fix(electron): packaged app shipped without a session secret — index/AI auth was dead on real installs; add AI entry point to the mail view

Root cause of "No local mail index available in this session" on a real
mailbox in the packaged .app, found by probing the live packaged build:
getSessionSecret() has four sources (env, env file, wizard config,
config file) and the desktop shell provided NONE — getDesktopDefaults()
sets JMAP_SERVER_URL (which also skips the setup wizard that would have
persisted a secret) but never a SESSION_SECRET. So every login's POST
/api/auth/stalwart-context 500'd, the jmap_stalwart_ctx cookie was never
minted, and every server-side-identity feature 401'd forever: encrypted
local index, offline replica, S/MIME enrolment, AI server class. The AI
retrieval leg renders any non-OK as "no local index", so the failure was
completely silent. Every test had masked this by injecting its own
SESSION_SECRET into the child env.

Fix 1 — electron/main.ts ensureSessionSecretFile(): a 64-hex-char secret
generated once per install, persisted 0600 under userData, handed to the
server as SESSION_SECRET_FILE (value stays out of the env block; an
operator-provided SESSION_SECRET env var still wins by resolution order).

Fix 2 — page.tsx boot catch-up now RETRIES (4s/20s/60s) instead of one
silent shot: the first attempt races login's own auth-context POST, and a
401 on that race used to mean an empty index until the next app restart.
requestIndex() already separates permanent (404/503 unavailable) from
retryable failures, so the retry is cheap and self-limiting.

Fix 3 — new components/ai/ai-ask-button.tsx: the AI Assistant finally has
an entry point in the MAIN mail view (Sparkles button next to the search
filter) opening a compact Ask dialog — same askMail client, same persisted
provider settings as the Settings pane. When nothing is configured it
deep-links to Settings → AI Assistant, where local-discovery's one-click
Connect does setup.

e2e hardened to prove the whole thing honestly: SESSION_SECRET explicitly
EMPTY in the launch env (the per-install secret must carry auth), the
manual sync/reindex calls removed (the automatic boot catch-up must build
the index on its own — polled, not triggered), and the toolbar entry
point asserted. Passing: auto-built index, discovery banner, Connect, and
a grounded answer citing the one email containing the fact.

Gate: tsc clean, eslint clean, 2502/2502 unit tests, e2e passing.

app/(main)/[locale]/page.tsx

@@ -67,6 +67,7 @@ import { findDraftIdentityId, resolveReplyFrom, type ReplyFromResolution } from
 import { buildReplyRecipients, isSelfSent } from "@/lib/reply-recipients";
 import { useProMultiAccountIdentities } from "@/hooks/use-pro-multi-account-identities";
 import { Search, Filter, ChevronDown, X, Paperclip, Star, Mail, MailOpen, RotateCcw, PenSquare, PenLine, CheckSquare, Square, AlertTriangle } from "lucide-react";
+import { AiAskButton } from "@/components/ai/ai-ask-button";
 import { ResizeHandle } from "@/components/layout/resize-handle";
 import { Button } from "@/components/ui/button";
 import { useConfig } from "@/hooks/use-config";
@@ -1070,37 +1071,58 @@ export default function Home() {
     // buildStatePollingRequest covers Mailbox/Email/Calendar/CalendarEvent/
     // SieveScript only). So backfill a bounded recent window once per session,
     // after push is wired. Fire-and-forget; a no-op outside Electron.
-    const catchUpTimer = setTimeout(() => {
+    //
-      void (async () => {
+    // RETRIED, not one-shot. The first attempt races the login flow's own
-        try {
+    // POST /api/auth/stalwart-context (stores/auth-store.ts's
-          const { catchUpIndex } = await import('@/lib/mail-index-client');
+    // syncStalwartAuthContext) - if the index route is hit before that cookie
-          await catchUpIndex(
+    // is minted it 401s, and a single silent attempt would leave the index
-            useAccountStore.getState().getActiveAccount()?.cookieSlot,
+    // empty until the next app restart with nothing telling anyone why (this
-          );
+    // exact silence hid the packaged app's missing-SESSION_SECRET bug against
-        } catch {
+    // a real mailbox). requestIndex() already distinguishes the permanent
-          /* the index is optional */
+    // cases (404/503 -> unavailable) from the retryable ones, so retrying is
+    // cheap and self-limiting.
+    const catchUpRetryDelaysMs = [4000, 20000, 60000];
+    let catchUpCancelled = false;
+    let catchUpTimer: ReturnType<typeof setTimeout> | undefined;
+
+    const runCatchUp = async (attempt: number) => {
+      if (catchUpCancelled) return;
+      try {
+        const { catchUpIndex } = await import('@/lib/mail-index-client');
+        const result = await catchUpIndex(
+          useAccountStore.getState().getActiveAccount()?.cookieSlot,
+        );
+        if (!result.ok && !result.unavailable && attempt + 1 < catchUpRetryDelaysMs.length) {
+          catchUpTimer = setTimeout(() => void runCatchUp(attempt + 1), catchUpRetryDelaysMs[attempt + 1]);
+          return;
         }
-        // The offline REPLICA's launch catch-up. Same reasoning as the index's,
+      } catch {
-        // plus one of its own: a `/changes` cursor cannot tell us about anything
+        /* the index is optional */
-        // that happened while the process was dead, so a cycle at launch is what
+      }
-        // drains the backlog. One cycle is bounded, so a first sync of a large
+      // The offline REPLICA's launch catch-up. Same reasoning as the index's,
-        // mailbox needs several - `chainSync` runs them with a hard cap.
+      // plus one of its own: a `/changes` cursor cannot tell us about anything
-        //
+      // that happened while the process was dead, so a cycle at launch is what
-        // Sequenced AFTER the index rather than in parallel: both write the same
+      // drains the backlog. One cycle is bounded, so a first sync of a large
-        // SQLite file, and although `busy_timeout` makes concurrent writers safe,
+      // mailbox needs several - `chainSync` runs them with a hard cap.
-        // there is no reason to spend the contention during first paint.
+      //
-        try {
+      // Sequenced AFTER the index (including its retries) rather than in
-          const { chainSync } = await import('@/lib/offline-replica-client');
+      // parallel: both write the same SQLite file, and although `busy_timeout`
-          await chainSync({ slot: useAccountStore.getState().getActiveAccount()?.cookieSlot });
+      // makes concurrent writers safe, there is no reason to spend the
-        } catch {
+      // contention during first paint.
-          /* the replica is optional */
+      if (catchUpCancelled) return;
-        }
+      try {
-      })();
+        const { chainSync } = await import('@/lib/offline-replica-client');
-      // Deliberately after the initial mailbox fetch settles: the catch-up is a
+        await chainSync({ slot: useAccountStore.getState().getActiveAccount()?.cookieSlot });
-      // background nicety and must not compete with first paint.
+      } catch {
-    }, 4000);
+        /* the replica is optional */
+      }
+    };
+    // Deliberately after the initial mailbox fetch settles: the catch-up is a
+    // background nicety and must not compete with first paint.
+    catchUpTimer = setTimeout(() => void runCatchUp(0), catchUpRetryDelaysMs[0]);
 
     return () => {
+      catchUpCancelled = true;
       clearTimeout(catchUpTimer);
       cleanups.forEach((fn) => fn());
     };
@@ -3164,6 +3186,7 @@ export default function Home() {
                       </span>
                     )}
                   </button>
+                  <AiAskButton />
                 </div>
               </div>
 

components/ai/ai-ask-button.tsx

@@ -0,0 +1,250 @@
+'use client';
+
+// The AI Assistant's entry point in the MAIN mail view — a Sparkles button in
+// the search toolbar that opens a compact Ask dialog. Until this existed, the
+// only way to ask the assistant anything was the "Try it" box buried in
+// Settings → AI Assistant, which is a configuration screen, not a workflow.
+//
+// Deliberately reuses the exact same wire client (lib/ai/local-client's
+// askMail) and the exact same persisted provider settings as the Settings
+// pane — this is a second door to the same room, not a second room. When no
+// provider is configured yet, the dialog deep-links to the Settings pane
+// (where local-discovery offers the one-click Connect) instead of duplicating
+// that setup flow here.
+
+import { useCallback, useEffect, useRef, useState } from 'react';
+import { useRouter } from 'next/navigation';
+import { AlertTriangle, Loader2, Settings2, Sparkles, X } from 'lucide-react';
+import { cn } from '@/lib/utils';
+import { Button } from '@/components/ui/button';
+import { apiFetch } from '@/lib/browser-navigation';
+import { DEFAULT_AI_POLICY, type AiPolicy } from '@/lib/ai/types';
+import { supportsLocalLlm } from '@/lib/platform-capabilities';
+import { getAiApiKey } from '@/lib/ai/key-store';
+import { loadAiSettings, type AiLocalSettings } from '@/lib/ai/local-settings';
+import { askMail, type AskResult } from '@/lib/ai/local-client';
+
+function useAiPolicy(): { policy: AiPolicy; loaded: boolean } {
+  const [policy, setPolicy] = useState<AiPolicy>(DEFAULT_AI_POLICY);
+  const [loaded, setLoaded] = useState(false);
+  useEffect(() => {
+    let cancelled = false;
+    (async () => {
+      try {
+        const res = await apiFetch('/api/ai/policy');
+        if (res.ok && !cancelled) setPolicy(await res.json());
+      } catch {
+        /* stays at DEFAULT (disabled) — the button simply doesn't render */
+      } finally {
+        if (!cancelled) setLoaded(true);
+      }
+    })();
+    return () => {
+      cancelled = true;
+    };
+  }, []);
+  return { policy, loaded };
+}
+
+/** Mirrors the Settings pane's canAsk gating: is any provider actually ready? */
+function providerConfigured(settings: AiLocalSettings, policy: AiPolicy): boolean {
+  const classes = policy.entitlement.classes;
+  switch (settings.provider) {
+    case 'local':
+      return supportsLocalLlm() && classes.includes('local') && !!settings.localModel;
+    case 'server':
+      return classes.includes('server') && !!settings.serverModel;
+    case 'public': {
+      const active = settings.publicProfiles.find((p) => p.id === settings.activeProfileId) ?? null;
+      return classes.includes('public') && !!active && settings.publicConsentAccepted;
+    }
+    default:
+      return false;
+  }
+}
+
+export function AiAskButton() {
+  const router = useRouter();
+  const { policy, loaded } = useAiPolicy();
+  const [open, setOpen] = useState(false);
+  // Re-read on every open: the user may have just configured a provider in
+  // Settings and come straight back here — a mount-time snapshot would still
+  // say "not configured".
+  const [settings, setSettings] = useState<AiLocalSettings>(() => loadAiSettings());
+
+  const [question, setQuestion] = useState('');
+  const [asking, setAsking] = useState(false);
+  const [askResult, setAskResult] = useState<AskResult | null>(null);
+  const [askError, setAskError] = useState<string | null>(null);
+  const textareaRef = useRef<HTMLTextAreaElement>(null);
+
+  const openDialog = useCallback(() => {
+    setSettings(loadAiSettings());
+    setAskResult(null);
+    setAskError(null);
+    setOpen(true);
+  }, []);
+
+  useEffect(() => {
+    if (!open) return;
+    textareaRef.current?.focus();
+    const onKey = (e: KeyboardEvent) => {
+      if (e.key === 'Escape') setOpen(false);
+    };
+    window.addEventListener('keydown', onKey);
+    return () => window.removeEventListener('keydown', onKey);
+  }, [open]);
+
+  const configured = providerConfigured(settings, policy);
+  const canAsk = configured && question.trim().length > 0 && !asking;
+
+  const runAsk = useCallback(async () => {
+    if (!canAsk) return;
+    setAsking(true);
+    setAskError(null);
+    setAskResult(null);
+    try {
+      const activeProfile = settings.publicProfiles.find((p) => p.id === settings.activeProfileId) ?? null;
+      const key = activeProfile ? getAiApiKey(activeProfile.id) : null;
+      const result = await askMail(question.trim(), {
+        provider: settings.provider as 'local' | 'server' | 'public',
+        localBaseUrl: settings.localBaseUrl,
+        localModel: settings.localModel,
+        serverModel: settings.serverModel,
+        publicProfile: activeProfile && key ? { baseUrl: activeProfile.baseUrl, model: activeProfile.model, apiKey: key } : null,
+      });
+      setAskResult(result);
+    } catch (err) {
+      setAskError(err instanceof Error ? err.message : String(err));
+    } finally {
+      setAsking(false);
+    }
+  }, [canAsk, question, settings]);
+
+  const goToSettings = useCallback(() => {
+    // The Settings page's one-shot deep-link channel (see readPersistedTab in
+    // app/(main)/[locale]/settings/page.tsx) — lands directly on the AI pane,
+    // where local-discovery's Connect banner does the actual setup.
+    try {
+      sessionStorage.setItem('settings-deep-link-tab', 'ai_assistant');
+    } catch {
+      /* private mode — the settings page just opens on its default tab */
+    }
+    setOpen(false);
+    router.push('/settings');
+  }, [router]);
+
+  // Hidden entirely when the admin gate is off or no provider class is
+  // allowed — same visibility rule as the Settings pane itself.
+  if (!loaded || !policy.enabled || policy.entitlement.classes.length === 0) return null;
+
+  return (
+    <>
+      <button
+        type="button"
+        onClick={openDialog}
+        className="flex-shrink-0 p-2 rounded-md transition-colors text-muted-foreground hover:text-foreground hover:bg-muted"
+        title="AI Assistant"
+        aria-label="AI Assistant"
+        data-tour="ai-assistant"
+      >
+        <Sparkles className="w-4 h-4" />
+      </button>
+
+      {open && (
+        <div
+          className="fixed inset-0 z-50 flex items-start justify-center bg-black/50 p-4 pt-[10vh]"
+          onMouseDown={(e) => {
+            if (e.target === e.currentTarget) setOpen(false);
+          }}
+          role="dialog"
+          aria-modal="true"
+          aria-label="AI Assistant"
+        >
+          <div className="w-full max-w-xl rounded-xl border border-border bg-popover text-popover-foreground shadow-2xl">
+            <div className="flex items-center justify-between border-b border-border px-4 py-3">
+              <div className="flex items-center gap-2">
+                <Sparkles className="w-4 h-4 text-primary" />
+                <h2 className="text-sm font-semibold">AI Assistant</h2>
+              </div>
+              <button
+                type="button"
+                onClick={() => setOpen(false)}
+                className="p-1 rounded-md text-muted-foreground hover:text-foreground hover:bg-muted transition-colors"
+                aria-label="Close"
+              >
+                <X className="w-4 h-4" />
+              </button>
+            </div>
+
+            <div className="flex flex-col gap-3 p-4">
+              {!configured ? (
+                <>
+                  <p className="text-sm text-muted-foreground">
+                    No AI provider is set up yet. Pick one in Settings — if Ollama is running on this machine, a
+                    one-click Connect is waiting there.
+                  </p>
+                  <div>
+                    <Button size="sm" onClick={goToSettings}>
+                      <Settings2 className="w-3.5 h-3.5 me-1.5" />
+                      Open AI settings
+                    </Button>
+                  </div>
+                </>
+              ) : (
+                <>
+                  <textarea
+                    ref={textareaRef}
+                    value={question}
+                    onChange={(e) => setQuestion(e.target.value)}
+                    onKeyDown={(e) => {
+                      if ((e.metaKey || e.ctrlKey) && e.key === 'Enter') void runAsk();
+                    }}
+                    rows={3}
+                    placeholder="Ask a question about your mail…"
+                    className="w-full px-3 py-2 text-sm rounded-md bg-muted border border-border text-foreground focus:outline-none focus:ring-2 focus:ring-ring transition-colors duration-150 resize-y"
+                  />
+                  <div className="flex items-center gap-3">
+                    <Button size="sm" onClick={() => void runAsk()} disabled={!canAsk}>
+                      {asking && <Loader2 className="w-3.5 h-3.5 me-1.5 animate-spin" />}
+                      Ask
+                    </Button>
+                    <span className="text-xs text-muted-foreground">⌘⏎ to send</span>
+                  </div>
+
+                  {askError && (
+                    <div className="flex items-start gap-2 rounded-lg border border-destructive/40 bg-destructive/5 p-3">
+                      <AlertTriangle className="w-4 h-4 mt-0.5 text-destructive shrink-0" />
+                      <p className="text-sm text-destructive">{askError}</p>
+                    </div>
+                  )}
+
+                  {askResult && (
+                    <div className={cn('flex flex-col gap-2 rounded-lg border border-border p-4', 'max-h-[45vh] overflow-y-auto')}>
+                      {askResult.unaugmented && (
+                        <p className="text-xs text-muted-foreground italic">
+                          No local mail index available in this session — answered without retrieval context.
+                        </p>
+                      )}
+                      <p className="text-sm text-foreground whitespace-pre-wrap">{askResult.answer}</p>
+                      {askResult.sources.length > 0 && (
+                        <div className="flex flex-col gap-0.5 border-t border-border pt-2 mt-1">
+                          <span className="text-xs font-medium text-muted-foreground">Sources</span>
+                          {askResult.sources.map((s, i) => (
+                            <span key={s.id} className="text-xs text-muted-foreground truncate">
+                              [{i + 1}] {s.subject}
+                            </span>
+                          ))}
+                        </div>
+                      )}
+                    </div>
+                  )}
+                </>
+              )}
+            </div>
+          </div>
+        </div>
+      )}
+    </>
+  );
+}

e2e/electron-ai-local-index.spec.ts

@@ -68,7 +68,13 @@ test.describe('Electron desktop shell - local LLM answers from the real encrypte
         VNCMAIL_TEST_FIXED_PORT: String(FIXED_PORT),
         DEV_MOCK_JMAP: 'true',
         JMAP_SERVER_URL: `${ORIGIN}/api/dev-jmap`,
-        SESSION_SECRET: 'electron-ai-local-index-verify-32-chars-min',
+        // Deliberately NO SESSION_SECRET: the desktop shell must supply its
+        // own per-install secret (electron/main.ts's ensureSessionSecretFile)
+        // or the auth-context cookie can never be minted and every index
+        // route 401s. Up to 1.7.8 the packaged app shipped exactly that way,
+        // and every test masked it by injecting a secret here — this test
+        // now proves the shell stands on its own.
+        SESSION_SECRET: '',
         // Deliberately UNSET: isolates grounding to the local FTS leg (see
         // module header) — the server embeddings leg 404s cleanly instead
         // of silently also being able to answer the question.
@@ -93,41 +99,37 @@ test.describe('Electron desktop shell - local LLM answers from the real encrypte
     await devLoginContainer.getByRole('button').click();
     await appWindow.waitForURL((url) => !url.pathname.includes('login'), { timeout: 20000 });
 
-    // ── 2. Build the real encrypted local index: delta-sync the mock
+    // ── 2. Wait for the AUTOMATIC boot catch-up to build the encrypted
-    // account's mail into the replica store, then write it into SQLite/FTS5.
+    // index — NO manual /api/offline/sync or /api/offline/reindex calls.
-    // Chains /api/offline/sync while unfinishedWork is true, capped so a
+    // This is the load-bearing change from this spec's first version: the
-    // real bug can't hang the test forever. ──
+    // real user experience is "log in, index appears on its own", and the
-    const syncOutcome = await appWindow.evaluate(async () => {
+    // first version's manual calls proved only that the plumbing COULD
-      let unfinished = true;
+    // work, not that anything actually drives it. page.tsx schedules the
-      let calls = 0;
+    // first attempt ~4s after the authenticated mail page mounts (with
-      const statuses: number[] = [];
+    // retries at 20s/60s for the login race), so poll generously. ──
-      while (unfinished && calls < 10) {
+    await expect
-        const res = await fetch('/api/offline/sync', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: '{}' });
+      .poll(
-        statuses.push(res.status);
+        async () =>
-        if (!res.ok) break;
+          appWindow.evaluate(async () => {
-        const body = await res.json();
+            const res = await fetch(`/api/offline/search?q=${encodeURIComponent('Villa sul Lago check-in')}&limit=6`);
-        unfinished = body.unfinishedWork === true;
+            if (!res.ok) return `http-${res.status}`;
-        calls++;
+            const body = await res.json().catch(() => null);
-      }
+            const hits = (body?.hits ?? []) as Array<{ title?: string }>;
-      const reindexRes = await fetch('/api/offline/reindex', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ catchUp: true }) });
+            return hits.some((h) => /villa sul lago/i.test(h.title ?? '')) ? 'hit' : 'indexed-but-empty';
-      return { syncStatuses: statuses, syncCalls: calls, reindexStatus: reindexRes.status, reindexBody: await reindexRes.json().catch(() => null) };
+          }),
-    });
+        {
-    console.log('[ai-local-index] sync+reindex outcome:', JSON.stringify(syncOutcome));
+          timeout: 90000,
-    expect(syncOutcome.syncStatuses.every((s) => s === 200)).toBe(true);
+          intervals: [2000],
-    expect(syncOutcome.reindexStatus).toBe(200);
+          message:
+            'the boot catch-up (page.tsx) must build the index automatically after login — http-401 here means the auth-context cookie was never minted (the missing-SESSION_SECRET class of bug), http-404 means the key channel/store dir never activated',
+        },
+      )
+      .toBe('hit');
 
-    // ── 3. Prove the local index itself is real and queryable BEFORE
+    // ── 3. The new toolbar entry point must be present in the main mail
-    // touching the LLM at all — isolates "is the SQLite/FTS5 index working"
+    // view — the AI Assistant is a feature of the app, not of the Settings
-    // from "did the model use it correctly". ──
+    // page. ──
-    const directSearch = await appWindow.evaluate(async () => {
+    await expect(appWindow.getByRole('button', { name: 'AI Assistant' })).toBeVisible({ timeout: 10000 });
-      const res = await fetch(`/api/offline/search?q=${encodeURIComponent('Villa sul Lago check-in')}&limit=6`);
-      return { status: res.status, body: await res.json().catch(() => null) };
-    });
-    console.log('[ai-local-index] direct /api/offline/search result:', JSON.stringify(directSearch.body));
-    expect(directSearch.status, 'the encrypted local index must be reachable (200), not 404 (feature disabled) or 503 (no key channel)').toBe(200);
-    expect(directSearch.body?.ok).toBe(true);
-    const hitTitles = (directSearch.body?.hits ?? []).map((h: { title?: string }) => h.title ?? '');
-    expect(hitTitles.some((t: string) => /villa sul lago/i.test(t)), `expected a "Villa sul Lago" hit in the real index, got: ${JSON.stringify(hitTitles)}`).toBe(true);
 
     // ── 4. Navigate to the real AI Assistant settings UI and use the
     // local-discovery "Connect" banner — the exact flow a real user takes,

electron/main.ts

@@ -9,6 +9,7 @@
 import { app, BrowserWindow, ipcMain, Notification } from "electron";
 import { autoUpdater } from "electron-updater";
 import { spawn, type ChildProcess } from "node:child_process";
+import { randomBytes } from "node:crypto";
 import { createServer } from "node:net";
 import { get as httpGet } from "node:http";
 import path from "node:path";
@@ -115,6 +116,50 @@ function getDesktopDefaults(): Record<string, string> {
   };
 }
 
+/**
+ * Per-install session secret for the standalone server.
+ *
+ * The server's cookie crypto (lib/auth/crypto.ts) refuses to mint the
+ * `jmap_stalwart_ctx` auth-context cookie without a >=32-char SESSION_SECRET,
+ * and every server-side-identity feature hangs off that cookie: the encrypted
+ * local search index and offline replica (their routes 401 without it),
+ * S/MIME enrolment, and the AI `server` class. A web deployment gets the
+ * secret from an operator (env var or the setup wizard); the desktop shell
+ * has NO operator, and up to 1.7.8 the packaged app simply shipped without
+ * one — so every login's stalwart-context POST failed with 500, the index
+ * stayed permanently empty, and the AI assistant answered "No local mail
+ * index available in this session" against real accounts. Caught live on a
+ * real mailbox, not by tests: every test run had injected its own
+ * SESSION_SECRET into the child env, masking exactly this.
+ *
+ * Generated once per install (64 hex chars, comfortably over the minimum),
+ * persisted 0600 under userData next to the rest of the per-user state, and
+ * handed to the server as SESSION_SECRET_FILE rather than SESSION_SECRET so
+ * the value itself stays out of the child's environment block. A
+ * deployment-provided SESSION_SECRET env var still wins — getSessionSecret()
+ * resolves the env var before the file.
+ */
+function ensureSessionSecretFile(): string | null {
+  const secretPath = path.join(app.getPath("userData"), "session-secret");
+  try {
+    const existing = fs.readFileSync(secretPath, "utf8").trim();
+    if (existing.length >= 32) return secretPath;
+  } catch {
+    /* first run — generate below */
+  }
+  try {
+    fs.mkdirSync(path.dirname(secretPath), { recursive: true });
+    fs.writeFileSync(secretPath, randomBytes(32).toString("hex"), { mode: 0o600 });
+    return secretPath;
+  } catch (cause) {
+    // Loud, because the downstream symptom is otherwise "index/AI features
+    // return 401" with no hint of why — but never fatal: reading mail does
+    // not depend on this cookie.
+    console.error("[electron] could not persist a session secret:", cause);
+    return null;
+  }
+}
+
 /**
  * Locates the standalone server's entrypoint. Packaged builds ship it as an
  * extraResource (see electron-builder.config.js) because .next/standalone
@@ -210,12 +255,19 @@ async function startStandaloneServer(): Promise<string> {
   // readable by any process running as the same OS user, which would defeat
   // using the OS keychain at all. The fd NUMBER below is not a secret; only
   // what travels over it is.
+  const sessionSecretFile = ensureSessionSecretFile();
+
   serverProcess = spawn(process.execPath, [serverEntry], {
     env: {
       // First, so any real deployment env (a future per-install override,
       // or this same binary run somewhere JMAP_SERVER_URL is already set)
       // wins over these desktop-shell defaults - see getDesktopDefaults().
       ...getDesktopDefaults(),
+      // Also before ...process.env: an operator-provided SESSION_SECRET or
+      // SESSION_SECRET_FILE must win over the per-install default (and a
+      // SESSION_SECRET env var outranks any file in getSessionSecret()'s
+      // resolution order regardless).
+      ...(sessionSecretFile ? { SESSION_SECRET_FILE: sessionSecretFile } : {}),
       ...process.env,
       ELECTRON_RUN_AS_NODE: "1",
       PORT: String(port),