diff --git a/Dockerfile b/Dockerfile
index ddad334..84cd3a4 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,31 +1,9 @@
-FROM python:3.11-slim
+FROM ghcr.io/home-assistant/home-assistant:stable
 
-WORKDIR /app
-
-# Python deps first so layer cache survives code changes
-COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
-
-# Application code
-COPY main.py .
-COPY samsung_appliance/ ./samsung_appliance/
-
-# /config holds the ab0b0ac4 client cert + key. Mount from the host so
-# secrets aren't baked into the image.
-RUN mkdir -p /config
-
-# Unbuffered stdout so docker logs is live
-ENV PYTHONUNBUFFERED=1
-
-# Defaults — override in .env or `docker run -e …`. Per-appliance
-# keys (APPLIANCE_COUNT, APPLIANCE_<n>_*) have no universal default
-# and must be set in .env.
-ENV CERT_PATH=/config/ab0b0ac4_fullchain.pem \
-    KEY_PATH=/config/ab0b0ac4.key \
-    HA_DISCOVERY_PREFIX=homeassistant \
-    HEALTH_INTERVAL_S=60 \
-    HEARTBEAT_INTERVAL_S=600
-
-# No port — bridge is outbound-only (DTLS UDP to appliance, MQTT to broker).
-
-CMD ["python", "main.py"]
+# Home Assistant normally installs a custom integration's manifest.json
+# requirements itself at integration setup, but that depends on the
+# container having outbound network access at exactly that moment and
+# repeats the install attempt on every container recreate. Baking
+# smartthings-local into the image keeps the dev container usable
+# offline and avoids relying on that runtime install path.
+RUN pip3 install --no-cache-dir "smartthings-local>=0.1.0"
diff --git a/README.md b/README.md
index f270e5a..5e3f888 100644
--- a/README.md
+++ b/README.md
@@ -76,11 +76,13 @@ Entities appear under one HA device per appliance, named `Samsung Appliance (<ip
 ### Docker Compose dev environment
 
 ```sh
-docker compose up -d
+docker compose up -d --build
 docker compose logs -f
 ```
 
-Runs the official `home-assistant/home-assistant:stable` image with `network_mode: host` (required, since DTLS is UDP and won't traverse Docker's bridge NAT to reach LAN appliances) and `custom_components/localthings/` bind-mounted read-only into `ha_config/custom_components/`. Bump `custom_components.localthings` to `debug` in `ha_config/configuration.yaml` for verbose protocol logging.
+The `Dockerfile` builds on the official `home-assistant/home-assistant:stable` image and pre-installs `smartthings-local`, so the dependency is present at container start instead of depending on HA's own runtime pip-install step (which needs outbound network access at exactly the moment the integration loads, and repeats on every container recreate). Re-run with `--build` whenever the pinned `smartthings-local` version changes.
+
+`docker-compose.yml` sets `network_mode: host`, which is required since DTLS is UDP and won't traverse Docker's bridge NAT to reach LAN appliances, and bind-mounts `custom_components/localthings/` read-only into `ha_config/custom_components/`. Bump `custom_components.localthings` to `debug` in `ha_config/configuration.yaml` for verbose protocol logging.
 
 ### Tests
 
diff --git a/docker-compose.yml b/docker-compose.yml
index b935434..10825d7 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,6 +1,7 @@
 services:
   homeassistant:
-    image: ghcr.io/home-assistant/home-assistant:stable
+    build: .
+    image: localthings-ha-dev
     container_name: localthings-ha
     # host networking is required — DTLS runs over UDP and won't
     # traverse Docker's bridge NAT to reach LAN appliances.