diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ace7f57..8d1b7fb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,15 +17,25 @@ concurrency:
 jobs:
   check:
     runs-on: ubuntu-latest
+    strategy:
+      # Test the oldest Node we claim to support (package.json engines)
+      # alongside current, so "works on my machine" can't hide an engines
+      # violation.
+      matrix:
+        node-version: [22, 24]
     steps:
       # Actions are pinned to commit SHAs (supply-chain hardening); the
       # trailing comment records the human-readable version. v6 runs on the
       # Node 24 action runtime, clearing the Node 20 deprecation warning.
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          # No step here pushes or calls the API; don't leave the token in
+          # .git/config for the rest of the job.
+          persist-credentials: false
 
       - uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
         with:
-          node-version: 24
+          node-version: ${{ matrix.node-version }}
           cache: npm
 
       - run: npm ci
@@ -42,3 +52,16 @@ jobs:
       - run: npm run coverage
 
       - run: npm run build
+
+  # Merge gate: branch protection requires a single status named "check".
+  # Reporting that name from an aggregate job (instead of the matrix legs,
+  # whose names carry the Node version) keeps the required-check name
+  # stable no matter how the matrix changes.
+  ci-ok:
+    name: check
+    needs: check
+    if: always()
+    runs-on: ubuntu-latest
+    steps:
+      - name: Fail unless every matrix leg succeeded
+        run: test "${{ needs.check.result }}" = "success"
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index a883b1c..11ba793 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -58,7 +58,7 @@ jobs:
       # version twice, so re-running this workflow for an existing tag will
       # fail here — bump the version instead.
       - name: Sign the Firefox .xpi with Mozilla (AMO)
-        if: env.AMO_JWT_ISSUER != ''
+        if: env.AMO_JWT_ISSUER != '' && env.AMO_JWT_SECRET != ''
         run: |
           version="$(node -p "require('./manifest.json').version")"
           mkdir -p /tmp/xpi-src /tmp/xpi-signed
@@ -75,7 +75,9 @@ jobs:
       # Upload the .zip to the Chrome Web Store and publish. Google's
       # review still happens asynchronously on their side afterwards.
       - name: Publish to the Chrome Web Store
-        if: env.CWS_EXTENSION_ID != ''
+        if: >-
+          env.CWS_EXTENSION_ID != '' && env.CWS_CLIENT_ID != '' &&
+          env.CWS_CLIENT_SECRET != '' && env.CWS_REFRESH_TOKEN != ''
         env:
           EXTENSION_ID: ${{ env.CWS_EXTENSION_ID }}
           CLIENT_ID: ${{ env.CWS_CLIENT_ID }}
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fa786e2..42210ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,42 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Release packaging omitted `checks.js`, so published `.zip`/`.xpi` builds
+  shipped without the status-checks helpers the content script depends on.
+  The packaged file list is now derived from `manifest.json` (plus popup
+  `<script>` tags) instead of being hand-maintained, missing files fail the
+  build, and a packaging test verifies the archive contents in CI.
+- The status-checks indicator now refreshes when GitHub updates a check's
+  label in place (e.g. running → successful) instead of waiting for
+  unrelated DOM changes.
+- The popup now reflects a preference change made via the in-page toggle
+  while it is open.
+- A corrupted stored preference value no longer desyncs the toggle label
+  from the actual sort order; anything unrecognized falls back to newest.
+
+- Status-word matching in the checks indicator uses word boundaries, so a
+  check _named_ e.g. `failover-suite` or `cancellation-service` that passed
+  is no longer misreported as failing.
+
+### Added
+
+- Accessible labels (`aria-label`) on the injected toggle button and
+  status-checks indicator.
+- 128px toolbar icon variants wired into the action icon set.
+- The popup follows the browser's light/dark preference instead of always
+  rendering dark.
+
+### Changed
+
+- The per-page GitHub DOM selectors moved from `content.js` into a new
+  `pages.js` module, and `background.js` became importable under Node —
+  both are now covered by unit tests (79 tests total), including the page
+  structures for the Conversation, modern Commits, and legacy Commits
+  views.
+- CI runs on both the minimum supported Node (22) and current (24).
+
 ## [1.1.0] - 2026-06-04
 
 ### Added
diff --git a/README.md b/README.md
index a65701c..0c3f0b6 100644
--- a/README.md
+++ b/README.md
@@ -115,15 +115,22 @@ source files in this repo as-is. To make a change, edit the source, reload
 the extension at `chrome://extensions` (or re-install the temporary add-on
 in Firefox), and refresh a PR page.
 
-| File            | Purpose                                               |
-| --------------- | ----------------------------------------------------- |
-| `manifest.json` | Extension definition (Manifest V3, Chrome + Firefox)  |
-| `constants.js`  | Shared constants (storage key, order values)          |
-| `reorder.js`    | Pure DOM-reordering helpers (unit-tested)             |
-| `content.js`    | Runs on PR pages; reorders comments, draws the toggle |
-| `background.js` | Keeps the toolbar icon in sync with the current tab   |
-| `popup.html`    | Toolbar popup UI                                      |
-| `popup.js`      | Popup behavior; reads/writes saved preference         |
+| File            | Purpose                                                   |
+| --------------- | --------------------------------------------------------- |
+| `manifest.json` | Extension definition (Manifest V3, Chrome + Firefox)      |
+| `constants.js`  | Shared constants (storage key, order values)              |
+| `reorder.js`    | Pure DOM-reordering helpers (unit-tested)                 |
+| `checks.js`     | PR status-checks detection helpers (unit-tested)          |
+| `pages.js`      | Per-page GitHub DOM selectors and targets (unit-tested)   |
+| `content.js`    | Runs on PR pages; wires storage, observers, and the UI    |
+| `background.js` | Keeps the toolbar icon in sync with the tab (unit-tested) |
+| `popup.html`    | Toolbar popup UI                                          |
+| `popup.js`      | Popup behavior; reads/writes saved preference             |
+
+When GitHub ships a UI change that breaks reordering, the selectors to
+update live in `pages.js` (timeline/commits targets) and `checks.js`
+(status-checks box); each has jsdom tests with fixtures mirroring the real
+page structure, so start by updating the fixture to match the new DOM.
 
 ### Dev tooling (optional)
 
@@ -134,7 +141,8 @@ extension — they only help when contributing.
 npm install      # install dev dependencies
 npm run lint     # ESLint
 npm run format   # Prettier (writes)
-npm test         # Vitest unit tests for reorder.js
+npm run typecheck # tsc --checkJs over the extension sources
+npm test         # Vitest unit tests (reorder, checks, constants, packaging)
 npm run build    # produce the .zip / .xpi (version read from manifest.json)
 ```
 
diff --git a/background.js b/background.js
index 96226fa..c89f07a 100644
--- a/background.js
+++ b/background.js
@@ -8,56 +8,87 @@
 // We use chrome.tabs events instead of messages from the content script
 // so the icon updates correctly even when the user navigates to a
 // non-PR URL (where the content script doesn't run).
+//
+// Structured like the other modules: the logic lives in a factory so
+// Node tests can import and exercise it against a stubbed chrome API,
+// while listener registration stays synchronous at load time (an MV3
+// service-worker requirement — events fired while the worker was asleep
+// are only redelivered to listeners registered during startup).
 
-const ACTIVE_PATH = { 16: "icon-16.png", 48: "icon-48.png" };
-const DISABLED_PATH = { 16: "icon-16-disabled.png", 48: "icon-48-disabled.png" };
-
-// Matches any PR page the extension is active on:
-//   /owner/repo/pull/N            (Conversation)
-//   /owner/repo/pull/N/commits    (Commits)
-// All other sub-paths (/files, /checks, deep diff anchors) leave the
-// toolbar icon in the disabled state.
-const ACTIVE_URL_RE =
-  /^https:\/\/github\.com\/[^/]+\/[^/]+\/pull\/\d+(?:\/commits)?\/?(?:[?#].*)?$/;
-
-/** @param {unknown} url */
-function isActiveUrl(url) {
-  return typeof url === "string" && ACTIVE_URL_RE.test(url);
-}
-
-/**
- * @param {number | undefined} tabId
- * @param {string | undefined} url
- */
-function setIconForTab(tabId, url) {
-  const path = isActiveUrl(url) ? ACTIVE_PATH : DISABLED_PATH;
-  chrome.action.setIcon({ tabId, path }).catch(() => {
-    // Tab may have been closed between the event and our call; ignore.
-  });
-}
-
-// Initial state on install / browser start: walk existing tabs.
-function syncAllTabs() {
-  chrome.tabs.query({}, (tabs) => {
-    for (const tab of tabs) setIconForTab(tab.id, tab.url);
-  });
-}
-
-chrome.runtime.onInstalled.addListener(syncAllTabs);
-chrome.runtime.onStartup.addListener(syncAllTabs);
-
-// URL changes — covers both full page loads and pushState/replaceState soft nav.
-chrome.tabs.onUpdated.addListener((tabId, changeInfo, tab) => {
-  if (changeInfo.url || changeInfo.status === "complete") {
-    setIconForTab(tabId, changeInfo.url || tab.url);
+(function (root, factory) {
+  const api = factory();
+  if (typeof module !== "undefined" && module.exports) {
+    module.exports = api;
+  } else {
+    Object.assign(root, api);
+  }
+
+  if (typeof chrome !== "undefined" && chrome.runtime) {
+    chrome.runtime.onInstalled.addListener(api.syncAllTabs);
+    chrome.runtime.onStartup.addListener(api.syncAllTabs);
+    chrome.tabs.onUpdated.addListener(api.handleTabUpdated);
+    chrome.tabs.onActivated.addListener(api.handleTabActivated);
+  }
+})(typeof globalThis !== "undefined" ? globalThis : this, function () {
+  const ACTIVE_PATH = { 16: "icon-16.png", 48: "icon-48.png", 128: "icon-128.png" };
+  const DISABLED_PATH = {
+    16: "icon-16-disabled.png",
+    48: "icon-48-disabled.png",
+    128: "icon-128-disabled.png",
+  };
+
+  // Matches any PR page the extension is active on:
+  //   /owner/repo/pull/N            (Conversation)
+  //   /owner/repo/pull/N/commits    (Commits)
+  // All other sub-paths (/files, /checks, deep diff anchors) leave the
+  // toolbar icon in the disabled state.
+  const ACTIVE_URL_RE =
+    /^https:\/\/github\.com\/[^/]+\/[^/]+\/pull\/\d+(?:\/commits)?\/?(?:[?#].*)?$/;
+
+  /** @param {unknown} url */
+  function isActiveUrl(url) {
+    return typeof url === "string" && ACTIVE_URL_RE.test(url);
+  }
+
+  /**
+   * @param {number | undefined} tabId
+   * @param {string | undefined} url
+   */
+  function setIconForTab(tabId, url) {
+    const path = isActiveUrl(url) ? ACTIVE_PATH : DISABLED_PATH;
+    chrome.action.setIcon({ tabId, path }).catch(() => {
+      // Tab may have been closed between the event and our call; ignore.
+    });
+  }
+
+  // Initial state on install / browser start: walk existing tabs.
+  function syncAllTabs() {
+    chrome.tabs.query({}, (tabs) => {
+      for (const tab of tabs) setIconForTab(tab.id, tab.url);
+    });
+  }
+
+  // URL changes — covers both full page loads and pushState/replaceState soft nav.
+  /**
+   * @param {number} tabId
+   * @param {chrome.tabs.OnUpdatedInfo} changeInfo
+   * @param {chrome.tabs.Tab} tab
+   */
+  function handleTabUpdated(tabId, changeInfo, tab) {
+    if (changeInfo.url || changeInfo.status === "complete") {
+      setIconForTab(tabId, changeInfo.url || tab.url);
+    }
+  }
+
+  // Tab activation — make sure the toolbar reflects the now-focused tab
+  // even if it was opened/loaded in the background.
+  /** @param {{ tabId: number }} activeInfo */
+  function handleTabActivated({ tabId }) {
+    chrome.tabs.get(tabId, (tab) => {
+      if (chrome.runtime.lastError) return;
+      setIconForTab(tabId, tab.url);
+    });
   }
-});
 
-// Tab activation — make sure the toolbar reflects the now-focused tab
-// even if it was opened/loaded in the background.
-chrome.tabs.onActivated.addListener(({ tabId }) => {
-  chrome.tabs.get(tabId, (tab) => {
-    if (chrome.runtime.lastError) return;
-    setIconForTab(tabId, tab.url);
-  });
+  return { isActiveUrl, setIconForTab, syncAllTabs, handleTabUpdated, handleTabActivated };
 });
diff --git a/checks.js b/checks.js
index 5fffe6b..bc41e1b 100644
--- a/checks.js
+++ b/checks.js
@@ -45,6 +45,17 @@
       .filter(Boolean);
   }
 
+  // Status-phrase patterns. Word boundaries plus explicit word forms keep
+  // a check *named* e.g. "failover-suite" or "cancellation-service" from
+  // tripping the failure branch when its label reads "... successful in 2m"
+  // (bare substring matching used to misreport those as failing). A check
+  // name that itself contains a standalone status word (e.g. "error-pages")
+  // is still ambiguous — labels are all GitHub's accessible rows give us.
+  const FAILING_RE =
+    /\b(fail(?:ed|ing|ure|s)?|error(?:ed|s)?|timed out|cancel(?:l?ed)?|denied|action required)\b/i;
+  const RUNNING_RE = /\b(in[ _]progress|pending|queued|running|waiting|expected)\b/i;
+  const PASSING_RE = /\b(success(?:ful)?|passed|passing)\b/i;
+
   // Aggregate the check-row labels into a coarse { key, label, color }.
   // Precedence: any failure -> failing; else any in-flight -> running;
   // else any success -> passing; else unknown. Checked in that order so a
@@ -55,13 +66,13 @@
     /** @param {RegExp} re */
     const any = (re) => list.some((l) => re.test(l));
 
-    if (any(/(fail|error|timed out|cancel|denied|action required)/i)) {
+    if (any(FAILING_RE)) {
       return { key: "failing", label: "✗ Checks failing", color: "#d1242f" };
     }
-    if (any(/(in progress|in_progress|pending|queued|running|waiting|expected)/i)) {
+    if (any(RUNNING_RE)) {
       return { key: "running", label: "• Checks running", color: "#9a6700" };
     }
-    if (any(/(success|passed|passing)/i)) {
+    if (any(PASSING_RE)) {
       return { key: "passing", label: "✓ Checks passing", color: "#1a7f37" };
     }
     return { key: "unknown", label: "• Checks status", color: "#1f6feb" };
diff --git a/constants.js b/constants.js
index f54d504..c1437e1 100644
--- a/constants.js
+++ b/constants.js
@@ -15,10 +15,18 @@
     Object.assign(root, factory());
   }
 })(typeof globalThis !== "undefined" ? globalThis : this, function () {
-  return {
-    // chrome.storage.local key holding the user's order preference.
-    STORAGE_KEY: "prCommentOrder",
-    // Allowed values for that preference.
-    ORDER: { NEWEST: "newest", OLDEST: "oldest" },
-  };
+  // chrome.storage.local key holding the user's order preference.
+  const STORAGE_KEY = "prCommentOrder";
+  // Allowed values for that preference.
+  const ORDER = { NEWEST: "newest", OLDEST: "oldest" };
+
+  // Coerce whatever came out of storage into a valid order value. Storage
+  // is a system boundary: a stale or corrupted value must not leave the
+  // button label saying one thing while the sort does another.
+  /** @param {unknown} value */
+  function normalizeOrder(value) {
+    return value === ORDER.OLDEST ? ORDER.OLDEST : ORDER.NEWEST;
+  }
+
+  return { STORAGE_KEY, ORDER, normalizeOrder };
 });
diff --git a/content.js b/content.js
index 3e328e1..7ad1fb1 100644
--- a/content.js
+++ b/content.js
@@ -13,128 +13,15 @@
 // page. Non-supported PR sub-tabs (Files Changed, Checks) are ignored.
 
 (() => {
-  // STORAGE_KEY and ORDER come from constants.js (loaded first);
-  // firstMatchingTarget and applyOrderToTarget come from reorder.js.
+  // STORAGE_KEY, ORDER, and normalizeOrder come from constants.js (loaded
+  // first); applyOrderToTarget from reorder.js; getPageConfig (and every
+  // GitHub DOM selector) from pages.js; the checks helpers from checks.js.
   const RESET_VERSION_KEY = "prrcDefaultResetVersion";
   const CURRENT_RESET_VERSION = 1;
   const BUTTON_ID = "pr-reverse-comments-toggle";
   const CHECKS_STATUS_ID = "pr-reverse-comments-checks-status";
 
-  // Per-page configuration. `getTargets()` returns an array of
-  //   { el, item, descendant }
-  // — one entry per DOM region that should be reversed. Conversation has
-  // exactly one (the timeline); Commits has many (the list of date
-  // groups, plus the inner <ol> of every individual date group).
-  const PAGE_CONFIGS = [
-    {
-      name: "conversation",
-      pathRe: /^\/[^/]+\/[^/]+\/pull\/\d+\/?$/,
-      getTargets: () => {
-        const candidates = [
-          { container: ".js-discussion", item: ".js-timeline-item" },
-          {
-            container: '[data-testid="issue-viewer-issue-container"]',
-            item: '[data-testid^="issue-viewer-comment"]',
-          },
-          { container: '[data-testid="pr-timeline"]', item: '[data-testid^="pr-timeline-item"]' },
-          { container: ".pull-discussion-timeline", item: ".js-timeline-item" },
-        ];
-        const t = firstMatchingTarget(candidates);
-        const targets = t ? [t] : [];
-
-        // The batch as a whole is one .js-timeline-item (reversed by the
-        // target above); also reverse the individual commits inside each
-        // "added N commits" batch so they read newest-first too.
-        targets.push(...pushedCommitTargets());
-
-        return targets;
-      },
-    },
-    {
-      name: "commits",
-      pathRe: /^\/[^/]+\/[^/]+\/pull\/\d+\/commits\/?$/,
-      getTargets: () => {
-        const targets = [];
-
-        // Modern React-rendered Commits page. Structure (May 2026):
-        //   <div data-testid="commits-list">
-        //     <div class="prc-Timeline-Timeline-...">              ← Timeline wrapper
-        //       <div class="… Timeline-Item …">                    ← day group N
-        //         <h3 data-testid="commit-group-title">Commits on …</h3>
-        //         <ul data-listview-component="items-list">
-        //           <li data-testid="commit-row-item">…</li>       ← commit within day
-        //           …
-        //         </ul>
-        //       </div>
-        //       <div class="… Timeline-Item …">…</div>             ← day group N+1
-        //       …
-        //     </div>
-        //   </div>
-        //
-        // To make "newest first" feel right we have to reverse two
-        // levels at once: the .Timeline-Item day groups (so the most
-        // recent day moves to the top), AND the <li> commits inside
-        // each day's <ul> (so within a day the latest commit is on
-        // top). Doing only one of them gives a confusing half-flipped
-        // result.
-        const commitsList = document.querySelector('[data-testid="commits-list"]');
-        if (commitsList) {
-          const dayGroups = commitsList.querySelectorAll(".Timeline-Item");
-
-          // 1) Reverse the day groups themselves (only meaningful if 2+).
-          if (dayGroups.length >= 2) {
-            const dayParent = dayGroups[0].parentElement;
-            if (dayParent) {
-              targets.push({
-                el: dayParent,
-                item: ".Timeline-Item",
-                descendant: false,
-              });
-            }
-          }
-
-          // 2) Reverse commits within each day's <ul>.
-          for (const group of dayGroups) {
-            const ul = group.querySelector('ul[data-listview-component="items-list"]');
-            if (
-              ul &&
-              ul.querySelectorAll(':scope > li[data-testid="commit-row-item"]').length >= 2
-            ) {
-              targets.push({
-                el: ul,
-                item: 'li[data-testid="commit-row-item"]',
-                descendant: false,
-              });
-            }
-          }
-
-          if (targets.length) return targets;
-        }
-
-        // Legacy Rails-rendered Commits page: .js-commit-group date
-        // groups wrapping per-day ordered lists.
-        const groupTarget = firstMatchingTarget([
-          { container: ".js-commits-list", item: ".js-commit-group" },
-          { container: "#commits_bucket", item: ".js-commit-group" },
-        ]);
-        if (groupTarget) targets.push(groupTarget);
-
-        for (const group of document.querySelectorAll(".js-commit-group")) {
-          const ol = group.querySelector("ol");
-          if (ol && ol.querySelectorAll(":scope > li").length >= 2) {
-            targets.push({
-              el: ol,
-              item: ":scope > li",
-              descendant: false,
-            });
-          }
-        }
-
-        return targets;
-      },
-    },
-  ];
-
+  /** @type {PrrcOrder} */
   let currentOrder = ORDER.NEWEST;
   let isSorting = false;
   /** @type {MutationObserver[]} */
@@ -143,8 +30,7 @@
   let activeTargets = []; // [{ el, item, ... }]
 
   function getCurrentPageConfig() {
-    const path = location.pathname;
-    return PAGE_CONFIGS.find((c) => c.pathRe.test(path)) || null;
+    return getPageConfig(location.pathname);
   }
 
   function onSupportedPage() {
@@ -302,6 +188,9 @@
       indicator.textContent = state.label;
       indicator.style.border = `1px solid ${state.color}`;
       indicator.style.color = state.color;
+      // The visible label leans on color and a glyph (✓/✗/•); spell the
+      // status out for assistive tech.
+      indicator.setAttribute("aria-label", `PR status checks: ${state.key}. Jump to checks`);
     }
 
     if (indicator !== anchor.previousElementSibling) {
@@ -311,13 +200,16 @@
 
   /** @param {HTMLElement} btn */
   function updateButtonLabel(btn) {
+    const next = currentOrder === ORDER.NEWEST ? ORDER.OLDEST : ORDER.NEWEST;
     btn.textContent = currentOrder === ORDER.NEWEST ? "↓ Newest first" : "↑ Oldest first";
-    btn.title = `Click to switch to ${currentOrder === ORDER.NEWEST ? ORDER.OLDEST : ORDER.NEWEST} first`;
+    btn.title = `Click to switch to ${next} first`;
+    // The arrow glyph is decorative; give assistive tech a plain-text label.
+    btn.setAttribute("aria-label", `Comment order: ${currentOrder} first. Switch to ${next} first`);
   }
 
   chrome.storage.onChanged.addListener((changes, area) => {
     if (area !== "local" || !changes[STORAGE_KEY]) return;
-    currentOrder = /** @type {string} */ (changes[STORAGE_KEY].newValue || ORDER.NEWEST);
+    currentOrder = normalizeOrder(changes[STORAGE_KEY].newValue);
     const btn = document.getElementById(BUTTON_ID);
     if (btn) updateButtonLabel(btn);
     applyOrder(currentOrder);
@@ -371,7 +263,16 @@
 
   function startBodyWatcher() {
     const bodyObs = new MutationObserver(scheduleRebindIfNeeded);
-    bodyObs.observe(document.body, { childList: true, subtree: true });
+    // aria-label is watched because GitHub updates a check row's label in
+    // place (e.g. "in progress" -> "successful") without any structural
+    // mutation; without it the checks indicator would go stale until some
+    // unrelated DOM churn happened to fire the observer.
+    bodyObs.observe(document.body, {
+      childList: true,
+      subtree: true,
+      attributes: true,
+      attributeFilter: ["aria-label"],
+    });
   }
 
   async function init() {
@@ -381,7 +282,7 @@
       await chrome.storage.local.set({ [RESET_VERSION_KEY]: CURRENT_RESET_VERSION });
       currentOrder = ORDER.NEWEST;
     } else {
-      currentOrder = /** @type {string} */ (stored[STORAGE_KEY] || ORDER.NEWEST);
+      currentOrder = normalizeOrder(stored[STORAGE_KEY]);
     }
 
     startBodyWatcher();
@@ -392,7 +293,11 @@
     scheduleRebindIfNeeded();
   }
 
-  init();
+  init().catch((err) => {
+    // A storage failure here leaves the extension inert on this page; make
+    // the cause visible instead of an unhandled rejection.
+    console.error("[pr-reverse-comments] initialization failed:", err);
+  });
 
   // Fast paths for the soft-nav events GitHub does fire — avoid waiting
   // for the next DOM mutation tick. The body watcher above is the real
diff --git a/eslint.config.mjs b/eslint.config.mjs
index 37fc335..291673d 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -7,9 +7,11 @@ import prettier from "eslint-config-prettier";
 const sharedGlobals = {
   STORAGE_KEY: "readonly",
   ORDER: "readonly",
+  normalizeOrder: "readonly",
   firstMatchingTarget: "readonly",
   pushedCommitTargets: "readonly",
   applyOrderToTarget: "readonly",
+  getPageConfig: "readonly",
   findChecksBox: "readonly",
   getCheckLabels: "readonly",
   deriveChecksState: "readonly",
@@ -23,7 +25,7 @@ export default [
   // UMD modules: run in the browser (extension) AND under Node (tests),
   // so they legitimately reference both `globalThis`/window and module.
   {
-    files: ["constants.js", "reorder.js", "checks.js"],
+    files: ["constants.js", "reorder.js", "checks.js", "pages.js"],
     languageOptions: {
       globals: { ...globals.browser, ...globals.node, ...sharedGlobals },
     },
@@ -37,11 +39,11 @@ export default [
     },
   },
 
-  // Background service worker.
+  // Background service worker (UMD so its logic is testable under Node).
   {
     files: ["background.js"],
     languageOptions: {
-      globals: { ...globals.serviceworker, chrome: "readonly" },
+      globals: { ...globals.serviceworker, ...globals.node, chrome: "readonly" },
     },
   },
 
diff --git a/manifest.json b/manifest.json
index ee5808b..b444597 100644
--- a/manifest.json
+++ b/manifest.json
@@ -14,7 +14,8 @@
     "default_title": "GitHub PR Reverse Comments",
     "default_icon": {
       "16": "icon-16-disabled.png",
-      "48": "icon-48-disabled.png"
+      "48": "icon-48-disabled.png",
+      "128": "icon-128-disabled.png"
     },
     "default_popup": "popup.html"
   },
@@ -25,7 +26,7 @@
   "content_scripts": [
     {
       "matches": ["https://github.com/*/*/pull/*"],
-      "js": ["constants.js", "reorder.js", "checks.js", "content.js"],
+      "js": ["constants.js", "reorder.js", "checks.js", "pages.js", "content.js"],
       "run_at": "document_idle"
     }
   ],
diff --git a/package-lock.json b/package-lock.json
index 5c68e1b..ffb6331 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -4058,9 +4058,9 @@
       }
     },
     "node_modules/undici": {
-      "version": "7.27.0",
-      "resolved": "https://registry.npmjs.org/undici/-/undici-7.27.0.tgz",
-      "integrity": "sha512-+t2Z/GwkZQDtu00813aP66ygViGtPHKhhoFZpQKpKrE+9jIgES+Zw+mFNaDWOVRKiuJjuqKHzD3B1sfGg8+ZOQ==",
+      "version": "7.28.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-7.28.0.tgz",
+      "integrity": "sha512-cRZYrTDwWznlnRiPjggAGxZXanty6M8RV1ff8Wm4LWXBp7/IG8v5DnOm74DtUBp9OONpK75YlPnIjQqX0dBDtA==",
       "dev": true,
       "license": "MIT",
       "engines": {
diff --git a/package.json b/package.json
index d1106b5..2e8087f 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,14 @@
   "version": "1.1.0",
   "description": "Dev tooling for the GitHub PR Reverse Comments browser extension. The extension itself has no build step; these scripts only lint, format, test, and package it.",
   "private": true,
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/ShiosOS/github-pr-reverse-comments.git"
+  },
+  "homepage": "https://github.com/ShiosOS/github-pr-reverse-comments#readme",
+  "bugs": {
+    "url": "https://github.com/ShiosOS/github-pr-reverse-comments/issues"
+  },
   "engines": {
     "node": ">=22"
   },
diff --git a/pages.js b/pages.js
new file mode 100644
index 0000000..d85a0fe
--- /dev/null
+++ b/pages.js
@@ -0,0 +1,156 @@
+// @ts-check
+// Per-page target configuration: which URL paths the extension acts on and
+// which DOM regions get reversed there. This is where all the GitHub DOM
+// selectors live — the part most likely to break when GitHub ships a UI
+// change — so it is factored out of content.js and unit-tested under jsdom
+// with fixtures mirroring the real page structures.
+//
+// `getTargets()` returns an array of { el, item, descendant } — one entry
+// per DOM region that should be reversed. Conversation has one (the
+// timeline) plus one per "added N commits" batch; Commits has many (the
+// list of date groups, plus the inner list of every individual date group).
+//
+// Browser: attaches getPageConfig to the global scope (loaded after
+// reorder.js, before content.js). Node: exports it for tests.
+
+(function (root, factory) {
+  if (typeof module !== "undefined" && module.exports) {
+    const { firstMatchingTarget, pushedCommitTargets } = require("./reorder.js");
+    module.exports = factory(firstMatchingTarget, pushedCommitTargets);
+  } else {
+    const r = /** @type {*} */ (root);
+    Object.assign(root, factory(r.firstMatchingTarget, r.pushedCommitTargets));
+  }
+})(
+  typeof globalThis !== "undefined" ? globalThis : this,
+  function (
+    /** @type {(candidates: { container: string; item: string }[]) => PrrcTarget | null} */
+    firstMatchingTarget,
+    /** @type {(root?: ParentNode) => PrrcTarget[]} */
+    pushedCommitTargets,
+  ) {
+    /** @type {PrrcPageConfig[]} */
+    const PAGE_CONFIGS = [
+      {
+        name: "conversation",
+        pathRe: /^\/[^/]+\/[^/]+\/pull\/\d+\/?$/,
+        getTargets: () => {
+          const candidates = [
+            { container: ".js-discussion", item: ".js-timeline-item" },
+            {
+              container: '[data-testid="issue-viewer-issue-container"]',
+              item: '[data-testid^="issue-viewer-comment"]',
+            },
+            {
+              container: '[data-testid="pr-timeline"]',
+              item: '[data-testid^="pr-timeline-item"]',
+            },
+            { container: ".pull-discussion-timeline", item: ".js-timeline-item" },
+          ];
+          const t = firstMatchingTarget(candidates);
+          const targets = t ? [t] : [];
+
+          // The batch as a whole is one .js-timeline-item (reversed by the
+          // target above); also reverse the individual commits inside each
+          // "added N commits" batch so they read newest-first too.
+          targets.push(...pushedCommitTargets());
+
+          return targets;
+        },
+      },
+      {
+        name: "commits",
+        pathRe: /^\/[^/]+\/[^/]+\/pull\/\d+\/commits\/?$/,
+        getTargets: () => {
+          /** @type {PrrcTarget[]} */
+          const targets = [];
+
+          // Modern React-rendered Commits page. Structure (May 2026):
+          //   <div data-testid="commits-list">
+          //     <div class="prc-Timeline-Timeline-...">              ← Timeline wrapper
+          //       <div class="… Timeline-Item …">                    ← day group N
+          //         <h3 data-testid="commit-group-title">Commits on …</h3>
+          //         <ul data-listview-component="items-list">
+          //           <li data-testid="commit-row-item">…</li>       ← commit within day
+          //           …
+          //         </ul>
+          //       </div>
+          //       <div class="… Timeline-Item …">…</div>             ← day group N+1
+          //       …
+          //     </div>
+          //   </div>
+          //
+          // To make "newest first" feel right we have to reverse two
+          // levels at once: the .Timeline-Item day groups (so the most
+          // recent day moves to the top), AND the <li> commits inside
+          // each day's <ul> (so within a day the latest commit is on
+          // top). Doing only one of them gives a confusing half-flipped
+          // result.
+          const commitsList = document.querySelector('[data-testid="commits-list"]');
+          if (commitsList) {
+            const dayGroups = commitsList.querySelectorAll(".Timeline-Item");
+
+            // 1) Reverse the day groups themselves (only meaningful if 2+).
+            if (dayGroups.length >= 2) {
+              const dayParent = dayGroups[0].parentElement;
+              if (dayParent) {
+                targets.push({
+                  el: dayParent,
+                  item: ".Timeline-Item",
+                  descendant: false,
+                });
+              }
+            }
+
+            // 2) Reverse commits within each day's <ul>.
+            for (const group of dayGroups) {
+              const ul = group.querySelector('ul[data-listview-component="items-list"]');
+              if (
+                ul &&
+                ul.querySelectorAll(':scope > li[data-testid="commit-row-item"]').length >= 2
+              ) {
+                targets.push({
+                  el: ul,
+                  item: 'li[data-testid="commit-row-item"]',
+                  descendant: false,
+                });
+              }
+            }
+
+            if (targets.length) return targets;
+          }
+
+          // Legacy Rails-rendered Commits page: .js-commit-group date
+          // groups wrapping per-day ordered lists.
+          const groupTarget = firstMatchingTarget([
+            { container: ".js-commits-list", item: ".js-commit-group" },
+            { container: "#commits_bucket", item: ".js-commit-group" },
+          ]);
+          if (groupTarget) targets.push(groupTarget);
+
+          for (const group of document.querySelectorAll(".js-commit-group")) {
+            const ol = group.querySelector("ol");
+            if (ol && ol.querySelectorAll(":scope > li").length >= 2) {
+              targets.push({
+                el: ol,
+                item: ":scope > li",
+                descendant: false,
+              });
+            }
+          }
+
+          return targets;
+        },
+      },
+    ];
+
+    // The config whose pathRe matches the given location.pathname, or null
+    // on unsupported pages (Files Changed, Checks, issues, everything else).
+    /** @param {string} pathname */
+    function getPageConfig(pathname) {
+      return PAGE_CONFIGS.find((c) => c.pathRe.test(pathname)) || null;
+    }
+
+    return { getPageConfig };
+  },
+);
diff --git a/popup.html b/popup.html
index 29d72d2..8e15919 100644
--- a/popup.html
+++ b/popup.html
@@ -4,6 +4,28 @@
     <meta charset="utf-8" />
     <title>PR Reverse Comments</title>
     <style>
+      /* GitHub-ish palette; follows the browser's light/dark preference
+         instead of forcing dark on light-mode users. */
+      :root {
+        color-scheme: light dark;
+        --bg: #ffffff;
+        --fg: #1f2328;
+        --fg-muted: #59636e;
+        --btn-bg: #f6f8fa;
+        --btn-border: #d1d9e0;
+        --btn-hover: #eef1f4;
+        --accent: #1f6feb;
+      }
+      @media (prefers-color-scheme: dark) {
+        :root {
+          --bg: #0d1117;
+          --fg: #c9d1d9;
+          --fg-muted: #8b949e;
+          --btn-bg: #21262d;
+          --btn-border: #30363d;
+          --btn-hover: #30363d;
+        }
+      }
       body {
         font:
           13px -apple-system,
@@ -13,8 +35,8 @@
         width: 220px;
         margin: 0;
         padding: 12px;
-        background: #0d1117;
-        color: #c9d1d9;
+        background: var(--bg);
+        color: var(--fg);
       }
       h1 {
         font-size: 13px;
@@ -22,7 +44,7 @@
       }
       p {
         margin: 0 0 10px 0;
-        color: #8b949e;
+        color: var(--fg-muted);
         font-size: 11px;
       }
       .row {
@@ -32,20 +54,20 @@
       button {
         flex: 1;
         padding: 6px 8px;
-        background: #21262d;
-        color: #c9d1d9;
-        border: 1px solid #30363d;
+        background: var(--btn-bg);
+        color: var(--fg);
+        border: 1px solid var(--btn-border);
         border-radius: 6px;
         cursor: pointer;
         font-size: 12px;
       }
       button.active {
-        background: #1f6feb;
-        border-color: #1f6feb;
+        background: var(--accent);
+        border-color: var(--accent);
         color: #fff;
       }
       button:hover:not(.active) {
-        background: #30363d;
+        background: var(--btn-hover);
       }
     </style>
   </head>
diff --git a/popup.js b/popup.js
index d3f7c95..52166a8 100644
--- a/popup.js
+++ b/popup.js
@@ -1,5 +1,6 @@
 // @ts-check
-// STORAGE_KEY and ORDER come from constants.js (loaded first in popup.html).
+// STORAGE_KEY, ORDER, and normalizeOrder come from constants.js (loaded
+// first in popup.html).
 
 const buttons = {
   [ORDER.NEWEST]: document.getElementById("newest"),
@@ -14,7 +15,7 @@ function render(order) {
 
 async function init() {
   const stored = await chrome.storage.local.get(STORAGE_KEY);
-  render(/** @type {string} */ (stored[STORAGE_KEY] || ORDER.NEWEST));
+  render(normalizeOrder(stored[STORAGE_KEY]));
 }
 
 for (const [order, btn] of Object.entries(buttons)) {
@@ -24,4 +25,11 @@ for (const [order, btn] of Object.entries(buttons)) {
   });
 }
 
+// Keep the popup in step with the in-page toggle button: both write the
+// same storage key, so a change from either side re-renders here.
+chrome.storage.onChanged.addListener((changes, area) => {
+  if (area !== "local" || !changes[STORAGE_KEY]) return;
+  render(normalizeOrder(changes[STORAGE_KEY].newValue));
+});
+
 init();
diff --git a/scripts/build.mjs b/scripts/build.mjs
index a750ac6..81a93e9 100644
--- a/scripts/build.mjs
+++ b/scripts/build.mjs
@@ -3,9 +3,16 @@
 // The version is read from manifest.json — the single source of truth — so
 // bumping the extension version never means editing this script or a
 // filename by hand.
+//
+// The file list is derived from manifest.json (content scripts, background
+// scripts, icons, popup) plus the <script src> tags of any packaged HTML
+// page, rather than hand-maintained. A hand-maintained list once shipped a
+// broken build by omitting checks.js; deriving the list makes that class of
+// mistake impossible, and the existence check below turns a missing file
+// into a build failure instead of a silently broken archive.
 
 import { createWriteStream } from "node:fs";
-import { readFile } from "node:fs/promises";
+import { readFile, stat } from "node:fs/promises";
 import { fileURLToPath } from "node:url";
 import { createRequire } from "node:module";
 import path from "node:path";
@@ -16,23 +23,32 @@ const archiver = require("archiver");
 
 const root = path.dirname(path.dirname(fileURLToPath(import.meta.url)));
 
-// Files the browser actually loads. Everything else (tests, configs,
-// node_modules, docs) is dev-only and must not ship.
-const INCLUDE = [
-  "manifest.json",
-  "constants.js",
-  "reorder.js",
-  "content.js",
-  "background.js",
-  "popup.html",
-  "popup.js",
-  "icon-16.png",
-  "icon-16-disabled.png",
-  "icon-48.png",
-  "icon-48-disabled.png",
-  "icon-128.png",
-  "icon-128-disabled.png",
-];
+/** Collect every file the browser loads, straight from the manifest. */
+async function collectFiles(manifest) {
+  const files = new Set(["manifest.json"]);
+
+  for (const cs of manifest.content_scripts ?? []) {
+    for (const f of cs.js ?? []) files.add(f);
+    for (const f of cs.css ?? []) files.add(f);
+  }
+
+  if (manifest.background?.service_worker) files.add(manifest.background.service_worker);
+  for (const f of manifest.background?.scripts ?? []) files.add(f);
+
+  for (const f of Object.values(manifest.icons ?? {})) files.add(f);
+  for (const f of Object.values(manifest.action?.default_icon ?? {})) files.add(f);
+  if (manifest.action?.default_popup) files.add(manifest.action.default_popup);
+
+  // HTML pages pull in their own scripts via <script src>.
+  for (const f of [...files].filter((f) => f.endsWith(".html"))) {
+    const html = await readFile(path.join(root, f), "utf8");
+    for (const [, src] of html.matchAll(/<script\s+[^>]*src="([^"]+)"/g)) {
+      files.add(src);
+    }
+  }
+
+  return [...files].sort();
+}
 
 function zipTo(outPath, files) {
   return new Promise((resolve, reject) => {
@@ -48,15 +64,26 @@ function zipTo(outPath, files) {
 
 const manifest = JSON.parse(await readFile(path.join(root, "manifest.json"), "utf8"));
 const { version, name } = manifest;
-const base = "github-pr-reverse-comments";
+const files = await collectFiles(manifest);
+
+// Fail loudly if the manifest references a file that doesn't exist.
+const missing = [];
+for (const f of files) {
+  await stat(path.join(root, f)).catch(() => missing.push(f));
+}
+if (missing.length) {
+  console.error(`Referenced files not found: ${missing.join(", ")}`);
+  process.exit(1);
+}
 
+const base = "github-pr-reverse-comments";
 const zipName = `${base}.zip`;
 const xpiName = `${base}-${version}.xpi`;
 
 // Identical contents; the .xpi extension is just what Firefox expects.
-const zipBytes = await zipTo(path.join(root, zipName), INCLUDE);
-await zipTo(path.join(root, xpiName), INCLUDE);
+const zipBytes = await zipTo(path.join(root, zipName), files);
+await zipTo(path.join(root, xpiName), files);
 
-console.log(`Built ${name} v${version}`);
+console.log(`Built ${name} v${version} (${files.length} files)`);
 console.log(`  ${zipName} (${zipBytes} bytes)`);
 console.log(`  ${xpiName}`);
diff --git a/test/background.test.mjs b/test/background.test.mjs
new file mode 100644
index 0000000..c21a9ef
--- /dev/null
+++ b/test/background.test.mjs
@@ -0,0 +1,148 @@
+// background.js is exercised against a stubbed chrome API: the stub is
+// installed before the (dynamic) import so the module's synchronous
+// listener registration runs against it, exactly as it does in the browser.
+
+import { describe, it, expect, beforeAll, beforeEach, vi } from "vitest";
+
+const setIcon = vi.fn(() => Promise.resolve());
+const tabsQuery = vi.fn();
+const tabsGet = vi.fn();
+const fakeEvent = () => ({ addListener: vi.fn() });
+
+const chromeStub = {
+  runtime: { onInstalled: fakeEvent(), onStartup: fakeEvent(), lastError: undefined },
+  tabs: { onUpdated: fakeEvent(), onActivated: fakeEvent(), query: tabsQuery, get: tabsGet },
+  action: { setIcon },
+};
+
+let background;
+
+beforeAll(async () => {
+  globalThis.chrome = chromeStub;
+  background = (await import("../background.js")).default;
+});
+
+beforeEach(() => {
+  setIcon.mockClear();
+  tabsQuery.mockClear();
+  tabsGet.mockClear();
+  chromeStub.runtime.lastError = undefined;
+});
+
+describe("module load", () => {
+  it("registers all four event listeners synchronously", () => {
+    // MV3 requirement: listeners must attach during worker startup.
+    expect(chromeStub.runtime.onInstalled.addListener).toHaveBeenCalledWith(background.syncAllTabs);
+    expect(chromeStub.runtime.onStartup.addListener).toHaveBeenCalledWith(background.syncAllTabs);
+    expect(chromeStub.tabs.onUpdated.addListener).toHaveBeenCalledWith(background.handleTabUpdated);
+    expect(chromeStub.tabs.onActivated.addListener).toHaveBeenCalledWith(
+      background.handleTabActivated,
+    );
+  });
+});
+
+describe("isActiveUrl", () => {
+  it.each([
+    "https://github.com/owner/repo/pull/1",
+    "https://github.com/owner/repo/pull/123/",
+    "https://github.com/owner/repo/pull/123?diff=split",
+    "https://github.com/owner/repo/pull/123#issuecomment-1",
+    "https://github.com/owner/repo/pull/123/commits",
+    "https://github.com/owner/repo/pull/123/commits/?page=2",
+  ])("accepts %s", (url) => {
+    expect(background.isActiveUrl(url)).toBe(true);
+  });
+
+  it.each([
+    "https://github.com/owner/repo/pull/123/files",
+    "https://github.com/owner/repo/pull/123/checks",
+    "https://github.com/owner/repo/pull/123/commits/abc123",
+    "https://github.com/owner/repo/issues/123",
+    "https://github.com/owner/repo",
+    "https://github.com/owner/repo/pulls",
+    "http://github.com/owner/repo/pull/1", // not https
+    "https://example.com/owner/repo/pull/1", // not github.com
+    "https://github.evil.example/owner/repo/pull/1",
+    undefined,
+    42,
+  ])("rejects %s", (url) => {
+    expect(background.isActiveUrl(url)).toBe(false);
+  });
+});
+
+describe("setIconForTab", () => {
+  it("sets the active icon set on PR pages", () => {
+    background.setIconForTab(7, "https://github.com/o/r/pull/1");
+    expect(setIcon).toHaveBeenCalledWith({
+      tabId: 7,
+      path: { 16: "icon-16.png", 48: "icon-48.png", 128: "icon-128.png" },
+    });
+  });
+
+  it("sets the disabled icon set elsewhere (including unknown URLs)", () => {
+    background.setIconForTab(7, undefined);
+    expect(setIcon).toHaveBeenCalledWith({
+      tabId: 7,
+      path: {
+        16: "icon-16-disabled.png",
+        48: "icon-48-disabled.png",
+        128: "icon-128-disabled.png",
+      },
+    });
+  });
+
+  it("swallows setIcon rejections (tab closed mid-flight)", async () => {
+    setIcon.mockImplementationOnce(() => Promise.reject(new Error("No tab with id")));
+    background.setIconForTab(9, "https://github.com/o/r/pull/1");
+    // Must not surface as an unhandled rejection.
+    await new Promise((r) => setTimeout(r, 0));
+  });
+});
+
+describe("handleTabUpdated", () => {
+  it("updates on URL change", () => {
+    background.handleTabUpdated(1, { url: "https://github.com/o/r/pull/2" }, { id: 1 });
+    expect(setIcon).toHaveBeenCalledTimes(1);
+  });
+
+  it("updates on load completion using the tab's URL", () => {
+    background.handleTabUpdated(1, { status: "complete" }, { url: "https://github.com/o/r" });
+    expect(setIcon).toHaveBeenCalledTimes(1);
+  });
+
+  it("ignores unrelated updates (e.g. title changes)", () => {
+    background.handleTabUpdated(1, { title: "New title" }, { id: 1 });
+    expect(setIcon).not.toHaveBeenCalled();
+  });
+});
+
+describe("handleTabActivated", () => {
+  it("looks the tab up and sets its icon", () => {
+    tabsGet.mockImplementation((tabId, cb) => cb({ id: tabId, url: "https://github.com/o/r" }));
+    background.handleTabActivated({ tabId: 3 });
+    expect(tabsGet).toHaveBeenCalledWith(3, expect.any(Function));
+    expect(setIcon).toHaveBeenCalledTimes(1);
+  });
+
+  it("bails out when the tab is already gone (runtime.lastError)", () => {
+    tabsGet.mockImplementation((tabId, cb) => {
+      chromeStub.runtime.lastError = { message: "No tab with id" };
+      cb(undefined);
+    });
+    background.handleTabActivated({ tabId: 3 });
+    expect(setIcon).not.toHaveBeenCalled();
+  });
+});
+
+describe("syncAllTabs", () => {
+  it("sets the icon for every open tab", () => {
+    tabsQuery.mockImplementation((_filter, cb) =>
+      cb([
+        { id: 1, url: "https://github.com/o/r/pull/1" },
+        { id: 2, url: "https://example.com" },
+      ]),
+    );
+    background.syncAllTabs();
+    expect(setIcon).toHaveBeenCalledTimes(2);
+  });
+});
diff --git a/test/build.test.mjs b/test/build.test.mjs
new file mode 100644
index 0000000..893b6b8
--- /dev/null
+++ b/test/build.test.mjs
@@ -0,0 +1,70 @@
+// Integration test for scripts/build.mjs: run the real packaging script
+// and verify the archive contains every file the browser will ask for.
+// This guards against the class of bug where a script is added to
+// manifest.json but the release archive doesn't ship it (which once
+// happened with checks.js, producing broken store builds).
+
+import { describe, it, expect, beforeAll } from "vitest";
+import { execFile } from "node:child_process";
+import { promisify } from "node:util";
+import { readFile } from "node:fs/promises";
+import { fileURLToPath } from "node:url";
+import path from "node:path";
+
+const run = promisify(execFile);
+const root = path.dirname(path.dirname(fileURLToPath(import.meta.url)));
+const zipPath = path.join(root, "github-pr-reverse-comments.zip");
+
+/** @type {string[]} */
+let entries = [];
+let manifest;
+
+beforeAll(async () => {
+  manifest = JSON.parse(await readFile(path.join(root, "manifest.json"), "utf8"));
+  await run("node", [path.join(root, "scripts", "build.mjs")]);
+  const { stdout } = await run("unzip", ["-Z1", zipPath]);
+  entries = stdout.split(/\r?\n/).filter(Boolean);
+}, 30_000);
+
+describe("packaged archive", () => {
+  it("contains the manifest itself", () => {
+    expect(entries).toContain("manifest.json");
+  });
+
+  it("contains every content script listed in manifest.json", () => {
+    for (const cs of manifest.content_scripts) {
+      for (const f of cs.js) expect(entries).toContain(f);
+    }
+  });
+
+  it("contains the background scripts", () => {
+    expect(entries).toContain(manifest.background.service_worker);
+    for (const f of manifest.background.scripts) expect(entries).toContain(f);
+  });
+
+  it("contains the popup page and the scripts it loads", async () => {
+    const popup = manifest.action.default_popup;
+    expect(entries).toContain(popup);
+    const html = await readFile(path.join(root, popup), "utf8");
+    for (const [, src] of html.matchAll(/<script\s+[^>]*src="([^"]+)"/g)) {
+      expect(entries).toContain(src);
+    }
+  });
+
+  it("contains every icon referenced by the manifest", () => {
+    for (const f of Object.values(manifest.icons)) expect(entries).toContain(f);
+    for (const f of Object.values(manifest.action.default_icon)) expect(entries).toContain(f);
+  });
+
+  it("ships no dev-only files", () => {
+    const forbidden = entries.filter(
+      (e) =>
+        e.startsWith("node_modules/") ||
+        e.startsWith("test/") ||
+        e.startsWith(".github/") ||
+        /\.(mjs|md|lock)$/.test(e) ||
+        e.startsWith("."),
+    );
+    expect(forbidden).toEqual([]);
+  });
+});
diff --git a/test/checks.test.mjs b/test/checks.test.mjs
index 23585aa..8a16d51 100644
--- a/test/checks.test.mjs
+++ b/test/checks.test.mjs
@@ -73,6 +73,24 @@ describe("deriveChecksState", () => {
     expect(deriveChecksState("everything successful").key).toBe("passing");
   });
 
+  it("is not fooled by status words embedded in check names", () => {
+    // Substring matching used to classify these as failing.
+    expect(deriveChecksState(["failover-suite successful in 2m"]).key).toBe("passing");
+    expect(deriveChecksState(["cancellation-service successful in 1m"]).key).toBe("passing");
+    expect(deriveChecksState(["unfailing-tests successful"]).key).toBe("passing");
+  });
+
+  it("still matches the real inflected status phrases", () => {
+    expect(deriveChecksState(["ci failed after 2m"]).key).toBe("failing");
+    expect(deriveChecksState(["ci failure"]).key).toBe("failing");
+    expect(deriveChecksState(["deploy cancelled after 10s"]).key).toBe("failing");
+    expect(deriveChecksState(["deploy canceled after 10s"]).key).toBe("failing");
+    expect(deriveChecksState(["lint timed out"]).key).toBe("failing");
+    expect(deriveChecksState(["review action required"]).key).toBe("failing");
+    expect(deriveChecksState(["build queued"]).key).toBe("running");
+    expect(deriveChecksState(["build in_progress"]).key).toBe("running");
+  });
+
   it("matches the real captured check set (running: one is waiting)", () => {
     expect(deriveChecksState(REAL_LABELS).key).toBe("running");
   });
diff --git a/test/constants.test.mjs b/test/constants.test.mjs
new file mode 100644
index 0000000..4ae16be
--- /dev/null
+++ b/test/constants.test.mjs
@@ -0,0 +1,19 @@
+import { describe, it, expect } from "vitest";
+import constants from "../constants.js";
+
+const { ORDER, normalizeOrder } = constants;
+
+describe("normalizeOrder", () => {
+  it("passes through the two valid values", () => {
+    expect(normalizeOrder(ORDER.NEWEST)).toBe(ORDER.NEWEST);
+    expect(normalizeOrder(ORDER.OLDEST)).toBe(ORDER.OLDEST);
+  });
+
+  it("falls back to newest for anything else from storage", () => {
+    expect(normalizeOrder(undefined)).toBe(ORDER.NEWEST);
+    expect(normalizeOrder(null)).toBe(ORDER.NEWEST);
+    expect(normalizeOrder("")).toBe(ORDER.NEWEST);
+    expect(normalizeOrder("descending")).toBe(ORDER.NEWEST);
+    expect(normalizeOrder(42)).toBe(ORDER.NEWEST);
+  });
+});
diff --git a/test/pages.test.mjs b/test/pages.test.mjs
new file mode 100644
index 0000000..c2281fa
--- /dev/null
+++ b/test/pages.test.mjs
@@ -0,0 +1,182 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import pages from "../pages.js";
+
+const { getPageConfig } = pages;
+
+beforeEach(() => {
+  document.body.innerHTML = "";
+});
+
+describe("getPageConfig — path routing", () => {
+  it("matches the Conversation page, with and without a trailing slash", () => {
+    expect(getPageConfig("/owner/repo/pull/123")?.name).toBe("conversation");
+    expect(getPageConfig("/owner/repo/pull/123/")?.name).toBe("conversation");
+  });
+
+  it("matches the Commits page, with and without a trailing slash", () => {
+    expect(getPageConfig("/owner/repo/pull/123/commits")?.name).toBe("commits");
+    expect(getPageConfig("/owner/repo/pull/123/commits/")?.name).toBe("commits");
+  });
+
+  it("rejects unsupported PR sub-tabs and other pages", () => {
+    expect(getPageConfig("/owner/repo/pull/123/files")).toBeNull();
+    expect(getPageConfig("/owner/repo/pull/123/checks")).toBeNull();
+    expect(getPageConfig("/owner/repo/pull/123/commits/abc123")).toBeNull();
+    expect(getPageConfig("/owner/repo/issues/123")).toBeNull();
+    expect(getPageConfig("/owner/repo/pull/not-a-number")).toBeNull();
+    expect(getPageConfig("/owner/repo")).toBeNull();
+    expect(getPageConfig("/")).toBeNull();
+  });
+});
+
+describe("conversation targets", () => {
+  function buildTimeline(itemCount) {
+    const timeline = document.createElement("div");
+    timeline.className = "js-discussion";
+    for (let i = 0; i < itemCount; i++) {
+      const item = document.createElement("div");
+      item.className = "js-timeline-item";
+      timeline.appendChild(item);
+    }
+    document.body.appendChild(timeline);
+    return timeline;
+  }
+
+  it("targets the classic .js-discussion timeline", () => {
+    const timeline = buildTimeline(3);
+    const targets = getPageConfig("/o/r/pull/1").getTargets();
+    expect(targets).toHaveLength(1);
+    expect(targets[0]).toMatchObject({ el: timeline, item: ".js-timeline-item" });
+  });
+
+  it("falls back to the React issue-viewer container", () => {
+    const container = document.createElement("div");
+    container.setAttribute("data-testid", "issue-viewer-issue-container");
+    for (const id of ["issue-viewer-comment-1", "issue-viewer-comment-2"]) {
+      const item = document.createElement("div");
+      item.setAttribute("data-testid", id);
+      container.appendChild(item);
+    }
+    document.body.appendChild(container);
+
+    const targets = getPageConfig("/o/r/pull/1").getTargets();
+    expect(targets).toHaveLength(1);
+    expect(targets[0].el).toBe(container);
+  });
+
+  it("adds a target per pushed-commit batch alongside the timeline", () => {
+    buildTimeline(2);
+    // "added N commits" batch: header + sibling wrapper of .TimelineItem.
+    const header = document.createElement("div");
+    header.id = "commits-pushed-abc123";
+    const wrapper = document.createElement("div");
+    for (let i = 0; i < 2; i++) {
+      const commit = document.createElement("div");
+      commit.className = "TimelineItem";
+      wrapper.appendChild(commit);
+    }
+    document.body.append(header, wrapper);
+
+    const targets = getPageConfig("/o/r/pull/1").getTargets();
+    expect(targets).toHaveLength(2);
+    expect(targets[1]).toMatchObject({ el: wrapper, item: ".TimelineItem" });
+  });
+
+  it("returns no targets on an unrecognized DOM", () => {
+    document.body.innerHTML = "<main><p>not a PR timeline</p></main>";
+    expect(getPageConfig("/o/r/pull/1").getTargets()).toEqual([]);
+  });
+});
+
+describe("commits targets — modern React page", () => {
+  // Mirrors the May 2026 structure documented in pages.js.
+  function buildModernCommitsPage(commitsPerDay) {
+    const list = document.createElement("div");
+    list.setAttribute("data-testid", "commits-list");
+    const timeline = document.createElement("div");
+    timeline.className = "prc-Timeline-Timeline-x";
+    for (const count of commitsPerDay) {
+      const day = document.createElement("div");
+      day.className = "Timeline-Item";
+      const ul = document.createElement("ul");
+      ul.setAttribute("data-listview-component", "items-list");
+      for (let i = 0; i < count; i++) {
+        const li = document.createElement("li");
+        li.setAttribute("data-testid", "commit-row-item");
+        ul.appendChild(li);
+      }
+      day.appendChild(ul);
+      timeline.appendChild(day);
+    }
+    list.appendChild(timeline);
+    document.body.appendChild(list);
+    return { timeline };
+  }
+
+  it("targets the day groups AND each day's multi-commit list", () => {
+    const { timeline } = buildModernCommitsPage([2, 3]);
+    const targets = getPageConfig("/o/r/pull/1/commits").getTargets();
+    // 1 day-group target + 2 per-day list targets.
+    expect(targets).toHaveLength(3);
+    expect(targets[0]).toMatchObject({ el: timeline, item: ".Timeline-Item" });
+  });
+
+  it("skips the day-group target when there is a single day", () => {
+    buildModernCommitsPage([2]);
+    const targets = getPageConfig("/o/r/pull/1/commits").getTargets();
+    expect(targets).toHaveLength(1);
+    expect(targets[0].item).toBe('li[data-testid="commit-row-item"]');
+  });
+
+  it("skips per-day lists holding fewer than 2 commits", () => {
+    buildModernCommitsPage([2, 1]);
+    const targets = getPageConfig("/o/r/pull/1/commits").getTargets();
+    // Day-group target + only the 2-commit day's list.
+    expect(targets).toHaveLength(2);
+  });
+});
+
+describe("commits targets — legacy Rails page", () => {
+  function buildLegacyCommitsPage(commitsPerGroup) {
+    const list = document.createElement("div");
+    list.className = "js-commits-list";
+    for (const count of commitsPerGroup) {
+      const group = document.createElement("div");
+      group.className = "js-commit-group";
+      const ol = document.createElement("ol");
+      for (let i = 0; i < count; i++) ol.appendChild(document.createElement("li"));
+      group.appendChild(ol);
+      list.appendChild(group);
+    }
+    document.body.appendChild(list);
+    return list;
+  }
+
+  it("targets the group list and each multi-commit group", () => {
+    const list = buildLegacyCommitsPage([2, 3]);
+    const targets = getPageConfig("/o/r/pull/1/commits").getTargets();
+    expect(targets).toHaveLength(3);
+    expect(targets[0]).toMatchObject({ el: list, item: ".js-commit-group" });
+  });
+
+  it("skips single-commit groups", () => {
+    buildLegacyCommitsPage([2, 1]);
+    const targets = getPageConfig("/o/r/pull/1/commits").getTargets();
+    expect(targets).toHaveLength(2);
+  });
+
+  it("falls through to legacy when a modern commits-list is present but empty", () => {
+    const empty = document.createElement("div");
+    empty.setAttribute("data-testid", "commits-list");
+    document.body.appendChild(empty);
+    buildLegacyCommitsPage([2, 2]);
+
+    const targets = getPageConfig("/o/r/pull/1/commits").getTargets();
+    expect(targets).toHaveLength(3);
+  });
+
+  it("returns no targets on an unrecognized DOM", () => {
+    document.body.innerHTML = "<main><p>nothing commit-shaped</p></main>";
+    expect(getPageConfig("/o/r/pull/1/commits").getTargets()).toEqual([]);
+  });
+});
diff --git a/tsconfig.json b/tsconfig.json
index 3ffc1da..90fc0af 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -16,6 +16,7 @@
     "constants.js",
     "reorder.js",
     "checks.js",
+    "pages.js",
     "content.js",
     "background.js",
     "popup.js",
diff --git a/types/globals.d.ts b/types/globals.d.ts
index 4e4a675..9122576 100644
--- a/types/globals.d.ts
+++ b/types/globals.d.ts
@@ -1,9 +1,12 @@
 // Ambient declarations for the symbols shared across content scripts.
 //
-// constants.js / reorder.js / checks.js attach these to the global scope
-// (the extension injects them into one shared world), and content.js reads
-// them as bare globals. Declaring them here lets `tsc --checkJs` verify
-// content.js without each file having to import the others.
+// constants.js / reorder.js / checks.js / pages.js attach these to the
+// global scope (the extension injects them into one shared world), and
+// content.js reads them as bare globals. Declaring them here lets
+// `tsc --checkJs` verify content.js without each file having to import
+// the others.
+
+type PrrcOrder = "newest" | "oldest";
 
 interface PrrcTarget {
   el: Element;
@@ -11,8 +14,14 @@ interface PrrcTarget {
   descendant: boolean;
 }
 
+interface PrrcPageConfig {
+  name: string;
+  pathRe: RegExp;
+  getTargets(): PrrcTarget[];
+}
+
 interface PrrcChecksState {
-  key: string;
+  key: "failing" | "running" | "passing" | "unknown";
   label: string;
   color: string;
 }
@@ -20,7 +29,8 @@ interface PrrcChecksState {
 // constants.js — declared with `var` so they also appear on `globalThis`
 // (the UMD modules read `globalThis.ORDER`).
 declare var STORAGE_KEY: string;
-declare var ORDER: { NEWEST: string; OLDEST: string };
+declare var ORDER: { NEWEST: "newest"; OLDEST: "oldest" };
+declare function normalizeOrder(value: unknown): PrrcOrder;
 
 // reorder.js
 declare function firstMatchingTarget(
@@ -29,6 +39,9 @@ declare function firstMatchingTarget(
 declare function pushedCommitTargets(root?: ParentNode): PrrcTarget[];
 declare function applyOrderToTarget(target: PrrcTarget, order: string): boolean;
 
+// pages.js
+declare function getPageConfig(pathname: string): PrrcPageConfig | null;
+
 // checks.js
 declare function findChecksBox(root?: ParentNode): Element | null;
 declare function getCheckLabels(root?: ParentNode): string[];
diff --git a/vitest.config.mjs b/vitest.config.mjs
index 0c66d72..83af241 100644
--- a/vitest.config.mjs
+++ b/vitest.config.mjs
@@ -13,11 +13,10 @@ export default defineConfig({
       // provider under-reports with the threads pool in some sandboxed/CI
       // environments.
       provider: "istanbul",
-      // Measure only the pure, unit-tested logic modules. content.js,
-      // background.js, and popup.js are DOM/chrome glue exercised in a real
-      // browser, not under jsdom, so including them would report misleading
-      // zeros.
-      include: ["constants.js", "reorder.js", "checks.js"],
+      // Measure the unit-tested logic modules. content.js and popup.js are
+      // thin DOM/chrome glue exercised in a real browser, not under jsdom,
+      // so including them would report misleading zeros.
+      include: ["constants.js", "reorder.js", "checks.js", "pages.js", "background.js"],
       reporter: ["text", "lcov"],
       // Branches sits a little lower than the rest: each module's UMD
       // wrapper has a browser-global branch that can't run under Node tests.