diff --git a/.env.example b/.env.example
index a62d10f4..b6b3b439 100644
--- a/.env.example
+++ b/.env.example
@@ -21,6 +21,12 @@ SESSION_SECRET=
 # Useful when the server reaches LibreChat on a different URL than the browser.
 # API_SERVER_URL=http://localhost:3080
 
+# Browser-facing URL of the admin panel itself. When set, its origin is sent to
+# LibreChat's OAuth exchange instead of deriving it from request headers. Only
+# needed when a proxy strips the Origin header and forwards no x-forwarded-proto
+# or x-forwarded-host metadata. Mirror LibreChat's ADMIN_PANEL_URL value.
+# ADMIN_PANEL_PUBLIC_URL=https://example.com/admin
+
 # Force SSO-only login (hides the email/password form)
 # ADMIN_SSO_ONLY=false
 
diff --git a/README.md b/README.md
index 508c60d7..3cbf6398 100644
--- a/README.md
+++ b/README.md
@@ -45,6 +45,7 @@ docker compose down     # stop
 | `VITE_API_BASE_URL`             | **Yes** (Docker)                    | `http://localhost:3080` (local dev only)                                         | LibreChat API server URL; use `http://host.docker.internal:<port>` in Docker                    |
 | `VITE_BASE_PATH`                | No                                  | `/`                                                                              | URL subpath to serve the panel under (e.g., `/adminpanel`). Must match at build time and runtime |
 | `API_SERVER_URL`                | No                                  | Falls back to `VITE_API_BASE_URL`                                                | Server-side LibreChat API URL when the container reaches LibreChat differently than the browser |
+| `ADMIN_PANEL_PUBLIC_URL`        | No                                  | Derived from request headers                                                     | Browser-facing panel URL; set when a proxy strips `Origin` and forwards no proto/host metadata  |
 | `ADMIN_SSO_ONLY`                | No                                  | `false`                                                                          | Hide email/password form, SSO only                                                              |
 | `ADMIN_SSO_ENABLED`             | No                                  | `true`                                                                           | Set `false` to hide the SSO button (and auto-redirect) while keeping email/password login       |
 | `ADMIN_SESSION_IDLE_TIMEOUT_MS` | No                                  | `1800000` (30 min)                                                               | Session idle timeout in ms                                                                      |
diff --git a/src/server/auth.oauth.test.ts b/src/server/auth.oauth.test.ts
index 569f4803..206cbcac 100644
--- a/src/server/auth.oauth.test.ts
+++ b/src/server/auth.oauth.test.ts
@@ -197,6 +197,8 @@ describe('verifyAdminTokenFn', () => {
 });
 
 describe('oauthExchangeFn', () => {
+  const originalPublicUrl = process.env.ADMIN_PANEL_PUBLIC_URL;
+
   beforeEach(() => {
     fetchMock.mockReset();
     updateSession.mockReset();
@@ -204,6 +206,93 @@ describe('oauthExchangeFn', () => {
     sessionState.data = {};
     requestHeaders.clear();
     vi.stubGlobal('fetch', fetchMock);
+    delete process.env.ADMIN_PANEL_PUBLIC_URL;
+  });
+
+  afterEach(() => {
+    if (originalPublicUrl === undefined) delete process.env.ADMIN_PANEL_PUBLIC_URL;
+    else process.env.ADMIN_PANEL_PUBLIC_URL = originalPublicUrl;
+  });
+
+  it('sends the configured ADMIN_PANEL_PUBLIC_URL origin ahead of any header derivation', async () => {
+    process.env.ADMIN_PANEL_PUBLIC_URL = 'https://public.example.com/admin';
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('origin', 'http://other.test');
+    requestHeaders.set('host', 'admin-panel:3000');
+    requestHeaders.set('x-forwarded-host', 'internal-lb.local');
+    requestHeaders.set('x-forwarded-proto', 'http');
+    requestHeaders.set('referer', 'https://login.microsoftonline.com/');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: '3'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://public.example.com',
+      },
+      body: JSON.stringify({ code: '3'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
+  it('rejects a non-web ADMIN_PANEL_PUBLIC_URL scheme instead of sending a null origin', async () => {
+    process.env.ADMIN_PANEL_PUBLIC_URL = 'file:///etc/passwd';
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('origin', 'https://example.com');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: '8'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: '8'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+    expect(warnSpy).toHaveBeenCalledWith(
+      '[getRequestOrigin] Ignoring malformed ADMIN_PANEL_PUBLIC_URL:',
+      'file:///etc/passwd',
+    );
+  });
+
+  it('falls back to header derivation when ADMIN_PANEL_PUBLIC_URL is malformed', async () => {
+    process.env.ADMIN_PANEL_PUBLIC_URL = 'not a url';
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('origin', 'https://example.com');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: '4'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: '4'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+    expect(warnSpy).toHaveBeenCalledWith(
+      '[getRequestOrigin] Ignoring malformed ADMIN_PANEL_PUBLIC_URL:',
+      'not a url',
+    );
   });
 
   it('exchanges the callback code with the PKCE verifier stored in the admin session', async () => {
@@ -243,6 +332,174 @@ describe('oauthExchangeFn', () => {
     );
   });
 
+  it('derives the exchange Origin from the serving host when the callback carries the IdP referer', async () => {
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('referer', 'https://login.microsoftonline.com/');
+    requestHeaders.set('host', 'example.com');
+    requestHeaders.set('x-forwarded-proto', 'https');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    const result = await oauthExchangeFn({ data: { code: 'c'.repeat(64) } });
+
+    expect(result).toEqual({
+      error: false,
+      user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+    });
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: 'c'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
+  it('uses the first x-forwarded-proto value when the proxy chain appends multiple', async () => {
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('host', 'example.com');
+    requestHeaders.set('x-forwarded-proto', 'https, http');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: 'd'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: 'd'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
+  it('prefers x-forwarded-host over a proxy-rewritten upstream host', async () => {
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('host', 'admin-panel:3000');
+    requestHeaders.set('x-forwarded-host', 'example.com');
+    requestHeaders.set('x-forwarded-proto', 'https');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: 'e'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: 'e'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
+  it('uses the first x-forwarded-host value when the proxy chain appends multiple', async () => {
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('host', 'admin-panel:3000');
+    requestHeaders.set('x-forwarded-host', 'example.com, internal-lb.local');
+    requestHeaders.set('x-forwarded-proto', 'https');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: 'f'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: 'f'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
+  it('recovers the https scheme from a same-host referer when x-forwarded-proto is absent', async () => {
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('host', 'example.com');
+    requestHeaders.set('referer', 'https://example.com/admin/auth/openid/callback?code=abc');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: '1'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: '1'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
+  it('matches a same-host referer when the serving authority carries an explicit default port', async () => {
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('host', 'example.com:443');
+    requestHeaders.set('referer', 'https://example.com/admin/auth/openid/callback?code=abc');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: '7'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'https://example.com',
+      },
+      body: JSON.stringify({ code: '7'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
+  it('never adopts a foreign referer origin even when x-forwarded-proto is absent', async () => {
+    sessionState.data = { codeVerifier: 'verifier-123' };
+    requestHeaders.set('host', 'example.com');
+    requestHeaders.set('referer', 'https://login.microsoftonline.com/');
+    fetchMock.mockResolvedValueOnce(
+      jsonResponse(200, {
+        token: 'jwt-token',
+        user: { id: 'user-1', role: 'ADMIN', email: 'admin@example.com' },
+      }),
+    );
+
+    await oauthExchangeFn({ data: { code: '2'.repeat(64) } });
+
+    expect(fetchMock).toHaveBeenCalledWith('http://librechat.test/api/admin/oauth/exchange', {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        Origin: 'http://example.com',
+      },
+      body: JSON.stringify({ code: '2'.repeat(64), code_verifier: 'verifier-123' }),
+    });
+  });
+
   it('does not consume the one-time LibreChat exchange code when the PKCE verifier was lost', async () => {
     sessionState.data = {};
 
diff --git a/src/server/auth.ts b/src/server/auth.ts
index 8e7172b2..16b68e5b 100644
--- a/src/server/auth.ts
+++ b/src/server/auth.ts
@@ -21,24 +21,71 @@ function extractCookieValue(response: Response, name: string): string | undefine
   return undefined;
 }
 
-function getRequestOrigin(): string | undefined {
-  const origin = getRequestHeader('origin');
-  if (origin) return origin;
+/** Returns the origin of ADMIN_PANEL_PUBLIC_URL when configured, giving deployments behind proxies that strip Origin and forward no proto/host metadata a deterministic override. */
+function getConfiguredPublicOrigin(): string | undefined {
+  const publicUrl = process.env.ADMIN_PANEL_PUBLIC_URL;
+  if (!publicUrl) return undefined;
+  try {
+    const url = new URL(publicUrl);
+    if ((url.protocol === 'http:' || url.protocol === 'https:') && url.origin !== 'null') {
+      return url.origin;
+    }
+  } catch {
+    /* fall through to the warning */
+  }
+  console.warn('[getRequestOrigin] Ignoring malformed ADMIN_PANEL_PUBLIC_URL:', publicUrl);
+  return undefined;
+}
 
+const DEFAULT_SCHEME_PORTS: Record<string, string> = { 'https:': ':443', 'http:': ':80' };
+
+/** Returns the referer's origin only when its host matches the serving host, so a foreign referer (e.g. an IdP such as Azure EntraID's login.microsoftonline.com) can never be forwarded as the panel's own origin. `URL` strips the scheme's default port from the referer host, so an explicit default port on the serving authority (`example.com:443`) is stripped before comparing. */
+function getSameHostRefererOrigin(host: string): string | undefined {
   const referer = getRequestHeader('referer');
-  if (referer) {
-    try {
-      return new URL(referer).origin;
-    } catch {
-      return undefined;
-    }
+  if (!referer) return undefined;
+  try {
+    const url = new URL(referer);
+    const defaultPort = DEFAULT_SCHEME_PORTS[url.protocol] ?? '';
+    const servingHost = host.toLowerCase();
+    const normalizedHost =
+      defaultPort && servingHost.endsWith(defaultPort)
+        ? servingHost.slice(0, -defaultPort.length)
+        : servingHost;
+    return url.host.toLowerCase() === normalizedHost ? url.origin : undefined;
+  } catch {
+    return undefined;
   }
+}
+
+/**
+ * Resolves the admin panel's browser-visible origin for LibreChat's exchange-code
+ * origin binding.
+ *
+ * Order: the configured `ADMIN_PANEL_PUBLIC_URL` origin, then the `origin` header,
+ * then the first `x-forwarded-host` value (Host-rewriting proxies replace `host` with
+ * the internal upstream authority) combined with the first `x-forwarded-proto` value.
+ * When no forwarded proto is available, a same-host referer recovers the scheme for
+ * HTTPS deployments whose proxy strips `Origin` without setting `x-forwarded-proto`.
+ * A foreign referer is never used: it identifies whatever page or IdP initiated the
+ * request, and forwarding it makes LibreChat reject the exchange code as expired even
+ * though authentication succeeded.
+ */
+function getRequestOrigin(): string | undefined {
+  const configuredOrigin = getConfiguredPublicOrigin();
+  if (configuredOrigin) return configuredOrigin;
 
-  const host = getRequestHeader('host');
+  const origin = getRequestHeader('origin');
+  if (origin) return origin;
+
+  const forwardedHost = getRequestHeader('x-forwarded-host');
+  const host = forwardedHost?.split(',')[0]?.trim() || getRequestHeader('host');
   if (!host) return undefined;
 
-  const proto = getRequestHeader('x-forwarded-proto') ?? 'http';
-  return `${proto}://${host}`;
+  const forwardedProto = getRequestHeader('x-forwarded-proto');
+  const proto = forwardedProto?.split(',')[0]?.trim();
+  if (proto) return `${proto}://${host}`;
+
+  return getSameHostRefererOrigin(host) ?? `http://${host}`;
 }
 
 export const adminLoginFn = createServerFn({ method: 'POST' })
@@ -197,7 +244,8 @@ export const verifyAdminTokenFn = createServerFn({ method: 'GET' }).handler(asyn
       return { valid: false, error: 'Session expired due to inactivity' };
     }
 
-    const needsRevalidation = !lastVerified || now - lastVerified > sessionConfig.revalidationInterval;
+    const needsRevalidation =
+      !lastVerified || now - lastVerified > sessionConfig.revalidationInterval;
 
     if (needsRevalidation) {
       try {