diff --git a/src/lib/serverpulsFormat.js b/src/lib/serverpulsFormat.js
index 082a296..984f92c 100644
--- a/src/lib/serverpulsFormat.js
+++ b/src/lib/serverpulsFormat.js
@@ -57,6 +57,23 @@ export function formatNumber(v, digits = 2) {
   return nf(digits).format(v)
 }
 
+// Richtung eines Kachel-Deltas: unter 1e-9 gilt als unverändert (flat).
+export function deltaDir(d) {
+  return Math.abs(d) < 1e-9 ? 'flat' : d > 0 ? 'up' : 'down'
+}
+
+// Vorzeichen zur Richtung: '+', Minuszeichen U+2212, bei flat nichts.
+export function deltaSign(dir) {
+  return dir === 'up' ? '+' : dir === 'down' ? '−' : ''
+}
+
+// Badge-Ton je Warnstufe; liest nur das erste Argument (.map(levelTone) reicht Index und Array mit).
+const LEVEL_TONES = { ok: 'ok', medium: 'warn', critical: 'danger' }
+
+export function levelTone(level) {
+  return Object.prototype.hasOwnProperty.call(LEVEL_TONES, level) ? LEVEL_TONES[level] : 'muted'
+}
+
 // --- Zeitachsen (Europe/Berlin, de-DE) ---
 const TZ = 'Europe/Berlin'
 const dtf = (opts) => new Intl.DateTimeFormat('de-DE', { timeZone: TZ, ...opts })
diff --git a/tests/unit/serverpulsFormat.test.mjs b/tests/unit/serverpulsFormat.test.mjs
index 8baae31..0379f44 100644
--- a/tests/unit/serverpulsFormat.test.mjs
+++ b/tests/unit/serverpulsFormat.test.mjs
@@ -2,7 +2,7 @@ import test from 'node:test'
 import assert from 'node:assert/strict'
 import { loadModule } from './load.mjs'
 
-const { formatBytes, formatDelta, ageLabel, usedPct, axisTimeKind, formatAxisTick, formatLegendTime } = await loadModule('src/lib/serverpulsFormat.js')
+const { formatBytes, formatDelta, deltaDir, deltaSign, levelTone, ageLabel, usedPct, axisTimeKind, formatAxisTick, formatLegendTime } = await loadModule('src/lib/serverpulsFormat.js')
 
 test('formatBytes: de-DE, Basis 1024', () => {
   assert.equal(formatBytes(1288490189), '1,2 GB')
@@ -20,6 +20,19 @@ test('formatDelta', () => {
   assert.equal(formatDelta(0).dir, 'flat')
 })
 
+test('deltaDir und deltaSign: Richtung und Vorzeichen der Kachel-Deltas', () => {
+  assert.deepEqual([deltaDir(0), deltaDir(5e-10), deltaDir(-5e-10)], ['flat', 'flat', 'flat'])
+  assert.equal(deltaDir(0.4), 'up')
+  assert.equal(deltaDir(-0.4), 'down')
+  assert.deepEqual([deltaSign('up'), deltaSign('down'), deltaSign('flat')], ['+', '−', ''])
+})
+
+test('levelTone: Badge-Ton je Stufe', () => {
+  assert.deepEqual(['ok', 'medium', 'critical'].map(levelTone), ['ok', 'warn', 'danger'])
+  assert.deepEqual([levelTone('low'), levelTone(undefined), levelTone('x')], ['muted', 'muted', 'muted'])
+  assert.deepEqual([levelTone('constructor'), levelTone('toString'), levelTone('__proto__')], ['muted', 'muted', 'muted'])
+})
+
 test('ageLabel: stale ab > 15 Min.', () => {
   const now = 1_000_000_000_000
   const a16 = ageLabel(now - 16 * 60000, now)