feat(ui): shared header — Sign in/Sign out and New Chat on every page; hide the Sources nav link from anonymous users

frontend/assets/app.js

@@ -63,6 +63,8 @@
  * All DOM ids match frontend/index.html.
  */
 
+import { fetchIsAdmin, initSharedHeader } from "/assets/header.js";
+
 const messagesEl = document.querySelector("#messages");
 const emptyState = document.querySelector("#empty-state");
 const suggestionsEl = document.querySelector("#suggestions");
@@ -756,9 +758,19 @@ function rememberBrainTurn(rawText, meta) {
  * tuning surface at all — the Tuning toggle + panel are removed from the
  * DOM (the story says "absent", not just hidden), /api/steering is never
  * fetched, and appendTuneButton injects nothing (new or restored
- * messages). Admin → Sign out (POST /api/logout + reload) + the full
- * phase-15 UI. Whoami is awaited BEFORE the phase-14 restore, so restored
- * brain bubbles never flash a Tune button that should not be there.
+ * messages). Admin → Sign out + the full phase-15 UI. Whoami is awaited
+ * BEFORE the phase-14 restore, so restored brain bubbles never flash a
+ * Tune button that should not be there.
+ *
+ * Phase 19: the whoami fetch, the Sign in / Sign out / Sources-nav
+ * toggling, and the #sign-out-btn click binding (POST /api/logout +
+ * reload) all moved to the shared header module (assets/header.js) —
+ * initSharedHeader() does the header toggling on every page, and
+ * fetchIsAdmin() is the single cached whoami, so this page still makes
+ * exactly one request per load. applyAuthState keeps only the
+ * chat-page-specific work (removing the tuning surface for anonymous
+ * visitors) — idempotent alongside the header module's own link/button
+ * toggling.
  */
 const signInLink = document.querySelector("#sign-in-link");
 const signOutBtn = document.querySelector("#sign-out-btn");
@@ -773,27 +785,6 @@ function applyAuthState() {
   }
 }
 
-async function loadAuthState() {
-  try {
-    const r = await fetch("/api/whoami");
-    if (r.ok) isAdmin = (await r.json()).authenticated === true;
-  } catch {
-    isAdmin = false; // API unreachable: anonymous-safe defaults
-  }
-  applyAuthState();
-  return isAdmin;
-}
-
-if (signOutBtn) {
-  signOutBtn.addEventListener("click", async () => {
-    signOutBtn.disabled = true;
-    try {
-      await fetch("/api/logout", { method: "POST" });
-    } catch { /* the reload resets the UI either way */ }
-    window.location.reload();
-  });
-}
-
 const newChatBtn = document.querySelector("#new-chat-btn");
 function startNewChat() {
   if (uiState === UI_STATE.thinking || uiState === UI_STATE.streaming) return;
@@ -983,9 +974,14 @@ composer.addEventListener("submit", handleSend);
 
 /* Boot: auth state FIRST — it decides whether the restored conversation
    gets Tune buttons and whether the steering UI exists at all (phase 16).
-   Phase 14: the conversation then comes back exactly as left. */
+   Phase 14: the conversation then comes back exactly as left. Phase 19:
+   the shared header module runs the whoami (cached — exactly one
+   request per page load) and toggles the Sign in/out pair + the Sources
+   nav link; applyAuthState() then applies the chat-page-only gating. */
 (async () => {
-  await loadAuthState();
+  await initSharedHeader(); // header.js: whoami + Sign in/out + #nav-sources
+  isAdmin = await fetchIsAdmin(); // the same cached promise — one whoami
+  applyAuthState(); // chat page: the admin-only tuning surface
   restoreConversation();
   loadSuggestions();
   loadHealth();

frontend/assets/document.js

@@ -15,8 +15,16 @@
  *
  * A missing document (unknown pair, missing params, network error) shows
  * the designed not-found card with a link back to the Sources page.
+ *
+ * Phase 19: the viewer joins the shared header (assets/header.js) — the
+ * whoami fetch is the module's cached promise (one request per page,
+ * shared with initSharedHeader's toggling), and the bar gains the New
+ * chat button: on a non-chat page "new chat" means going to the chat,
+ * fresh (clear the phase-14 conversation key, then navigate to "/").
  */
 
+import { clearChatStorage, fetchIsAdmin, initSharedHeader } from "/assets/header.js";
+
 const params = new URLSearchParams(window.location.search);
 const source = params.get("source") || "";
 const path = params.get("path") || "";
@@ -111,6 +119,27 @@ function showNotFound() {
   notFoundEl.hidden = false;
 }
 
+/* Phase 19: the shared header controls (Sign in / Sign out — exactly one
+ * visible) are toggled here; the viewer has no nav, so there is no
+ * #nav-sources for the module to touch. Independent of the doc fetch
+ * (its own IIFE — load() below never waits on it).
+ * (fetchIsAdmin is imported for parity with the other header consumers —
+ * the module's cached promise is the single whoami per page either way.) */
+(async () => {
+  await initSharedHeader();
+})();
+
+/* Phase 19: New chat on a non-chat page means "go to the chat, fresh":
+ * clear the phase-14 conversation key, then land on the chat page — its
+ * empty state, since the conversation is gone from storage. */
+const newChatBtn = document.querySelector("#new-chat-btn");
+if (newChatBtn) {
+  newChatBtn.addEventListener("click", () => {
+    clearChatStorage();
+    window.location.href = "/";
+  });
+}
+
 async function load() {
   try {
     if (!source || !path) {

frontend/assets/header.js

@@ -0,0 +1,96 @@
+/* Brain of Reese — shared header module (phase 19).
+ *
+ * Owner report 2026-08-23: clicking "Sources" made New Chat and Sign in
+ * vanish — the user expects ONE consistent bar on every page. This module
+ * is the single owner of the shared header controls:
+ *
+ *   • the Sign in / Sign out auth pair (phase 16, exactly one visible —
+ *     decided by /api/whoami at load);
+ *   • the "Sources" nav link (#nav-sources) — phase 19 UX revision
+ *     (owner permission 2026-08-23): hidden for anonymous on every page
+ *     that has a nav (chat, sources, login), revealed for admin. The
+ *     link SHIPS hidden in the HTML (anonymous-safe default — the
+ *     phase-16 "absent, not hidden" spirit), so no anonymous user ever
+ *     sees it for a frame;
+ *   • the sign-out click binding (POST /api/logout → reload) — moved
+ *     here from app.js so there is exactly one implementation;
+ *   • clearChatStorage() — the phase-14 conversation key, for the
+ *     New Chat buttons on the NON-CHAT pages (sources / document
+ *     viewer): a new chat means going to the chat, fresh.
+ *
+ * Every page loads this module (type="module", before its page script)
+ * and its page script calls initSharedHeader() once at boot. init…
+ * toggles ONLY the controls that exist on the page — a missing element
+ * is a no-op, which is how the login page reuses the module without
+ * gaining chat controls (no #new-chat-btn / #sign-in-link /
+ * #sign-out-btn in its markup → none appear).
+ *
+ * whoami is fetched at most ONCE per page load: the promise is cached in
+ * the module-level `adminPromise`, so app.js's tuning gate, the sources
+ * page's catalog gate, and the header toggling all share one request.
+ * Anonymous-safe: any network failure resolves to false (the anonymous
+ * UI), mirroring the per-page catch the pages used before phase 19.
+ *
+ * A10/A11 untouched: no API change, no CDN, no state beyond the cached
+ * promise; the soft gate page and the A10 API split are unchanged —
+ * this is UI visibility only.
+ */
+
+let adminPromise = null;
+
+/* The SINGLE /api/whoami call site for the whole frontend. First call
+   stores the promise in `adminPromise`; every later call — on this page
+   — returns the same promise, i.e. exactly one request per page load.
+   Anonymous-safe: non-2xx or a network failure resolves to false. */
+export function fetchIsAdmin() {
+  if (!adminPromise) {
+    adminPromise = fetch("/api/whoami")
+      .then(async (r) => (r.ok ? (await r.json()).authenticated === true : false))
+      .catch(() => false);
+  }
+  return adminPromise;
+}
+
+/* Toggle the shared header controls, only the ones present on this page
+   (querySelector, null-safe — missing → no-op). Returns the admin flag
+   so callers can reuse it instead of awaiting fetchIsAdmin() again (the
+   cached promise makes both awaits the same single request). */
+export async function initSharedHeader() {
+  const admin = await fetchIsAdmin();
+  const signIn = document.querySelector("#sign-in-link");
+  if (signIn) signIn.hidden = admin;
+  const signOut = document.querySelector("#sign-out-btn");
+  if (signOut) signOut.hidden = !admin;
+  const navSources = document.querySelector("#nav-sources");
+  if (navSources) navSources.hidden = !admin;
+  return admin;
+}
+
+/* Remove the phase-14 conversation key — same key + fail-silence
+   contract as app.js's clearStoredConversation: private mode or a
+   storage error is swallowed, the navigation still happens. */
+export function clearChatStorage() {
+  try {
+    localStorage.removeItem("bor.chat.v1");
+  } catch {
+    /* nothing was stored */
+  }
+}
+
+/* Sign-out binding (phase 16 behavior, now module-owned): runs at module
+   import, so every page that loads header.js gets it exactly once.
+   Disable during the call, POST /api/logout (the result is ignored —
+   the reload resets the UI either way), then reload so the header
+   re-resolves to the anonymous state (Sign in back, Sources gone). */
+const signOutBtn = document.querySelector("#sign-out-btn");
+if (signOutBtn) {
+  signOutBtn.addEventListener("click", async () => {
+    signOutBtn.disabled = true;
+    try {
+      await fetch("/api/logout", { method: "POST" });
+    } catch {
+      /* the reload resets the UI either way */
+    }
+    window.location.reload();
+  });
+}

frontend/assets/login.js

@@ -7,10 +7,18 @@
  * role=alert error region. On load, /api/whoami already says admin →
  * straight to `next`, no form.
  *
+ * Phase 19: the whoami check runs on the shared header module's cached
+ * promise (assets/header.js) — one request per page, and the module's
+ * initSharedHeader() toggles the (admin-only) Sources nav link. The
+ * login page carries no chat controls, so the module's missing-element
+ * no-op keeps this page control-free.
+ *
  * No CDN, no state in this file: the signed cookie is the whole session.
  * All DOM ids match frontend/login.html.
  */
 
+import { fetchIsAdmin, initSharedHeader } from "/assets/header.js";
+
 const form = document.querySelector("#login-form");
 const passwordInput = document.querySelector("#login-password");
 const submitBtn = document.querySelector("#login-submit");
@@ -33,14 +41,12 @@ function showError(message) {
   passwordInput.select();
 }
 
-async function alreadySignedIn() {
-  try {
-    const r = await fetch("/api/whoami");
-    if (!r.ok) return false;
-    return (await r.json()).authenticated === true;
-  } catch {
-    return false; // API unreachable: stay on the form — submit will explain
-  }
+/* Phase 19: the shared header module IS the whoami call site (cached
+ * promise, anonymous-safe) — same result as the private fetch it
+ * replaces: a network failure stays on the form (submit will explain).
+ */
+function alreadySignedIn() {
+  return fetchIsAdmin();
 }
 
 form.addEventListener("submit", async (e) => {
@@ -70,11 +76,15 @@ form.addEventListener("submit", async (e) => {
   }
 });
 
-/* Already the admin? Skip the form and go straight to the target. */
+/* Already the admin? Skip the form and go straight to the target.
+ * (For anonymous visitors, initSharedHeader toggles the Sources nav
+ * link — the only shared control this page carries; for the signed-in
+ * case the redirect above makes the toggle moot.) */
 (async () => {
   if (await alreadySignedIn()) {
     window.location.replace(safeNext());
     return;
   }
+  await initSharedHeader(); // phase 19: Sources link toggle (no chat controls here)
   passwordInput.focus();
 })();

frontend/assets/sources.js

@@ -4,8 +4,16 @@
  * full-width document table, or the designed empty state when nothing is
  * indexed yet. Cells are built with DOM APIs (textContent) — never
  * innerHTML with document-derived data (XSS-safe by construction).
+ *
+ * Phase 19: the page joins the shared header (assets/header.js) — the
+ * whoami gate below runs on the module's cached promise (one request per
+ * page, shared with the header toggling), and the header gains the New
+ * chat button: on a non-chat page "new chat" means going to the chat,
+ * fresh (clear the phase-14 conversation key, then navigate to "/").
  */
 
+import { clearChatStorage, fetchIsAdmin, initSharedHeader } from "/assets/header.js";
+
 const tbody = document.querySelector("#docs-tbody");
 const emptyEl = document.querySelector("#sources-empty");
 const tableWrap = document.querySelector(".table-wrap");
@@ -18,13 +26,22 @@ const statLast = document.querySelector("#stat-last");
 /* Phase 16: whoami BEFORE the docs fetch. Anonymous visitors get the
  * sign-in gate (stat cards + table hidden) and NO /api/docs call — the
  * catalog is admin-only. The document viewer itself stays public (the
- * soft rule), so the gate copy points at what keeps working. */
-async function isAdmin() {
-  try {
-    const r = await fetch("/api/whoami");
-    if (r.ok) return (await r.json()).authenticated === true;
-  } catch { /* API unreachable: anonymous-safe gate */ }
-  return false;
+ * soft rule), so the gate copy points at what keeps working.
+ * Phase 19: the whoami request is the shared header module's cached
+ * promise — the same single request initSharedHeader() awaited. */
+function isAdmin() {
+  return fetchIsAdmin();
+}
+
+/* Phase 19: New chat on a non-chat page means "go to the chat, fresh":
+ * clear the phase-14 conversation key, then land on the chat page — its
+ * empty state, since the conversation is gone from storage. */
+const newChatBtn = document.querySelector("#new-chat-btn");
+if (newChatBtn) {
+  newChatBtn.addEventListener("click", () => {
+    clearChatStorage();
+    window.location.href = "/";
+  });
 }
 
 function fmtDate(iso) {
@@ -112,6 +129,7 @@ function showEmpty() {
 }
 
 (async () => {
+  await initSharedHeader(); // phase 19: Sign in/out + Sources link in the shared bar
   if (!(await isAdmin())) {
     // Anonymous: gate in, catalog out, and no /api/docs request at all.
     if (statCards) statCards.hidden = true;

frontend/assets/styles.css

@@ -998,6 +998,19 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
 .doc-back:hover { background: #2a345f; }
 .doc-back svg { width: 16px; height: 16px; display: block; }
 .doc-title-block { min-width: 0; }
+/* Phase 19: the shared header controls reach the viewer bar (New chat
+   + Sign in / Sign out) — margin-left:auto pushes them to the right;
+   the title block keeps clipping (min-width: 0 above) so the two pills
+   fit while the bar still measures exactly --header-h. The reused
+   .new-chat-btn / .auth-link classes already carry the ≤640px icon-only
+   rules, so at 360px the bar is back pill + clipping title + two icon
+   pills (no overflow — test_responsive_polish pins scrollWidth). */
+.doc-header-actions {
+  margin-left: auto;
+  display: flex;
+  gap: 0.5rem;
+  align-items: center;
+}
 #doc-title {
   margin: 0;
   font-size: 1.3rem;