diff --git a/docs/_javascript/preset_test.js b/docs/_javascript/preset_test.js
new file mode 100644
index 00000000..783c5c39
--- /dev/null
+++ b/docs/_javascript/preset_test.js
@@ -0,0 +1,383 @@
+(function (global) {
+  "use strict";
+
+  const DEFAULTS = Object.freeze({
+    start: "2026-09-21T17:00:00-07:00",
+    end: "2026-09-23T17:00:00-07:00",
+    freq: "910.1",
+    bw: "500",
+    sf: "8",
+    cr: "7",
+  });
+  const VALID_BANDWIDTHS = Object.freeze([
+    7.8, 10.4, 15.6, 20.8, 31.25, 41.7, 62.5, 125, 250, 500,
+  ]);
+  const SCHEDULE_HORIZON_MS = 0x7fffffff;
+
+  class PresetTestError extends Error {}
+
+  function strictNumber(value, name) {
+    const text = String(value).trim();
+    if (!/^(?:\d+(?:\.\d*)?|\.\d+)$/.test(text)) {
+      throw new PresetTestError(name + " must be a decimal number");
+    }
+    const parsed = Number(text);
+    if (!Number.isFinite(parsed)) {
+      throw new PresetTestError(name + " is outside the supported range");
+    }
+    return parsed;
+  }
+
+  function strictInteger(value, name) {
+    const text = String(value).trim();
+    if (!/^\d+$/.test(text)) {
+      throw new PresetTestError(name + " must be an integer");
+    }
+    return Number(text);
+  }
+
+  function parseTimestamp(value, name) {
+    const text = String(value).trim();
+    let milliseconds;
+    if (/^\d{10}$/.test(text)) {
+      milliseconds = Number(text) * 1000;
+    } else if (/^\d{13}$/.test(text)) {
+      milliseconds = Number(text);
+    } else {
+      if (!/(?:Z|[+-]\d{2}:\d{2})$/i.test(text)) {
+        throw new PresetTestError(
+          name + " must include an explicit UTC offset such as Z or -07:00"
+        );
+      }
+      milliseconds = Date.parse(text);
+    }
+    if (!Number.isFinite(milliseconds)) {
+      throw new PresetTestError(
+        name + " must be ISO-8601 with an explicit offset, or a Unix timestamp"
+      );
+    }
+    return milliseconds;
+  }
+
+  function numberText(value) {
+    return String(Number(value));
+  }
+
+  function configFromSearch(search) {
+    const params = new URLSearchParams(search || "");
+    const raw = {};
+    Object.keys(DEFAULTS).forEach(function (key) {
+      raw[key] = params.has(key) ? params.get(key) : DEFAULTS[key];
+    });
+
+    const startMs = parseTimestamp(raw.start, "start");
+    const endMs = parseTimestamp(raw.end, "end");
+    const freq = strictNumber(raw.freq, "freq");
+    const bw = strictNumber(raw.bw, "bw");
+    const sf = strictInteger(raw.sf, "sf");
+    const cr = strictInteger(raw.cr, "cr");
+
+    if (endMs <= startMs) {
+      throw new PresetTestError("end must be later than start");
+    }
+    if (freq < 150 || freq > 2500) {
+      throw new PresetTestError("freq must be between 150 and 2500 MHz");
+    }
+    if (!VALID_BANDWIDTHS.some(function (allowed) {
+      return Math.abs(allowed - bw) < 0.01;
+    })) {
+      throw new PresetTestError(
+        "bw must be one of " + VALID_BANDWIDTHS.join(", ") + " kHz"
+      );
+    }
+    if (sf < 5 || sf > 12) {
+      throw new PresetTestError("sf must be between 5 and 12");
+    }
+    if (cr < 5 || cr > 8) {
+      throw new PresetTestError("cr must be between 5 and 8");
+    }
+
+    return Object.freeze({
+      startMs: startMs,
+      endMs: endMs,
+      startEpoch: Math.floor(startMs / 1000),
+      endEpoch: Math.floor(endMs / 1000),
+      freq: freq,
+      bw: bw,
+      sf: sf,
+      cr: cr,
+      freqText: numberText(freq),
+      bwText: numberText(bw),
+    });
+  }
+
+  function phaseAt(config, nowMs) {
+    if (nowMs < config.startMs) return "before";
+    if (nowMs < config.endMs) return "active";
+    return "ended";
+  }
+
+  function remainingMinutes(config, nowMs) {
+    return Math.max(0, Math.ceil((config.endMs - nowMs) / 60000));
+  }
+
+  function scheduleAvailability(config, nowMs) {
+    if (nowMs >= config.startMs) {
+      return { available: false, reason: "The start time has passed; use the immediate option." };
+    }
+    if (config.endMs - nowMs > SCHEDULE_HORIZON_MS) {
+      return {
+        available: false,
+        reason: "The end is outside the firmware's roughly 24-day horizon; return closer to the test.",
+      };
+    }
+    return { available: true, reason: "Ready to queue after the node clock is verified." };
+  }
+
+  function commandsFor(config, nowMs) {
+    const tuple = [config.freqText, config.bwText, config.sf, config.cr].join(",");
+    const minutes = remainingMinutes(config, nowMs);
+    return Object.freeze({
+      stockNow: "tempradio " + tuple + "," + minutes,
+      companionNow:
+        "set radio2.cross on\nset tempradio2 " + tuple + ",rxtx," + minutes,
+      stockScheduled:
+        "set tempradioat " + tuple + "," + config.startEpoch + "," + config.endEpoch +
+        "\nget tempradioat",
+      companionScheduled:
+        "set radio2.cross on\nset tempradioat2 " + tuple + ",rxtx," +
+        config.startEpoch + "," + config.endEpoch + "\nget tempradioat2",
+      stockCancelBefore: "get tempradioat\ndel tempradioat all",
+      stockCancelDuring: "normalradio",
+      companionCancelBefore:
+        "get tempradioat2\ndel tempradioat2 all\nset radio2.cross auto",
+      companionCancelDuring: "set tempradio2 off\nset radio2.cross auto",
+    });
+  }
+
+  function formatCountdown(milliseconds) {
+    let seconds = Math.max(0, Math.ceil(milliseconds / 1000));
+    const days = Math.floor(seconds / 86400);
+    seconds %= 86400;
+    const hours = Math.floor(seconds / 3600);
+    seconds %= 3600;
+    const minutes = Math.floor(seconds / 60);
+    seconds %= 60;
+    const parts = [];
+    if (days) parts.push(days + "d");
+    if (days || hours) parts.push(hours + "h");
+    if (days || hours || minutes) parts.push(minutes + "m");
+    parts.push(seconds + "s");
+    return parts.join(" ");
+  }
+
+  function formatPacific(milliseconds) {
+    return new Intl.DateTimeFormat("en-US", {
+      timeZone: "America/Los_Angeles",
+      weekday: "long",
+      year: "numeric",
+      month: "long",
+      day: "numeric",
+      hour: "numeric",
+      minute: "2-digit",
+      timeZoneName: "short",
+    }).format(new Date(milliseconds));
+  }
+
+  function formatUtc(milliseconds) {
+    return new Intl.DateTimeFormat("en-US", {
+      timeZone: "UTC",
+      year: "numeric",
+      month: "short",
+      day: "numeric",
+      hour: "2-digit",
+      minute: "2-digit",
+      second: "2-digit",
+      hour12: false,
+      timeZoneName: "short",
+    }).format(new Date(milliseconds));
+  }
+
+  function configuredUrl(config, baseUrl) {
+    const url = new URL(baseUrl);
+    url.search = "";
+    url.searchParams.set("start", new Date(config.startMs).toISOString());
+    url.searchParams.set("end", new Date(config.endMs).toISOString());
+    url.searchParams.set("freq", config.freqText);
+    url.searchParams.set("bw", config.bwText);
+    url.searchParams.set("sf", String(config.sf));
+    url.searchParams.set("cr", String(config.cr));
+    return url.toString();
+  }
+
+  function setText(root, selector, value) {
+    root.querySelectorAll(selector).forEach(function (element) {
+      element.textContent = value;
+    });
+  }
+
+  function setCommand(root, name, value) {
+    setText(root, '[data-command="' + name + '"]', value);
+    root.querySelectorAll('[data-copy-command="' + name + '"]').forEach(function (button) {
+      button.dataset.copyValue = value;
+    });
+  }
+
+  function setCommandEnabled(root, name, enabled) {
+    root.querySelectorAll('[data-copy-command="' + name + '"]').forEach(function (button) {
+      button.disabled = !enabled;
+    });
+  }
+
+  function fallbackCopy(text) {
+    const area = document.createElement("textarea");
+    area.value = text;
+    area.setAttribute("readonly", "");
+    area.style.position = "fixed";
+    area.style.opacity = "0";
+    document.body.appendChild(area);
+    area.select();
+    document.execCommand("copy");
+    area.remove();
+  }
+
+  function copyText(text) {
+    if (navigator.clipboard && navigator.clipboard.writeText) {
+      return navigator.clipboard.writeText(text).catch(function () {
+        fallbackCopy(text);
+      });
+    }
+    fallbackCopy(text);
+    return Promise.resolve();
+  }
+
+  function init(root) {
+    let config;
+    try {
+      config = configFromSearch(global.location ? global.location.search : "");
+    } catch (error) {
+      const box = root.querySelector('[data-role="config-error"]');
+      box.hidden = false;
+      box.textContent = "Invalid test URL: " + error.message;
+      root.querySelector('[data-role="content"]').hidden = true;
+      return;
+    }
+
+    setText(root, '[data-field="freq-display"]', config.freq.toFixed(3));
+    setText(root, '[data-field="bw-display"]', config.bwText);
+    setText(root, '[data-field="sf"]', String(config.sf));
+    setText(root, '[data-field="cr"]', String(config.cr));
+    setText(root, '[data-role="start-pacific"]', formatPacific(config.startMs));
+    setText(root, '[data-role="end-pacific"]', formatPacific(config.endMs));
+    setText(
+      root,
+      '[data-role="epoch-range"]',
+      config.startEpoch + " → " + config.endEpoch
+    );
+    setText(
+      root,
+      '[data-role="window-summary"]',
+      "A " + formatCountdown(config.endMs - config.startMs) +
+        " window. Saved primary settings return automatically at the end."
+    );
+
+    const staticCommands = commandsFor(config, config.startMs);
+    setCommand(root, "stock-scheduled", staticCommands.stockScheduled);
+    setCommand(root, "companion-scheduled", staticCommands.companionScheduled);
+    setCommand(root, "stock-cancel-before", staticCommands.stockCancelBefore);
+    setCommand(root, "stock-cancel-during", staticCommands.stockCancelDuring);
+    setCommand(root, "companion-cancel-before", staticCommands.companionCancelBefore);
+    setCommand(root, "companion-cancel-during", staticCommands.companionCancelDuring);
+    setCommand(
+      root,
+      "share-url",
+      configuredUrl(config, global.location ? global.location.href : "https://example.invalid/")
+    );
+
+    root.querySelectorAll("[data-copy-command]").forEach(function (button) {
+      button.addEventListener("click", function () {
+        const original = button.textContent;
+        copyText(button.dataset.copyValue || "").then(function () {
+          button.textContent = "Copied";
+          global.setTimeout(function () { button.textContent = original; }, 1600);
+        });
+      });
+    });
+
+    function render() {
+      const nowMs = Date.now();
+      const phase = phaseAt(config, nowMs);
+      const status = root.querySelector('[data-role="status"]');
+      const schedule = scheduleAvailability(config, nowMs);
+      const commands = commandsFor(config, nowMs);
+
+      status.dataset.state = phase;
+      if (phase === "before") {
+        status.textContent = "Scheduled";
+        setText(root, '[data-role="countdown-label"]', "Starts in");
+        setText(root, '[data-role="countdown"]', formatCountdown(config.startMs - nowMs));
+        setText(root, '[data-role="countdown-detail"]', "Do not use immediate TempRadio yet.");
+      } else if (phase === "active") {
+        status.textContent = "Test live";
+        setText(root, '[data-role="countdown-label"]', "Ends in");
+        setText(root, '[data-role="countdown"]', formatCountdown(config.endMs - nowMs));
+        setText(root, '[data-role="countdown-detail"]', "Temporary radios revert at zero.");
+      } else {
+        status.textContent = "Test finished";
+        setText(root, '[data-role="countdown-label"]', "Window closed");
+        setText(root, '[data-role="countdown"]', "0s");
+        setText(root, '[data-role="countdown-detail"]', "Temporary radios should be back on saved settings.");
+      }
+
+      setCommand(root, "stock-now", commands.stockNow);
+      setCommand(root, "companion-now", commands.companionNow);
+      setCommandEnabled(root, "stock-now", phase === "active");
+      setCommandEnabled(root, "companion-now", phase === "active");
+      setText(
+        root,
+        '[data-role="stock-now-note"]',
+        phase === "before"
+          ? "Available when the test starts; schedule it now with Option 2."
+          : phase === "active"
+            ? "The final argument is the live minutes remaining until the common end."
+            : "The test window has ended."
+      );
+
+      setCommandEnabled(root, "stock-scheduled", schedule.available);
+      setCommandEnabled(root, "companion-scheduled", schedule.available);
+      setText(root, '[data-role="stock-schedule-note"]', schedule.reason);
+
+      const nowEpoch = Math.floor(nowMs / 1000);
+      setText(root, '[data-role="browser-utc"]', formatUtc(nowMs));
+      setText(root, '[data-role="browser-epoch"]', String(nowEpoch));
+      setCommand(root, "set-clock", "time " + nowEpoch + "\nclock");
+    }
+
+    render();
+    global.setInterval(render, 1000);
+  }
+
+  const api = Object.freeze({
+    DEFAULTS: DEFAULTS,
+    VALID_BANDWIDTHS: VALID_BANDWIDTHS,
+    SCHEDULE_HORIZON_MS: SCHEDULE_HORIZON_MS,
+    PresetTestError: PresetTestError,
+    configFromSearch: configFromSearch,
+    phaseAt: phaseAt,
+    remainingMinutes: remainingMinutes,
+    scheduleAvailability: scheduleAvailability,
+    commandsFor: commandsFor,
+    formatCountdown: formatCountdown,
+    configuredUrl: configuredUrl,
+    init: init,
+  });
+
+  if (typeof module !== "undefined" && module.exports) module.exports = api;
+  global.MeshCorePresetTest = api;
+
+  if (typeof document !== "undefined") {
+    document.addEventListener("DOMContentLoaded", function () {
+      document.querySelectorAll("[data-preset-test]").forEach(init);
+    });
+  }
+})(typeof globalThis !== "undefined" ? globalThis : this);
diff --git a/docs/_stylesheets/preset_test.css b/docs/_stylesheets/preset_test.css
new file mode 100644
index 00000000..0923acff
--- /dev/null
+++ b/docs/_stylesheets/preset_test.css
@@ -0,0 +1,257 @@
+.preset-test {
+  --preset-accent: #b83280;
+  --preset-accent-dark: #8f245f;
+  --preset-cyan: #087f8c;
+  --preset-border: color-mix(in srgb, currentColor 18%, transparent);
+  margin: 1.25rem 0 2rem;
+}
+
+.preset-test section {
+  margin: 1.4rem 0;
+}
+
+.preset-test-hero {
+  border: 1px solid var(--preset-border);
+  border-top: 0.35rem solid var(--preset-accent);
+  border-radius: 0.75rem;
+  padding: 1.1rem 1.2rem 1.2rem;
+  background:
+    linear-gradient(135deg, color-mix(in srgb, var(--preset-accent) 9%, transparent), transparent 55%),
+    var(--md-default-bg-color);
+}
+
+.preset-test-eyebrow {
+  margin: 0 0 0.45rem;
+  color: var(--md-default-fg-color--light);
+  font-size: 0.72rem;
+  font-weight: 750;
+  letter-spacing: 0.1em;
+  text-transform: uppercase;
+}
+
+.preset-test-hero-row,
+.preset-test-card-heading {
+  display: flex;
+  justify-content: space-between;
+  gap: 1rem;
+  align-items: flex-start;
+}
+
+.preset-test-hero h2 {
+  margin: 0;
+  font-size: clamp(1.35rem, 4vw, 2.15rem);
+  letter-spacing: -0.025em;
+}
+
+.preset-test-hero-row p {
+  margin-bottom: 0;
+}
+
+.preset-test-status,
+.preset-test-card-heading > span {
+  flex: 0 0 auto;
+  border-radius: 999px;
+  padding: 0.22rem 0.55rem;
+  background: color-mix(in srgb, var(--preset-cyan) 12%, transparent);
+  color: var(--preset-cyan);
+  font-size: 0.7rem;
+  font-weight: 750;
+  letter-spacing: 0.05em;
+  text-transform: uppercase;
+}
+
+.preset-test-status[data-state="active"] {
+  background: color-mix(in srgb, #1b8f4b 14%, transparent);
+  color: #168143;
+}
+
+.preset-test-status[data-state="ended"] {
+  background: color-mix(in srgb, currentColor 9%, transparent);
+  color: var(--md-default-fg-color--light);
+}
+
+.preset-test-clock {
+  display: grid;
+  grid-template-columns: auto 1fr;
+  gap: 0.1rem 0.8rem;
+  align-items: baseline;
+  margin: 1.2rem 0;
+  padding: 0.8rem 0;
+  border-block: 1px solid var(--preset-border);
+}
+
+.preset-test-clock-label {
+  color: var(--md-default-fg-color--light);
+  font-weight: 650;
+}
+
+.preset-test-clock strong {
+  color: var(--preset-accent);
+  font-family: var(--md-code-font-family);
+  font-size: clamp(1.35rem, 4vw, 2rem);
+}
+
+.preset-test-clock > span:last-child {
+  grid-column: 2;
+  color: var(--md-default-fg-color--light);
+  font-size: 0.82rem;
+}
+
+.preset-test-window {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr));
+  gap: 0.8rem;
+  margin: 0;
+}
+
+.preset-test-window div,
+.preset-test-clock-check > div {
+  min-width: 0;
+}
+
+.preset-test-window dt,
+.preset-test-clock-check span {
+  color: var(--md-default-fg-color--light);
+  font-size: 0.72rem;
+  font-weight: 700;
+  letter-spacing: 0.05em;
+  text-transform: uppercase;
+}
+
+.preset-test-window dd {
+  margin: 0.18rem 0 0;
+  overflow-wrap: anywhere;
+}
+
+.preset-test-warning,
+.preset-test-error {
+  border-left: 0.32rem solid #d97706;
+  border-radius: 0.35rem;
+  padding: 0.85rem 1rem;
+  background: color-mix(in srgb, #d97706 9%, transparent);
+}
+
+.preset-test-warning h2 {
+  margin-top: 0;
+}
+
+.preset-test-warning p {
+  margin-bottom: 0;
+}
+
+.preset-test-error {
+  color: var(--md-code-hl-number-color);
+  font-weight: 650;
+}
+
+.preset-test-grid,
+.preset-test-cancel-grid {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 1rem;
+}
+
+.preset-test-cancel-grid {
+  grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
+}
+
+.preset-test-card {
+  min-width: 0;
+  border: 1px solid var(--preset-border);
+  border-radius: 0.65rem;
+  padding: 0.9rem 1rem 1rem;
+  background: var(--md-default-bg-color);
+}
+
+.preset-test-card h3 {
+  margin-top: 0;
+}
+
+.preset-test-card-heading h3 {
+  padding-right: 0.5rem;
+}
+
+.preset-test-card pre,
+.preset-test > [data-role="content"] > section > pre {
+  margin: 0.8rem 0;
+  border: 1px solid var(--preset-border);
+  border-radius: 0.35rem;
+}
+
+.preset-test-card pre code,
+.preset-test > [data-role="content"] > section > pre code {
+  white-space: pre-wrap;
+  overflow-wrap: anywhere;
+}
+
+.preset-test button {
+  border: 0;
+  border-radius: 0.25rem;
+  padding: 0.55rem 0.8rem;
+  background: var(--preset-accent);
+  color: #fff;
+  cursor: pointer;
+  font: inherit;
+  font-size: 0.78rem;
+  font-weight: 750;
+}
+
+.preset-test button:hover:not(:disabled),
+.preset-test button:focus-visible:not(:disabled) {
+  background: var(--preset-accent-dark);
+}
+
+.preset-test button:disabled {
+  cursor: not-allowed;
+  opacity: 0.42;
+}
+
+.preset-test-note {
+  margin-bottom: 0;
+  color: var(--md-default-fg-color--light);
+  font-size: 0.82rem;
+}
+
+.preset-test-clock-check {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 0.8rem;
+  margin: 1rem 0;
+}
+
+.preset-test-clock-check > div {
+  display: grid;
+  gap: 0.2rem;
+  border: 1px solid var(--preset-border);
+  border-radius: 0.5rem;
+  padding: 0.75rem 0.9rem;
+}
+
+.preset-test-clock-check strong {
+  overflow-wrap: anywhere;
+  font-family: var(--md-code-font-family);
+}
+
+@media (max-width: 44rem) {
+  .preset-test-grid,
+  .preset-test-grid--clock,
+  .preset-test-clock-check {
+    grid-template-columns: 1fr;
+  }
+
+  .preset-test-hero-row {
+    display: grid;
+  }
+
+  .preset-test-status {
+    justify-self: start;
+  }
+
+  .preset-test-clock {
+    grid-template-columns: 1fr;
+  }
+
+  .preset-test-clock > span:last-child {
+    grid-column: 1;
+  }
+}
diff --git a/docs/index.md b/docs/index.md
index 0703d07f..2b5d465f 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -11,6 +11,7 @@ Below are a few quick start guides.
 - [Full Companion feature switches](./full_companion_features.md)
 - [Frequently Asked Questions](./faq.md)
 - [Firmware Picker](./firmware_picker.md)
+- [Temporary Radio Test Command Generator](./preset_test.md)
 - [CLI Commands](./cli_commands.md)
 - [LoRa CLI Host Service](./host_cli_service.md)
 - [Filter Policy Playground](./filter_tool.md)
diff --git a/docs/preset_test.md b/docs/preset_test.md
new file mode 100644
index 00000000..f7538bba
--- /dev/null
+++ b/docs/preset_test.md
@@ -0,0 +1,233 @@
+# Temporary radio test command generator
+
+Use this page to join the shared temporary radio test without overwriting the
+node's saved primary radio settings. The default window is **Monday,
+September 21, 2026 at 5:00 PM through Wednesday, September 23 at 5:00 PM
+Pacific time** (48 hours), using **910.1 MHz, 500 kHz, SF8, CR7**.
+
+The page reads the complete test definition from its URL. Change the query
+parameters to reuse it for a different window or radio tuple; no source edit is
+required.
+
+<div class="preset-test" data-preset-test>
+  <div class="preset-test-error" data-role="config-error" role="alert" hidden></div>
+
+  <div data-role="content">
+    <section class="preset-test-hero" aria-labelledby="preset-test-title">
+      <p class="preset-test-eyebrow">MeshCore · temporary preset test</p>
+      <div class="preset-test-hero-row">
+        <div>
+          <h2 id="preset-test-title">
+            <span data-field="freq-display">910.100</span> MHz /
+            <span data-field="bw-display">500</span> kHz /
+            SF<span data-field="sf">8</span> /
+            CR<span data-field="cr">7</span>
+          </h2>
+          <p data-role="window-summary"></p>
+        </div>
+        <span class="preset-test-status" data-role="status" data-state="before">Scheduled</span>
+      </div>
+
+      <div class="preset-test-clock" aria-live="polite">
+        <span class="preset-test-clock-label" data-role="countdown-label">Starts in</span>
+        <strong data-role="countdown">—</strong>
+        <span data-role="countdown-detail">—</span>
+      </div>
+
+      <dl class="preset-test-window">
+        <div><dt>Start</dt><dd data-role="start-pacific"></dd></div>
+        <div><dt>End</dt><dd data-role="end-pacific"></dd></div>
+        <div><dt>Firmware epochs</dt><dd><code data-role="epoch-range"></code></dd></div>
+      </dl>
+    </section>
+
+    <section class="preset-test-warning" aria-labelledby="save-settings-title">
+      <h2 id="save-settings-title">Before changing a radio</h2>
+      <p>
+        Run <code>get radio</code> and record the saved primary tuple. Both
+        primary TempRadio methods return to that saved tuple; they do not store
+        a return tuple inside the temporary command. On a Companion, also run
+        <code>get radio2</code> and <code>get radio2.cross</code> so you can restore
+        any non-default secondary-profile setup.
+      </p>
+    </section>
+
+    <section aria-labelledby="clock-check-title">
+      <h2 id="clock-check-title">Check the node clock before scheduling</h2>
+      <p>
+        <code>tempradioat</code> and <code>tempradioat2</code> use UTC Unix time.
+        Run <code>clock</code> on every node and compare it with the browser UTC
+        time below. It should agree to within about a minute. A wrong clock can
+        start late, start immediately, or cause the schedule to be rejected.
+      </p>
+
+      <div class="preset-test-clock-check">
+        <div>
+          <span>Browser UTC now</span>
+          <strong data-role="browser-utc">—</strong>
+        </div>
+        <div>
+          <span>Browser Unix time</span>
+          <strong data-role="browser-epoch">—</strong>
+        </div>
+      </div>
+
+      <div class="preset-test-grid preset-test-grid--clock">
+        <article class="preset-test-card">
+          <h3>Remote admin session</h3>
+          <p>
+            In a MeshCore client that supplies the sender timestamp, sync and
+            then verify:
+          </p>
+          <pre><code>clock sync
+clock</code></pre>
+        </article>
+
+        <article class="preset-test-card">
+          <h3>Local USB or browser console</h3>
+          <p>Copy this fresh, run it immediately, and then verify with <code>clock</code>:</p>
+          <pre><code data-command="set-clock">time 0
+clock</code></pre>
+          <button type="button" data-copy-command="set-clock">Copy current clock command</button>
+        </article>
+      </div>
+
+      <p class="preset-test-note">
+        The schedule must be queued while both its start and end are in the
+        future and within the firmware's roughly 24-day scheduling horizon.
+        Scheduled entries are held in RAM and disappear if the node reboots.
+      </p>
+    </section>
+
+    <section aria-labelledby="join-now-title">
+      <h2 id="join-now-title">Option 1: switch when the test begins</h2>
+      <p>
+        Open this page after the start time. Its timeout shrinks so every node
+        returns at the same end time. These copy buttons remain disabled before
+        the window to prevent an early switch.
+      </p>
+
+      <div class="preset-test-grid">
+        <article class="preset-test-card">
+          <div class="preset-test-card-heading">
+            <h3>Stock repeater, room server, or sensor</h3>
+            <span>Primary radio</span>
+          </div>
+          <pre><code data-command="stock-now"></code></pre>
+          <button type="button" data-copy-command="stock-now">Copy command</button>
+          <p class="preset-test-note" data-role="stock-now-note"></p>
+        </article>
+
+        <article class="preset-test-card">
+          <div class="preset-test-card-heading">
+            <h3>Companion using both frequencies</h3>
+            <span>Dual profile</span>
+          </div>
+          <pre><code data-command="companion-now"></code></pre>
+          <button type="button" data-copy-command="companion-now">Copy commands</button>
+          <p class="preset-test-note">
+            <code>rxtx</code> permits transmission on the second profile;
+            <code>radio2.cross on</code> copies ordinary Companion traffic across
+            the primary and temporary profiles.
+          </p>
+        </article>
+      </div>
+    </section>
+
+    <section aria-labelledby="schedule-title">
+      <h2 id="schedule-title">Option 2: schedule it in advance</h2>
+      <p>
+        Use this only after checking the clock above. The exact UTC epochs are
+        built into the commands, so the node switches at the common start and
+        restores its saved configuration at the common end.
+      </p>
+
+      <div class="preset-test-grid">
+        <article class="preset-test-card">
+          <div class="preset-test-card-heading">
+            <h3>Stock repeater, room server, or sensor</h3>
+            <span>Primary schedule</span>
+          </div>
+          <pre><code data-command="stock-scheduled"></code></pre>
+          <button type="button" data-copy-command="stock-scheduled">Copy schedule commands</button>
+          <p class="preset-test-note" data-role="stock-schedule-note"></p>
+        </article>
+
+        <article class="preset-test-card">
+          <div class="preset-test-card-heading">
+            <h3>Companion using both frequencies</h3>
+            <span>Dual-profile schedule</span>
+          </div>
+          <pre><code data-command="companion-scheduled"></code></pre>
+          <button type="button" data-copy-command="companion-scheduled">Copy schedule commands</button>
+          <p class="preset-test-note">
+            Crossing is saved independently and remains <code>on</code> after the
+            temporary second profile ends. Restore its previous value after the
+            test; <code>auto</code> is the normal default.
+          </p>
+        </article>
+      </div>
+    </section>
+
+    <section aria-labelledby="cancel-title">
+      <h2 id="cancel-title">Cancel or leave the test</h2>
+      <p>
+        Use the command for the node type and timing. The <code>all</code> forms
+        remove every temporary schedule in that family. To preserve another
+        schedule, first run the corresponding <code>get</code> command and replace
+        <code>all</code> with its displayed entry number.
+      </p>
+
+      <div class="preset-test-cancel-grid">
+        <article class="preset-test-card">
+          <h3>Stock · before it starts</h3>
+          <pre><code data-command="stock-cancel-before"></code></pre>
+          <button type="button" data-copy-command="stock-cancel-before">Copy cancel commands</button>
+        </article>
+
+        <article class="preset-test-card">
+          <h3>Stock · while it is running</h3>
+          <pre><code data-command="stock-cancel-during"></code></pre>
+          <button type="button" data-copy-command="stock-cancel-during">Copy restore command</button>
+          <p class="preset-test-note">
+            <code>normalradio</code> cancels pending and active primary TempRadio
+            windows and restores the saved primary tuple after its reply drains.
+          </p>
+        </article>
+
+        <article class="preset-test-card">
+          <h3>Companion · before it starts</h3>
+          <pre><code data-command="companion-cancel-before"></code></pre>
+          <button type="button" data-copy-command="companion-cancel-before">Copy cancel commands</button>
+        </article>
+
+        <article class="preset-test-card">
+          <h3>Companion · while it is running</h3>
+          <pre><code data-command="companion-cancel-during"></code></pre>
+          <button type="button" data-copy-command="companion-cancel-during">Copy restore commands</button>
+          <p class="preset-test-note">
+            If <code>get radio2.cross</code> was not <code>auto</code> before the
+            test, restore that recorded value instead.
+          </p>
+        </article>
+      </div>
+    </section>
+
+    <section aria-labelledby="share-title">
+      <h2 id="share-title">Reuse this page for another test</h2>
+      <p>
+        Set <code>start</code> and <code>end</code> to ISO-8601 timestamps with an
+        explicit UTC offset, or to Unix epoch seconds. Set <code>freq</code>,
+        <code>bw</code>, <code>sf</code>, and <code>cr</code> to the desired radio
+        tuple. The current configuration link is normalized to UTC.
+      </p>
+      <pre><code>?start=2026-09-21T17:00:00-07:00&amp;end=2026-09-23T17:00:00-07:00&amp;freq=910.1&amp;bw=500&amp;sf=8&amp;cr=7</code></pre>
+      <button type="button" data-copy-command="share-url">Copy configured page URL</button>
+    </section>
+  </div>
+</div>
+
+The scheduled commands require current full-parser firmware. Companion
+`tempradio2` and `tempradioat2` require a build with dual-radio-profile support.
+If a node reports an unknown command, update it or use only a method that its
+installed firmware documents.
diff --git a/mkdocs.yml b/mkdocs.yml
index 2449f960..3b1a271b 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -20,8 +20,10 @@ extra_css:
   - _stylesheets/firmware_picker.css
   - _stylesheets/telemetry_decoder.css
   - _stylesheets/filter_tool.css
+  - _stylesheets/preset_test.css
 
 extra_javascript:
   - _javascript/firmware_picker.js
   - _javascript/telemetry_decoder.js
   - _javascript/filter_tool.js
+  - _javascript/preset_test.js
diff --git a/test/test_preset_test.js b/test/test_preset_test.js
new file mode 100644
index 00000000..7cf3dc7a
--- /dev/null
+++ b/test/test_preset_test.js
@@ -0,0 +1,90 @@
+"use strict";
+
+const assert = require("assert");
+const tool = require("../docs/_javascript/preset_test.js");
+
+const query =
+  "?start=2026-09-21T17:00:00-07:00" +
+  "&end=2026-09-23T17:00:00-07:00" +
+  "&freq=910.1&bw=500&sf=8&cr=7";
+const config = tool.configFromSearch(query);
+const defaults = tool.configFromSearch("");
+
+assert.strictEqual(config.startEpoch, 1790035200);
+assert.strictEqual(config.endEpoch, 1790208000);
+assert.strictEqual(config.endEpoch - config.startEpoch, 48 * 60 * 60);
+assert.strictEqual(config.freq, 910.1);
+assert.strictEqual(config.sf, 8);
+assert.strictEqual(config.cr, 7);
+assert.strictEqual(defaults.startEpoch, config.startEpoch);
+assert.strictEqual(defaults.endEpoch, config.endEpoch);
+assert.strictEqual(defaults.freq, config.freq);
+
+const before = Date.parse("2026-09-21T16:59:00-07:00");
+const active = Date.parse("2026-09-21T17:00:30-07:00");
+const ended = Date.parse("2026-09-23T17:00:00-07:00");
+assert.strictEqual(tool.phaseAt(config, before), "before");
+assert.strictEqual(tool.phaseAt(config, active), "active");
+assert.strictEqual(tool.phaseAt(config, ended), "ended");
+assert.strictEqual(tool.remainingMinutes(config, active), 2880);
+
+const commands = tool.commandsFor(config, active);
+assert.strictEqual(commands.stockNow, "tempradio 910.1,500,8,7,2880");
+assert.strictEqual(
+  commands.stockScheduled,
+  "set tempradioat 910.1,500,8,7,1790035200,1790208000\nget tempradioat"
+);
+assert.strictEqual(
+  commands.companionNow,
+  "set radio2.cross on\nset tempradio2 910.1,500,8,7,rxtx,2880"
+);
+assert.strictEqual(
+  commands.companionScheduled,
+  "set radio2.cross on\n" +
+    "set tempradioat2 910.1,500,8,7,rxtx,1790035200,1790208000\n" +
+    "get tempradioat2"
+);
+
+assert.strictEqual(tool.scheduleAvailability(config, before).available, true);
+assert.strictEqual(tool.scheduleAvailability(config, active).available, false);
+assert.strictEqual(
+  tool.scheduleAvailability(config, config.endMs - tool.SCHEDULE_HORIZON_MS - 1).available,
+  false
+);
+
+assert.throws(
+  () => tool.configFromSearch("?start=bad"),
+  /start must include an explicit UTC offset/
+);
+assert.throws(
+  () => tool.configFromSearch("?start=2026-09-21T17:00:00"),
+  /start must include an explicit UTC offset/
+);
+assert.throws(
+  () => tool.configFromSearch("?bw=123"),
+  /bw must be one of/
+);
+assert.throws(
+  () => tool.configFromSearch("?start=1790208000&end=1790035200"),
+  /end must be later/
+);
+
+const changed = tool.configFromSearch(
+  "?start=1790035200&end=1790208000&freq=915.25&bw=125&sf=10&cr=5"
+);
+assert.strictEqual(
+  tool.commandsFor(changed, changed.startMs).stockNow,
+  "tempradio 915.25,125,10,5,2880"
+);
+
+const shared = new URL(tool.configuredUrl(
+  changed,
+  "https://example.test/preset-test/?stale=yes#commands"
+));
+assert.strictEqual(shared.searchParams.get("start"), "2026-09-22T00:00:00.000Z");
+assert.strictEqual(shared.searchParams.get("end"), "2026-09-24T00:00:00.000Z");
+assert.strictEqual(shared.searchParams.get("freq"), "915.25");
+assert.strictEqual(shared.searchParams.has("stale"), false);
+assert.strictEqual(shared.hash, "#commands");
+
+process.stdout.write("preset test command generator checks passed\n");