diff --git a/apps/desktop/electron/backend-health.test.ts b/apps/desktop/electron/backend-health.test.ts
index f542f58c31d9..99be2630a7f6 100644
--- a/apps/desktop/electron/backend-health.test.ts
+++ b/apps/desktop/electron/backend-health.test.ts
@@ -2,7 +2,17 @@ import assert from 'node:assert/strict'
 
 import { test } from 'vitest'
 
-import { DEFAULT_HEALTH_PROBE_TIMEOUT_MS, isMissingHealthEndpointError, waitForHermesReady } from './backend-health'
+import {
+  DEFAULT_HEALTH_PROBE_TIMEOUT_MS,
+  isAuthRejectionError,
+  isGatedMissingHealthError,
+  isMissingHealthEndpointError,
+  isReauthRequiredError,
+  waitForHermesReady
+} from './backend-health'
+
+const GATE_401 =
+  '401: {"error":"unauthenticated","detail":"Unauthorized","reason":"no_cookie","login_url":"/login"}'
 
 test('uses lightweight /api/health for current backends', async () => {
   const calls: string[][] = []
@@ -134,3 +144,198 @@ test('recognizes missing-route shapes only', () => {
   assert.equal(isMissingHealthEndpointError(new Error('Timed out connecting to Hermes backend after 15000ms')), false)
   assert.equal(isMissingHealthEndpointError(new Error('500: boom')), false)
 })
+
+// --- Gated backends that predate /api/health (release 0.19.0 and earlier) ---
+//
+// The dashboard auth gate runs ahead of the SPA catch-all, so on a backend
+// without the route an ANONYMOUS probe is rejected as unauthenticated rather
+// than 404 — verified against a simulated 0.19.0 backend:
+//   credential-free: /api/health -> 401 no_cookie, /api/status -> 200
+//   credentialed:    /api/health -> 404,           /api/sessions -> 200
+
+test('anonymous gate-shaped 401 falls back to /api/status (backend predates /api/health)', async () => {
+  const calls: string[][] = []
+
+  await waitForHermesReady('http://192.168.1.132:9119', {
+    token: null,
+    fetchPublicJson: async url => {
+      calls.push(['public', url])
+      throw new Error(GATE_401)
+    },
+    fetchJson: async (url, token) => {
+      calls.push(['token', url, token == null ? 'null' : token])
+
+      return { version: '0.19.0', auth_required: true }
+    },
+    sleep: async () => {},
+    timeoutMs: 100,
+    pollMs: 1
+  })
+
+  assert.deepEqual(calls, [
+    ['public', 'http://192.168.1.132:9119/api/health'],
+    ['token', 'http://192.168.1.132:9119/api/status', 'null']
+  ])
+})
+
+test('a credentialed 401 fails fast for reauth instead of reporting a dead session ready', async () => {
+  // The regression a blanket 401->fallback introduces: /api/status is public,
+  // so an expired session would answer 200 and boot would report "ready",
+  // deferring the no_cookie to the first real API call.
+  const calls: string[][] = []
+
+  await assert.rejects(
+    waitForHermesReady('https://gateway.example', {
+      token: 'session-token',
+      fetchPublicJson: async () => {
+        throw new Error('public probe must not be used when credentialed')
+      },
+      fetchJson: async url => {
+        calls.push(['status', url])
+
+        return { version: '0.19.0' }
+      },
+      probeHealth: async url => {
+        calls.push(['probe', url])
+        throw new Error(GATE_401)
+      },
+      probeIsCredentialed: true,
+      sleep: async () => {},
+      timeoutMs: 100,
+      pollMs: 1
+    }),
+    (error: any) => {
+      assert.equal(isReauthRequiredError(error), true)
+      assert.equal(error.needsOauthLogin, true)
+      assert.match(error.message, /remote gateway session has expired/i)
+
+      return true
+    }
+  )
+
+  // Fail fast: never reached the public /api/status leg.
+  assert.deepEqual(calls, [['probe', 'https://gateway.example/api/health']])
+})
+
+test('a credentialed 403 is also a terminal reauth failure', async () => {
+  await assert.rejects(
+    waitForHermesReady('https://gateway.example', {
+      fetchPublicJson: async () => ({}),
+      fetchJson: async () => ({}),
+      probeHealth: async () => {
+        throw new Error('403: {"detail":"Forbidden"}')
+      },
+      probeIsCredentialed: true,
+      sleep: async () => {},
+      timeoutMs: 100,
+      pollMs: 1
+    }),
+    (error: any) => isReauthRequiredError(error)
+  )
+})
+
+test('a credentialed probe still uses the 404 fallback for a genuinely missing route', async () => {
+  // With credentials the gate lets the request through to the SPA catch-all,
+  // so an old backend answers a real 404 — that must still fall back, not be
+  // mistaken for a rejected session.
+  const calls: string[][] = []
+
+  await waitForHermesReady('https://gateway.example', {
+    token: 'session-token',
+    fetchPublicJson: async () => {
+      throw new Error('public probe must not be used when credentialed')
+    },
+    fetchJson: async url => {
+      calls.push(['status', url])
+
+      return { version: '0.19.0' }
+    },
+    probeHealth: async url => {
+      calls.push(['probe', url])
+      throw new Error('404: {"detail":"Not Found"}')
+    },
+    probeIsCredentialed: true,
+    sleep: async () => {},
+    timeoutMs: 100,
+    pollMs: 1
+  })
+
+  assert.deepEqual(calls, [
+    ['probe', 'https://gateway.example/api/health'],
+    ['status', 'https://gateway.example/api/status']
+  ])
+})
+
+test('a non-gate 401 keeps polling rather than skipping a misconfigured health route', async () => {
+  const calls: string[][] = []
+  let currentTime = 0
+
+  await assert.rejects(
+    waitForHermesReady('http://127.0.0.1:9000', {
+      fetchPublicJson: async url => {
+        calls.push(['public', url])
+        throw new Error('401: {"detail":"Unauthorized"}')
+      },
+      fetchJson: async url => {
+        calls.push(['token', url])
+      },
+      sleep: async () => {},
+      now: () => {
+        currentTime += 20
+
+        return currentTime
+      },
+      timeoutMs: 50,
+      pollMs: 1
+    }),
+    /401: \{"detail":"Unauthorized"\}/
+  )
+
+  assert.ok(calls.length > 0)
+  assert.ok(calls.every(call => call[0] === 'public' && call[1].endsWith('/api/health')))
+})
+
+test('credentialed 5xx and 429 keep polling — only 401/403 are terminal', async () => {
+  for (const transient of ['500: boom', '429: {"detail":"Too Many Requests"}']) {
+    let attempts = 0
+    let currentTime = 0
+
+    await assert.rejects(
+      waitForHermesReady('https://gateway.example', {
+        fetchPublicJson: async () => ({}),
+        fetchJson: async () => ({}),
+        probeHealth: async () => {
+          attempts += 1
+          throw new Error(transient)
+        },
+        probeIsCredentialed: true,
+        sleep: async () => {},
+        now: () => {
+          currentTime += 20
+
+          return currentTime
+        },
+        timeoutMs: 100,
+        pollMs: 1
+      }),
+      (error: any) => isReauthRequiredError(error) === false
+    )
+
+    assert.ok(attempts > 1, `${transient} should have retried, got ${attempts} attempt(s)`)
+  }
+})
+
+test('error-shape predicates', () => {
+  assert.equal(isGatedMissingHealthError(new Error(GATE_401)), true)
+  assert.equal(isGatedMissingHealthError(new Error('401: {"detail":"Unauthorized"}')), false)
+  assert.equal(isGatedMissingHealthError(new Error('404: {"detail":"Not Found"}')), false)
+
+  assert.equal(isAuthRejectionError(new Error(GATE_401)), true)
+  assert.equal(isAuthRejectionError(new Error('403: {"detail":"Forbidden"}')), true)
+  assert.equal(isAuthRejectionError(new Error('404: {"detail":"Not Found"}')), false)
+  assert.equal(isAuthRejectionError(new Error('429: slow down')), false)
+  assert.equal(isAuthRejectionError(new Error('500: boom')), false)
+
+  // A gated 401 must NOT be conflated with a missing route by the 404 predicate.
+  assert.equal(isMissingHealthEndpointError(new Error(GATE_401)), false)
+})
diff --git a/apps/desktop/electron/backend-health.ts b/apps/desktop/electron/backend-health.ts
index 623208545e20..3da6c7a80fa7 100644
--- a/apps/desktop/electron/backend-health.ts
+++ b/apps/desktop/electron/backend-health.ts
@@ -20,14 +20,72 @@ export interface HermesReadyOptions {
   healthProbeTimeoutMs?: number
   sleep?: (ms: number) => Promise<void>
   now?: () => number
+  /**
+   * Credentialed health probe. When supplied, readiness is probed with the
+   * connection's own credentials instead of anonymously — which is what lets
+   * a gated backend answer 404 for a genuinely missing /api/health, and what
+   * makes a 401 from this probe mean "session rejected" rather than "route
+   * behind a gate". Defaults to the credential-free `fetchPublicJson`.
+   */
+  probeHealth?: (url: string, options?: { timeoutMs?: number }) => Promise<unknown>
+  /**
+   * Whether `probeHealth` actually presents credentials. Distinguishes the
+   * two very different meanings of a 401 (see `waitForHermesReady`).
+   */
+  probeIsCredentialed?: boolean
 }
 
+export const REMOTE_SESSION_EXPIRED_MESSAGE =
+  'Your remote gateway session has expired. Open Settings → Gateway and click "Sign in" again.'
+
 export function isMissingHealthEndpointError(error: unknown): boolean {
   const message = error instanceof Error ? error.message : String(error ?? '')
 
   return /^404:/.test(message) || message.includes('endpoint is likely missing')
 }
 
+/**
+ * True for a hard auth rejection (401/403) as opposed to a transient failure.
+ * Deliberately shape-based: 429 is a throttle and 5xx is a server fault, and
+ * both must keep polling.
+ */
+export function isAuthRejectionError(error: unknown): boolean {
+  const message = error instanceof Error ? error.message : String(error ?? '')
+
+  return /^40[13]:/.test(message)
+}
+
+/**
+ * True for an auth rejection carrying the dashboard gate's "no session at all"
+ * shape. On a backend that predates `/api/health`, the gate runs ahead of the
+ * SPA catch-all, so an unknown `/api/*` path is rejected as unauthenticated
+ * instead of 404 — this is the signal that an ANONYMOUS probe cannot reach the
+ * route, and the reason a credential-free 401 must fall back to `/api/status`
+ * rather than be reported as a boot failure.
+ */
+export function isGatedMissingHealthError(error: unknown): boolean {
+  const message = error instanceof Error ? error.message : String(error ?? '')
+
+  return isAuthRejectionError(error) && message.includes('no_cookie')
+}
+
+/** Tag a terminal reauth failure the main process latches and the overlay keys on. */
+export function makeReauthRequiredError(detail?: string): Error {
+  const error = new Error(REMOTE_SESSION_EXPIRED_MESSAGE) as any
+  error.needsOauthLogin = true
+  error.isReauthRequired = true
+
+  if (detail) {
+    error.detail = detail
+  }
+
+  return error
+}
+
+export function isReauthRequiredError(error: unknown): boolean {
+  return Boolean((error as any)?.isReauthRequired)
+}
+
 function supersededError() {
   const error: any = new Error('SSH bootstrap was superseded by newer connection settings.')
   error.kind = 'superseded'
@@ -59,6 +117,8 @@ export async function waitForHermesReady(baseUrl: string, options: HermesReadyOp
 
   const base = baseUrl.replace(/\/+$/, '')
   const deadline = now() + timeoutMs
+  const probeHealth = options.probeHealth ?? options.fetchPublicJson
+  const probeIsCredentialed = Boolean(options.probeIsCredentialed)
   let lastError: unknown = null
   let useStatusFallback = false
 
@@ -71,16 +131,30 @@ export async function waitForHermesReady(baseUrl: string, options: HermesReadyOp
       if (useStatusFallback) {
         await options.fetchJson(`${base}/api/status`, options.token)
       } else {
-        await options.fetchPublicJson(`${base}/api/health`, { timeoutMs: healthProbeTimeoutMs })
+        await probeHealth(`${base}/api/health`, { timeoutMs: healthProbeTimeoutMs })
       }
 
       return
     } catch (error) {
       lastError = error
 
-      // Only an explicitly missing route means the backend predates
-      // /api/health; timeouts and server errors keep polling health.
-      if (!useStatusFallback && isMissingHealthEndpointError(error)) {
+      // A confirmed 401/403 from a CREDENTIALED probe means the session was
+      // rejected, not that the route is missing. Fail fast into a reauth
+      // state: falling back to the public /api/status would answer 200 and
+      // report a dead session as "ready", deferring the failure to the first
+      // real API call. Applies to the /api/status leg too — it is routed
+      // through the same credentials.
+      if (probeIsCredentialed && isAuthRejectionError(error)) {
+        throw makeReauthRequiredError(error instanceof Error ? error.message : String(error))
+      }
+
+      // An explicitly missing route means the backend predates /api/health.
+      // So does a gate-shaped 401 on an ANONYMOUS probe: the dashboard auth
+      // gate runs ahead of the SPA catch-all, so a pre-/api/health backend
+      // rejects the unknown path as unauthenticated instead of 404 and a
+      // credential-free probe can never observe the 404. Timeouts, 5xx, 429,
+      // and non-gate 401s keep polling health.
+      if (!useStatusFallback && (isMissingHealthEndpointError(error) || isGatedMissingHealthError(error))) {
         useStatusFallback = true
 
         continue
diff --git a/apps/desktop/electron/backend-start-failure.test.ts b/apps/desktop/electron/backend-start-failure.test.ts
index 0888d65fbc41..36d352d66cc2 100644
--- a/apps/desktop/electron/backend-start-failure.test.ts
+++ b/apps/desktop/electron/backend-start-failure.test.ts
@@ -2,7 +2,7 @@ import assert from 'node:assert/strict'
 
 import { test } from 'vitest'
 
-import { shouldLatchBackendStartFailure } from './backend-start-failure'
+import { shouldLatchBackendStartFailure, shouldLatchRemoteReauthFailure } from './backend-start-failure'
 
 test('latches a LOCAL backend failure so the install-retry loop is broken', () => {
   assert.equal(shouldLatchBackendStartFailure({ attemptedRemote: false }), true)
@@ -21,3 +21,32 @@ test('the two branches are mutually exclusive (a failure either latches or stays
     assert.equal(latched, !attemptedRemote)
   }
 })
+
+test('latches a CONFIRMED remote reauth failure so the overlay stays clickable', () => {
+  // Without this the non-latching remote path re-runs startHermes on every
+  // getConnection/api call, re-emits running:true, and the overlay hides
+  // itself — the "Sign in" button flickers away before it can be clicked.
+  assert.equal(shouldLatchRemoteReauthFailure({ attemptedRemote: true, isReauth: true }), true)
+})
+
+test('does not latch a transient remote failure as reauth', () => {
+  // A mint timeout or a host unreachable across sleep must still self-heal.
+  assert.equal(shouldLatchRemoteReauthFailure({ attemptedRemote: true, isReauth: false }), false)
+})
+
+test('never latches a LOCAL failure as reauth (that is backendStartFailure job)', () => {
+  assert.equal(shouldLatchRemoteReauthFailure({ attemptedRemote: false, isReauth: true }), false)
+  assert.equal(shouldLatchRemoteReauthFailure({ attemptedRemote: false, isReauth: false }), false)
+})
+
+test('the two latches never fire for the same failure', () => {
+  // They are complementary, not overlapping: local failures latch via
+  // backendStartFailure, confirmed remote reauth latches via its own flag.
+  for (const attemptedRemote of [true, false]) {
+    for (const isReauth of [true, false]) {
+      const start = shouldLatchBackendStartFailure({ attemptedRemote })
+      const reauth = shouldLatchRemoteReauthFailure({ attemptedRemote, isReauth })
+      assert.ok(!(start && reauth), `both latched for remote=${attemptedRemote} reauth=${isReauth}`)
+    }
+  }
+})
diff --git a/apps/desktop/electron/backend-start-failure.ts b/apps/desktop/electron/backend-start-failure.ts
index 4998b0164a70..3c5ffdbcad91 100644
--- a/apps/desktop/electron/backend-start-failure.ts
+++ b/apps/desktop/electron/backend-start-failure.ts
@@ -39,3 +39,34 @@ export interface BackendStartFailureContext {
 export function shouldLatchBackendStartFailure(context: BackendStartFailureContext): boolean {
   return !context.attemptedRemote
 }
+
+export interface RemoteReauthFailureContext {
+  /** True when the boot that just failed was dialing a REMOTE (or cloud) backend. */
+  attemptedRemote: boolean
+  /**
+   * True when the failure was a CONFIRMED auth rejection (a credentialed
+   * probe got 401/403), not a transient connectivity fault.
+   */
+  isReauth: boolean
+}
+
+/**
+ * Whether a failed remote boot should latch as a reauth failure.
+ *
+ * This is the deliberate counterpart to `shouldLatchBackendStartFailure`,
+ * which never latches a remote failure because remote faults are usually
+ * transient and must stay retryable. A *confirmed* reauth rejection is the
+ * exception: it cannot self-heal, because nothing will change until the user
+ * signs in again.
+ *
+ * Without a latch, the non-latching remote path actively prevents recovery.
+ * Every subsequent `getConnection`/`api` call re-runs `startHermes`, re-emits
+ * `running: true`, and the boot-failure overlay (`visible = Boolean(boot.error)
+ * && !boot.running`) hides itself — so the "Sign in" button flickers out from
+ * under the user before they can click it. Latching holds the overlay still
+ * and clickable. Cleared on every recovery path (reset, repair, apply-config,
+ * and a confirmed sign-in) so a fresh session boots normally.
+ */
+export function shouldLatchRemoteReauthFailure(context: RemoteReauthFailureContext): boolean {
+  return context.attemptedRemote && context.isReauth
+}
diff --git a/apps/desktop/electron/main.ts b/apps/desktop/electron/main.ts
index 89b350f1b4b9..f967aa24c3b8 100644
--- a/apps/desktop/electron/main.ts
+++ b/apps/desktop/electron/main.ts
@@ -34,10 +34,10 @@ import { stopBackendChild as stopBackendChildImpl } from './backend-child'
 import { dashboardFallbackArgs, sourceDeclaresServe } from './backend-command'
 import { createBackendConnectionState } from './backend-connection-state'
 import { buildDesktopBackendEnv, normalizeHermesHomeRoot } from './backend-env'
-import { waitForHermesReady } from './backend-health'
+import { isReauthRequiredError, waitForHermesReady } from './backend-health'
 import { canImportHermesCli, shouldTrustHermesOverride, verifyHermesCli } from './backend-probes'
 import { waitForDashboardPortAnnouncement } from './backend-ready'
-import { shouldLatchBackendStartFailure } from './backend-start-failure'
+import { shouldLatchBackendStartFailure, shouldLatchRemoteReauthFailure } from './backend-start-failure'
 import { detectRemoteDisplay, isWindowsBinaryPathInWsl, isWslEnvironment } from './bootstrap-platform'
 import { runBootstrap } from './bootstrap-runner'
 import { applyConnectionChange, resolveTerminalConnection } from './connection-apply'
@@ -119,7 +119,13 @@ import {
 } from './hardening'
 import { createLinkTitleWindow, guardLinkTitleSession, readLinkTitleWindowTitle } from './link-title-window'
 import { ensureMainWindow } from './main-window-lifecycle'
-import { oauthSessionIsLive, resolveJsonBody, resolveOauthRestAuth } from './native-auth-decisions'
+import {
+  oauthGuardMayHardFail,
+  oauthSessionIsLive,
+  resolveJsonBody,
+  resolveOauthRestAuth,
+  resolveReadinessProbeAuth
+} from './native-auth-decisions'
 import {
   nativeRefreshUrl,
   type NativeTokenSet,
@@ -1016,6 +1022,13 @@ let bootstrapFailure = null
 // Latched non-bootstrap backend spawn failure — stops getConnection() from
 // respawning hermes serve backend children in a tight loop while boot is broken.
 let backendStartFailure = null
+// Latched CONFIRMED remote reauth failure. Remote failures deliberately do not
+// latch via backendStartFailure (they're usually transient and must stay
+// retryable), but a rejected session cannot self-heal — and the non-latching
+// path actively breaks recovery: each retry re-emits running:true and hides
+// the boot-failure overlay, so the "Sign in" button flickers away before it
+// can be clicked. Cleared on every recovery path and on a confirmed sign-in.
+let remoteReauthFailure = null
 // Active first-launch install, so the renderer's Cancel button (and app quit)
 // can abort the in-flight install.sh/ps1 instead of leaving it running.
 let bootstrapAbortController = null
@@ -4815,12 +4828,87 @@ function closePreviewWatchers() {
   }
 }
 
-async function waitForHermes(baseUrl, token, signal?) {
+// Best-effort read of a gateway's advertised auth providers, cached per base
+// URL for the life of the process. Used by the oauth pre-flight guard to tell
+// a password-provider gateway (which cannot satisfy the bearer/cookie checks
+// by design) from a real OAuth one. Any failure returns [] so callers keep the
+// strict guard — backends predating /api/auth/providers are unaffected.
+const gatewayAuthProvidersCache = new Map<string, any[]>()
+
+async function gatewayAuthProviders(baseUrl) {
+  const cached = gatewayAuthProvidersCache.get(baseUrl)
+
+  if (cached) {
+    return cached
+  }
+
+  let providers = []
+
+  try {
+    const body = (await fetchPublicJson(`${baseUrl}/api/auth/providers`, { timeoutMs: 8_000 })) as any
+
+    if (Array.isArray(body?.providers)) {
+      providers = body.providers
+        .filter(p => p && typeof p === 'object')
+        .map(p => ({ name: String(p.name || ''), supportsPassword: Boolean(p.supports_password) }))
+        .filter(p => p.name)
+    }
+  } catch {
+    // Optional metadata — an unreadable list keeps the strict guard.
+  }
+
+  gatewayAuthProvidersCache.set(baseUrl, providers)
+
+  return providers
+}
+
+// Build the readiness probe for a connection's auth mode. A gated gateway
+// must be probed with the SAME credentials the rest of the connection uses:
+// an anonymous probe 401s forever against a live session, and it can never
+// see the 404 that identifies a backend predating /api/health (the auth gate
+// answers before the SPA catch-all). `probeIsCredentialed` tells
+// waitForHermesReady how to read a 401 — rejected session vs gated route.
+async function buildReadinessHealthProbe(baseUrl, authMode, token) {
+  const nativeAt = authMode === 'oauth' ? await ensureNativeAccessToken(baseUrl).catch(() => null) : null
+  const probeAuth = resolveReadinessProbeAuth(authMode, nativeAt, token)
+
+  if (probeAuth.kind === 'bearer') {
+    return {
+      // fetchJson takes the bearer via `options.bearer` — a raw `headers`
+      // option is ignored, so passing one here would silently probe
+      // uncredentialed and reintroduce the 401 loop.
+      probeHealth: (url, options: any = {}) => fetchJson(url, null, { ...options, bearer: probeAuth.token }),
+      probeIsCredentialed: true
+    }
+  }
+
+  if (probeAuth.kind === 'cookie') {
+    return {
+      probeHealth: (url, options: any = {}) => fetchJsonViaOauthSession(url, options),
+      probeIsCredentialed: true
+    }
+  }
+
+  if (probeAuth.kind === 'token' && probeAuth.token) {
+    return {
+      probeHealth: (url, options: any = {}) => fetchJson(url, probeAuth.token, options),
+      probeIsCredentialed: true
+    }
+  }
+
+  return { probeHealth: fetchPublicJson, probeIsCredentialed: false }
+}
+
+async function waitForHermes(baseUrl, token, signal?, authMode?) {
+  const { probeHealth, probeIsCredentialed } = await buildReadinessHealthProbe(baseUrl, authMode, token)
+
   return waitForHermesReady(baseUrl, {
     token,
     signal,
     fetchPublicJson,
-    fetchJson
+    fetchJson: probeIsCredentialed ? (url, _token, options) => probeHealth(url, options) : fetchJson,
+    probeHealth,
+    probeIsCredentialed
   })
 }
 
@@ -6822,7 +6910,10 @@ async function buildRemoteConnection(
     // here would reject a freshly-completed native sign-in and loop the UI back
     // into "not signed in" even though mintGatewayWsTicket would succeed with
     // the stored bearer.
-    if (!oauthSessionIsLive(hasNativeSession(baseUrl), await hasLiveOauthSession(baseUrl))) {
+    if (
+      !oauthSessionIsLive(hasNativeSession(baseUrl), await hasLiveOauthSession(baseUrl)) &&
+      oauthGuardMayHardFail(await gatewayAuthProviders(baseUrl))
+    ) {
       const err = new Error(
         'Remote Hermes gateway uses OAuth, but you are not signed in. ' +
           'Open Settings → Gateway and click "Sign in", or switch back to Local.'
@@ -7063,7 +7154,7 @@ async function bootstrapSshConnectionInner(profile, sshConfig, reuseToken, sourc
       forward: (localPort, remotePort) => ssh.forward(localPort, remotePort),
       cancelForward: (localPort, remotePort) => ssh.cancelForward(localPort, remotePort),
       pickLocalPort,
-      waitForHermes: (baseUrl, token) => waitForHermes(baseUrl, token, lease.signal),
+      waitForHermes: (baseUrl, token) => waitForHermes(baseUrl, token, lease.signal, 'token'),
       probeReuseProof: sshProbeReuseProof,
       adoptServedToken: adoptServedDashboardToken,
       rememberLog: sshRememberLog,
@@ -7536,6 +7627,7 @@ function stopBackendChild(child) {
 // switch / crash recovery), which still resets boot progress + reloads.
 function resetHermesConnection({ soft = false } = {}) {
   backendStartFailure = null
+  remoteReauthFailure = null
   remoteLiveness.clear()
   const hermesProcess = backendConnectionState.invalidate()
   stopBackendChild(hermesProcess)
@@ -7736,7 +7828,7 @@ async function spawnPoolBackend(profile, entry) {
   const remote = await resolveRemoteBackend(profile)
 
   if (remote) {
-    await waitForHermes(remote.baseUrl, remote.token)
+    await waitForHermes(remote.baseUrl, remote.token, undefined, remote.authMode)
 
     return {
       ...remote,
@@ -7928,6 +8020,13 @@ async function startHermes() {
     throw backendStartFailure
   }
 
+  // A confirmed remote reauth rejection is terminal until the user signs in.
+  // Short-circuiting here keeps the boot-failure overlay latched and its
+  // "Sign in" button clickable, instead of re-driving boot on every retry.
+  if (remoteReauthFailure) {
+    throw remoteReauthFailure
+  }
+
   // E2E: simulate a boot failure without breaking the real backend. The boot
   // progresses a few steps, then fails with the given error message.
   if (BOOT_FAKE_ERROR) {
@@ -7954,7 +8053,7 @@ async function startHermes() {
   const connectionPromise = (async () => {
     const connectRemote = async remote => {
       await advanceBootProgress('backend.remote', `Connecting to remote Hermes backend at ${remote.baseUrl}`, 24)
-      await waitForHermes(remote.baseUrl, remote.token)
+      await waitForHermes(remote.baseUrl, remote.token, undefined, remote.authMode)
       updateBootProgress({
         phase: 'backend.ready',
         message: 'Remote Hermes backend is ready',
@@ -8191,6 +8290,12 @@ async function startHermes() {
       backendStartFailure = error instanceof Error ? error : new Error(message)
     }
 
+    // A confirmed reauth rejection latches separately: it can't self-heal, and
+    // leaving it unlatched hides the overlay's "Sign in" button on every retry.
+    if (shouldLatchRemoteReauthFailure({ attemptedRemote, isReauth: isReauthRequiredError(error) })) {
+      remoteReauthFailure = error instanceof Error ? error : new Error(message)
+    }
+
     updateBootProgress(
       {
         error: message,
@@ -8994,6 +9099,7 @@ ipcMain.handle('hermes:bootstrap:reset', async () => {
   await teardownPrimaryBackendAndWait()
   bootstrapFailure = null
   backendStartFailure = null
+  remoteReauthFailure = null
   getFirstRunSetupGate().resetForRetry()
   resetBootstrapSnapshot()
 
@@ -9016,6 +9122,7 @@ ipcMain.handle('hermes:bootstrap:repair', async () => {
 
   bootstrapFailure = null
   backendStartFailure = null
+  remoteReauthFailure = null
   getFirstRunSetupGate().resetForRepair()
   resetHermesConnection()
 
@@ -9125,6 +9232,9 @@ ipcMain.handle('hermes:connection-config:oauth-login', async (_event, rawUrl) =>
       })
 
       _storeNativeTokens(baseUrl, tokens)
+      // Confirmed sign-in — release the reauth latch so the next
+      // startHermes() re-dials instead of replaying the stale rejection.
+      remoteReauthFailure = null
 
       return { ok: true, baseUrl, connected: true }
     } catch (error) {
@@ -9141,7 +9251,16 @@ ipcMain.handle('hermes:connection-config:oauth-login', async (_event, rawUrl) =>
   // Legacy embedded-webview cookie flow.
   await openOauthLoginWindow(baseUrl)
 
-  return { ok: true, baseUrl, connected: await hasOauthSessionCookie(baseUrl) }
+  const connected = await hasOauthSessionCookie(baseUrl)
+
+  // Only a CONFIRMED sign-in releases the latch. A cancelled/closed login
+  // window must leave it set, or the overlay's "Sign in" button starts
+  // flickering again on the next retry.
+  if (connected) {
+    remoteReauthFailure = null
+  }
+
+  return { ok: true, baseUrl, connected }
 })
 ipcMain.handle('hermes:connection-config:oauth-logout', async (_event, rawUrl) => {
   const baseUrl = rawUrl ? normalizeRemoteBaseUrl(rawUrl) : ''
diff --git a/apps/desktop/electron/native-auth-decisions.test.ts b/apps/desktop/electron/native-auth-decisions.test.ts
index 09f648c87192..d4cfc068cd66 100644
--- a/apps/desktop/electron/native-auth-decisions.test.ts
+++ b/apps/desktop/electron/native-auth-decisions.test.ts
@@ -1,7 +1,7 @@
 /**
- * Regression tests for electron/native-auth-decisions.ts — the three pure
- * decision seams behind the RFC 8252 native-app auth flow, each of which was a
- * real runtime bug that the mocked flow tests could not catch.
+ * Regression tests for electron/native-auth-decisions.ts — the pure decision
+ * seams behind the RFC 8252 native-app auth flow, each of which was a real
+ * runtime bug that the mocked flow tests could not catch.
  *
  * Run via the vitest `electron` project (electron/**\/*.test.ts).
  */
@@ -10,7 +10,13 @@ import assert from 'node:assert/strict'
 
 import { test } from 'vitest'
 
-import { oauthSessionIsLive, resolveJsonBody, resolveOauthRestAuth } from './native-auth-decisions'
+import {
+  oauthGuardMayHardFail,
+  oauthSessionIsLive,
+  resolveJsonBody,
+  resolveOauthRestAuth,
+  resolveReadinessProbeAuth
+} from './native-auth-decisions'
 
 // --- 1. body encoding (guards the double-JSON.stringify 422) ---
 
@@ -66,3 +72,61 @@ test('resolveOauthRestAuth falls back to cookie when there is no native token',
   // Empty string is not a usable bearer — must fall back, not send "Bearer ".
   assert.deepEqual(resolveOauthRestAuth(''), { kind: 'cookie' })
 })
+
+// --- 4. readiness-probe auth (guards the credential-free 401 boot loop) ---
+
+test('resolveReadinessProbeAuth reuses the oauth bearer-vs-cookie choice', () => {
+  assert.deepEqual(resolveReadinessProbeAuth('oauth', 'native-at'), { kind: 'bearer', token: 'native-at' })
+  assert.deepEqual(resolveReadinessProbeAuth('oauth', null), { kind: 'cookie' })
+  assert.deepEqual(resolveReadinessProbeAuth('oauth', ''), { kind: 'cookie' })
+})
+
+test('resolveReadinessProbeAuth sends the session token for a token gateway', () => {
+  assert.deepEqual(resolveReadinessProbeAuth('token', null, 'session-token'), {
+    kind: 'token',
+    token: 'session-token'
+  })
+  assert.deepEqual(resolveReadinessProbeAuth('token', null, null), { kind: 'token', token: null })
+})
+
+test('resolveReadinessProbeAuth stays public for local and unknown modes', () => {
+  // A loopback backend has no gate; sending credentials it never issued is
+  // meaningless, and an unknown mode must not invent a credential.
+  assert.deepEqual(resolveReadinessProbeAuth('local', 'native-at', 'session-token'), { kind: 'public' })
+  assert.deepEqual(resolveReadinessProbeAuth(undefined, 'native-at', 'session-token'), { kind: 'public' })
+  assert.deepEqual(resolveReadinessProbeAuth('something-new', null, null), { kind: 'public' })
+})
+
+// --- 5. oauth guard vs password gateways (guards the false "not signed in") ---
+
+test('oauthGuardMayHardFail is false only when EVERY provider is password-based', () => {
+  assert.equal(oauthGuardMayHardFail([{ name: 'basic', supportsPassword: true }]), false)
+  assert.equal(
+    oauthGuardMayHardFail([
+      { name: 'basic', supportsPassword: true },
+      { name: 'ldap', supportsPassword: true }
+    ]),
+    false
+  )
+})
+
+test('oauthGuardMayHardFail keeps the strict guard for oauth and mixed deployments', () => {
+  assert.equal(oauthGuardMayHardFail([{ name: 'nous', supportsPassword: false }]), true)
+  assert.equal(
+    oauthGuardMayHardFail([
+      { name: 'nous', supportsPassword: false },
+      { name: 'basic', supportsPassword: true }
+    ]),
+    true
+  )
+})
+
+test('oauthGuardMayHardFail keeps the strict guard when the list is unusable', () => {
+  // Backends predating /api/auth/providers, or an unreachable probe, must not
+  // silently weaken the guard.
+  assert.equal(oauthGuardMayHardFail([]), true)
+  assert.equal(oauthGuardMayHardFail(null), true)
+  assert.equal(oauthGuardMayHardFail(undefined), true)
+  assert.equal(oauthGuardMayHardFail('nonsense' as any), true)
+  assert.equal(oauthGuardMayHardFail([{ supportsPassword: true }]), true)
+})
diff --git a/apps/desktop/electron/native-auth-decisions.ts b/apps/desktop/electron/native-auth-decisions.ts
index d76746f669a3..c0978c3ecddc 100644
--- a/apps/desktop/electron/native-auth-decisions.ts
+++ b/apps/desktop/electron/native-auth-decisions.ts
@@ -21,7 +21,17 @@
  *      native bearer when present, else the cookie partition. Cookie-only
  *      routing returns 401 no_cookie for a cookieless native session.
  *
- * All three are trivial once named; the value is the test that pins the
+ *   4. resolveReadinessProbeAuth — the boot readiness probe must authenticate
+ *      the same way the rest of the connection does. A credential-free probe
+ *      against a gated gateway 401s forever; worse, it cannot tell a missing
+ *      route from a rejected session (see backend-health.ts).
+ *
+ *   5. oauthGuardMayHardFail — `auth_required: true` means "this gateway is
+ *      gated", NOT "this gateway speaks OAuth". A password-provider gateway
+ *      can satisfy neither the native-bearer nor the OAuth-partition-cookie
+ *      check by design, so the pre-flight guard must not hard-fail it.
+ *
+ * All five are trivial once named; the value is the test that pins the
  * contract so the god-file call sites can't drift back to the buggy shape.
  */
 
@@ -60,3 +70,75 @@ export function resolveOauthRestAuth(nativeAccessToken: string | null | undefine
 
   return { kind: 'cookie' }
 }
+
+export type ReadinessProbeAuth = OauthRestAuth | { kind: 'token'; token: string | null } | { kind: 'public' }
+
+/**
+ * Decide how the boot readiness probe authenticates.
+ *
+ * The probe must present the SAME credentials the rest of the connection
+ * will use. A credential-free probe against a gated gateway 401s until the
+ * boot deadline even though the session is perfectly valid — and because the
+ * dashboard auth gate runs ahead of the SPA catch-all, an unknown `/api/*`
+ * path answers 401 rather than 404, so the probe also cannot detect a backend
+ * that predates `/api/health`. Sending credentials is what lets a missing
+ * route surface as a real 404 (see `isMissingHealthEndpointError`).
+ *
+ * `oauth` reuses `resolveOauthRestAuth` so the probe and every other oauth
+ * REST call make the identical bearer-vs-cookie choice. `token` presents the
+ * connection's session token. `local` (and anything unrecognized) stays
+ * public: a loopback backend has no gate, and sending credentials it never
+ * issued would be meaningless.
+ */
+export function resolveReadinessProbeAuth(
+  authMode: string | null | undefined,
+  nativeAccessToken?: string | null,
+  connectionToken?: string | null
+): ReadinessProbeAuth {
+  if (authMode === 'oauth') {
+    return resolveOauthRestAuth(nativeAccessToken)
+  }
+
+  if (authMode === 'token') {
+    return { kind: 'token', token: connectionToken ?? null }
+  }
+
+  return { kind: 'public' }
+}
+
+export interface AdvertisedAuthProvider {
+  name?: string
+  supportsPassword?: boolean
+}
+
+/**
+ * Whether the oauth pre-flight guard may hard-fail a connection for "not
+ * signed in".
+ *
+ * `authModeFromStatus` maps the gateway's `auth_required: true` onto
+ * `'oauth'`, but that flag only means the dashboard is GATED — it says
+ * nothing about how you authenticate. A gateway whose providers are all
+ * username/password cannot satisfy the guard's checks by construction:
+ * `start_login` raises NotImplementedError, `/auth/native/authorize` rejects
+ * password providers, and its cookies are set by a plain password-login POST
+ * rather than the `/auth/callback` redirect the OAuth partition is primed
+ * for. Hard-failing there rejects a live session one line before the
+ * ws-ticket mint that would have succeeded against that very partition.
+ *
+ * Returns false only when EVERY advertised provider is password-based. An
+ * unknown or empty list keeps the strict guard, so backends that predate
+ * `/api/auth/providers` are unaffected.
+ */
+export function oauthGuardMayHardFail(providers: AdvertisedAuthProvider[] | null | undefined): boolean {
+  if (!Array.isArray(providers) || providers.length === 0) {
+    return true
+  }
+
+  const named = providers.filter(provider => provider && typeof provider === 'object' && provider.name)
+
+  if (named.length === 0) {
+    return true
+  }
+
+  return !named.every(provider => provider.supportsPassword)
+}
diff --git a/contributors/emails/0301chris@gmail.com b/contributors/emails/0301chris@gmail.com
new file mode 100644
index 000000000000..e606f25d4666
--- /dev/null
+++ b/contributors/emails/0301chris@gmail.com
@@ -0,0 +1,2 @@
+0301chris
+# PR #71555 salvage (desktop: gated /api/health readiness probe)
diff --git a/contributors/emails/leo@gtmcore.ai b/contributors/emails/leo@gtmcore.ai
new file mode 100644
index 000000000000..b61779c6ff74
--- /dev/null
+++ b/contributors/emails/leo@gtmcore.ai
@@ -0,0 +1,2 @@
+leoprodz
+# PR #71602 salvage (desktop: gated /api/health readiness probe)
diff --git a/contributors/emails/liruixinch@outlook.com b/contributors/emails/liruixinch@outlook.com
new file mode 100644
index 000000000000..a1cf96ff89db
--- /dev/null
+++ b/contributors/emails/liruixinch@outlook.com
@@ -0,0 +1,2 @@
+HexLab98
+# PR #71205 salvage (desktop: gated /api/health readiness probe)
diff --git a/contributors/emails/stephenlopez2030@gmail.com b/contributors/emails/stephenlopez2030@gmail.com
new file mode 100644
index 000000000000..e0710ccbcad4
--- /dev/null
+++ b/contributors/emails/stephenlopez2030@gmail.com
@@ -0,0 +1,2 @@
+Slopez2023
+# PR #71668 salvage (desktop: gated /api/health readiness probe)