diff --git a/apps/desktop/extensions/ai-sidebar/moshpit.js b/apps/desktop/extensions/ai-sidebar/moshpit.js
index 4dc3401..4a2078a 100644
--- a/apps/desktop/extensions/ai-sidebar/moshpit.js
+++ b/apps/desktop/extensions/ai-sidebar/moshpit.js
@@ -77,17 +77,45 @@ export function moshpitBypassHosts(config) {
   return hosts;
 }
 
+/**
+ * Bases that a previous version shipped as its default and that must not
+ * survive an upgrade.
+ *
+ * A stored value beats the shipped default — that is the point of storing one —
+ * but it makes a settings write indistinguishable from a deliberate choice. An
+ * install that ever persisted moshcoding.com as its parking base keeps pointing
+ * at a route that has never existed, through every future release, and no
+ * amount of shipping the right default fixes it.
+ *
+ * So a stored value that merely repeats a superseded default is treated as
+ * absent. A base someone actually chose is untouched, because it will not be on
+ * this list.
+ */
+const SUPERSEDED_BASES = new Set([
+  'https://moshcoding.com',   // parking, before /n/ existed
+  'http://moshcoding.com',
+]);
+
+/** A stored base, unless it is a stale default in disguise. */
+function storedBase(value, fallback) {
+  const base = String(value || '').trim().replace(/\/+$/, '');
+  if (!base || SUPERSEDED_BASES.has(base)) return fallback.replace(/\/+$/, '');
+  return base;
+}
+
 /** Read the settings the options page writes. */
 export async function moshpitConfig() {
   const { moshpitConfig: cfg } = await chrome.storage.local.get('moshpitConfig');
   return {
     mode: cfg?.mode === 'moshpit' ? 'moshpit' : 'clearnet',
-    registryBase: (cfg?.registryBase || DEFAULT_REGISTRY_BASE).replace(/\/+$/, ''),
-    consoleBase: (cfg?.consoleBase || DEFAULT_CONSOLE_BASE).replace(/\/+$/, ''),
-    parkingBase: (cfg?.parkingBase || DEFAULT_PARKING_BASE).replace(/\/+$/, ''),
+    registryBase: storedBase(cfg?.registryBase, DEFAULT_REGISTRY_BASE),
+    consoleBase: storedBase(cfg?.consoleBase, DEFAULT_CONSOLE_BASE),
+    parkingBase: storedBase(cfg?.parkingBase, DEFAULT_PARKING_BASE),
   };
 }
 
+export { SUPERSEDED_BASES, storedBase };
+
 /**
  * Split a hostname the way the registry does: exactly one label and one TLD.
  * Anything else (`a.b.c`, a bare `localhost`, an IP) is not a Moshpit name and
diff --git a/apps/desktop/extensions/ai-sidebar/moshpit.test.js b/apps/desktop/extensions/ai-sidebar/moshpit.test.js
index 3481b7c..8b74628 100644
--- a/apps/desktop/extensions/ai-sidebar/moshpit.test.js
+++ b/apps/desktop/extensions/ai-sidebar/moshpit.test.js
@@ -260,3 +260,34 @@ describe('parking sends a name somewhere that exists', () => {
     expect(js.parkingUrlFor('a b.eggs')).toBe('https://pit.moshcode.sh/n/a%20b.eggs');
   });
 });
+
+describe('a stored setting must not outlive the default it copied', () => {
+  it('ignores a base that is only a superseded default', () => {
+    // The bug this fixes: an install that ever persisted moshcoding.com keeps
+    // pointing at a route that has never existed, through every future
+    // release, and shipping the right default does nothing about it.
+    expect(js.storedBase('https://moshcoding.com', 'https://pit.moshcode.sh'))
+      .toBe('https://pit.moshcode.sh');
+    expect(js.storedBase('http://moshcoding.com', 'https://pit.moshcode.sh'))
+      .toBe('https://pit.moshcode.sh');
+    expect(js.storedBase('https://moshcoding.com/', 'https://pit.moshcode.sh'))
+      .toBe('https://pit.moshcode.sh', 'a trailing slash is the same value');
+  });
+
+  it('keeps a base someone actually chose', () => {
+    // Only stale defaults are on the list, so a real choice is never on it.
+    expect(js.storedBase('https://my.pit', 'https://pit.moshcode.sh')).toBe('https://my.pit');
+    expect(js.storedBase('https://my.pit/', 'https://pit.moshcode.sh')).toBe('https://my.pit');
+  });
+
+  it('falls through to the shipped default when nothing is stored', () => {
+    for (const empty of ['', '   ', null, undefined]) {
+      expect(js.storedBase(empty, 'https://pit.moshcode.sh')).toBe('https://pit.moshcode.sh');
+    }
+  });
+
+  it('lists the base that caused this', () => {
+    expect(js.SUPERSEDED_BASES.has('https://moshcoding.com')).toBe(true);
+    expect(js.SUPERSEDED_BASES.has('https://pit.moshcode.sh')).toBe(false);
+  });
+});
diff --git a/apps/desktop/extensions/ai-sidebar/options.js b/apps/desktop/extensions/ai-sidebar/options.js
index 8ffe2dc..33b05e2 100644
--- a/apps/desktop/extensions/ai-sidebar/options.js
+++ b/apps/desktop/extensions/ai-sidebar/options.js
@@ -388,12 +388,20 @@ el("syncUrl").addEventListener("change", async () => {
   });
 });
 async function saveMoshpit() {
-  await chrome.storage.local.set({
-    moshpitConfig: {
-      mode: el("moshpitMode").value === "moshpit" ? "moshpit" : "clearnet",
-      registryBase: el("moshpitRegistry").value.trim(),
-    },
-  });
+  // Only what was actually filled in. Writing an empty field would store "",
+  // and a stored value — even an empty one — is a decision this code then has
+  // to keep honouring. Leaving a field out is what lets it keep following
+  // whatever the shipped default becomes.
+  const registryBase = el("moshpitRegistry").value.trim();
+  const previous = (await chrome.storage.local.get("moshpitConfig")).moshpitConfig || {};
+  const next = {
+    ...previous,
+    mode: el("moshpitMode").value === "moshpit" ? "moshpit" : "clearnet",
+  };
+  if (registryBase) next.registryBase = registryBase;
+  else delete next.registryBase;
+
+  await chrome.storage.local.set({ moshpitConfig: next });
   flash(
     "savedMoshpit",
     el("moshpitMode").value === "moshpit"