simstudioai · icecrasher321 · Jul 29, 2026 · Jul 18, 2026 · Jul 18, 2026 · Jul 18, 2026
diff --git a/apps/desktop/README.md b/apps/desktop/README.md
@@ -1,6 +1,6 @@
 # Sim Desktop (macOS)
 
-A thin Electron shell around the hosted Sim web app. The renderer loads the configured origin (default `https://sim.ai`) as a normal top-level page in a bundled, pinned Chromium — rendering is identical to Chrome of that version on every machine. No UI is re-implemented and no server stack is bundled.
+A thin Electron shell around the hosted Sim web app. The renderer loads the configured origin (default `https://www.sim.ai` — the origin the server actually serves; the apex 301s there) as a normal top-level page in a bundled, pinned Chromium — rendering is identical to Chrome of that version on every machine. No UI is re-implemented and no server stack is bundled.
 
 ## Layout
 
@@ -44,7 +44,7 @@ e2e/                # Playwright _electron smoke suite
 ```bash
 bun install                 # workspace root
 cd apps/desktop
-bun run dev                 # bundle + launch against https://sim.ai
+bun run dev                 # bundle + launch against https://www.sim.ai
 SIM_DESKTOP_ORIGIN=http://localhost:3000 bun run dev   # against local sim
 ```
 
@@ -74,7 +74,7 @@ Deviations from the original plan doc (deliberate):
 
 ## Provider matrix (U5 spike — keep current)
 
-Host lists live in `src/main/navigation.ts` (`SYSTEM_BROWSER_IDP_HOSTS`, `IN_WINDOW_IDP_HOSTS`). Verified so far: Google + Microsoft blocked (by policy, not spike); GitHub assumed lenient. **Before GA, run the spike**: GitHub sign-in, consumer-Microsoft, a sample of integration connects (Notion, Slack, Linear, Atlassian, Box, Dropbox), SSO, and Turnstile-on-signup in a packaged build, then update the lists and this section.
+The host list lives in `src/main/navigation.ts` (`SYSTEM_BROWSER_IDP_HOSTS`) and now applies to **integration connects only** — sign-in always goes through the system-browser handoff whatever the IdP, so no provider needs to be classified as embed-tolerant for login. (The old `IN_WINDOW_IDP_HOSTS` list existed to keep GitHub sign-in in-window; embedding a login is a one-way door in a chrome-less shell and splits better-auth's OAuth state across two cookie jars, so it was removed.) Verified so far: Google + Microsoft block embedding by policy. **Before GA, run the spike** for connects: a sample of integration connects (Notion, Slack, Linear, Atlassian, Box, Dropbox) plus SSO and Turnstile-on-signup in a packaged build, then update the list and this section.
 
 ## Web-app coupling contract (audit on web-app changes)
 

diff --git a/apps/desktop/scripts/build.ts b/apps/desktop/scripts/build.ts
@@ -7,7 +7,7 @@ const watch = process.argv.includes('--watch')
 // non-prod environment): SIM_DESKTOP_DEFAULT_ORIGIN=https://www.dev.sim.ai.
 // Baked into the bundle so it applies to fresh installs with no settings —
 // unlike the SIM_DESKTOP_ORIGIN env var, which only affects terminal-launched
-// processes. Official builds leave it unset (default https://sim.ai).
+// processes. Official builds leave it unset (default https://www.sim.ai).
 const bakedDefaultOrigin = process.env.SIM_DESKTOP_DEFAULT_ORIGIN ?? ''
 if (
   bakedDefaultOrigin &&

diff --git a/apps/desktop/scripts/install-local.ts b/apps/desktop/scripts/install-local.ts
@@ -40,9 +40,11 @@ const CHANNEL_FLAGS: Record<string, ChannelIdentity> = {
     appId: 'ai.sim.desktop.staging',
     origin: 'https://www.staging.sim.ai',
   },
-  // Bare sim.ai, matching official prod builds (config.ts) — www.sim.ai
-  // would land in a different cookie partition than a real install.
-  '--prod': { name: 'Sim', appId: 'ai.sim.desktop', origin: 'https://sim.ai' },
+  // Origin left unset, exactly as official prod builds do, so this install
+  // resolves the same DEFAULT_ORIGIN (config.ts) and therefore the same cookie
+  // partition as a real one. Naming an origin here re-creates the drift that
+  // pinned prod to the apex while the server serves www.
+  '--prod': { name: 'Sim', appId: 'ai.sim.desktop' },
 }
 
 const DEFAULT_IDENTITY: ChannelIdentity = { name: 'Sim', appId: 'ai.sim.desktop' }

diff --git a/apps/desktop/src/main/config.ts b/apps/desktop/src/main/config.ts
@@ -15,6 +15,13 @@ const logger = createLogger('DesktopConfig')
  * define replaces the env read at bundle time, so a packaged app never
  * consults the runtime environment for this. http is accepted only for
  * loopback origins (the localhost dev-server channel).
+ *
+ * This must be the origin the server actually *serves*, not a hostname that
+ * redirects to it. Every environment canonicalizes the apex to `www` (the load
+ * balancer 301s `sim.ai` → `www.sim.ai`), and the navigation guards compare
+ * origins for exact equality — so an apex origin here silently leaves every
+ * page off-origin, which reclassifies social login as an integration connect
+ * and strands the sign-in in the browser with no way back.
  */
 function isValidBakedOrigin(origin: string | undefined): origin is string {
   if (!origin) return false
@@ -29,7 +36,7 @@ function isValidBakedOrigin(origin: string | undefined): origin is string {
 
 export const DEFAULT_ORIGIN = isValidBakedOrigin(process.env.SIM_DESKTOP_DEFAULT_ORIGIN)
   ? process.env.SIM_DESKTOP_DEFAULT_ORIGIN
-  : 'https://sim.ai'
+  : 'https://www.sim.ai'
 
 /**
  * The environment a build is keyed to, derived from its baked default origin.

diff --git a/apps/desktop/src/main/menu.test.ts b/apps/desktop/src/main/menu.test.ts
@@ -74,6 +74,7 @@ describe('buildMenuTemplate', () => {
     expect(submenu(template, 'View').map((item) => item.label ?? item.role ?? item.type)).toEqual([
       'Toggle Sidebar',
       'separator',
+      'Back',
       'Reload',
       'separator',
       'Actual Size',

diff --git a/apps/desktop/src/main/menu.ts b/apps/desktop/src/main/menu.ts
@@ -55,6 +55,21 @@ export function buildMenuTemplate(deps: MenuDeps): MenuItemConstructorOptions[]
       click: deps.toggleSidebar,
     },
     { type: 'separator' },
+    /**
+     * The shell has no browser chrome, so an in-window integration connect
+     * that leaves the app origin (the IdP's consent page) is otherwise a
+     * one-way door for anyone who decides not to finish it.
+     */
+    {
+      label: 'Back',
+      accelerator: 'CmdOrCtrl+[',
+      click: withWindow((win) => {
+        const history = win.webContents.navigationHistory
+        if (history.canGoBack()) {
+          history.goBack()
+        }
+      }),
+    },
     {
       label: 'Reload',
       accelerator: 'CmdOrCtrl+R',

diff --git a/apps/desktop/src/main/navigation.test.ts b/apps/desktop/src/main/navigation.test.ts
@@ -13,7 +13,7 @@ import {
   openExternalSafe,
 } from '@/main/navigation'
 
-const APP = 'https://sim.ai'
+const APP = 'https://www.sim.ai'
 
 describe('classifyNavigation', () => {
   it('keeps same-origin navigation in-app', () => {
@@ -65,12 +65,24 @@ describe('classifyNavigation', () => {
     ).toBe('idp-system-connect')
   })
 
-  it('keeps verified-lenient IdPs in-window from the login surface', () => {
+  it('routes every sign-in to the system browser, including IdPs that tolerate embedding', () => {
+    // GitHub used to be kept in-window. Embedded, it is a one-way door (no
+    // browser chrome to back out of) and it splits better-auth's OAuth state
+    // cookie across two user agents, which comes back `state_mismatch`.
     expect(
       classifyNavigation('https://github.com/login/oauth/authorize?client_id=x', {
         appOrigin: APP,
         currentUrl: `${APP}/login`,
       })
+    ).toBe('idp-system-login')
+  })
+
+  it('keeps the same IdP in-window when it is an integration connect', () => {
+    expect(
+      classifyNavigation('https://github.com/login/oauth/authorize?client_id=x', {
+        appOrigin: APP,
+        currentUrl: `${APP}/workspace/ws1/integrations/github`,
+      })
     ).toBe('idp-in-window')
   })
 

diff --git a/apps/desktop/src/main/navigation.ts b/apps/desktop/src/main/navigation.ts
@@ -24,10 +24,10 @@ export interface NavigationContext {
 }
 
 /**
- * IdP hosts that hard-block OAuth inside embedded user agents. Navigation to
- * these hosts is cancelled and rerouted: from an auth surface the app starts
- * the system-browser login handoff; from anywhere else it offers to finish the
- * integration connect in the browser (tokens land server-side either way).
+ * IdP hosts that hard-block OAuth inside embedded user agents. An integration
+ * connect heading for one of these is cancelled and offered as a finish-in-the-
+ * browser flow instead (tokens land server-side either way). Sign-in never
+ * consults this list — see {@link classifyNavigation}.
  */
 export const SYSTEM_BROWSER_IDP_HOSTS: readonly string[] = [
   'accounts.google.com',
@@ -38,14 +38,6 @@ export const SYSTEM_BROWSER_IDP_HOSTS: readonly string[] = [
   'sts.windows.net',
 ]
 
-/**
- * IdP hosts verified lenient toward embedded user agents (the U5 provider
- * matrix). Only consulted for navigations leaving an auth surface — everywhere
- * else unknown hosts already stay in-window because same-window departures
- * from workspace pages are OAuth connect flows in this app.
- */
-export const IN_WINDOW_IDP_HOSTS: readonly string[] = ['github.com']
-
 const AUTH_SURFACE_PREFIXES: readonly string[] = [
   '/login',
   '/signup',
@@ -101,11 +93,21 @@ export function isAuthSurfacePath(pathname: string): boolean {
  * Classifies a top-level navigation (will-navigate / will-redirect).
  *
  * Same-window departures to non-origin hosts are OAuth flows in this app —
- * regular external links always go through window.open — so unknown hosts stay
- * in-window (lenient IdP assumption) except for the known embedded-blocking
- * hosts, which are rerouted through the system browser. Departures from auth
- * surfaces default to the system browser because SSO IdPs need real-browser
- * device claims.
+ * regular external links always go through window.open.
+ *
+ * A departure from an auth surface is a *sign-in*, and sign-in always runs in
+ * the system browser (RFC 8252), whatever the IdP. Embedding one is a one-way
+ * door: the shell has no browser chrome, so a user who reaches the IdP and
+ * decides not to continue has no way back to the app. It also splits the flow
+ * across two cookie jars — better-auth binds its OAuth state cookie to the user
+ * agent that started the flow, so an in-window start that finishes anywhere
+ * else comes back `state_mismatch`. The handoff keeps the whole flow in one
+ * jar and hands a one-time token back over the loopback.
+ *
+ * Everything else is an integration connect from a workspace page: those stay
+ * in-window (the session cookie is already in this partition) unless the IdP
+ * hard-blocks embedded user agents, which is what {@link
+ * SYSTEM_BROWSER_IDP_HOSTS} enumerates.
  */
 export function classifyNavigation(rawUrl: string, ctx: NavigationContext): MainNavigationAction {
   if (rawUrl === 'about:blank') {
@@ -125,16 +127,13 @@ export function classifyNavigation(rawUrl: string, ctx: NavigationContext): Main
   const fromAuthSurface = current
     ? current.origin === ctx.appOrigin && isAuthSurfacePath(current.pathname)
     : false
-  if (matchesHostList(url.hostname, SYSTEM_BROWSER_IDP_HOSTS)) {
-    return fromAuthSurface ? 'idp-system-login' : 'idp-system-connect'
+  if (fromAuthSurface) {
+    return 'idp-system-login'
   }
-  if (matchesHostList(url.hostname, IN_WINDOW_IDP_HOSTS)) {
-    return 'idp-in-window'
-  }
-  if (current && current.origin !== ctx.appOrigin) {
-    return 'idp-in-window'
+  if (matchesHostList(url.hostname, SYSTEM_BROWSER_IDP_HOSTS)) {
+    return 'idp-system-connect'
   }
-  return fromAuthSurface ? 'idp-system-login' : 'idp-in-window'
+  return 'idp-in-window'
 }
 
 /**