diff --git a/server/public/chat.html b/server/public/chat.html
index 3c00f184403..ba0ee210dc1 100644
--- a/server/public/chat.html
+++ b/server/public/chat.html
@@ -3418,6 +3418,30 @@ <h2>Ask Addie</h2>
         return fetch(url, { ...options, headers, credentials: 'include' });
       }
 
+      async function isOrganizationSelectionConflict(response) {
+        if (response.status !== 403) return false;
+        try {
+          const data = await response.clone().json();
+          return data?.error === 'An unambiguous organization selection is required';
+        } catch (e) {
+          return false;
+        }
+      }
+
+      async function switchSessionOrganization(organizationId) {
+        if (typeof organizationId !== 'string' || !organizationId.trim() || nativeAuthToken) return false;
+        try {
+          const response = await authFetch('/auth/switch-organization', {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ target_organization_id: organizationId.trim() }),
+          });
+          return response.ok;
+        } catch (e) {
+          return false;
+        }
+      }
+
       function getSelectedOrganizationId() {
         const urlOrg = new URLSearchParams(window.location.search).get('org');
         if (urlOrg) return urlOrg;
@@ -5377,7 +5401,7 @@ <h2>Ask Addie</h2>
 
         try {
           const selectedOrganizationId = getSelectedOrganizationId();
-          const response = await authFetch('/api/addie/chat/stream', {
+          const postStream = () => authFetch('/api/addie/chat/stream', {
             method: 'POST',
             headers: {
               'Content-Type': 'application/json',
@@ -5395,6 +5419,15 @@ <h2>Ask Addie</h2>
               retry: retrying,
             }),
           });
+          let response = await postStream();
+          // The org picker only changes the local selection. When the session
+          // is bound to another org, rebind it once and resend: auth rejected
+          // the request before the chat route saw it.
+          if (await isOrganizationSelectionConflict(response)
+              && await switchSessionOrganization(selectedOrganizationId)) {
+            requestId = crypto.randomUUID();
+            response = await postStream();
+          }
           requestId = validChatRequestId(response.headers.get('X-Request-ID')) || requestId;
 
           if (!response.ok) {
diff --git a/server/src/http.ts b/server/src/http.ts
index bf44b11c815..a43a1b460f6 100644
--- a/server/src/http.ts
+++ b/server/src/http.ts
@@ -78,7 +78,7 @@ import { resolveUserNameWithFallbacks, sanitizeName } from "./utils/resolve-user
 import { scrubCommunityAuthorizedAgents } from "./utils/community-adagents.js";
 import { formatPerspectiveUrlAsMarkdownDestination, normalizePerspectiveExternalUrl } from "./utils/perspective-url.js";
 import { decodeHtmlEntities } from "./utils/html-entities.js";
-import { requireAuth, requireAdmin, requireGlobalAdmin, optionalAuth, invalidateSessionCache, isDevModeEnabled, getDevUser, getAvailableDevUsers, getDevSessionCookieName, encodeDevSessionCookie, DEV_USERS, type DevUserConfig } from "./middleware/auth.js";
+import { requireAuth, requireAdmin, requireGlobalAdmin, optionalAuth, invalidateSessionCache, switchSessionOrganization, isDevModeEnabled, getDevUser, getAvailableDevUsers, getDevSessionCookieName, encodeDevSessionCookie, DEV_USERS, type DevUserConfig } from "./middleware/auth.js";
 import { invitationRateLimiter, brandCreationRateLimiter, notificationRateLimiter, emailPrefsRateLimiter, adminContentWriteRateLimiter, newsletterSubscribeRateLimiter, newsletterConfirmRateLimiter, agentCardValidationRateLimiter } from "./middleware/rate-limit.js";
 import { findOrCreateUserByEmail } from "./auth/workos-client.js";
 import { sendNewsletterConfirmation } from "./notifications/email.js";
@@ -8447,6 +8447,11 @@ ${p.category ? `<category>${p.category}</category>\n` : ''}<url>${publishedUrl}<
     });
 
 
+    // POST /auth/switch-organization - Rebind the WorkOS session to another org
+    // the user belongs to. Client org pickers only change local selection, and
+    // an explicit selector that differs from the session org is rejected.
+    this.app.post('/auth/switch-organization', requireAuth, switchSessionOrganization);
+
     // GET /auth/logout - Clear session and redirect
     this.app.get('/auth/logout', async (req, res) => {
       // Dev mode: clear dev-session cookie and redirect to home
diff --git a/server/src/middleware/auth.ts b/server/src/middleware/auth.ts
index b33cc04c1ef..701134ae643 100644
--- a/server/src/middleware/auth.ts
+++ b/server/src/middleware/auth.ts
@@ -892,6 +892,62 @@ function sendAuthorizationStateError(error: unknown, res: Response, includeTrans
   return false;
 }
 
+/**
+ * Rebind the caller's sealed WorkOS session to another organization.
+ * Request fields never select authority on their own: WorkOS verifies the
+ * membership during the refresh, and later requests carry the new provider org.
+ * Mount behind requireAuth. The target uses its own field so it is not read as
+ * a conflicting organization selector by the auth middleware.
+ */
+export async function switchSessionOrganization(req: Request, res: Response) {
+  const target = req.body?.target_organization_id;
+  if (typeof target !== 'string' || !target.trim()) {
+    return res.status(400).json({ error: 'target_organization_id is required' });
+  }
+  const sessionCookie = req.headers.authorization === undefined ? req.cookies?.['wos-session'] : undefined;
+  if (!sessionCookie) {
+    return res.status(400).json({ error: 'Organization switching requires a browser session' });
+  }
+
+  const cacheKey = hashSessionCookie(sessionCookie);
+  try {
+    // The cookie's refresh token may already be rotated by a concurrent refresh.
+    const current = sessionCache.get(cacheKey)?.newSealedSession
+      ?? await getRefreshedSession(cacheKey)
+      ?? sessionCookie;
+    const result = await workos.userManagement.loadSealedSession({
+      sessionData: current,
+      cookiePassword: WORKOS_COOKIE_PASSWORD,
+    }).refresh({ cookiePassword: WORKOS_COOKIE_PASSWORD, organizationId: target.trim() });
+
+    if (!result.authenticated || !result.sealedSession) {
+      if ('retryable' in result && result.retryable) {
+        return res.status(503).json({ error: 'Authentication service temporarily unavailable' });
+      }
+      logger.info(
+        { userId: req.user?.id, reason: 'reason' in result ? result.reason : undefined },
+        'Session organization switch rejected',
+      );
+      return res.status(403).json({ error: 'Unable to switch to that organization' });
+    }
+
+    sessionCache.delete(cacheKey);
+    setSessionCookie(res, result.sealedSession);
+    // Other instances holding the old cookie adopt the switched session.
+    storeRefreshedSession(cacheKey, result.sealedSession).catch((err) => {
+      logger.error({ err }, 'Failed to store switched session — other instances may force re-auth');
+    });
+    return res.json({ organization_id: target.trim() });
+  } catch (error) {
+    if (isTransientAuthError(error)) {
+      logger.warn({ err: error }, 'Authentication service unavailable during organization switch');
+      return res.status(503).json({ error: 'Authentication service temporarily unavailable' });
+    }
+    logger.warn({ err: error, userId: req.user?.id }, 'Session organization switch failed');
+    return res.status(403).json({ error: 'Unable to switch to that organization' });
+  }
+}
+
 /**
  * Middleware to require authentication
  * Checks for WorkOS session cookie and loads user info
diff --git a/server/tests/integration/content-my-content.test.ts b/server/tests/integration/content-my-content.test.ts
index bcd5dbe1190..138b6d7f3a3 100644
--- a/server/tests/integration/content-my-content.test.ts
+++ b/server/tests/integration/content-my-content.test.ts
@@ -54,6 +54,7 @@ vi.mock('../../src/middleware/auth.js', () => {
     invalidateSessionCache: vi.fn(),
     invalidateBanCache: vi.fn(),
     invalidateSessionsForUsers: vi.fn(),
+    switchSessionOrganization: vi.fn(),
     isDevModeEnabled: () => false,
     getDevUser: () => null,
     getAvailableDevUsers: () => ({}),
diff --git a/server/tests/integration/event-speakers.test.ts b/server/tests/integration/event-speakers.test.ts
index 0a19a7ba00b..12812f61b41 100644
--- a/server/tests/integration/event-speakers.test.ts
+++ b/server/tests/integration/event-speakers.test.ts
@@ -42,6 +42,7 @@ vi.mock('../../src/middleware/auth.js', () => {
     invalidateSessionCache: vi.fn(),
     invalidateBanCache: vi.fn(),
     invalidateSessionsForUsers: vi.fn(),
+    switchSessionOrganization: vi.fn(),
     isDevModeEnabled: () => false,
     getDevUser: () => null,
     getAvailableDevUsers: () => ({}),
diff --git a/server/tests/integration/events-draft-preview.test.ts b/server/tests/integration/events-draft-preview.test.ts
index fe4193ea5cc..75e5434c110 100644
--- a/server/tests/integration/events-draft-preview.test.ts
+++ b/server/tests/integration/events-draft-preview.test.ts
@@ -43,6 +43,7 @@ vi.mock('../../src/middleware/auth.js', () => {
     invalidateSessionCache: vi.fn(),
     invalidateBanCache: vi.fn(),
     invalidateSessionsForUsers: vi.fn(),
+    switchSessionOrganization: vi.fn(),
     isDevModeEnabled: () => false,
     getDevUser: () => null,
     getAvailableDevUsers: () => ({}),
diff --git a/server/tests/integration/perspective-assets.test.ts b/server/tests/integration/perspective-assets.test.ts
index ab6e03cce61..617eb0ca3da 100644
--- a/server/tests/integration/perspective-assets.test.ts
+++ b/server/tests/integration/perspective-assets.test.ts
@@ -50,6 +50,7 @@ vi.mock('../../src/middleware/auth.js', () => {
     invalidateSessionCache: vi.fn(),
     invalidateBanCache: vi.fn(),
     invalidateSessionsForUsers: vi.fn(),
+    switchSessionOrganization: vi.fn(),
     isDevModeEnabled: () => false,
     getDevUser: () => null,
     getAvailableDevUsers: () => ({}),
diff --git a/server/tests/unit/chat-request-errors.test.ts b/server/tests/unit/chat-request-errors.test.ts
index 205e111f41d..f39ac6e6673 100644
--- a/server/tests/unit/chat-request-errors.test.ts
+++ b/server/tests/unit/chat-request-errors.test.ts
@@ -16,8 +16,12 @@ const sse = (event: string, body: unknown) => new Response(
   { headers: { 'Content-Type': 'text/event-stream', 'X-Request-ID': id } },
 );
 
-async function openChat(reply: (attempt: number) => Response, organization?: string, csrfRetry = false) {
+async function openChat(
+  reply: (attempt: number) => Response, organization?: string, csrfRetry = false,
+  switchReply: () => Response = () => json({}, 404),
+) {
   const requests: Array<{ body: Record<string, unknown>; headers: Headers }> = [];
+  const switches: Array<Record<string, unknown>> = [];
   dom = new JSDOM(html, {
     url: 'https://example.test/chat', runScripts: 'dangerously', pretendToBeVisual: true,
     beforeParse(window) {
@@ -34,6 +38,10 @@ async function openChat(reply: (attempt: number) => Response, organization?: str
         if (url.startsWith('/api/me/addie-home')) return json({ html: '', css: '' });
         if (url === '/api/addie/chat/threads') return json({ conversations: [] });
         if (url === '/api/si/sessions/user') return json({ sessions: [] });
+        if (url === '/auth/switch-organization') {
+          switches.push(JSON.parse(String(options?.body)));
+          return switchReply();
+        }
         if (url === '/api/addie/chat/stream') {
           requests.push({ body: JSON.parse(String(options?.body)), headers: new Headers(options?.headers) });
           return reply(requests.length);
@@ -51,19 +59,21 @@ async function openChat(reply: (attempt: number) => Response, organization?: str
   await vi.waitFor(() => expect((window.document.getElementById('sendButton') as HTMLButtonElement).disabled).toBe(false));
   window.document.getElementById('sendButton')!.click();
   await vi.waitFor(() => expect(requests.length).toBeGreaterThan(0));
-  return { document: window.document, requests };
+  return { document: window.document, requests, switches };
 }
 
 describe('chat requests and actionable failure UI', () => {
   it.each([undefined, '', '   '])('omits an absent/empty organization selector (%s)', async (org) => {
-    const { requests } = await openChat(() => json({}, 403), org);
+    const { document, requests } = await openChat(() => json({}, 403), org);
+    await vi.waitFor(() => expect(document.querySelector('.chat-request-error')).not.toBeNull());
     expect(requests[0].body).not.toHaveProperty('organization_id');
     expect(requests[0].headers.get('X-Request-ID')).toMatch(/^[0-9a-f-]{36}$/);
     expect(requests[0].body.client_request_id).not.toBe(requests[0].headers.get('X-Request-ID'));
   });
 
   it('retains a selected organization without inferring another one', async () => {
-    const { requests } = await openChat(() => json({}, 403), 'org_selected');
+    const { document, requests } = await openChat(() => json({}, 403), 'org_selected');
+    await vi.waitFor(() => expect(document.querySelector('.chat-request-error')).not.toBeNull());
     expect(requests[0].body.organization_id).toBe('org_selected');
   });
 
@@ -127,6 +137,44 @@ describe('chat requests and actionable failure UI', () => {
     expect(document.querySelector('.chat-request-reference')?.textContent).toContain(id);
   });
 
+  const conflict = () => json({ error: 'An unambiguous organization selection is required' }, 403, { 'X-Request-ID': id });
+
+  it('rebinds the session to the selected organization and resends once', async () => {
+    const { document, requests, switches } = await openChat(
+      (attempt) => attempt === 1 ? conflict() : sse('text', { text: 'Hello from your organization' }),
+      'org_selected', false, () => json({ organization_id: 'org_selected' }),
+    );
+    await vi.waitFor(() => expect(requests).toHaveLength(2));
+    // The retried stream is the one consumed: its EOF offers recovery, not the org error.
+    await vi.waitFor(() => expect(document.querySelector('.reply-recovery__action')).not.toBeNull());
+    expect(switches).toEqual([{ target_organization_id: 'org_selected' }]);
+    expect(requests).toHaveLength(2);
+    expect(requests[1].body).toEqual(requests[0].body);
+    expect(requests[1].headers.get('X-Request-ID')).not.toBe(requests[0].headers.get('X-Request-ID'));
+    expect(document.querySelector('.chat-request-error')?.textContent ?? '').not.toContain('Choose your organization again');
+  });
+
+  it('shows the organization error when the session cannot be rebound', async () => {
+    const { document, requests, switches } = await openChat(
+      conflict, 'org_selected', false, () => json({ error: 'Unable to switch to that organization' }, 403),
+    );
+    await vi.waitFor(() => expect(document.querySelector('.chat-request-error')?.textContent).toContain('Choose your organization again'));
+    expect(switches).toHaveLength(1);
+    expect(requests).toHaveLength(1);
+  });
+
+  it('does not switch organizations without a selection or for other 403s', async () => {
+    const withoutSelection = await openChat(conflict);
+    await vi.waitFor(() => expect(withoutSelection.document.querySelector('.chat-request-error')).not.toBeNull());
+    expect(withoutSelection.switches).toHaveLength(0);
+    dom.window.close();
+
+    const otherForbidden = await openChat(() => json({ error: 'Forbidden' }, 403), 'org_selected');
+    await vi.waitFor(() => expect(otherForbidden.document.querySelector('.chat-request-error')).not.toBeNull());
+    expect(otherForbidden.switches).toHaveLength(0);
+    expect(otherForbidden.requests).toHaveLength(1);
+  });
+
   it('retries a CSRF cookie-expiry 403 once using its fresh token and preserves correlation', async () => {
     const token = 'a'.repeat(64);
     const { document, requests } = await openChat((attempt) => attempt === 1
diff --git a/server/tests/unit/session-organization-switch.test.ts b/server/tests/unit/session-organization-switch.test.ts
new file mode 100644
index 00000000000..ac610cf7667
--- /dev/null
+++ b/server/tests/unit/session-organization-switch.test.ts
@@ -0,0 +1,119 @@
+/** Switching orgs rebinds the WorkOS session; request fields never grant authority. */
+import { createHash } from 'node:crypto';
+import express from 'express';
+import supertest from 'supertest';
+import { afterAll, beforeEach, describe, expect, it, vi } from 'vitest';
+
+const mocks = vi.hoisted(() => ({
+  loadSealedSession: vi.fn(), refresh: vi.fn(),
+  getRefreshedSession: vi.fn(), storeRefreshedSession: vi.fn(),
+}));
+vi.hoisted(() => {
+  process.env.DEV_USER_EMAIL = '';
+  process.env.DEV_USER_ID = '';
+  process.env.WORKOS_API_KEY ??= 'sk_test';
+  process.env.WORKOS_CLIENT_ID ??= 'client_test';
+  process.env.WORKOS_COOKIE_PASSWORD ??= 'placeholder-cookie-password-32-bytes-min';
+});
+vi.mock('@workos-inc/node', () => ({
+  WorkOS: vi.fn(function WorkOS() {
+    return {
+      userManagement: { loadSealedSession: mocks.loadSealedSession },
+      apiKeys: { createValidation: vi.fn() },
+    };
+  }),
+}));
+vi.mock('../../src/db/session-refresh-db.js', () => ({
+  getRefreshedSession: mocks.getRefreshedSession,
+  storeRefreshedSession: mocks.storeRefreshedSession,
+  cleanExpiredRefreshes: vi.fn().mockResolvedValue(0),
+}));
+import { stopAuthTimers, switchSessionOrganization } from '../../src/middleware/auth.js';
+
+const COOKIE = 'sealed-session-bound-to-org-pinnacle';
+const hash = (value: string) => createHash('sha256').update(value).digest('hex');
+
+function app(headers: Record<string, string> = {}, cookie: string | null = COOKIE) {
+  const server = express();
+  server.use(express.json());
+  server.use((req, _res, next) => {
+    req.cookies = cookie === null ? {} : { 'wos-session': cookie };
+    Object.assign(req.headers, headers);
+    next();
+  });
+  server.post('/auth/switch-organization', switchSessionOrganization);
+  return supertest(server);
+}
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  mocks.loadSealedSession.mockReturnValue({ refresh: mocks.refresh });
+  mocks.getRefreshedSession.mockResolvedValue(undefined);
+  mocks.storeRefreshedSession.mockResolvedValue(undefined);
+  mocks.refresh.mockResolvedValue({ authenticated: true, sealedSession: 'sealed-session-bound-to-org-other' });
+});
+afterAll(() => stopAuthTimers());
+
+describe('switchSessionOrganization', () => {
+  it('asks WorkOS to rebind the session and replaces the cookie', async () => {
+    const response = await app().post('/auth/switch-organization').send({ target_organization_id: ' org_other ' });
+
+    expect(response.status).toBe(200);
+    expect(response.body).toEqual({ organization_id: 'org_other' });
+    expect(mocks.loadSealedSession).toHaveBeenCalledWith(expect.objectContaining({ sessionData: COOKIE }));
+    expect(mocks.refresh).toHaveBeenCalledWith(expect.objectContaining({ organizationId: 'org_other' }));
+    expect(response.headers['set-cookie']?.[0]).toMatch(/^wos-session=sealed-session-bound-to-org-other;.*HttpOnly/);
+    expect(mocks.storeRefreshedSession).toHaveBeenCalledWith(hash(COOKIE), 'sealed-session-bound-to-org-other');
+  });
+
+  it('refreshes from a session another instance already rotated', async () => {
+    mocks.getRefreshedSession.mockResolvedValue('rotated-sealed-session');
+    await app().post('/auth/switch-organization').send({ target_organization_id: 'org_other' });
+    expect(mocks.loadSealedSession).toHaveBeenCalledWith(expect.objectContaining({ sessionData: 'rotated-sealed-session' }));
+  });
+
+  it.each([{}, { target_organization_id: '' }, { target_organization_id: '  ' }, { target_organization_id: ['org_other'] }])(
+    'rejects a missing or unusable target %j', async (body) => {
+      const response = await app().post('/auth/switch-organization').send(body);
+      expect(response.status).toBe(400);
+      expect(mocks.refresh).not.toHaveBeenCalled();
+    },
+  );
+
+  it('does not rebind bearer-authenticated callers', async () => {
+    const response = await app({ authorization: 'Bearer sk_org_key' })
+      .post('/auth/switch-organization').send({ target_organization_id: 'org_other' });
+    expect(response.status).toBe(400);
+    expect(mocks.refresh).not.toHaveBeenCalled();
+  });
+
+  it('requires a browser session cookie', async () => {
+    const response = await app({}, null).post('/auth/switch-organization').send({ target_organization_id: 'org_other' });
+    expect(response.status).toBe(400);
+    expect(mocks.refresh).not.toHaveBeenCalled();
+  });
+
+  it('keeps the current session when WorkOS rejects the organization', async () => {
+    mocks.refresh.mockResolvedValue({ authenticated: false, reason: 'invalid_grant' });
+    const response = await app().post('/auth/switch-organization').send({ target_organization_id: 'org_not_mine' });
+
+    expect(response.status).toBe(403);
+    expect(response.body).toEqual({ error: 'Unable to switch to that organization' });
+    expect(response.headers['set-cookie']).toBeUndefined();
+    expect(mocks.storeRefreshedSession).not.toHaveBeenCalled();
+  });
+
+  it('reports a retryable WorkOS failure as unavailable', async () => {
+    mocks.refresh.mockResolvedValue({ authenticated: false, reason: 'network', retryable: true });
+    const response = await app().post('/auth/switch-organization').send({ target_organization_id: 'org_other' });
+    expect(response.status).toBe(503);
+    expect(response.headers['set-cookie']).toBeUndefined();
+  });
+
+  it('does not leak provider errors', async () => {
+    mocks.refresh.mockRejectedValue(new Error('WorkOS said: membership om_123 missing'));
+    const response = await app().post('/auth/switch-organization').send({ target_organization_id: 'org_other' });
+    expect(response.status).toBe(403);
+    expect(JSON.stringify(response.body)).not.toContain('om_123');
+  });
+});