diff --git a/apps/client/src/services/server.ts b/apps/client/src/services/server.ts
index 627e28622a..d9b776babc 100644
--- a/apps/client/src/services/server.ts
+++ b/apps/client/src/services/server.ts
@@ -93,7 +93,7 @@ async function upload(url: string, fileToUpload: File, componentId?: string, met
     const formData = new FormData();
     formData.append("upload", fileToUpload);
 
-    return await $.ajax({
+    const doUpload = async () => $.ajax({
         url: window.glob.baseApiUrl + url,
         headers: await getHeaders(componentId ? {
             "trilium-component-id": componentId
@@ -104,6 +104,18 @@ async function upload(url: string, fileToUpload: File, componentId?: string, met
         contentType: false, // NEEDED, DON'T REMOVE THIS
         processData: false // NEEDED, DON'T REMOVE THIS
     });
+
+    try {
+        return await doUpload();
+    } catch (e: unknown) {
+        // jQuery rejects with the jqXHR object
+        const jqXhr = e as JQuery.jqXHR;
+        if (jqXhr?.status && isCsrfError(jqXhr.status, jqXhr.responseText)) {
+            await refreshCsrfToken();
+            return await doUpload();
+        }
+        throw e;
+    }
 }
 
 let idCounter = 1;
@@ -112,12 +124,55 @@ const idToRequestMap: Record<string, RequestData> = {};
 
 let maxKnownEntityChangeId = 0;
 
+let csrfRefreshInProgress: Promise<void> | null = null;
+
+/**
+ * Re-fetches /bootstrap to obtain a fresh CSRF token. This is needed when the
+ * server session expires (e.g. mobile tab backgrounded for a long time) and the
+ * existing CSRF token is no longer valid.
+ *
+ * Coalesces concurrent calls so only one bootstrap request is in-flight at a time.
+ */
+async function refreshCsrfToken(): Promise<void> {
+    if (csrfRefreshInProgress) {
+        return csrfRefreshInProgress;
+    }
+
+    csrfRefreshInProgress = (async () => {
+        try {
+            const response = await fetch(`./bootstrap${window.location.search}`, { cache: "no-store" });
+            if (response.ok) {
+                const json = await response.json();
+                glob.csrfToken = json.csrfToken;
+            }
+        } finally {
+            csrfRefreshInProgress = null;
+        }
+    })();
+
+    return csrfRefreshInProgress;
+}
+
+function isCsrfError(status: number, responseText: string): boolean {
+    if (status !== 403) {
+        return false;
+    }
+    try {
+        const body = JSON.parse(responseText);
+        return body.message === "Invalid CSRF token";
+    } catch {
+        return false;
+    }
+}
+
 interface CallOptions {
     data?: unknown;
     silentNotFound?: boolean;
     silentInternalServerError?: boolean;
     // If `true`, the value will be returned as a string instead of a JavaScript object if JSON, XMLDocument if XML, etc.
     raw?: boolean;
+    /** Used internally to prevent infinite retry loops on CSRF refresh. */
+    csrfRetried?: boolean;
 }
 
 async function call<T>(method: string, url: string, componentId?: string, options: CallOptions = {}) {
@@ -167,7 +222,7 @@ function ajax(url: string, method: string, data: unknown, headers: Headers, opts
             type: method,
             headers,
             timeout: 60000,
-            success: (body, textStatus, jqXhr) => {
+            success: (body, _textStatus, jqXhr) => {
                 const respHeaders: Headers = {};
 
                 jqXhr
@@ -192,7 +247,25 @@ function ajax(url: string, method: string, data: unknown, headers: Headers, opts
                     // don't report requests that are rejected by the browser, usually when the user is refreshing or going to a different page.
                     rej("rejected by browser");
                     return;
-                } else if (opts.silentNotFound && jqXhr.status === 404) {
+                }
+
+                // If the CSRF token is stale (e.g. session expired while tab was backgrounded),
+                // refresh it and retry the request once.
+                if (!opts.csrfRetried && isCsrfError(jqXhr.status, jqXhr.responseText)) {
+                    try {
+                        await refreshCsrfToken();
+                        // Rebuild headers so the fresh glob.csrfToken is picked up
+                        const retryHeaders = await getHeaders({ "trilium-component-id": headers["trilium-component-id"] });
+                        const retryResult = await ajax(url, method, data, retryHeaders, { ...opts, csrfRetried: true });
+                        res(retryResult);
+                        return;
+                    } catch (retryErr) {
+                        rej(retryErr);
+                        return;
+                    }
+                }
+
+                if (opts.silentNotFound && jqXhr.status === 404) {
                     // report nothing
                 } else if (opts.silentInternalServerError && jqXhr.status === 500) {
                     // report nothing
diff --git a/apps/server-e2e/src/layout/tab_bar.spec.ts b/apps/server-e2e/src/layout/tab_bar.spec.ts
index c408114a0d..8ab1cf7c46 100644
--- a/apps/server-e2e/src/layout/tab_bar.spec.ts
+++ b/apps/server-e2e/src/layout/tab_bar.spec.ts
@@ -75,8 +75,10 @@ test("Tabs are restored in right order", async ({ page, context }) => {
     await expect(app.getActiveTab()).toContainText("Mermaid");
 
     // Select the mid one.
+    const recentNotesSaved = page.waitForResponse((resp) => resp.url().includes("/api/recent-notes") && resp.ok());
     await (await app.getTab(1)).click();
     await expect(app.noteTreeActiveNote).toContainText("Text notes");
+    await recentNotesSaved;
 
     // Refresh the page and check the order.
     await app.goto( { preserveTabs: true });
diff --git a/apps/server/src/routes/csrf_protection.ts b/apps/server/src/routes/csrf_protection.ts
index b7c5f8d5cb..684d1ec81e 100644
--- a/apps/server/src/routes/csrf_protection.ts
+++ b/apps/server/src/routes/csrf_protection.ts
@@ -1,9 +1,17 @@
+import crypto from "crypto";
 import { doubleCsrf } from "csrf-csrf";
+
 import sessionSecret from "../services/session_secret.js";
 import { isElectron } from "../services/utils.js";
 
 export const CSRF_COOKIE_NAME = "trilium-csrf";
 
+// In Electron, API calls go through an IPC bypass (routes/electron.ts) that uses a
+// FakeRequest with a static session ID, while the bootstrap request goes through real
+// Express with a real session. This mismatch causes CSRF validation to always fail.
+// We use a per-instance random identifier so each Electron process still gets unique tokens.
+const electronSessionId = crypto.randomUUID();
+
 const doubleCsrfUtilities = doubleCsrf({
     getSecret: () => sessionSecret,
     cookieOptions: {
@@ -13,7 +21,7 @@ const doubleCsrfUtilities = doubleCsrf({
         httpOnly: !isElectron // set to false for Electron, see https://github.com/TriliumNext/Trilium/pull/966
     },
     cookieName: CSRF_COOKIE_NAME,
-    getSessionIdentifier: (req) => req.session.id
+    getSessionIdentifier: (req) => isElectron ? electronSessionId : req.session.id
 });
 
 export const { generateCsrfToken, doubleCsrfProtection } = doubleCsrfUtilities;