diff --git a/js/constants.js b/js/constants.js
index 8efdc688..38600fe9 100644
--- a/js/constants.js
+++ b/js/constants.js
@@ -1,7 +1,159 @@
-export const URL_FIRST_ENABLED = true;
-export const ACCEPT_LEGACY_V1 = true;
-export const WSS_TRACKERS = [
-  "wss://tracker.openwebtorrent.com",
-  "wss://tracker.btorrent.xyz",
-  "wss://tracker.webtorrent.dev",
-];
+const DEFAULT_FLAGS = Object.freeze({
+  URL_FIRST_ENABLED: true,   // try URL before magnet in the player
+  ACCEPT_LEGACY_V1: true,    // accept v1 magnet-only notes
+  WSS_TRACKERS: Object.freeze([
+    "wss://tracker.openwebtorrent.com",
+    "wss://tracker.btorrent.xyz",
+    "wss://tracker.webtorrent.dev",
+  ]),
+});
+
+const globalScope = typeof globalThis === "object" && globalThis ? globalThis : undefined;
+
+const runtimeFlags = (() => {
+  if (globalScope && typeof globalScope.__BITVID_RUNTIME_FLAGS__ === "object") {
+    return globalScope.__BITVID_RUNTIME_FLAGS__;
+  }
+  const initial = {
+    URL_FIRST_ENABLED: DEFAULT_FLAGS.URL_FIRST_ENABLED,
+    ACCEPT_LEGACY_V1: DEFAULT_FLAGS.ACCEPT_LEGACY_V1,
+    WSS_TRACKERS: [...DEFAULT_FLAGS.WSS_TRACKERS],
+  };
+  if (globalScope) {
+    globalScope.__BITVID_RUNTIME_FLAGS__ = initial;
+  }
+  return initial;
+})();
+
+function coerceBoolean(value, fallback) {
+  if (typeof value === "boolean") {
+    return value;
+  }
+  if (typeof value === "string") {
+    const normalized = value.trim().toLowerCase();
+    if (!normalized) {
+      return fallback;
+    }
+    if (["false", "0", "off", "no"].includes(normalized)) {
+      return false;
+    }
+    if (["true", "1", "on", "yes"].includes(normalized)) {
+      return true;
+    }
+  }
+  if (value == null) {
+    return fallback;
+  }
+  return Boolean(value);
+}
+
+function sanitizeTrackerList(candidate) {
+  const input = Array.isArray(candidate) ? candidate : DEFAULT_FLAGS.WSS_TRACKERS;
+  const seen = new Set();
+  const sanitized = [];
+
+  for (const tracker of input) {
+    if (typeof tracker !== "string") {
+      continue;
+    }
+    const trimmed = tracker.trim();
+    if (!trimmed) {
+      continue;
+    }
+    if (!/^wss:\/\//i.test(trimmed)) {
+      continue;
+    }
+    const normalized = trimmed.toLowerCase();
+    if (seen.has(normalized)) {
+      continue;
+    }
+    seen.add(normalized);
+    sanitized.push(trimmed);
+  }
+
+  if (!sanitized.length) {
+    return [...DEFAULT_FLAGS.WSS_TRACKERS];
+  }
+
+  return sanitized;
+}
+
+function freezeTrackers(list) {
+  return Object.freeze([...list]);
+}
+
+export let URL_FIRST_ENABLED = coerceBoolean(
+  runtimeFlags.URL_FIRST_ENABLED,
+  DEFAULT_FLAGS.URL_FIRST_ENABLED
+);
+
+export let ACCEPT_LEGACY_V1 = coerceBoolean(
+  runtimeFlags.ACCEPT_LEGACY_V1,
+  DEFAULT_FLAGS.ACCEPT_LEGACY_V1
+);
+
+export let WSS_TRACKERS = freezeTrackers(
+  sanitizeTrackerList(runtimeFlags.WSS_TRACKERS)
+);
+
+Object.defineProperty(runtimeFlags, "URL_FIRST_ENABLED", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    return URL_FIRST_ENABLED;
+  },
+  set(next) {
+    URL_FIRST_ENABLED = coerceBoolean(next, DEFAULT_FLAGS.URL_FIRST_ENABLED);
+  },
+});
+
+Object.defineProperty(runtimeFlags, "ACCEPT_LEGACY_V1", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    return ACCEPT_LEGACY_V1;
+  },
+  set(next) {
+    ACCEPT_LEGACY_V1 = coerceBoolean(next, DEFAULT_FLAGS.ACCEPT_LEGACY_V1);
+  },
+});
+
+Object.defineProperty(runtimeFlags, "WSS_TRACKERS", {
+  configurable: true,
+  enumerable: true,
+  get() {
+    return [...WSS_TRACKERS];
+  },
+  set(next) {
+    WSS_TRACKERS = freezeTrackers(sanitizeTrackerList(next));
+  },
+});
+
+// Ensure the runtime object reflects the sanitized defaults immediately.
+runtimeFlags.URL_FIRST_ENABLED = URL_FIRST_ENABLED;
+runtimeFlags.ACCEPT_LEGACY_V1 = ACCEPT_LEGACY_V1;
+runtimeFlags.WSS_TRACKERS = WSS_TRACKERS;
+
+export function setUrlFirstEnabled(next) {
+  runtimeFlags.URL_FIRST_ENABLED = next;
+  return URL_FIRST_ENABLED;
+}
+
+export function setAcceptLegacyV1(next) {
+  runtimeFlags.ACCEPT_LEGACY_V1 = next;
+  return ACCEPT_LEGACY_V1;
+}
+
+export function setWssTrackers(next) {
+  runtimeFlags.WSS_TRACKERS = next;
+  return WSS_TRACKERS;
+}
+
+export function resetRuntimeFlags() {
+  setUrlFirstEnabled(DEFAULT_FLAGS.URL_FIRST_ENABLED);
+  setAcceptLegacyV1(DEFAULT_FLAGS.ACCEPT_LEGACY_V1);
+  setWssTrackers(DEFAULT_FLAGS.WSS_TRACKERS);
+}
+
+export const RUNTIME_FLAGS = runtimeFlags;
+