diff --git a/scripts/start_ursim.sh b/scripts/start_ursim.sh
index 977fb16cf..cd366057f 100755
--- a/scripts/start_ursim.sh
+++ b/scripts/start_ursim.sh
@@ -404,27 +404,46 @@ post_setup_polyscopex()
     curl -L -o "$urcapx_file" "$URCAPX_DOWNLOAD_URL"
   fi
 
-  # Prefer a published host mapping for HTTP (needed on Docker Desktop / NAT where the
-  # container IP is unreachable). Fall back to the container IP when nothing is published.
-  local forwarded_endpoint http_host
-  if forwarded_endpoint=$(get_forwarded_access_endpoint 80); then
-    http_host="$forwarded_endpoint"
-  else
-    http_host="$IP_ADDRESS"
+  # UrService is reachable on the container IP from another container on ursim_net
+  # (CI). A published host port is required on Docker Desktop, where that IP is
+  # not routed. Probe both, and install the URCap through whichever answers.
+  local forwarded_endpoint=""
+  forwarded_endpoint=$(get_forwarded_access_endpoint 80) || forwarded_endpoint=""
+  local -a base_urls=("http://${IP_ADDRESS}")
+  if [[ -n "$forwarded_endpoint" ]]; then
+    base_urls+=("http://${forwarded_endpoint}")
   fi
-  local base_url="http://${http_host}"
-  local urcaps_url="${base_url}/universal-robots/urservice/api/v1/urcaps"
+  local urcaps_path="/universal-robots/urservice/api/v1/urcaps"
+  # Overall wait for UrService. Override with URSIM_URSERVICE_TIMEOUT (seconds).
+  local urservice_timeout="${URSIM_URSERVICE_TIMEOUT:-300}"
+  local urcaps_url=""
+  local base status_code
+  local deadline=$((SECONDS + urservice_timeout))
 
   echo -ne "Starting URSim. Waiting for UrService to be up..."
-  status_code=$(curl --retry-connrefused -f --write-out "%{http_code}" --silent --output /dev/null "$urcaps_url")
-
-  until [ "$status_code" == "200" ]
-  do
-    sleep 1
-    echo -ne "."
-    status_code=$(curl --retry-connrefused -f --write-out "%{http_code}" --silent --output /dev/null "$urcaps_url")
+  while [[ -z "$urcaps_url" && "$SECONDS" -lt "$deadline" ]]; do
+    for base in "${base_urls[@]}"; do
+      status_code=$(
+        curl --connect-timeout 2 --max-time 5 --silent --output /dev/null \
+          --write-out "%{http_code}" "${base}${urcaps_path}" || true
+      )
+      if [[ "$status_code" == "200" ]]; then
+        urcaps_url="${base}${urcaps_path}"
+        break
+      fi
+    done
+    if [[ -z "$urcaps_url" ]]; then
+      sleep 1
+      echo -ne "."
+    fi
   done
 
+  if [[ -z "$urcaps_url" ]]; then
+    echo ""
+    echo "Timed out after ${urservice_timeout}s waiting for UrService. Tried: ${base_urls[*]}"
+    return 1
+  fi
+
   echo ""; echo "UrService is up"
 
   echo "Installing URCapX $urcapx_file"
@@ -666,7 +685,13 @@ main() {
   trap "$TRAP_CMD" SIGINT SIGTERM
 
 
-  eval "post_setup_${ROBOT_SERIES}"
+  if ! "post_setup_${ROBOT_SERIES}"; then
+    if [ "$DETACHED" = false ]; then
+      docker container kill "$CONTAINER_NAME" > /dev/null 2>&1 || true
+      docker container wait "$CONTAINER_NAME" > /dev/null 2>&1 || true
+    fi
+    exit 1
+  fi
 
   if [ "$DETACHED" = false ]; then
   echo "To exit, press CTRL+C"
diff --git a/tests/test_start_ursim.bats b/tests/test_start_ursim.bats
index 5c2e802a0..f86e4d050 100644
--- a/tests/test_start_ursim.bats
+++ b/tests/test_start_ursim.bats
@@ -981,7 +981,7 @@ stub_docker_port() {
   [[ "$output" != *"Access PolyScope X: http://192."* ]]
 }
 
-@test "post_setup_polyscopex uses forwarded endpoint for http calls" {
+@test "post_setup_polyscopex uses container IP for http calls when it responds" {
   IP_ADDRESS="192.168.56.101"
   CONTAINER_NAME="ursim"
   DOCKER_PORT_MAP='80=127.0.0.1:8000'
@@ -1000,15 +1000,73 @@ stub_docker_port() {
   touch "$URCAP_STORAGE/external-control-0.0.0.urcapx"
   URSIM_VERSION="10.8.0"
 
+  run post_setup_polyscopex
+  echo "$output"
+  echo "curl log:"; cat "$CURL_LOG"
+  [ "$status" -eq 0 ]
+  grep -F "http://192.168.56.101/universal-robots/urservice/api/v1/urcaps" "$CURL_LOG"
+  ! grep -F "http://127.0.0.1:8000/universal-robots/urservice/api/v1/urcaps" "$CURL_LOG"
+  rm -f "$CURL_LOG"
+}
+
+@test "post_setup_polyscopex uses forwarded endpoint when container IP is unreachable" {
+  IP_ADDRESS="192.168.56.101"
+  CONTAINER_NAME="ursim"
+  DOCKER_PORT_MAP='80=127.0.0.1:8000'
+  stub_docker_port
+  get_download_url_urcapx() { URCAPX_VERSION="0.0.0"; URCAPX_DOWNLOAD_URL=""; }
+  CURL_LOG=$(mktemp)
+  curl() {
+    printf '%s\n' "$*" >> "$CURL_LOG"
+    if [[ "$*" == *"--form"* ]]; then
+      return 0
+    fi
+    if [[ "$*" == *"http://192.168.56.101/universal-robots/urservice/api/v1/urcaps"* ]]; then
+      echo "000"
+      return 7
+    fi
+    echo "200"
+  }
+  URCAP_STORAGE=/tmp/ursim-test-urcaps-post-setup
+  mkdir -p "$URCAP_STORAGE"
+  touch "$URCAP_STORAGE/external-control-0.0.0.urcapx"
+  URSIM_VERSION="10.8.0"
+
   run post_setup_polyscopex
   echo "$output"
   echo "curl log:"; cat "$CURL_LOG"
   [ "$status" -eq 0 ]
   grep -F "http://127.0.0.1:8000/universal-robots/urservice/api/v1/urcaps" "$CURL_LOG"
-  ! grep -F "http://192.168.56.101/universal-robots/urservice/api/v1/urcaps" "$CURL_LOG"
   rm -f "$CURL_LOG"
 }
 
+@test "post_setup_polyscopex times out when UrService does not respond" {
+  IP_ADDRESS="192.168.56.101"
+  CONTAINER_NAME="ursim"
+  DOCKER_PORT_MAP='80=127.0.0.1:8000'
+  stub_docker_port
+  get_download_url_urcapx() { URCAPX_VERSION="0.0.0"; URCAPX_DOWNLOAD_URL=""; }
+  curl() {
+    if [[ "$*" == *"--form"* ]]; then
+      return 0
+    fi
+    echo "000"
+    return 7
+  }
+  URCAP_STORAGE=/tmp/ursim-test-urcaps-post-setup
+  mkdir -p "$URCAP_STORAGE"
+  touch "$URCAP_STORAGE/external-control-0.0.0.urcapx"
+  URSIM_VERSION="10.8.0"
+  URSIM_URSERVICE_TIMEOUT=1
+
+  run post_setup_polyscopex
+  echo "$output"
+  [ "$status" -ne 0 ]
+  [[ "$output" == *"Timed out after 1s waiting for UrService."* ]]
+  [[ "$output" == *"http://192.168.56.101"* ]]
+  [[ "$output" == *"http://127.0.0.1:8000"* ]]
+}
+
 @test "post_setup_polyscopex falls back to IP_ADDRESS for http calls when unpublished" {
   IP_ADDRESS="192.168.56.101"
   CONTAINER_NAME="ursim"