diff --git a/internal/api/agent_install_command_shared_test.go b/internal/api/agent_install_command_shared_test.go
index 3c495430a5..b689ff4111 100644
--- a/internal/api/agent_install_command_shared_test.go
+++ b/internal/api/agent_install_command_shared_test.go
@@ -14,6 +14,17 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func requirePrivateBootstrapPrivilegeDispatch(t *testing.T, command string) {
+	t.Helper()
+	// The shared producer selects its root/sudo argv inside an isolated
+	// subshell. Duplicating the credential reader into literal root and sudo
+	// branches would exceed the common pasted-line budget.
+	require.Contains(t, command, `elif command -v sudo >/dev/null 2>&1; then sudo -v;`)
+	require.Contains(t, command, `if [ "$(id -u)" -eq 0 ]; then set --; else set -- sudo; fi;`)
+	require.Contains(t, command, `"$@" bash -c `)
+	require.Equal(t, 1, strings.Count(command, "bash -c "), "the privileged body must be emitted once")
+}
+
 func TestNormalizeProxmoxInstallType(t *testing.T) {
 	installType, err := normalizeProxmoxInstallType(" PBS ")
 	require.NoError(t, err)
@@ -92,7 +103,7 @@ func TestBuildProxmoxAgentInstallCommand(t *testing.T) {
 	require.NotContains(t, command, "token-123")
 	require.Contains(t, command, `--token-file "$token_file"`)
 	require.Contains(t, command, `token_dir=$(mktemp -d /tmp/pulse-agent-bootstrap.XXXXXX)`)
-	require.Contains(t, command, `sudo bash -c`)
+	requirePrivateBootstrapPrivilegeDispatch(t, command)
 	require.Contains(t, command, `rmdir -- "$token_dir"`)
 	require.Contains(t, command, "pbs")
 	require.NotContains(t, command, "--enable-commands")
@@ -213,7 +224,7 @@ func TestBuildContainerRuntimeAgentInstallCommand_UsesLifecycleTransport(t *test
 	require.Contains(t, command, "--enable-host")
 	require.NotContains(t, command, "--enable-host=false")
 	require.Contains(t, command, "--interval 30s")
-	require.Contains(t, command, `sudo bash -c`)
+	requirePrivateBootstrapPrivilegeDispatch(t, command)
 	require.Contains(t, command, "--preflight-only --output json --non-interactive")
 	require.Contains(t, command, `read -r -s -p`)
 	require.NotContains(t, command, "| bash")
@@ -262,7 +273,7 @@ func TestBuildSetupScriptCommand_OmitsTokenWhenNotProvided(t *testing.T) {
 
 	require.Contains(t, command, "curl -fsSL "+posixShellQuote("https://pulse.example.com/api/setup-script?type=pbs")+` -o "$install_script"`)
 	require.Contains(t, command, `if [ "$(id -u)" -eq 0 ]; then`)
-	require.Contains(t, command, `sudo bash -c`)
+	requirePrivateBootstrapPrivilegeDispatch(t, command)
 	require.NotContains(t, command, "PULSE_SETUP_TOKEN=")
 }
 
diff --git a/internal/api/configapi/install_command_test.go b/internal/api/configapi/install_command_test.go
index d46eb77acc..e619f7983c 100644
--- a/internal/api/configapi/install_command_test.go
+++ b/internal/api/configapi/install_command_test.go
@@ -40,6 +40,16 @@ exit_sent = False
 command_ready = not history
 command_tail = b""
 send_tail_at = 0
+signal_observation = None
+def reader_signal_state(reader):
+    # Linux-only diagnostic fields, never cmdline, environment or input. Other
+    # platforms retain the sent/exit/terminal observations without these masks.
+    try:
+        with open("/proc/%d/status" % reader) as f:
+            return {k: v.strip() for k, v in (line.split(":", 1) for line in f)
+                    if k in ("Name", "State", "SigBlk", "SigIgn", "SigCgt", "SigPnd", "ShdPnd")}
+    except OSError:
+        return {"status": "unavailable"}
 deadline = time.monotonic() + 15
 while time.monotonic() < deadline:
     ready, _, _ = select.select([master], [], [], .1)
@@ -87,19 +97,30 @@ while time.monotonic() < deadline:
                 # signalling the entire session kills that observation owner.
                 with open(os.path.join(env["FAKE_ROOT"], "reader-pid")) as f:
                     reader = int(f.read())
+                signal_observation = {"signal": p["signal_on_prompt"], "sent": False,
+                                      "before": reader_signal_state(reader)}
                 os.kill(reader, getattr(signal, "SIG" + p["signal_on_prompt"]))
+                signal_observation["sent"] = True
             else:
                 os.write(master, (p["input"] + "\n").encode())
             sent = True
     if child.poll() is not None and not ready: break
 else:
+    if signal_observation:
+        signal_observation["at_deadline"] = reader_signal_state(reader)
     os.killpg(child.pid, signal.SIGKILL)
-    output += b"\nPTY fixture deadline expired\n"
+    output += ("\nPTY fixture deadline expired (prompt accepted=%s, signal sent=%s)\n" %
+               (sent, bool(signal_observation and signal_observation["sent"]))).encode()
 code = child.wait()
 final_tty = termios.tcgetattr(tty_watch)
 if initial_tty != final_tty:
     output += b"\nBootstrap did not restore complete terminal settings\n"
     code = 1
+if p.get("signal_on_prompt"):
+    observation = signal_observation or {"signal": p["signal_on_prompt"], "sent": False}
+    observation.update(exit=code, complete_tty_restored=initial_tty == final_tty)
+    with open(os.path.join(env["FAKE_ROOT"], "signal-observation"), "w") as f:
+        json.dump(observation, f, sort_keys=True)
 os.close(tty_watch)
 os.close(master)
 sys.stdout.buffer.write(output)
diff --git a/internal/api/configapi/portable_bootstrap_test.go b/internal/api/configapi/portable_bootstrap_test.go
index ec76a2a6b1..beb6b52a9d 100644
--- a/internal/api/configapi/portable_bootstrap_test.go
+++ b/internal/api/configapi/portable_bootstrap_test.go
@@ -205,6 +205,21 @@ func TestPrivateBootstrapRealBusyBoxInput(t *testing.T) {
 				root, env := portableBootstrapFixture(t, "busybox")
 				command := caller.build("issued-separately")
 				out, err := runPortableBootstrap(t, command, tc.input, env, "", tc.signalName)
+				if tc.signalName != "" {
+					body, readErr := os.ReadFile(filepath.Join(root, "signal-observation"))
+					if readErr != nil {
+						t.Fatal("signal execution observation missing")
+					}
+					var observation struct {
+						Sent bool `json:"sent"`
+					}
+					if json.Unmarshal(body, &observation) != nil || !observation.Sent {
+						t.Fatal("requested reader signal was not actually sent")
+					}
+					// This fixed-field record contains no command, input or environment.
+					// Keep delivery separate from a successful cleanup assertion.
+					t.Logf("reader signal observation: %s", body)
+				}
 				if (err != nil) != tc.failure {
 					t.Fatalf("BusyBox bootstrap result=%v, expected failure=%t\n%s", err, tc.failure, out)
 				}
diff --git a/internal/api/router_low_coverage_additional_test.go b/internal/api/router_low_coverage_additional_test.go
index 3e6a8ce694..579cfa8bbf 100644
--- a/internal/api/router_low_coverage_additional_test.go
+++ b/internal/api/router_low_coverage_additional_test.go
@@ -179,7 +179,8 @@ func TestHandleDiagnosticsDockerPrepareToken_Success(t *testing.T) {
 	if !strings.Contains(payload["installCommand"].(string), "--enable-docker") {
 		t.Fatalf("expected install command to enable docker metrics: %q", payload["installCommand"])
 	}
-	if !strings.Contains(payload["installCommand"].(string), `sudo bash -c`) || !strings.Contains(payload["installCommand"].(string), `--token-file "$token_file"`) {
+	requirePrivateBootstrapPrivilegeDispatch(t, payload["installCommand"].(string))
+	if !strings.Contains(payload["installCommand"].(string), `--token-file "$token_file"`) {
 		t.Fatal("expected install command to preserve private token input through root or sudo")
 	}
 	for _, field := range []string{"installCommand", "systemdServiceSnippet"} {