFIX=/opt/ltspice/.wine \
+    WINEDEBUG=-all \
+    WINEDLLOVERRIDES="mscoree=;mshtml="
+# Keep one Xvfb up for the whole init -- xvfb-run tears the display down the
+# moment wineboot returns, leaving wineserver's lingering processes to spin on
+# a dead X server (fatal XIO errors, hung build). Explicit display + timeouts
+# make the step deterministic and unable to hang.
+RUN Xvfb :99 -screen 0 1024x768x16 -nolisten tcp >/tmp/xvfb-build.log 2>&1 & \
+    sleep 2 && \
+    DISPLAY=:99 timeout 90 wineboot --init && \
+    DISPLAY=:99 timeout 30 wineserver -w; \
+    wineserver -k 2>/dev/null; pkill Xvfb 2>/dev/null; \
+    rm -f /tmp/.X99-lock /tmp/.X11-unix/X99; true
+
+# Seed LTspice's settings file so batch (-b) runs skip the one-time first-run
+# consent dialog (which otherwise blocks even in batch mode and the sim hangs).
+# Captured from a broken-in install; LastRunVersion/CaptureAnalytics are the
+# lines that matter. Without this the LTspice engine times out on every run.
+COPY --chown=spicebook:spicebook ltspice-config/LTspice.ini \
+    /opt/ltspice/.wine/drive_c/users/spicebook/AppData/Roaming/LTspice.ini
+
 EXPOSE 8000
 
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
 CMD ["python", "-m", "uvicorn", "spicebook.main:app", "--host", "0.0.0.0", "--port", "8000"]
diff --git a/backend/docker-entrypoint.sh b/backend/docker-entrypoint.sh
new file mode 100644
index 0000000..fe0f7f5
--- /dev/null
+++ b/backend/docker-entrypoint.sh
@@ -0,0 +1,34 @@
+#!/bin/bash
+# Wire the host-mounted LTspice binaries into the writable LTSPICE_DIR (which
+# holds the Wine prefix baked at image build), start a virtual display for
+# Wine, then hand off to the CMD.
+set -e
+
+src=/opt/ltspice-src
+dst=${LTSPICE_DIR:-/opt/ltspice}
+
+# The LTspice install is mounted read-only from the host; symlink the three
+# things mcltspice's config references (exe, lib, examples) next to the prefix.
+if [ -d "$src" ]; then
+    for item in LTspice.exe lib examples; do
+        if [ -e "$src/$item" ]; then
+            ln -sfn "$src/$item" "$dst/$item"
+        fi
+    done
+fi
+
+# LTspice opens an X connection even in batch (-b) mode, so give Wine a
+# headless display. Clear any stale lock first -- the build-time Xvfb on the
+# same display can leave /tmp/.X99-lock baked into the image, which would make
+# a naive "already running?" check skip startup (one container = one Xvfb).
+if [ -n "$DISPLAY" ]; then
+    rm -f "/tmp/.X${DISPLAY#:}-lock"
+    Xvfb "$DISPLAY" -screen 0 1024x768x16 -nolisten tcp >/tmp/xvfb.log 2>&1 &
+    # Give the server a moment to come up before the app can ask for it.
+    for _ in 1 2 3 4 5 6 7 8 9 10; do
+        [ -e "/tmp/.X11-unix/X${DISPLAY#:}" ] && break
+        sleep 0.3
+    done
+fi
+
+exec "$@"
diff --git a/backend/ltspice-config/LTspice.ini b/backend/ltspice-config/LTspice.ini
new file mode 100644
index 0000000..991f683
Binary files /dev/null and b/backend/ltspice-config/LTspice.ini differ
diff --git a/docker-compose.prod.yml b/docker-compose.prod.yml
index 6ddf302..0d6a3f5 100644
--- a/docker-compose.prod.yml
+++ b/docker-compose.prod.yml
@@ -6,6 +6,16 @@ services:
       target: prod
     expose:
       - "8000"
+    # LTspice engine is GATED. The backend image ships Wine 11.10 + the prefix,
+    # and the host carries ./ltspice (exe/lib/examples), but LTspice v26 stalls
+    # at graphics init under headless Wine in this slim image (works on the dev
+    # desktop). Without LTSPICE_DIR the engine reports "unavailable" and fails
+    # fast instead of hanging. To resume debugging, uncomment the two blocks:
+    # volumes:
+    #   - ./ltspice:/opt/ltspice-src:ro
+    # environment:
+    #   - LTSPICE_DIR=/opt/ltspice
+    #   - DISPLAY=:99
     networks:
       - default
       - caddy