diff --git a/src/frontend/web/von_interface/static/js/domUtils.js b/src/frontend/web/von_interface/static/js/domUtils.js
index e19ef7ce..85963eb0 100644
--- a/src/frontend/web/von_interface/static/js/domUtils.js
+++ b/src/frontend/web/von_interface/static/js/domUtils.js
@@ -1,3 +1,4 @@
+import './utils/footerPreferences.js';
 import { openSettingsTabAndFocus } from './utils/settingsNavigation.js';
 import { parseStoredContextValue } from './utils/runtimeIdentityBootstrap.js';
 import { applyLocalModelPreferenceOverlay, getEffectiveLocalModelPreference } from './utils/localModelPreferences.js';
diff --git a/src/frontend/web/von_interface/static/js/settingsPage.js b/src/frontend/web/von_interface/static/js/settingsPage.js
index 0aa27541..81f59579 100644
--- a/src/frontend/web/von_interface/static/js/settingsPage.js
+++ b/src/frontend/web/von_interface/static/js/settingsPage.js
@@ -1,3 +1,4 @@
+import { resetFooterPreferences } from './utils/footerPreferences.js';
 import { modelSettingsRequest, renderModelInventory } from './modelInventory.js';
 import { profileButton } from './components/participantProfile.js';
 import { CONVERSATION_LAYOUT_KEY, CONVERSATION_LAYOUT_KEYS, CONVERSATION_TRAY_HOVER_KEY, loadConversationLayoutPreferences, normaliseConversationLayout, saveConversationLayoutPreference } from './utils/conversationLayoutPreferences.js';
@@ -222,10 +223,12 @@ const SETTINGS_CONCERN_CONFIG = Object.freeze({
   conversations: Object.freeze({
     sectionIds: Object.freeze([
       'conversation-history-settings',
+      'footer-settings',
       'speech-settings',
     ]),
     anchorIds: Object.freeze([
       'conversation-history-settings',
+      'footer-settings',
       'speech-settings',
     ]),
   }),
@@ -5548,6 +5551,7 @@ document.getElementById('refreshDeprecationMetricsButton')?.addEventListener('cl
 // Reset local preferences button
 document.getElementById('resetLocalPrefsButton')?.addEventListener('click', () => {
   try {
+    resetFooterPreferences();
     setStoredJson(LS_ORG_KEY, null);
     setSessionScopedNamespace(null);
     localStorage.removeItem(LS_LANG_KEY);
diff --git a/src/frontend/web/von_interface/static/js/utils/conversationRuntimeCost.js b/src/frontend/web/von_interface/static/js/utils/conversationRuntimeCost.js
index 4a55ffa7..6043f6ab 100644
--- a/src/frontend/web/von_interface/static/js/utils/conversationRuntimeCost.js
+++ b/src/frontend/web/von_interface/static/js/utils/conversationRuntimeCost.js
@@ -55,18 +55,18 @@ function mergeCost(base, overlay) {
 
 function formatAmount(amount, currency) {
   if (amount === null) return '';
-  const roundToCents = amount > 0.02;
+  const belowCent = amount > 0 && amount < 0.01;
+  const displayedAmount = belowCent ? 0.01 : amount;
+  let formatted;
   try {
-    return new Intl.NumberFormat('en-NZ', {
-      style: 'currency',
-      currency,
-      minimumFractionDigits: roundToCents ? 2 : (amount > 0 && amount < 0.01 ? 4 : 2),
-      maximumFractionDigits: roundToCents ? 2 : 6,
-    }).format(amount);
+    formatted = new Intl.NumberFormat('en-NZ', {
+      style: 'currency', currency,
+      minimumFractionDigits: 2, maximumFractionDigits: 2,
+    }).format(displayedAmount);
   } catch (_) {
-    const fractionDigits = roundToCents ? 2 : 6;
-    return `${currency === 'USD' ? 'US$' : `${currency} `}${amount.toFixed(fractionDigits)}`;
+    formatted = `${currency === 'USD' ? 'US$' : `${currency} `}${displayedAmount.toFixed(2)}`;
   }
+  return `${belowCent ? '< ' : ''}${formatted}`;
 }
 
 function describeCost(cost, { compact = false } = {}) {
diff --git a/src/frontend/web/von_interface/static/js/utils/footerPreferences.js b/src/frontend/web/von_interface/static/js/utils/footerPreferences.js
new file mode 100644
index 00000000..84957882
--- /dev/null
+++ b/src/frontend/web/von_interface/static/js/utils/footerPreferences.js
@@ -0,0 +1,84 @@
+// Presentation preferences are browser-local, like conversation layout choices.
+export const FOOTER_PREFERENCES_KEY = 'von:footerVisibility';
+export const FOOTER_ITEMS = Object.freeze({
+  model: ['Model', true],
+  conversationCost: ['Conversation cost estimate', true],
+  user: ['User', true],
+  organisation: ['Organisation', true],
+  language: ['Language', false],
+  database: ['Database and connection details', false],
+  uptime: ['Server uptime', false],
+  runtimeCost: ['Cost estimate since server restart', false],
+  build: ['Build revision and timestamp', false],
+  diagnostics: ['Expert process and indexing details (when available)', false],
+});
+
+let fallback = null;
+export function loadFooterPreferences() {
+  let stored = fallback;
+  if (!stored) {
+    try { stored = JSON.parse(localStorage.getItem(FOOTER_PREFERENCES_KEY)); } catch (_) { }
+  }
+  return Object.fromEntries(Object.entries(FOOTER_ITEMS).map(([key, [, defaultValue]]) =>
+    [key, typeof stored?.[key] === 'boolean' ? stored[key] : defaultValue]));
+}
+
+export function applyFooterPreferences() {
+  const preferences = loadFooterPreferences();
+  for (const [key, value] of Object.entries(preferences)) {
+    document.documentElement.setAttribute(`data-footer-${key.toLowerCase()}`, String(value));
+    const control = document.querySelector(`[data-footer-preference="${key}"]`);
+    if (control) control.checked = value;
+  }
+}
+
+export function saveFooterPreference(key, value) {
+  if (!Object.hasOwn(FOOTER_ITEMS, key)) return;
+  const preferences = { ...loadFooterPreferences(), [key]: Boolean(value) };
+  try {
+    localStorage.setItem(FOOTER_PREFERENCES_KEY, JSON.stringify(preferences));
+    fallback = null;
+  } catch (_) { fallback = preferences; }
+  applyFooterPreferences();
+  // Embedded Settings shares localStorage but does not get a storage event in
+  // the writing window. Notify its parent without reloading footer data.
+  try { window.parent.dispatchEvent(new CustomEvent('von-footer-preferences-changed')); } catch (_) { }
+}
+
+export function resetFooterPreferences() {
+  try {
+    localStorage.removeItem(FOOTER_PREFERENCES_KEY);
+    fallback = null;
+  } catch (_) {
+    fallback = Object.fromEntries(Object.entries(FOOTER_ITEMS).map(([key, [, value]]) => [key, value]));
+  }
+  applyFooterPreferences();
+  try { window.parent.dispatchEvent(new CustomEvent('von-footer-preferences-changed')); } catch (_) { }
+}
+
+export function mountFooterPreferences() {
+  const container = document.getElementById('footerVisibilitySettings');
+  if (container && !container.children.length) {
+    for (const [key, [name]] of Object.entries(FOOTER_ITEMS)) {
+      const label = document.createElement('label');
+      const input = document.createElement('input');
+      input.type = 'checkbox';
+      input.dataset.footerPreference = key;
+      input.addEventListener('change', () => saveFooterPreference(key, input.checked));
+      label.append(input, document.createTextNode(` ${name}`));
+      container.append(label);
+    }
+  }
+  applyFooterPreferences();
+}
+
+window.addEventListener('storage', (event) => {
+  if (event.key === FOOTER_PREFERENCES_KEY || event.key === null) applyFooterPreferences();
+});
+window.addEventListener('von-footer-preferences-changed', applyFooterPreferences);
+applyFooterPreferences();
+if (document.readyState === 'loading') {
+  document.addEventListener('DOMContentLoaded', mountFooterPreferences);
+} else {
+  mountFooterPreferences();
+}
diff --git a/src/frontend/web/von_interface/static/styles.css b/src/frontend/web/von_interface/static/styles.css
index 092b7541..5c2e86e5 100644
--- a/src/frontend/web/von_interface/static/styles.css
+++ b/src/frontend/web/von_interface/static/styles.css
@@ -6566,7 +6566,7 @@ footer {
     left: 0;
     right: 0;
     min-height: 40px;
-    /* Allow footer to grow if content wraps */
+    /* Keep footer information on one scrollable row. */
     margin-top: 0;
     /* REMOVED: margin-top as it's fixed */
     font-size: 0.8rem;
@@ -6592,7 +6592,7 @@ footer {
     left: 0;
     right: 0;
     min-height: 40px;
-    /* Allow footer to grow if content wraps */
+    /* Keep footer information on one scrollable row. */
     display: flex;
     align-items: center;
     justify-content: space-between;
@@ -13360,12 +13360,6 @@ button.prompt-vontology-cartouche {
     color: #991b1b;
 }
 
-@media (max-width: 760px) {
-    .server-build-info {
-        display: none;
-    }
-}
-
 .footer-separator {
     margin: 0 4px;
     opacity: 0.5;
@@ -18639,3 +18633,60 @@ body.settings-body {
     min-height: 44px;
     padding: 4px;
 }
+
+/* Footer presentation preferences also apply to the narrow-screen details panel. */
+.footer-container,
+.mobile-footer-details-panel .footer-container {
+    flex-direction: row;
+    flex-wrap: nowrap;
+    justify-content: flex-start;
+    overflow-x: auto;
+    white-space: nowrap;
+    backdrop-filter: none;
+    -webkit-backdrop-filter: none;
+}
+.footer-container > *,
+.footer-container .footer-segment,
+.footer-container .db-conn-badge { flex: 0 0 auto; }
+.footer-container .footer-info,
+.mobile-footer-details-panel .footer-info,
+.footer-container .pid-indicator {
+    display: flex;
+    flex-direction: row;
+    align-items: center;
+    gap: 12px;
+    white-space: nowrap;
+}
+.footer-container .footer-separator { display: none; }
+.footer-container .footer-info:empty,
+.footer-container .pid-indicator:empty { display: none; }
+.footer-visibility-settings { display: grid; gap: 10px; }
+.footer-visibility-settings label { display: flex; align-items: center; gap: 6px; }
+/* Fixed panels escape the scroll container's clipping boundary. */
+.footer-container .footer-org-menu,
+.footer-container .conversation-runtime-cost-details {
+    position: fixed;
+    left: 12px;
+    right: auto;
+    bottom: var(--von-fixed-footer-clearance, 64px);
+    white-space: normal;
+    max-height: min(420px, 60vh);
+    overflow-y: auto;
+}
+.mobile-footer-details-panel .footer-container .conversation-runtime-cost-details {
+    top: calc(var(--von-fixed-shell-height, 60px) + 72px);
+    bottom: auto;
+}
+html[data-footer-model="false"] .footer-container .conversation-model-controls { display: none; }
+html[data-footer-conversationcost="false"] .footer-container #modelInfoFooter > .conversation-runtime-cost-segment { display: none; }
+html[data-footer-user="false"] .footer-container .footer-user-segment { display: none; }
+html[data-footer-organisation="false"] .footer-container .footer-org-switcher { display: none; }
+html[data-footer-language="false"] .footer-container #languageIndicator { display: none; }
+html[data-footer-database="false"] .footer-container .db-conn-badge { display: none; }
+html[data-footer-uptime="false"] .footer-container #serverUptimeInfo { display: none; }
+html[data-footer-runtimecost="false"] .footer-container #serverRuntimeCostInfo { display: none; }
+html[data-footer-build="false"] .footer-container #serverBuildInfo { display: none; }
+html[data-footer-diagnostics="false"] .footer-container #serverPidFooter { display: none; }
+html[data-footer-uptime="false"][data-footer-runtimecost="false"][data-footer-build="false"] #serverUptimeFooter { display: none; }
+
+.footer-container [hidden] { display: none !important; }
diff --git a/src/frontend/web/von_interface/templates/settings_tab.html b/src/frontend/web/von_interface/templates/settings_tab.html
index ae700ffa..157eb63c 100644
--- a/src/frontend/web/von_interface/templates/settings_tab.html
+++ b/src/frontend/web/von_interface/templates/settings_tab.html
@@ -121,6 +121,13 @@ <h2>Current Organisation Configuration</h2>
             </div>
         </section>
 
+        <section id="footer-settings" data-settings-concern="conversations">
+            <h2>Footer</h2>
+            <p class="settings-note">Choose what appears in the footer. These preferences are saved in this browser.
+                Extra information scrolls horizontally.</p>
+            <div id="footerVisibilitySettings" class="footer-visibility-settings"></div>
+        </section>
+
         <section id="conversation-history-settings" data-settings-concern="conversations">
             <h2>Conversations</h2>
             <p class="settings-note">These preferences are stored in this browser and control which conversations appear
diff --git a/src/frontend/web/von_interface/templates/von_interface.html b/src/frontend/web/von_interface/templates/von_interface.html
index eeafaa52..cdcfafb3 100644
--- a/src/frontend/web/von_interface/templates/von_interface.html
+++ b/src/frontend/web/von_interface/templates/von_interface.html
@@ -188,13 +188,13 @@ <h1 class="global-organisation-title" title="Current organisation">
   </div>
 
   <!-- Footer for Model Info -->
-  <div class="footer-container">
+  <div class="footer-container" tabindex="0" role="region" aria-label="Footer information">
     <p id="modelInfoFooter" class="footer-info">
 
     </p>
     <p id="languageIndicator" class="language-indicator">🌐 en-NZ</p>
     <p id="serverUptimeFooter" class="pid-indicator" title="Process uptime">
-      <span class="footer-label">Uptime:</span> <span id="serverUptimeValue" title="Process uptime">-</span>
+      <span id="serverUptimeInfo"><span class="footer-label">Uptime:</span> <span id="serverUptimeValue" title="Process uptime">-</span></span>
       <span id="serverRuntimeCostInfo" class="conversation-runtime-cost-segment server-runtime-cost-segment" hidden>
         <span class="footer-separator">|</span>
         <button id="serverRuntimeCostButton"
diff --git a/tests/browser/footerPresentation.cjs b/tests/browser/footerPresentation.cjs
new file mode 100644
index 00000000..d8945f8c
--- /dev/null
+++ b/tests/browser/footerPresentation.cjs
@@ -0,0 +1,104 @@
+// Candidate-source browser fixture: no backend, credentials, or model requests.
+const { chromium, expect } = require('@playwright/test');
+const fs = require('node:fs');
+const path = require('node:path');
+const http = require('node:http');
+const root = path.resolve(__dirname, '../../src/frontend/web/von_interface');
+const template = fs.readFileSync(path.join(root, 'templates/von_interface.html'), 'utf8');
+const footer = template.slice(template.indexOf('  <!-- Footer for Model Info -->'), template.indexOf('  <!-- RAG Status Modal -->')).replace(/{%.*?%}/g, '');
+const settings = fs.readFileSync(path.join(root, 'templates/settings_tab.html'), 'utf8').match(/<section id="footer-settings"[\s\S]*?<\/section>/)[0];
+const html = `<link rel="stylesheet" href="/static/styles.css">${settings}${footer}<script type="module">
+import { setModelInfoFooterText } from '/static/js/domUtils.js';
+import { mountFooterPreferences } from '/static/js/utils/footerPreferences.js';
+localStorage.setItem('von_current_user', JSON.stringify({name:'Footer Test User', concept_id:'#V#footer_test'}));
+const summary = { estimated_cost: {status:'estimated', currency:'USD', amount:0.014889} };
+window.__vonConversationRuntimeCostSnapshot = {context:{conversation_session_id:'footer-fixture'}, baseline:{conversation:summary,since_restart:summary}};
+await setModelInfoFooterText();
+mountFooterPreferences();
+document.querySelector('#serverBuildInfo').hidden = false;
+document.querySelector('#serverBuildValue').textContent = 'abcdef123456 2026-09-13T16:40:50.344900+00:00';
+window.fixtureReady = true;
+</script>`;
+const server = http.createServer((req, res) => {
+    if (req.url === '/') { res.setHeader('Content-Type', 'text/html'); return res.end(html); }
+    if (!req.url.startsWith('/static/') || req.url.includes('..')) { res.writeHead(404); return res.end(); }
+    const file = path.join(root, req.url.split('?')[0]);
+    res.setHeader('Content-Type', file.endsWith('.js') ? 'text/javascript' : 'text/css');
+    try { res.end(fs.readFileSync(file)); } catch { res.writeHead(404); res.end(); }
+});
+(async () => {
+    await new Promise(resolve => server.listen(0, '127.0.0.1', resolve));
+    const browser = await chromium.launch({headless:true});
+    const page = await browser.newPage();
+    const errors = [];
+    page.on('pageerror', error => errors.push(error.message));
+    await page.route('**/api/**', route => {
+        const url = route.request().url();
+        let body = {};
+        if (/\/settings\/?$/.test(url)) body = {active_llm:{model:'gpt-6-astra',provider:'openai'}};
+        if (url.includes('/auth/status')) body = {authenticated:true,email:'footer@example.test'};
+        if (url.includes('capability-index/status')) body = {ready:true,status:'ready'};
+        if (url.includes('my_organisations')) body = {organisations:[{concept_id:'#V#footer_org',name:'Footer Fixture Organisation',role:'member'}]};
+        return route.fulfill({json:body});
+    });
+    const evidence = [];
+    try {
+        await page.goto(`http://127.0.0.1:${server.address().port}`);
+        await page.waitForFunction(() => window.fixtureReady);
+        await expect(page.locator('#serverUptimeFooter')).toBeHidden();
+        await expect(page.locator('#languageIndicator')).toBeHidden();
+        await expect(page.locator('[data-cost-scope="conversation"]')).toContainText('US$0.01');
+        for (const checkbox of await page.locator('[data-footer-preference]').all()) await checkbox.check();
+        await expect(page.locator('#serverBuildInfo')).toBeVisible();
+        await page.reload();
+        await page.waitForFunction(() => window.fixtureReady);
+        await expect(page.locator('[data-footer-preference="build"]')).toBeChecked();
+        for (const width of [1297, 493, 320]) {
+            await page.setViewportSize({width,height:800});
+            await expect(page.locator('#serverBuildInfo')).toBeVisible();
+            const measurement = await page.locator('.footer-container').evaluate(el => {
+                const items = [...el.children].filter(child => getComputedStyle(child).display !== 'none');
+                const centres = items.map(child => { const r = child.getBoundingClientRect(); return r.y+r.height/2; });
+                el.scrollLeft = el.scrollWidth;
+                return {width:innerWidth, clientWidth:el.clientWidth, scrollWidth:el.scrollWidth, scrollLeft:el.scrollLeft, centreSpread:Math.max(...centres)-Math.min(...centres), height:el.getBoundingClientRect().height};
+            });
+            expect(measurement.centreSpread).toBeLessThan(2);
+            if (width <= 493) expect(measurement.scrollLeft).toBeGreaterThan(0);
+            evidence.push(measurement);
+            await page.locator('.footer-container').evaluate(el => { el.scrollLeft = 0; });
+            await page.locator('[data-cost-scope="conversation"]').click();
+            const panel = page.locator('#modelInfoFooter .conversation-runtime-cost-details');
+            await expect(panel).toBeVisible();
+            const box = await panel.boundingBox();
+            expect(box.x).toBeGreaterThanOrEqual(0);
+            expect(box.x + box.width).toBeLessThanOrEqual(width);
+            expect(await panel.evaluate(el => {const r=el.getBoundingClientRect();return el.contains(document.elementFromPoint(r.x+5,r.y+5));})).toBe(true);
+            await page.locator('[data-cost-scope="conversation"]').click();
+        }
+        await page.locator('.footer-org-menu-trigger').click();
+        const organisationMenu = page.locator('.footer-org-menu');
+        await expect(organisationMenu).toBeVisible();
+        expect(await organisationMenu.evaluate(el => {const r=el.getBoundingClientRect();return el.contains(document.elementFromPoint(r.x+5,r.y+5));})).toBe(true);
+        await page.locator('.footer-org-menu-trigger').click();
+        // The responsive shell reparents the same footer into its details panel.
+        await page.evaluate(() => {
+            const panel = document.createElement('div');
+            panel.className = 'mobile-footer-details-panel';
+            document.body.append(panel);
+            panel.append(document.querySelector('.footer-container'));
+        });
+        const mobile = await page.locator('.footer-container').evaluate(el => ({height:el.getBoundingClientRect().height, width:el.clientWidth, scrollWidth:el.scrollWidth, direction:getComputedStyle(el).flexDirection}));
+        expect(mobile.direction).toBe('row');
+        expect(mobile.scrollWidth).toBeGreaterThan(mobile.width);
+        expect(mobile.height).toBeLessThan(80);
+        evidence.push({mobileDetails:mobile});
+        await page.locator('[data-footer-preference="conversationCost"]').uncheck();
+        await expect(page.locator('[data-cost-scope="conversation"]')).toBeHidden();
+        expect(errors).toEqual([]);
+        const output = process.argv[2] || '.run/footer-presentation';
+        fs.mkdirSync(output,{recursive:true});
+        await page.screenshot({path:path.join(output,'footer-320.png'),fullPage:true});
+        fs.writeFileSync(path.join(output,'measurements.json'), JSON.stringify({fixture:'candidate source with mocked API reads',evidence},null,2));
+        console.log(JSON.stringify(evidence));
+    } finally { await browser.close(); server.close(); }
+})().catch(error => { console.error(error); server.close(); process.exitCode=1; });
diff --git a/tests/frontend/footerBuildInfo.test.js b/tests/frontend/footerBuildInfo.test.js
index d023f952..6c30f256 100644
--- a/tests/frontend/footerBuildInfo.test.js
+++ b/tests/frontend/footerBuildInfo.test.js
@@ -49,13 +49,4 @@ describe('footer build information', () => {
         expect(mainSource).toContain('commitTimestamp ? `Commit time ${commitTimestamp}` : null');
     });
 
-    test('hides build information, but not uptime, below the footer crowding threshold', () => {
-        expect(styles).toMatch(
-            /@media \(max-width:\s*760px\)\s*\{\s*\.server-build-info\s*\{\s*display:\s*none;/
-        );
-        expect(styles).not.toMatch(
-            /@media \(max-width:\s*760px\)[\s\S]*?#serverUptimeFooter\s*\{\s*display:\s*none;/
-        );
-        expect(styles).toMatch(/#serverUptimeFooter\s*\{\s*white-space:\s*nowrap;/);
-    });
 });
diff --git a/tests/frontend/footerPreferences.test.js b/tests/frontend/footerPreferences.test.js
new file mode 100644
index 00000000..c3cf555e
--- /dev/null
+++ b/tests/frontend/footerPreferences.test.js
@@ -0,0 +1,47 @@
+const { FOOTER_ITEMS, FOOTER_PREFERENCES_KEY, loadFooterPreferences, mountFooterPreferences, resetFooterPreferences } = require('../../src/frontend/web/von_interface/static/js/utils/footerPreferences.js');
+const { formatConversationRuntimeCostFooter } = require('../../src/frontend/web/von_interface/static/js/utils/conversationRuntimeCost.js');
+
+beforeEach(() => { localStorage.clear(); document.body.innerHTML = '<div id="footerVisibilitySettings"></div>'; });
+
+test('footer controls persist choices and restore them after remounting', () => {
+    mountFooterPreferences();
+    expect(document.querySelectorAll('input')).toHaveLength(Object.keys(FOOTER_ITEMS).length);
+    expect(loadFooterPreferences()).toMatchObject({ model: true, user: true, organisation: true, build: false, runtimeCost: false });
+    document.querySelector('[data-footer-preference="build"]').click();
+    expect(JSON.parse(localStorage.getItem(FOOTER_PREFERENCES_KEY)).build).toBe(true);
+    document.getElementById('footerVisibilitySettings').replaceChildren();
+    mountFooterPreferences();
+    expect(document.querySelector('[data-footer-preference="build"]').checked).toBe(true);
+    expect(document.documentElement.getAttribute('data-footer-build')).toBe('true');
+});
+
+test('malformed and non-boolean saved preferences use defaults', () => {
+    localStorage.setItem(FOOTER_PREFERENCES_KEY, '{');
+    expect(loadFooterPreferences().model).toBe(true);
+    localStorage.setItem(FOOTER_PREFERENCES_KEY, JSON.stringify({ build: 'false', model: false }));
+    expect(loadFooterPreferences()).toMatchObject({ build: false, model: false });
+});
+
+test.each([[0.014889, 'US$0.01'], [0.0199, 'US$0.02'], [0.000012, '< US$0.01'], [0, 'US$0.00'], [12.3456, 'US$12.35']])('both footer costs consistently format %s', (amount, expected) => {
+    const summary = { estimated_cost: { status: 'estimated', currency: 'USD', amount } };
+    const result = formatConversationRuntimeCostFooter({ context: { conversation_session_id: 'fixture' }, baseline: { conversation: summary, since_restart: summary } });
+    expect(result.desktopText).toBe(`Est. cost: Chat ${expected}`);
+    expect(result.runtimeText).toBe(`Est. ${expected}`);
+});
+
+test('unavailable cost is not rendered as a zero', () => {
+    const result = formatConversationRuntimeCostFooter({ context: { conversation_session_id: 'fixture' }, baseline: { conversation: {} } });
+    expect(result.desktopText).toContain('unavailable');
+    expect(result.desktopText).not.toContain('0.00');
+});
+
+
+test('reset restores the default controls and observes later saved changes', () => {
+    mountFooterPreferences();
+    document.querySelector('[data-footer-preference="build"]').click();
+    resetFooterPreferences();
+    expect(document.querySelector('[data-footer-preference="build"]').checked).toBe(false);
+    localStorage.setItem(FOOTER_PREFERENCES_KEY, JSON.stringify({ build: true }));
+    window.dispatchEvent(new StorageEvent('storage', { key: FOOTER_PREFERENCES_KEY }));
+    expect(document.querySelector('[data-footer-preference="build"]').checked).toBe(true);
+});