fix(headroom): support Docker sidecar proxy

Treat configured Headroom proxy as running when its /health endpoint
responds, even if local headroom CLI is not installed. Dashboard
Start/Stop stays limited to local loopback proxies while external
Docker sidecars can be enabled via HEADROOM_URL.

Closes #1948

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/db/repos/settingsRepo.js

@@ -2,6 +2,7 @@ import { getAdapter } from "../driver.js";
 import { parseJson, stringifyJson } from "../helpers/jsonCol.js";
 
 const DEFAULT_MITM_ROUTER_BASE = "http://localhost:20128";
+const DEFAULT_HEADROOM_URL = process.env.HEADROOM_URL || "http://localhost:8787";
 
 const DEFAULT_SETTINGS = {
   cloudEnabled: false,
@@ -35,7 +36,7 @@ const DEFAULT_SETTINGS = {
   dnsToolEnabled: {},
   rtkEnabled: true,
   headroomEnabled: false,
-  headroomUrl: "http://localhost:8787",
+  headroomUrl: DEFAULT_HEADROOM_URL,
   headroomCompressUserMessages: false,
   cavemanEnabled: false,
   cavemanLevel: "full",

src/lib/headroom/detect.js

@@ -29,6 +29,9 @@ const EXTENDED_PATH = [...EXTRA_BINS, process.env.PATH || ""].filter(Boolean).jo
 const PYTHON_CANDIDATES = ["python3.13", "python3.12", "python3.11", "python3.10", "python3", "python"];
 const MIN_VERSION = [3, 10];
 const HEADROOM_HEALTH_TIMEOUT_MS = 1500;
+const LOOPBACK_HOSTS = new Set(["localhost", "127.0.0.1", "::1", "[::1]", "0.0.0.0"]);
+
+export const DEFAULT_HEADROOM_URL = process.env.HEADROOM_URL || "http://localhost:8787";
 
 // Detect whether the headroom CLI is installed and where its binary lives.
 export function findHeadroomBinary() {
@@ -79,11 +82,21 @@ export async function probeProxyRunning(url) {
   }
 }
 
+export function isLoopbackHeadroomUrl(url) {
+  try {
+    const parsed = new URL(url);
+    return LOOPBACK_HOSTS.has(parsed.hostname);
+  } catch {
+    return false;
+  }
+}
+
 // Aggregate status for the dashboard: installed, running, python interpreter.
 export async function getHeadroomStatus(url) {
   const path = findHeadroomBinary();
   const python = findPython310();
   const installed = Boolean(path);
-  const running = installed ? await probeProxyRunning(url) : false;
-  return { installed, path, running, python };
+  const running = await probeProxyRunning(url);
+  const localUrl = isLoopbackHeadroomUrl(url);
+  return { installed, path, running, python, localUrl, canStart: installed && localUrl };
 }