diff --git a/apps/sim/app/workspace/[workspaceId]/prefetch.ts b/apps/sim/app/workspace/[workspaceId]/prefetch.ts
index ebabb4df975..fbefbb33e7f 100644
--- a/apps/sim/app/workspace/[workspaceId]/prefetch.ts
+++ b/apps/sim/app/workspace/[workspaceId]/prefetch.ts
@@ -1,7 +1,11 @@
 import { createLogger } from '@sim/logger'
 import { getErrorMessage } from '@sim/utils/errors'
 import type { QueryClient } from '@tanstack/react-query'
-import { listWorkspacesContract, type WorkspaceHostContext } from '@/lib/api/contracts/workspaces'
+import {
+  getWorkspaceHostContextContract,
+  listWorkspacesContract,
+  type WorkspaceHostContext,
+} from '@/lib/api/contracts/workspaces'
 import { listMothershipChats } from '@/lib/copilot/chat/list-mothership-chats'
 import { isChatEnabled } from '@/lib/core/config/env-flags'
 import { getUserProfile } from '@/lib/users/queries'
@@ -40,7 +44,11 @@ export function prefetchWorkspaceHostContext(
 ): Promise<WorkspaceHostContext | null> {
   return queryClient.fetchQuery({
     queryKey: workspaceHostKeys.detail(workspaceId),
-    queryFn: () => getWorkspaceHostContextForViewer(workspaceId, userId),
+    /** Parsed through the response schema so the seed matches a client fetch, as the list seed does. */
+    queryFn: async () => {
+      const hostContext = await getWorkspaceHostContextForViewer(workspaceId, userId)
+      return hostContext && getWorkspaceHostContextContract.response.schema.parse(hostContext)
+    },
     staleTime: WORKSPACE_HOST_CONTEXT_STALE_TIME,
   })
 }
diff --git a/apps/sim/app/workspace/[workspaceId]/settings/navigation.hosted.test.ts b/apps/sim/app/workspace/[workspaceId]/settings/navigation.hosted.test.ts
new file mode 100644
index 00000000000..179f8018b23
--- /dev/null
+++ b/apps/sim/app/workspace/[workspaceId]/settings/navigation.hosted.test.ts
@@ -0,0 +1,67 @@
+/**
+ * @vitest-environment node
+ *
+ * Deployment-dependent settings routing, pinned on the hosted side. Separate from
+ * `navigation.test.ts` because the catalog it asserts against is a module-scope
+ * constant, so `isHosted` has to differ per file rather than per test.
+ */
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+vi.mock('@/lib/core/config/env-flags', async (importOriginal) => ({
+  ...((await importOriginal()) as Record<string, unknown>),
+  isHosted: true,
+}))
+
+import { resolveWorkspaceNavigation } from '@/components/settings/navigation'
+import {
+  allNavigationItems,
+  resolveSettingsSection,
+} from '@/app/workspace/[workspaceId]/settings/navigation'
+
+const ENTITLEMENTS = {
+  byok: true,
+  credentialGroups: true,
+  inbox: true,
+  customBlocks: true,
+  forks: true,
+  sandboxes: true,
+} as const
+
+describe('self-host section on a hosted deployment', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  /**
+   * A 404 renders from Next's `__next_error__` document, where no
+   * `NEXT_PUBLIC_*` constant is readable — so the segment must resolve.
+   */
+  it('resolves the segment so the page gate can redirect instead of 404ing', () => {
+    expect(resolveSettingsSection('self-host')).toEqual({
+      id: 'self-host',
+      meta: {
+        title: 'Self hosting',
+        description: 'Manage this deployment from the Sim managed service.',
+        docsLink: undefined,
+      },
+    })
+  })
+
+  it('keeps the section in the catalog, since availability is not the route’s call', () => {
+    expect(allNavigationItems.some(({ id }) => id === 'self-host')).toBe(true)
+  })
+
+  it('excludes the section from workspace navigation, which is what triggers the redirect', () => {
+    const navigation = resolveWorkspaceNavigation({
+      permission: 'admin',
+      permissionConfig: {},
+      entitlements: { ...ENTITLEMENTS },
+    })
+
+    expect(navigation.some(({ id }) => id === 'self-host')).toBe(false)
+  })
+
+  it('leaves a genuinely unknown segment unresolved, so it still 404s', () => {
+    expect(resolveSettingsSection('not-a-section')).toBeNull()
+  })
+})
diff --git a/apps/sim/app/workspace/[workspaceId]/settings/navigation.ts b/apps/sim/app/workspace/[workspaceId]/settings/navigation.ts
index 57de4bd4a04..91a094e30ff 100644
--- a/apps/sim/app/workspace/[workspaceId]/settings/navigation.ts
+++ b/apps/sim/app/workspace/[workspaceId]/settings/navigation.ts
@@ -1,5 +1,5 @@
 import {
-  buildUnifiedSettingsNavigation,
+  buildUnifiedSettingsCatalog,
   SETTINGS_NAVIGATION_BILLING_ENABLED,
   toSettingsHeaderMeta,
   type UnifiedNavigationSection,
@@ -23,7 +23,8 @@ export const sectionConfig: { key: NavigationSection; title: string }[] = [
   { key: 'platform', title: 'Platform' },
 ]
 
-export const allNavigationItems: NavigationItem[] = buildUnifiedSettingsNavigation()
+/** Unfiltered — the sidebar applies deployment and entitlement visibility from the host context. */
+export const allNavigationItems: NavigationItem[] = buildUnifiedSettingsCatalog()
 
 /**
  * Catalog entries indexed by id. Every routed navigation resolves a section, so the
diff --git a/apps/sim/app/workspace/[workspaceId]/w/components/sidebar/components/settings-sidebar/settings-sidebar.tsx b/apps/sim/app/workspace/[workspaceId]/w/components/sidebar/components/settings-sidebar/settings-sidebar.tsx
index 60c26715a5b..a2144716b20 100644
--- a/apps/sim/app/workspace/[workspaceId]/w/components/sidebar/components/settings-sidebar/settings-sidebar.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/w/components/sidebar/components/settings-sidebar/settings-sidebar.tsx
@@ -18,14 +18,16 @@ import { SettingsIntentLink } from '@/components/settings/settings-intent-link'
 import { useSession } from '@/lib/auth/auth-client'
 import { getSubscriptionAccessState } from '@/lib/billing/client'
 import { canViewWorkspaceBillingSettings } from '@/lib/billing/workspace-permissions'
-import { isHosted } from '@/lib/core/config/env-flags'
+import {
+  isBillingEnabled as isBillingEnabledAtModuleInit,
+  isHosted as isHostedAtModuleInit,
+} from '@/lib/core/config/env-flags'
 import { hasBrowserAgent, hasDesktopSettings, hasTerminal } from '@/lib/desktop'
 import { useWorkspaceHostContext } from '@/app/workspace/[workspaceId]/providers/workspace-host-provider'
 import { useUserPermissionsContext } from '@/app/workspace/[workspaceId]/providers/workspace-permissions-provider'
 import type { SettingsSection } from '@/app/workspace/[workspaceId]/settings/navigation'
 import {
   allNavigationItems,
-  isBillingEnabled,
   sectionConfig,
 } from '@/app/workspace/[workspaceId]/settings/navigation'
 import { SidebarSection } from '@/app/workspace/[workspaceId]/w/components/sidebar/components/sidebar-section'
@@ -123,6 +125,13 @@ export function SettingsSidebar({
 
   const { data: session } = useSession()
   const hostContext = useWorkspaceHostContext()
+  /**
+   * Server-resolved, not the `NEXT_PUBLIC_*` module constants: those read false on
+   * the `__next_error__` 404 document, which renders Sim Cloud's sidebar as
+   * self-hosted. Constants are the fallback for a host context predating the field.
+   */
+  const isHosted = hostContext.deployment?.isHosted ?? isHostedAtModuleInit
+  const isBillingEnabled = hostContext.deployment?.billingEnabled ?? isBillingEnabledAtModuleInit
   const { data: generalSettings } = useGeneralSettings()
   const { data: inboxConfig } = useInboxConfig(workspaceId)
   const { data: ssoProvidersData, isLoading: isLoadingSSO } = useSSOProviders({
@@ -148,10 +157,14 @@ export function SettingsSidebar({
     if (isHosted) return null
     if (!userId || isLoadingSSO) return null
     return ssoProvidersData?.providers?.some((p) => p.userId === userId) || false
-  }, [userId, ssoProvidersData?.providers, isLoadingSSO])
+  }, [isHosted, userId, ssoProvidersData?.providers, isLoadingSSO])
 
   const navigationItems = useMemo(() => {
     return allNavigationItems.filter((item) => {
+      if (item.requiresSelfHosted && isHosted) {
+        return false
+      }
+
       if (item.requiresDesktopSurface && !desktopSurfaces[item.requiresDesktopSurface]) {
         return false
       }
@@ -248,6 +261,8 @@ export function SettingsSidebar({
       return true
     })
   }, [
+    isHosted,
+    isBillingEnabled,
     hasTeamPlan,
     hasEnterprisePlan,
     isEnterprisePlan,
diff --git a/apps/sim/components/settings/navigation.test.ts b/apps/sim/components/settings/navigation.test.ts
index df3a5f0d5cd..c43b6ffd184 100644
--- a/apps/sim/components/settings/navigation.test.ts
+++ b/apps/sim/components/settings/navigation.test.ts
@@ -8,7 +8,7 @@ import { afterAll, beforeEach, describe, expect, it } from 'vitest'
 import {
   ACCOUNT_SETTINGS_ITEMS,
   ACCOUNT_SETTINGS_PATH_ALIASES,
-  buildUnifiedSettingsNavigation,
+  buildUnifiedSettingsCatalog,
   canMutateWorkspaceSettingsSection,
   getAccountSettingsHref,
   getWorkspaceSettingsHref,
@@ -37,12 +37,12 @@ afterAll(() => {
 describe('settings navigation boundaries', () => {
   it('keeps Custom Blocks opt-in on self-hosted deployments', () => {
     expect(
-      buildUnifiedSettingsNavigation().find(({ id }) => id === 'custom-blocks')?.selfHostedOverride
+      buildUnifiedSettingsCatalog().find(({ id }) => id === 'custom-blocks')?.selfHostedOverride
     ).toBe(false)
   })
 
   it('preserves the order of all four settings catalogs', () => {
-    expect(buildUnifiedSettingsNavigation().map(({ id }) => id)).toEqual([
+    expect(buildUnifiedSettingsCatalog().map(({ id }) => id)).toEqual([
       'general',
       'desktop',
       'browser',
@@ -103,7 +103,7 @@ describe('settings navigation boundaries', () => {
   it('keeps the Sandboxes section in the legacy self-hosted defaults', () => {
     setEnv({ NEXT_PUBLIC_SANDBOXES_ENABLED: undefined, NEXT_PUBLIC_E2B_ENABLED: undefined })
 
-    expect(buildUnifiedSettingsNavigation().map(({ id }) => id)).toContain('sandboxes')
+    expect(buildUnifiedSettingsCatalog().map(({ id }) => id)).toContain('sandboxes')
     expect(
       resolveWorkspaceNavigation({
         permission: 'admin',
@@ -123,13 +123,13 @@ describe('settings navigation boundaries', () => {
   /**
    * The Self-host section links out to the managed service that issues this
    * deployment's Chat keys. On Sim Cloud that surface is reached from the
-   * account plane instead, so the section must not exist there at all — in the
-   * sidebar catalog or in the workspace-plane gate the route consults.
+   * account plane instead, so the workspace-plane gate the route consults must
+   * drop it there. The catalog keeps it either way — see the test below.
    */
   it('shows the Self-host section only on a self-hosted deployment', () => {
     setEnvFlags({ isHosted: false })
 
-    expect(buildUnifiedSettingsNavigation().map(({ id }) => id)).toContain('self-host')
+    expect(buildUnifiedSettingsCatalog().map(({ id }) => id)).toContain('self-host')
     expect(
       resolveWorkspaceNavigation({
         permission: 'admin',
@@ -146,10 +146,14 @@ describe('settings navigation boundaries', () => {
     ).toContain('self-host')
   })
 
-  it('drops the Self-host section on hosted Sim', () => {
+  /**
+   * The catalog keeps the section on hosted Sim so the route can tell an
+   * unavailable section from an unknown one and redirect instead of 404ing.
+   */
+  it('drops the Self-host section from the hosted workspace gate but keeps it in the catalog', () => {
     setEnvFlags({ isHosted: true })
 
-    expect(buildUnifiedSettingsNavigation().map(({ id }) => id)).not.toContain('self-host')
+    expect(buildUnifiedSettingsCatalog().map(({ id }) => id)).toContain('self-host')
     expect(
       resolveWorkspaceNavigation({
         permission: 'admin',
@@ -172,7 +176,7 @@ describe('settings navigation boundaries', () => {
    * one colored item in a monochrome icon column.
    */
   it('marks the Self hosting section with a currentColor line icon', () => {
-    const selfHost = buildUnifiedSettingsNavigation().find(({ id }) => id === 'self-host')
+    const selfHost = buildUnifiedSettingsCatalog().find(({ id }) => id === 'self-host')
     const markup = renderToStaticMarkup(createElement(selfHost!.icon, {}))
 
     expect(selfHost?.label).toBe('Self hosting')
@@ -199,7 +203,7 @@ describe('settings navigation boundaries', () => {
     expect(new Set(selfHostIds).size).toBe(selfHostIds.length)
     expect(new Set(workspaceIds).size).toBe(workspaceIds.length)
     expect([...unifiedIds].sort()).toEqual(
-      buildUnifiedSettingsNavigation()
+      buildUnifiedSettingsCatalog()
         .map(({ id }) => id)
         .sort()
     )
@@ -245,7 +249,7 @@ describe('settings navigation boundaries', () => {
   })
 
   it('labels the members section consistently', () => {
-    const unifiedOrganization = buildUnifiedSettingsNavigation().find(
+    const unifiedOrganization = buildUnifiedSettingsCatalog().find(
       ({ id }) => id === 'organization'
     )
 
diff --git a/apps/sim/components/settings/navigation.ts b/apps/sim/components/settings/navigation.ts
index dcb92ef1beb..4290ffd5a0e 100644
--- a/apps/sim/components/settings/navigation.ts
+++ b/apps/sim/components/settings/navigation.ts
@@ -823,12 +823,19 @@ export const SETTINGS_SECTION_REGISTRY: readonly SettingsSectionRegistryEntry[]
   },
 ]
 
-export function buildUnifiedSettingsNavigation(): UnifiedSettingsNavigationItem[] {
+/**
+ * Every unified section this build knows how to render, including ones the
+ * current deployment does not offer.
+ *
+ * Route resolution reads this rather than the filtered navigation so an
+ * unavailable section stays a *known* segment the page gate can redirect to
+ * General. Resolving it to nothing answers 404 instead — and a 404 document
+ * breaks every `NEXT_PUBLIC_*` read (see `deployment` in
+ * `@/lib/api/contracts/workspaces`).
+ */
+export function buildUnifiedSettingsCatalog(): UnifiedSettingsNavigationItem[] {
   return SETTINGS_SECTION_REGISTRY.flatMap(({ label, icon, docsLink, unified }) => {
     if (!unified) return []
-    // Dropped here so the sidebar, the route's `parseSection` gate, and section
-    // metadata all agree that the section does not exist on Sim Cloud.
-    if (unified.requiresSelfHosted && isHosted) return []
     const { group, ...item } = unified
     return [
       {
diff --git a/apps/sim/lib/api/contracts/workspaces.ts b/apps/sim/lib/api/contracts/workspaces.ts
index beac7ce329f..a6fcdb0accb 100644
--- a/apps/sim/lib/api/contracts/workspaces.ts
+++ b/apps/sim/lib/api/contracts/workspaces.ts
@@ -274,6 +274,23 @@ export const workspaceHostContextSchema = z.object({
       credentialGroups: z.boolean(),
     })
     .optional(),
+  /**
+   * Deployment shape, resolved per request from `process.env` on the server.
+   *
+   * The client-side `NEXT_PUBLIC_*` module constants cannot be trusted for this:
+   * they are frozen at module init, and on Next's `__next_error__` document — the
+   * shell every 404 renders from — the root layout never runs, so `window.__ENV`
+   * is unassigned and every read comes back undefined.
+   *
+   * Optional for rolling compatibility; consumers fall back to those constants,
+   * which are correct on every document that runs the root layout.
+   */
+  deployment: z
+    .object({
+      isHosted: z.boolean(),
+      billingEnabled: z.boolean(),
+    })
+    .optional(),
 })
 
 export type WorkspaceHostContext = z.output<typeof workspaceHostContextSchema>
diff --git a/apps/sim/lib/billing/workspace-permissions.ts b/apps/sim/lib/billing/workspace-permissions.ts
index 41c57c574eb..c3b1f913d56 100644
--- a/apps/sim/lib/billing/workspace-permissions.ts
+++ b/apps/sim/lib/billing/workspace-permissions.ts
@@ -32,7 +32,9 @@ export function canViewWorkspaceBillingSettings(
   hostContext: WorkspaceHostContext,
   viewerUserId?: string | null
 ): boolean {
-  return isBillingEnabled && canManageWorkspaceBilling(hostContext, viewerUserId)
+  // Constant reads false on the `__next_error__` 404 document; see `deployment` in the contract.
+  const billingEnabled = hostContext.deployment?.billingEnabled ?? isBillingEnabled
+  return billingEnabled && canManageWorkspaceBilling(hostContext, viewerUserId)
 }
 
 /**
diff --git a/apps/sim/lib/workspaces/host-context.ts b/apps/sim/lib/workspaces/host-context.ts
index 0c66496eb27..f95b0d31226 100644
--- a/apps/sim/lib/workspaces/host-context.ts
+++ b/apps/sim/lib/workspaces/host-context.ts
@@ -1,6 +1,7 @@
 import { cache } from 'react'
 import type { WorkspaceHostContext } from '@/lib/api/contracts/workspaces'
 import { getWorkspaceOwnerSubscriptionAccess } from '@/lib/billing/core/workspace-access'
+import { isBillingEnabled, isHosted } from '@/lib/core/config/env-flags'
 import { isCredentialGroupsAvailable } from '@/lib/credential-groups/availability'
 import { getOrganizationSettingsAccess } from '@/lib/organizations/settings-access'
 import { checkWorkspaceAccess } from '@/lib/workspaces/permissions/utils'
@@ -48,6 +49,10 @@ async function resolveWorkspaceHostContextForViewer(
     features: {
       credentialGroups: credentialGroupsAvailable,
     },
+    deployment: {
+      isHosted,
+      billingEnabled: isBillingEnabled,
+    },
   }
 }