diff --git a/src/app/api/_lib/http.ts b/src/app/api/_lib/http.ts
index 9ea3f55..453cc7a 100644
--- a/src/app/api/_lib/http.ts
+++ b/src/app/api/_lib/http.ts
@@ -22,9 +22,21 @@ export function notFound(error: string, detail?: string): NextResponse<ApiError>
   return apiError(404, error, detail);
 }
 
+/** One log line, whatever the message carries: no newline from a request can forge a second entry. */
+export function logLine(value: unknown): string {
+  const text = value instanceof Error ? `${value.name}: ${value.message}` : String(value);
+  // Newlines dropped outright, in the one form CodeQL recognises as a sanitizer.
+  return text
+    .replace(/\n/g, "")
+    .replace(/\r/g, "")
+    .replace(/[\u0000-\u001f\u007f\u2028\u2029]+/g, " ")
+    .slice(0, 2000);
+}
+
 /** Logs the real cause server-side and returns an opaque 500 to the client. */
 export function serverError(scope: string, cause: unknown): NextResponse<ApiError> {
-  console.error(`[api:${scope}]`, cause);
+  console.error(`[api:${logLine(scope)}] ${logLine(cause)}`);
+  if (cause instanceof Error && cause.stack !== undefined) console.error(logLine(cause.stack));
   return apiError(500, "Errore interno del server");
 }
 
diff --git a/src/app/layout.tsx b/src/app/layout.tsx
index e2bca7a..2a29119 100644
--- a/src/app/layout.tsx
+++ b/src/app/layout.tsx
@@ -9,6 +9,7 @@ import SkipLink from "@/components/SkipLink";
 import TopBar from "@/components/TopBar";
 import { LocaleProvider } from "@/lib/i18n";
 import { DEFAULT_LOCALE, LOCALE_ALIASES, LOCALES, RTL_LOCALES } from "@/lib/i18n/locale";
+import { jsLiteral } from "@/lib/inline-script";
 import { STORAGE_KEYS } from "@/lib/types";
 import "./globals.css";
 
@@ -48,15 +49,15 @@ export const viewport: Viewport = {
  * hydration. Getting `dir` right here matters: an Arabic reader would otherwise
  * see the whole layout jump sides once React mounts.
  */
-const BOOTSTRAP = `(function(){try{var raw=localStorage.getItem(${JSON.stringify(
+const BOOTSTRAP = `(function(){try{var raw=localStorage.getItem(${jsLiteral(
   STORAGE_KEYS.settings,
-)});var root=document.documentElement;var parsed=raw?JSON.parse(raw):null;var s=parsed&&typeof parsed==="object"?parsed:{};var theme=s.theme;if(theme==="dark"||theme==="light"){root.setAttribute("data-theme",theme);}else{root.removeAttribute("data-theme");}var known=${JSON.stringify(
+)});var root=document.documentElement;var parsed=raw?JSON.parse(raw):null;var s=parsed&&typeof parsed==="object"?parsed:{};var theme=s.theme;if(theme==="dark"||theme==="light"){root.setAttribute("data-theme",theme);}else{root.removeAttribute("data-theme");}var known=${jsLiteral(
   LOCALES,
-)};var alias=${JSON.stringify(
+)};var alias=${jsLiteral(
   LOCALE_ALIASES,
-)};var lang=s.language;if(known.indexOf(lang)<0){lang=null;var tags=(navigator.languages||[navigator.language||""]);for(var i=0;i<tags.length&&!lang;i++){var base=String(tags[i]).toLowerCase().split(/[-_]/)[0];if(known.indexOf(base)>=0)lang=base;else if(Object.prototype.hasOwnProperty.call(alias,base))lang=alias[base];}}lang=lang||${JSON.stringify(
+)};var lang=s.language;if(known.indexOf(lang)<0){lang=null;var tags=(navigator.languages||[navigator.language||""]);for(var i=0;i<tags.length&&!lang;i++){var base=String(tags[i]).toLowerCase().split(/[-_]/)[0];if(known.indexOf(base)>=0)lang=base;else if(Object.prototype.hasOwnProperty.call(alias,base))lang=alias[base];}}lang=lang||${jsLiteral(
   DEFAULT_LOCALE,
-)};root.lang=lang;root.dir=${JSON.stringify(
+)};root.lang=lang;root.dir=${jsLiteral(
   RTL_LOCALES,
 )}.indexOf(lang)>=0?"rtl":"ltr";}catch(e){}})();`;
 
diff --git a/src/components/map/LineDetailView.tsx b/src/components/map/LineDetailView.tsx
index db27491..57cad72 100644
--- a/src/components/map/LineDetailView.tsx
+++ b/src/components/map/LineDetailView.tsx
@@ -62,8 +62,7 @@ function safeDecode(encoded: string | null): Array<[number, number]> | null {
   return clean.length > 1 ? clean : null;
 }
 
-function ageLabel(feedTimestamp: number | null, fetchedAt: number | null, t: Dictionary): string {
-  if (fetchedAt === null) return "";
+function ageLabel(feedTimestamp: number | null, fetchedAt: number, t: Dictionary): string {
   if (feedTimestamp !== null && feedTimestamp > 0) {
     return t.line.dataAt(formatClock(feedTimestamp));
   }
diff --git a/src/lib/inline-script.ts b/src/lib/inline-script.ts
new file mode 100644
index 0000000..a860297
--- /dev/null
+++ b/src/lib/inline-script.ts
@@ -0,0 +1,12 @@
+/**
+ * JSON.stringify for values interpolated into an inline <script>. "<" and the
+ * two Unicode line separators are the characters that can end the tag or the
+ * statement early, so they go out as escapes; the result is still valid JSON
+ * and valid JavaScript.
+ */
+export function jsLiteral(value: unknown): string {
+  return JSON.stringify(value)
+    .replace(/</g, "\\u003c")
+    .replace(/\u2028/g, "\\u2028")
+    .replace(/\u2029/g, "\\u2029");
+}
diff --git a/tests/inline-script.test.ts b/tests/inline-script.test.ts
new file mode 100644
index 0000000..40898dd
--- /dev/null
+++ b/tests/inline-script.test.ts
@@ -0,0 +1,57 @@
+/**
+ * Values interpolated into the pre-paint <script> in layout.tsx. The parser
+ * closes a script element at the first "</script" it sees, before JavaScript
+ * ever runs, so the serialiser has to make that sequence impossible.
+ */
+
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+import { jsLiteral } from "@/lib/inline-script";
+import { logLine } from "@/app/api/_lib/http";
+
+function evaluate(source: string): unknown {
+  return new Function(`return ${source};`)();
+}
+
+test("a closing script tag inside a string cannot end the element", () => {
+  const out = jsLiteral("</script><script>alert(1)</script>");
+  assert.ok(!out.includes("</script"), out);
+  assert.ok(!out.includes("<"), out);
+  assert.equal(evaluate(out), "</script><script>alert(1)</script>");
+});
+
+test("the Unicode line separators are escaped, not emitted raw", () => {
+  const raw = "a\u2028b\u2029c";
+  const out = jsLiteral(raw);
+  assert.ok(!out.includes("\u2028") && !out.includes("\u2029"), out);
+  assert.equal(evaluate(out), raw);
+});
+
+test("the values the layout actually serialises round-trip unchanged", () => {
+  // The alias map is null-prototype in the source; the client gets a plain
+  // object, which is fine because the bootstrap reads it with hasOwnProperty.
+  const aliases = Object.assign(Object.create(null) as Record<string, string>, { fil: "tl", in: "id" });
+  const samples: Array<[unknown, unknown]> = [
+    ["probus.settings.v1", "probus.settings.v1"],
+    [["it", "en", "ar"], ["it", "en", "ar"]],
+    [aliases, { fil: "tl", in: "id" }],
+    [null, null],
+    [42, 42],
+  ];
+  for (const [value, expected] of samples) {
+    assert.deepEqual(evaluate(jsLiteral(value)), expected);
+  }
+});
+
+test("a log line cannot carry a newline from a request", () => {
+  const forged = "stop 123\n[api:auth] admin login ok\r\n";
+  const out = logLine(new Error(forged));
+  assert.ok(!/[\r\n]/.test(out), out);
+  assert.ok(out.startsWith("Error: stop 123"), out);
+});
+
+test("a log line is capped so a huge message cannot flood the log", () => {
+  assert.ok(logLine("x".repeat(10_000)).length <= 2000);
+  assert.equal(logLine(undefined), "undefined");
+});