diff --git a/scripts/docker/install-sh-smoke/run.sh b/scripts/docker/install-sh-smoke/run.sh
index 1611df660446..7cf5a4362504 100755
--- a/scripts/docker/install-sh-smoke/run.sh
+++ b/scripts/docker/install-sh-smoke/run.sh
@@ -1,6 +1,34 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
+read_positive_int_env() {
+  local name="${1:?missing environment variable name}"
+  local fallback="${2:?missing fallback value}"
+  local value="${!name-}"
+  if [[ -z "${!name+x}" ]]; then
+    value="$fallback"
+  fi
+  if [[ ! "$value" =~ ^[0-9]+$ ]] || (( 10#$value < 1 )); then
+    echo "invalid $name: $value" >&2
+    return 2
+  fi
+  printf "%s\n" "$((10#$value))"
+}
+
+read_nonnegative_int_env() {
+  local name="${1:?missing environment variable name}"
+  local fallback="${2:?missing fallback value}"
+  local value="${!name-}"
+  if [[ -z "${!name+x}" ]]; then
+    value="$fallback"
+  fi
+  if [[ ! "$value" =~ ^[0-9]+$ ]]; then
+    echo "invalid $name: $value" >&2
+    return 2
+  fi
+  printf "%s\n" "$((10#$value))"
+}
+
 INSTALL_URL="${OPENCLAW_INSTALL_URL:-https://openclaw.bot/install.sh}"
 SMOKE_MODE="${OPENCLAW_INSTALL_SMOKE_MODE:-install}"
 SMOKE_PREVIOUS_VERSION="${OPENCLAW_INSTALL_SMOKE_PREVIOUS:-}"
@@ -18,8 +46,8 @@ FRESHNESS_VERSION="${OPENCLAW_INSTALL_FRESHNESS_VERSION:-latest}"
 # npm min-release-age is days; 10000 keeps the control failure independent of normal release cadence.
 FRESHNESS_MIN_RELEASE_AGE="${OPENCLAW_INSTALL_FRESHNESS_MIN_RELEASE_AGE:-10000}"
 FRESHNESS_NPM_VERSION="${OPENCLAW_INSTALL_FRESHNESS_NPM_VERSION:-11.14.1}"
-HEARTBEAT_INTERVAL="${OPENCLAW_INSTALL_SMOKE_HEARTBEAT_INTERVAL:-60}"
-INSTALL_COMMAND_TIMEOUT="${OPENCLAW_INSTALL_SMOKE_COMMAND_TIMEOUT:-900}"
+HEARTBEAT_INTERVAL="$(read_nonnegative_int_env OPENCLAW_INSTALL_SMOKE_HEARTBEAT_INTERVAL 60)"
+INSTALL_COMMAND_TIMEOUT="$(read_positive_int_env OPENCLAW_INSTALL_SMOKE_COMMAND_TIMEOUT 900)"
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 
 # shellcheck source=../install-sh-common/cli-verify.sh
@@ -75,7 +103,7 @@ run_with_heartbeat() {
   local label="$1"
   shift
   local interval="$HEARTBEAT_INTERVAL"
-  if ! [[ "$interval" =~ ^[0-9]+$ ]] || [[ "$interval" == "0" ]]; then
+  if [[ "$interval" == "0" ]]; then
     "$@"
     return
   fi
diff --git a/test/scripts/test-install-sh-docker.test.ts b/test/scripts/test-install-sh-docker.test.ts
index 29ac365127bb..4a6265434b2c 100644
--- a/test/scripts/test-install-sh-docker.test.ts
+++ b/test/scripts/test-install-sh-docker.test.ts
@@ -473,11 +473,12 @@ describe("install-sh smoke runner", () => {
     const script = readFileSync(SMOKE_RUNNER_PATH, "utf8");
 
     expect(script).toContain(
-      'HEARTBEAT_INTERVAL="${OPENCLAW_INSTALL_SMOKE_HEARTBEAT_INTERVAL:-60}"',
+      'HEARTBEAT_INTERVAL="$(read_nonnegative_int_env OPENCLAW_INSTALL_SMOKE_HEARTBEAT_INTERVAL 60)"',
     );
     expect(script).toContain(
-      'INSTALL_COMMAND_TIMEOUT="${OPENCLAW_INSTALL_SMOKE_COMMAND_TIMEOUT:-900}"',
+      'INSTALL_COMMAND_TIMEOUT="$(read_positive_int_env OPENCLAW_INSTALL_SMOKE_COMMAND_TIMEOUT 900)"',
     );
+    expect(script).toContain('if [[ "$interval" == "0" ]]; then');
     expect(script).toContain("run_with_heartbeat");
     expect(script).toContain("npm_install_global");
     expect(script).toContain('timeout --kill-after=30s "${INSTALL_COMMAND_TIMEOUT}s"');
@@ -491,6 +492,23 @@ describe("install-sh smoke runner", () => {
     expect(script).toContain("unterminated update JSON object");
   });
 
+  it.each([
+    ["command timeout", "OPENCLAW_INSTALL_SMOKE_COMMAND_TIMEOUT", "900s"],
+    ["heartbeat interval", "OPENCLAW_INSTALL_SMOKE_HEARTBEAT_INTERVAL", "60s"],
+  ])("rejects invalid install smoke %s before running npm", (_label, envName, value) => {
+    const result = spawnSync("bash", [SMOKE_RUNNER_PATH], {
+      encoding: "utf8",
+      env: {
+        ...process.env,
+        [envName]: value,
+      },
+    });
+
+    expect(result.status).toBe(2);
+    expect(result.stderr).toContain(`invalid ${envName}: ${value}`);
+    expect(result.stderr).not.toContain("unsupported OPENCLAW_INSTALL_SMOKE_MODE");
+  });
+
   it("covers plain npm global installs and npm-driven updates", () => {
     const script = readFileSync(SCRIPT_PATH, "utf8");
     const runner = readFileSync(SMOKE_RUNNER_PATH, "utf8");