Preserve native sessions during temporary server outages

src/App.svelte

@@ -1,6 +1,11 @@
 <script lang="ts">
   import { onMount } from 'svelte';
   import { invoke } from '@tauri-apps/api/core';
+  import { sessionResponseState, sessionRetryDelay } from './session-recovery.js';
+
+  let sessionRestoreTimer: ReturnType<typeof setTimeout> | undefined;
+  let sessionRestoreAttempt = 0;
+  let sessionRestoreGeneration = 0;
 
   type ClientSettings = { server_address: string; username: string };
 
@@ -63,30 +68,51 @@
 
   async function restoreNativeSession() {
     if (!nativeClientAvailable() || !username || !serverAddress) return;
+    const generation = ++sessionRestoreGeneration;
+    clearTimeout(sessionRestoreTimer);
+    let address = serverAddress;
+    const account = username;
+    const isCurrentRestore = () => generation === sessionRestoreGeneration && address === serverAddress && account === username;
     try {
       const safeServerAddress = validatedServerAddress(serverAddress);
       serverAddress = safeServerAddress;
+      address = safeServerAddress;
       const settings: ClientSettings = { server_address: safeServerAddress, username };
       const storedSession = await invoke<string | null>('load_server_session', { settings });
-      if (!storedSession) return;
+      if (!storedSession || !isCurrentRestore()) return;
       const response = await fetch(`${safeServerAddress}/api/v1/auth/session`, {
         headers: { authorization: `Bearer ${storedSession}` },
       });
-      if (!response.ok) {
+      if (!isCurrentRestore()) return;
+      const state = sessionResponseState(response.status);
+      if (state === 'revoked') {
         await invoke('clear_server_session', { settings });
+        if (!isCurrentRestore()) return;
+        sessionToken = '';
+        authenticated = false;
+        authError = 'Authentication revoked. Log in again.';
         return;
       }
+      if (state !== 'valid') throw new Error('Session verification unavailable');
       const result: { must_replace_credentials: boolean } = await response.json();
+      if (!isCurrentRestore()) return;
+      sessionRestoreAttempt = 0;
+      authError = '';
       sessionToken = storedSession;
       authenticated = true;
       mustReplaceCredentials = result.must_replace_credentials;
       connectionState = 'CONNECTED';
-      await loadAuthenticatedData();
+      await loadAuthenticatedData().catch(() => {
+        authError = 'Authenticated, but dashboard data could not be loaded.';
+      });
       if (mustReplaceCredentials) newUsername = username;
     } catch {
-      // A stale keyring session must not prevent the normal login form from opening.
-      sessionToken = '';
-      authenticated = false;
+      if (!isCurrentRestore()) return;
+      // Transport/server failures are not proof of revocation: preserve the keyring.
+      authError = 'Server unavailable. Retrying saved session.';
+      sessionRestoreTimer = setTimeout(() => {
+        if (isCurrentRestore()) void restoreNativeSession();
+      }, sessionRetryDelay(sessionRestoreAttempt++));
     }
   }
 
@@ -336,6 +362,8 @@
   }
 
   async function login() {
+    sessionRestoreGeneration += 1;
+    clearTimeout(sessionRestoreTimer);
     if (connectionState === 'INCOMPATIBLE') {
       authError = 'This client version is not compatible with the server.';
       return;
@@ -449,6 +477,8 @@
   }
 
   async function logout() {
+    sessionRestoreGeneration += 1;
+    clearTimeout(sessionRestoreTimer);
     realtimeSocket?.close();
     realtimeSocket = undefined;
     realtimeState = 'DISCONNECTED';

src/session-recovery.js

@@ -0,0 +1,14 @@
+/** Classify authoritative rejection separately from temporary server failures.
+ * @param {number} status HTTP response status.
+ */
+export function sessionResponseState(status) {
+  if (status === 401 || status === 403) return 'revoked';
+  return status >= 200 && status < 300 ? 'valid' : 'unavailable';
+}
+
+/** Milliseconds before each retry; attempt zero is the immediate first retry.
+ * @param {number} attempt Zero-based retry index.
+ */
+export function sessionRetryDelay(attempt) {
+  return [0, 3000, 10000, 15000][attempt] ?? 30000;
+}

src/session-recovery.test.js

@@ -0,0 +1,17 @@
+import assert from 'node:assert/strict';
+import { test } from 'node:test';
+import { sessionResponseState, sessionRetryDelay } from './session-recovery.js';
+
+test('only explicit authentication rejection invalidates a saved session', () => {
+  for (const status of [401, 403]) assert.equal(sessionResponseState(status), 'revoked');
+  for (const status of [404, 429, 500, 502, 503])
+    assert.equal(sessionResponseState(status), 'unavailable');
+  assert.equal(sessionResponseState(200), 'valid');
+});
+
+test('saved session retries follow the shared recovery schedule', () => {
+  assert.deepEqual(
+    Array.from({ length: 7 }, (_, attempt) => sessionRetryDelay(attempt)),
+    [0, 3000, 10000, 15000, 30000, 30000, 30000],
+  );
+});