diff --git a/cli/src/__tests__/service-manager.test.ts b/cli/src/__tests__/service-manager.test.ts
index f5f98b5ee15..f64a3125521 100644
--- a/cli/src/__tests__/service-manager.test.ts
+++ b/cli/src/__tests__/service-manager.test.ts
@@ -48,6 +48,14 @@ describe("service definition generation", () => {
     expect(unit).toContain('Environment="PAPERCLIP_HOME=/home/$$USER/%%i/.paperclip"');
   });
 
+  it.each([
+    ["instanceId", { instanceId: "team-a\nExecStartPre=/tmp/attack", shimPath: "/home/alice/.local/bin/paperclipai", homeDir: "/home/alice/.paperclip" }],
+    ["shimPath", { instanceId: "team-a", shimPath: "/home/alice/bin/paperclipai\r\nExecStartPre=/tmp/attack", homeDir: "/home/alice/.paperclip" }],
+    ["homeDir", { instanceId: "team-a", shimPath: "/home/alice/.local/bin/paperclipai", homeDir: "/home/alice/.paperclip\nEnvironment=ATTACK=1" }],
+  ])("rejects line breaks in the systemd %s", (_field, input) => {
+    expect(() => renderSystemdUnit(input)).toThrow("Systemd service values must not contain line breaks");
+  });
+
   it("generates a launchd agent with keepalive and instance logs", () => {
     const plist = renderLaunchdPlist({ instanceId: "team-a", shimPath: "/Users/alice/.local/bin/paperclipai", homeDir: "/Users/alice/.paperclip", stdoutPath: "/Users/alice/.paperclip/instances/team-a/logs/service.log", stderrPath: "/Users/alice/.paperclip/instances/team-a/logs/service.err.log" });
     expect(plist).toContain("ing.paperclip.paperclipai.team-a");
diff --git a/cli/src/services/service-manager.ts b/cli/src/services/service-manager.ts
index 57c608a642b..f284afa59b4 100644
--- a/cli/src/services/service-manager.ts
+++ b/cli/src/services/service-manager.ts
@@ -53,6 +53,9 @@ export const defaultCommandRunner: CommandRunner = async (command, args, options
 };
 
 function escapeSystemd(value: string): string {
+  if (/\r|\n/.test(value)) {
+    throw new Error("Systemd service values must not contain line breaks");
+  }
   return value
     .replaceAll("\\", "\\\\")
     .replaceAll('"', '\\"')
@@ -82,7 +85,7 @@ export function launchdServiceName(instanceId: string): string {
 
 export function renderSystemdUnit(input: { instanceId: string; shimPath: string; homeDir: string }): string {
   return `[Unit]
-Description=Paperclip AI (${input.instanceId})
+Description=Paperclip AI (${escapeSystemd(input.instanceId)})
 After=network.target
 StartLimitIntervalSec=60
 StartLimitBurst=5