diff --git a/tests/docker_image_test.sh b/tests/docker_image_test.sh
new file mode 100755
index 0000000..25d1d48
--- /dev/null
+++ b/tests/docker_image_test.sh
@@ -0,0 +1,22 @@
+#!/bin/bash
+
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+IMAGE_NAME="codex-action-smoke:local"
+
+if ! command -v docker >/dev/null 2>&1; then
+  echo "SKIP: docker is not available"
+  exit 0
+fi
+
+if ! docker info >/dev/null 2>&1; then
+  echo "SKIP: docker daemon is not available"
+  exit 0
+fi
+
+docker build -t "$IMAGE_NAME" "$ROOT_DIR"
+
+docker run --rm --entrypoint codex "$IMAGE_NAME" --version
+docker run --rm --entrypoint codex "$IMAGE_NAME" plugin list | grep -q "jsc@doc"
+docker run --rm --entrypoint codex "$IMAGE_NAME" plugin list | grep -q "jsc@code-review"
diff --git a/tests/entrypoint_test.sh b/tests/entrypoint_test.sh
index bc38fca..8055217 100755
--- a/tests/entrypoint_test.sh
+++ b/tests/entrypoint_test.sh
@@ -16,6 +16,7 @@ make_fake_codex() {
 
   cat > "$dir/codex" <<SH
 #!/bin/sh
+printf '%s\n' "\$*" > "\${CODEX_FAKE_ARGS:-/dev/null}"
 echo "$message"
 exit $exit_code
 SH
@@ -118,6 +119,30 @@ test_success_output() {
   rm -rf "$tmpdir"
 }
 
+test_empty_prompt() {
+  local tmpdir
+  tmpdir="$(mktemp -d)"
+  make_fake_codex "$tmpdir" 0 "codex ok"
+
+  run_entrypoint "$tmpdir" OAUTH="$(encoded_json '{}')" MODEL="gpt-test" PROMPT=""
+
+  grep -q "codex ok" "$tmpdir/github-output" || die "empty prompt output"
+  rm -rf "$tmpdir"
+}
+
+test_prompt_with_shell_characters() {
+  local tmpdir
+  local prompt
+  tmpdir="$(mktemp -d)"
+  prompt='hello; rm -rf / $(echo bad) "quoted"'
+  make_fake_codex "$tmpdir" 0 "codex ok"
+
+  run_entrypoint "$tmpdir" OAUTH="$(encoded_json '{}')" MODEL="gpt-test" PROMPT="$prompt" CODEX_FAKE_ARGS="$tmpdir/codex-args"
+
+  grep -qF "$prompt" "$tmpdir/codex-args" || die "prompt was not passed as one argument"
+  rm -rf "$tmpdir"
+}
+
 test_failure_output() {
   local tmpdir
   tmpdir="$(mktemp -d)"
@@ -140,6 +165,8 @@ test_missing_model
 test_invalid_base64
 test_non_object_json
 test_success_output
+test_empty_prompt
+test_prompt_with_shell_characters
 test_failure_output
 
 echo "entrypoint tests passed"