diff --git a/web/lib/test/probe-install.test.ts b/web/lib/test/probe-install.test.ts
new file mode 100644
index 0000000..a547145
--- /dev/null
+++ b/web/lib/test/probe-install.test.ts
@@ -0,0 +1,27 @@
+import { spawnSync } from 'node:child_process';
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { describe, expect, it } from 'vitest';
+
+const installer = fileURLToPath(new URL('../../public/install.sh', import.meta.url));
+
+describe('Relay Probe installer', () => {
+  it('parses under sh and exposes help without starting installation', () => {
+    expect(spawnSync('/bin/sh', ['-n', installer], { encoding: 'utf8' }).status).toBe(0);
+    const help = spawnSync('/bin/sh', [installer, '--help'], { encoding: 'utf8' });
+    expect(help.status).toBe(0);
+    expect(help.stdout).toContain('agent-relay-probe');
+  });
+
+  it('prints the platform under set -u without treating the ellipsis as part of its name', () => {
+    const source = readFileSync(installer, 'utf8');
+    const progressLine = source.split('\n').find((line) => line.includes('Downloading Agent Relay Probe for'));
+    expect(progressLine).toBeDefined();
+
+    const result = spawnSync('/bin/sh', ['-c', `set -u; platform=darwin-arm64; ${progressLine}`], {
+      encoding: 'utf8',
+    });
+    expect(result.status).toBe(0);
+    expect(result.stdout).toBe('Downloading Agent Relay Probe for darwin-arm64…\n');
+  });
+});
diff --git a/web/public/install.sh b/web/public/install.sh
index 345b308..105a696 100644
--- a/web/public/install.sh
+++ b/web/public/install.sh
@@ -53,7 +53,7 @@ else fail "A SHA-256 tool (sha256sum or shasum) is required."; fi
 probe_tmp=$(mktemp -d "${TMPDIR:-/tmp}/agent-relay-probe.XXXXXX")
 trap 'rm -rf "$probe_tmp"' EXIT HUP INT TERM
 download="$SITE_URL/downloads/agent-relay-probe/$platform/agent-relay-probe"
-printf '%s\n' "Downloading Agent Relay Probe for $platform…"
+printf '%s\n' "Downloading Agent Relay Probe for ${platform}…"
 curl --proto "$CURL_PROTOCOL" --max-time 120 --max-filesize 104857600 -fsS "$download" -o "$probe_tmp/agent-relay-probe" || fail "The native probe build is not available on this site for your platform."
 curl --proto "$CURL_PROTOCOL" --max-time 30 --max-filesize 1024 -fsS "$download.sha256" -o "$probe_tmp/checksum" || fail "Could not download the probe checksum."
 expected=$(awk 'NR == 1 { print $1 }' "$probe_tmp/checksum")