diff --git a/packages/core/src/database/migration/20260805200742_import_legacy_credentials.ts b/packages/core/src/database/migration/20260805200742_import_legacy_credentials.ts
index 3345500b97f2..0aa348713b80 100644
--- a/packages/core/src/database/migration/20260805200742_import_legacy_credentials.ts
+++ b/packages/core/src/database/migration/20260805200742_import_legacy_credentials.ts
@@ -80,7 +80,17 @@ export function importLegacyCredentials(tx: Parameters<DatabaseMigration.Migrati
 
       const credential =
         value.type === "api"
-          ? Credential.Key.make({ type: "key", key: value.key, metadata: value.metadata })
+          ? Credential.Key.make({
+              type: "key",
+              key: value.key,
+              // A legacy `server` value is file-controlled text and no first-party
+              // writer sets one on a key credential. Carrying it through would let
+              // an imported file point the stored key at an arbitrary host, so drop
+              // it here: imported keys use the configured default server.
+              metadata: value.metadata
+                ? Object.fromEntries(Object.entries(value.metadata).filter(([name]) => name !== "server"))
+                : undefined,
+            })
           : value.type === "wellknown"
             ? Credential.Key.make({ type: "key", key: value.token })
             : Credential.OAuth.make({
diff --git a/packages/core/src/plugin/provider/mars.ts b/packages/core/src/plugin/provider/mars.ts
index 4d3a304c2ca3..3886bd9b0090 100644
--- a/packages/core/src/plugin/provider/mars.ts
+++ b/packages/core/src/plugin/provider/mars.ts
@@ -9,7 +9,22 @@ import { Credential } from "../../credential.js"
 import { Integration } from "../../integration.js"
 import { Provider } from "../../provider.js"
 
-const defaultServer = (process.env.MARSAI_URL ?? "https://marsai.click").replace(/\/+$/, "").replace(/\/v1$/i, "")
+const fallbackServer = "https://marsai.click"
+
+function normalizeServer(raw: string) {
+  try {
+    const url = new URL(raw)
+    const loopback = url.hostname === "localhost" || url.hostname === "127.0.0.1" || url.hostname === "::1" || url.hostname === "[::1]"
+    if (url.protocol !== "https:" && !(url.protocol === "http:" && loopback)) return undefined
+    return `${url.origin}${url.pathname.replace(/\/+$/, "").replace(/\/v1$/i, "")}`
+  } catch {
+    return undefined
+  }
+}
+
+// MARSAI_URL gets the same check as a credential server. Without it the
+// fallback itself could point the key at a remote host over plaintext http.
+const defaultServer = (process.env.MARSAI_URL ? normalizeServer(process.env.MARSAI_URL) : undefined) ?? fallbackServer
 const integrationID = Integration.ID.make("marsai")
 const providerID = Provider.ID.make("marsai")
 const ModelsResponse = Schema.Struct({
@@ -27,7 +42,9 @@ const ModelsResponse = Schema.Struct({
 })
 
 function serverUrl(value: Credential.Key) {
-  return typeof value.metadata?.server === "string" ? value.metadata.server : defaultServer
+  const raw = value.metadata?.server
+  if (typeof raw !== "string") return defaultServer
+  return normalizeServer(raw) ?? defaultServer
 }
 
 function modelsFor(http: HttpClient.HttpClient, value: Credential.Key) {