diff --git a/instrumentation.ts b/instrumentation.ts
index c6cc6494..80d71bca 100644
--- a/instrumentation.ts
+++ b/instrumentation.ts
@@ -1,4 +1,8 @@
 import type { Instrumentation } from 'next'
+// Imported by exact path rather than through the `@/lib/observability` barrel:
+// this file's module graph is loaded in every runtime Next boots, and the
+// predicate is a dependency-free pure function.
+import { isClientDisconnectError } from '@/lib/observability/is-client-disconnect'
 
 export async function register() {
   // Instrumentation hook: currently a no-op.
@@ -23,8 +27,17 @@ export async function register() {
  * instrumentation-client.ts), which is what links a server error back to the
  * user's session replay. Absent that header the error is still captured, just
  * unattributed.
+ *
+ * A client that navigated away mid-stream is filtered out first: see
+ * `isClientDisconnectError`. Next reports those through this hook even though
+ * the response itself succeeded, and they are not exceptions. Next still
+ * writes its own stderr line for them, so they stay visible in Vercel's
+ * runtime-error table; what this drops is the false entry in Error Tracking
+ * and the awaited flush it would cost a healthy request.
  */
 export const onRequestError: Instrumentation.onRequestError = async (err, request) => {
+  if (isClientDisconnectError(err)) return
+
   try {
     const { getPostHogServer, flushAnalytics } = await import('@/lib/analytics/posthog-server')
     const posthog = getPostHogServer()
diff --git a/lib/company/__tests__/other-account-hint.test.ts b/lib/company/__tests__/other-account-hint.test.ts
index 23c9ed81..113dbd0a 100644
--- a/lib/company/__tests__/other-account-hint.test.ts
+++ b/lib/company/__tests__/other-account-hint.test.ts
@@ -10,20 +10,39 @@ import type { SupabaseClient } from '@supabase/supabase-js'
 
 const mockCreateServiceClient = vi.mocked(createServiceClient)
 
+interface QueryResult {
+  data?: unknown
+  error?: unknown
+}
+
 /**
- * Chainable query mock keyed by table name: every method returns the chain,
- * awaiting it resolves with the configured { data, error } for that table.
+ * Chainable query mock keyed by table name: every method returns the chain and
+ * records its arguments, and awaiting it resolves with the configured
+ * { data, error } for that table. A table may be given an ARRAY of results,
+ * consumed one per from() call with the last one repeating, so the chunked
+ * existence probe can be answered chunk by chunk.
  */
-function buildClient(resultsByTable: Record<string, { data?: unknown; error?: unknown }>) {
+function buildClient(resultsByTable: Record<string, QueryResult | QueryResult[]>) {
+  const queues = new Map<string, QueryResult[]>(
+    Object.entries(resultsByTable).map(([table, value]) => [
+      table,
+      Array.isArray(value) ? [...value] : [value],
+    ]),
+  )
+  const calls: Array<{ table: string; method: string; args: unknown[] }> = []
+
   return {
+    calls,
     from: vi.fn((table: string) => {
-      const result = {
-        data: resultsByTable[table]?.data ?? null,
-        error: resultsByTable[table]?.error ?? null,
-      }
+      const queue = queues.get(table) ?? []
+      const configured = (queue.length > 1 ? queue.shift() : queue[0]) ?? {}
+      const result = { data: configured.data ?? null, error: configured.error ?? null }
       const chain: Record<string, unknown> = {}
       for (const m of ['select', 'eq', 'in', 'is', 'limit', 'order', 'range']) {
-        chain[m] = () => chain
+        chain[m] = (...args: unknown[]) => {
+          calls.push({ table, method: m, args })
+          return chain
+        }
       }
       ;(chain as { then?: unknown }).then = (resolve: (v: unknown) => void) => resolve(result)
       return chain
@@ -31,6 +50,11 @@ function buildClient(resultsByTable: Record<string, { data?: unknown; error?: un
   }
 }
 
+/** The company filters the journal_entries existence probes were issued with. */
+function probeFilters(client: ReturnType<typeof buildClient>) {
+  return client.calls.filter((c) => c.table === 'journal_entries' && c.method === 'in')
+}
+
 const OWN_COMPANY = { id: 'own-co', org_number: '5560125790' }
 
 beforeEach(() => {
@@ -50,6 +74,36 @@ describe('shouldShowOtherAccountHint', () => {
     expect(mockCreateServiceClient).not.toHaveBeenCalled()
   })
 
+  it('scopes the own-account probe to the caller\'s companies', async () => {
+    // Without company_id the probe falls back on the RLS qual, which under the
+    // authenticated role turns into a sequential scan of journal_entries on
+    // the blocking Hem render.
+    const supabase = buildClient({
+      companies: { data: [OWN_COMPANY] },
+      journal_entries: { data: [{ id: 'je1' }] },
+    })
+
+    await expect(shouldShowOtherAccountHint(supabase as unknown as SupabaseClient)).resolves.toBe(false)
+    expect(probeFilters(supabase).map((c) => c.args)).toEqual([['company_id', ['own-co']]])
+  })
+
+  it('chunks the probe and stops at the first company with entries', async () => {
+    const many = Array.from({ length: 250 }, (_, i) => ({
+      id: `co-${i}`,
+      org_number: '5560125790',
+    }))
+    const supabase = buildClient({
+      companies: { data: many },
+      // First chunk finds nothing, second one does: the third must never run.
+      journal_entries: [{ data: [] }, { data: [{ id: 'je1' }] }, { data: [] }],
+    })
+
+    await expect(shouldShowOtherAccountHint(supabase as unknown as SupabaseClient)).resolves.toBe(false)
+    const chunks = probeFilters(supabase).map((c) => (c.args[1] as string[]).length)
+    expect(chunks).toEqual([100, 100])
+    expect(mockCreateServiceClient).not.toHaveBeenCalled()
+  })
+
   it('is true when the account is empty and a same-orgnr company elsewhere has entries', async () => {
     const supabase = buildClient({
       companies: { data: [OWN_COMPANY] },
diff --git a/lib/company/other-account-hint.ts b/lib/company/other-account-hint.ts
index 77072c49..eecec1e6 100644
--- a/lib/company/other-account-hint.ts
+++ b/lib/company/other-account-hint.ts
@@ -2,6 +2,38 @@ import type { SupabaseClient } from '@supabase/supabase-js'
 import { createServiceClient } from '@/lib/supabase/server'
 import { fetchAllRows } from '@/lib/supabase/fetch-all'
 
+/**
+ * Ids per existence probe. They travel in the PostgREST query string as
+ * `company_id=in.(uuid,uuid,...)`, so an unbounded list would eventually run
+ * past the gateway's request-header ceiling and be rejected outright. 100
+ * UUIDs is roughly 3.7 KB, comfortably inside it.
+ */
+const PROBE_CHUNK_SIZE = 100
+
+/**
+ * Does any of these companies have at least one journal entry?
+ *
+ * The company filter is what makes this an index probe: naming the ids lets
+ * Postgres use idx_journal_entries_company_id. Stops at the first chunk that
+ * finds a row. Throws on a query error, which the caller turns into "no hint".
+ */
+async function hasAnyJournalEntry(
+  client: SupabaseClient,
+  companyIds: string[],
+): Promise<boolean> {
+  for (let i = 0; i < companyIds.length; i += PROBE_CHUNK_SIZE) {
+    const { data, error } = await client
+      .from('journal_entries')
+      .select('id')
+      .in('company_id', companyIds.slice(i, i + PROBE_CHUNK_SIZE))
+      .limit(1)
+
+    if (error) throw new Error(error.message)
+    if ((data ?? []).length > 0) return true
+  }
+  return false
+}
+
 /**
  * Should the Hem page hint that the user may be signed in to the wrong
  * account? (#1231, the "Chillen" support case: BankID resolved to a stale
@@ -15,35 +47,41 @@ import { fetchAllRows } from '@/lib/supabase/fetch-all'
  *    NOT a member of, has at least one journal entry.
  *
  * The common case (an account with any bookkeeping at all) exits after one
- * indexed existence probe. The cross-account probe runs on the service
+ * company-scoped existence probe. The cross-account probe runs on the service
  * client but the result reduces to one boolean: nothing about the other
  * account is revealed beyond "your bookkeeping may live elsewhere".
  * Fails soft to false: this is an advisory line, never worth an error.
  */
 export async function shouldShowOtherAccountHint(supabase: SupabaseClient): Promise<boolean> {
   try {
-    // RLS scopes both reads to the caller's memberships. Company lists are
-    // paginated with fetchAllRows (PostgREST caps at 1000 rows; a byrå user
-    // can belong to many companies); it throws on error, which the outer
-    // catch turns into false. The journal_entries read stays a bare
-    // limit(1): it is an existence probe, not a listing.
-    const [ownCompanies, { data: ownEntries, error: entriesError }] = await Promise.all([
-      fetchAllRows<{ id: string; org_number: string | null }>(({ from, to }) =>
+    // RLS scopes every read here to the caller's memberships. Company lists
+    // are paginated with fetchAllRows (PostgREST caps at 1000 rows; a byrå
+    // user can belong to many companies); it throws on error, which the outer
+    // catch turns into false.
+    const ownCompanies = await fetchAllRows<{ id: string; org_number: string | null }>(
+      ({ from, to }) =>
         supabase
           .from('companies')
           .select('id, org_number')
           .is('archived_at', null)
           .order('id')
           .range(from, to),
-      ),
-      supabase.from('journal_entries').select('id').limit(1),
-    ])
+    )
 
-    if (entriesError) return false
     if (ownCompanies.length === 0) return false
-    if ((ownEntries ?? []).length > 0) return false
 
-    const ownIds = new Set(ownCompanies.map((c) => c.id))
+    // The probe needs the company list, so it runs after it rather than beside
+    // it. Leaving company_id out and letting RLS do the scoping reads as the
+    // cheaper form and is the opposite: under the `authenticated` role the RLS
+    // qual becomes a filter on the scan, so Postgres reads all of
+    // journal_entries (~900 ms measured on prod, 4.2 s worst observed) on the
+    // blocking Hem render instead of using idx_journal_entries_company_id
+    // (~2 ms). Naming the ids cannot change the answer: user_company_ids(),
+    // which journal_entries RLS uses, excludes archived companies, and so does
+    // the list above.
+    const ownIds = ownCompanies.map((c) => c.id)
+    if (await hasAnyJournalEntry(supabase, ownIds)) return false
+
     const orgNumbers = [
       ...new Set(ownCompanies.map((c) => c.org_number).filter((n): n is string => Boolean(n))),
     ]
@@ -60,17 +98,11 @@ export async function shouldShowOtherAccountHint(supabase: SupabaseClient): Prom
         .range(from, to),
     )
 
-    const otherIds = sameOrgCompanies.map((c) => c.id).filter((id) => !ownIds.has(id))
+    const ownIdSet = new Set(ownIds)
+    const otherIds = sameOrgCompanies.map((c) => c.id).filter((id) => !ownIdSet.has(id))
     if (otherIds.length === 0) return false
 
-    const { data: otherEntries, error: otherEntriesError } = await service
-      .from('journal_entries')
-      .select('id')
-      .in('company_id', otherIds)
-      .limit(1)
-
-    if (otherEntriesError) return false
-    return (otherEntries ?? []).length > 0
+    return await hasAnyJournalEntry(service, otherIds)
   } catch {
     // Service key unavailable (some self-hosted setups) or transient failure.
     return false
diff --git a/lib/observability/__tests__/is-client-disconnect.test.ts b/lib/observability/__tests__/is-client-disconnect.test.ts
new file mode 100644
index 00000000..71d5883a
--- /dev/null
+++ b/lib/observability/__tests__/is-client-disconnect.test.ts
@@ -0,0 +1,55 @@
+import { describe, it, expect } from 'vitest'
+import { isClientDisconnectError } from '../is-client-disconnect'
+
+describe('isClientDisconnectError', () => {
+  it('matches React\'s cancel error for a stream the client closed', () => {
+    expect(isClientDisconnectError(new Error('The destination stream closed early.'))).toBe(true)
+  })
+
+  it('matches the sibling cancel error React raises on a write failure', () => {
+    expect(
+      isClientDisconnectError(new Error('The destination stream errored while writing data.')),
+    ).toBe(true)
+  })
+
+  it('matches Next\'s own ResponseAborted error by name', () => {
+    const aborted = Object.assign(new Error('The response was aborted'), {
+      name: 'ResponseAborted',
+    })
+    expect(isClientDisconnectError(aborted)).toBe(true)
+  })
+
+  it('does not match an ordinary error', () => {
+    expect(isClientDisconnectError(new Error('boom'))).toBe(false)
+    expect(isClientDisconnectError(new TypeError('fetch failed'))).toBe(false)
+  })
+
+  it('does not match a real provider timeout or socket reset', () => {
+    // AbortSignal.timeout throws this shape all over lib/providers; treating
+    // it as a client disconnect would hide genuine integration failures.
+    expect(isClientDisconnectError(new DOMException('Aborted', 'AbortError'))).toBe(false)
+    expect(
+      isClientDisconnectError(Object.assign(new Error('socket hang up'), { code: 'ECONNRESET' })),
+    ).toBe(false)
+    expect(
+      isClientDisconnectError(
+        Object.assign(new Error('Premature close'), { code: 'ERR_STREAM_PREMATURE_CLOSE' }),
+      ),
+    ).toBe(false)
+  })
+
+  it('matches the message exactly, so a real error cannot hide behind the phrase', () => {
+    expect(
+      isClientDisconnectError(
+        new Error('Supabase query failed: The destination stream closed early.'),
+      ),
+    ).toBe(false)
+  })
+
+  it('is false for anything that is not an error object', () => {
+    expect(isClientDisconnectError(null)).toBe(false)
+    expect(isClientDisconnectError(undefined)).toBe(false)
+    expect(isClientDisconnectError('The destination stream closed early.')).toBe(false)
+    expect(isClientDisconnectError(42)).toBe(false)
+  })
+})
diff --git a/lib/observability/is-client-disconnect.ts b/lib/observability/is-client-disconnect.ts
new file mode 100644
index 00000000..3620c450
--- /dev/null
+++ b/lib/observability/is-client-disconnect.ts
@@ -0,0 +1,52 @@
+/**
+ * Is this error a client hanging up mid-response, rather than a failure?
+ *
+ * When a browser navigates away while a page or RSC payload is still
+ * streaming, the HTTP response closes, Next destroys the stream it handed
+ * React (`node_modules/next/dist/server/pipe-readable.js`), and React's
+ * `createCancelHandler` aborts the in-flight render with a bare
+ * `Error('The destination stream closed early.')`. Both renderers do it: the
+ * Flight server (react-server-dom-webpack-server.node.production.js:3922) and
+ * react-dom's SSR streamer (react-dom-server.node.production.js:7822, :8099).
+ * The response itself still completes: every occurrence we sampled in
+ * production rode on a 200.
+ *
+ * Next means to swallow these. `create-error-handler.js` early-returns on
+ * `isAbortError`, but that predicate knows only `name === 'AbortError'` and
+ * `name === 'ResponseAborted'` (pipe-readable.js:32), and React's cancel error
+ * is a plain `Error`, so it falls through to `onRequestError` and is reported
+ * as an exception that never happened. This predicate closes that gap on our
+ * side. It is a Next filtering gap, not a version bug: 16.3.1 and 16.3.4 are
+ * byte-identical here, so upgrading is not the fix.
+ *
+ * Matching is on the EXACT message. A React rewording brings the noise back,
+ * which is the safe direction; a substring match would let a real error hide
+ * behind the phrase.
+ *
+ * Deliberately NOT matched: a bare `AbortError`, `ECONNRESET`,
+ * `ERR_STREAM_PREMATURE_CLOSE`. Those are how this codebase's outbound calls
+ * report genuine failures (`AbortSignal.timeout` in `lib/http/fetch-with-timeout`
+ * and every provider client; `lib/providers/with-provider-call` treats them as
+ * retryable provider faults), and swallowing them would hide real integration
+ * breakage. They also buy nothing here: Next already filters `AbortError`
+ * before instrumentation ever sees it.
+ */
+
+const CLIENT_DISCONNECT_MESSAGES = new Set([
+  'The destination stream closed early.',
+  'The destination stream errored while writing data.',
+])
+
+/**
+ * Next's own error for a response the client aborted
+ * (`server/web/spec-extension/adapters/next-request.js:39`). Unlike a plain
+ * `AbortError`, this name is only ever produced by that one situation.
+ */
+const RESPONSE_ABORTED_NAME = 'ResponseAborted'
+
+export function isClientDisconnectError(error: unknown): boolean {
+  if (typeof error !== 'object' || error === null) return false
+  const { name, message } = error as { name?: unknown; message?: unknown }
+  if (name === RESPONSE_ABORTED_NAME) return true
+  return typeof message === 'string' && CLIENT_DISCONNECT_MESSAGES.has(message)
+}
diff --git a/lib/supabase/__tests__/middleware.test.ts b/lib/supabase/__tests__/middleware.test.ts
index 8a952c8d..79715dac 100644
--- a/lib/supabase/__tests__/middleware.test.ts
+++ b/lib/supabase/__tests__/middleware.test.ts
@@ -48,18 +48,44 @@ const state = vi.hoisted(() => ({
   // What the mocked isEmailOnBrandAllowlist returns (Rule 2 exemption).
   allowlisted: false,
   signOut: vi.fn(async () => ({ error: null })),
+  // Cookies auth-js writes through the `cookies.setAll` callback while
+  // getUser() runs: the ROTATED tokens after a successful refresh, and the
+  // maxAge-0 deletions when it removes a dead session. The middleware has to
+  // carry these onto whatever response it returns.
+  cookieWrites: [] as Array<{
+    name: string
+    value: string
+    options?: Record<string, unknown>
+  }>,
   // Row returned for user_preferences reads (the auto_logout mint lookup).
   userPreferences: null as null | { auto_logout: boolean },
   userPreferencesError: null as unknown,
 }))
 
 vi.mock('@supabase/ssr', () => ({
-  createServerClient: vi.fn(() => ({
+  createServerClient: vi.fn((
+    _url: string,
+    _key: string,
+    options: {
+      cookies: {
+        setAll: (
+          cookies: Array<{
+            name: string
+            value: string
+            options?: Record<string, unknown>
+          }>,
+        ) => void
+      }
+    },
+  ) => ({
     auth: {
-      getUser: vi.fn(async () => ({
-        data: { user: state.user },
-        error: state.authError,
-      })),
+      getUser: vi.fn(async () => {
+        if (state.cookieWrites.length > 0) options.cookies.setAll(state.cookieWrites)
+        return {
+          data: { user: state.user },
+          error: state.authError,
+        }
+      }),
       getClaims: vi.fn(async () => ({
         data: { claims: state.sessionId ? { session_id: state.sessionId } : {} },
       })),
@@ -176,6 +202,7 @@ describe('updateSession redirect destinations', () => {
     state.user = null
     state.sessionId = 'session-1'
     state.authError = null
+    state.cookieWrites = []
     state.aal = null
     state.factors = null
     state.company = {
@@ -479,6 +506,30 @@ describe('updateSession redirect destinations', () => {
       expect(locationOf(response)).toBe(`${ORIGIN}/login`)
     })
 
+    it('carries the cookies that clear a dead session', async () => {
+      // auth-js removes the session inside getUser() and queues the deletion
+      // on the response. Dropping it on the bounce made the browser replay
+      // the dead refresh token on /login, spending a second GoTrue 400 per
+      // expiry (paired 400s ~100 ms apart in production).
+      state.authError = { name: 'AuthApiError', code: 'refresh_token_not_found' }
+      state.cookieWrites = [
+        { name: 'sb-test-auth-token', value: '', options: { path: '/', maxAge: 0 } },
+      ]
+
+      const response = await run('/settings/tax', {
+        headers: {
+          cookie: `sb-test-auth-token=dead; ${SESSION_TIMEOUT_COOKIE}=stale`,
+        },
+      })
+
+      expect(response.status).toBe(307)
+      expect(new URL(locationOf(response)!).pathname).toBe('/login')
+      const cleared = response.cookies.get('sb-test-auth-token')
+      expect(cleared?.value).toBe('')
+      expect(cleared?.maxAge).toBe(0)
+      expect(response.cookies.get(SESSION_TIMEOUT_COOKIE)?.value).toBe('')
+    })
+
     it('drops a request path that normalises to a protocol-relative URL', async () => {
       // /..//evil.com normalises to the pathname //evil.com. Reflecting that
       // back as ?next= would hand the login page an off-origin destination.
@@ -595,6 +646,17 @@ describe('updateSession redirect destinations', () => {
       expect(url.pathname).toBe('/mfa/verify')
       expect(url.searchParams.get('returnTo')).toBeNull()
     })
+
+    it('carries the rotated auth cookie instead of re-minting it next request', async () => {
+      state.cookieWrites = [
+        { name: 'sb-test-auth-token', value: 'rotated', options: { path: '/' } },
+      ]
+
+      const response = await run('/settings/tax')
+
+      expect(new URL(locationOf(response)!).pathname).toBe('/mfa/verify')
+      expect(response.cookies.get('sb-test-auth-token')?.value).toBe('rotated')
+    })
   })
 
   describe('forced enrollment bounce to /mfa/enroll', () => {
diff --git a/lib/supabase/middleware.ts b/lib/supabase/middleware.ts
index c639b94a..4d8aa468 100644
--- a/lib/supabase/middleware.ts
+++ b/lib/supabase/middleware.ts
@@ -267,7 +267,12 @@ async function updateSessionInner(
         supabase.auth.mfa.getAuthenticatorAssuranceLevel(),
       )
       if (aal?.nextLevel === 'aal2' && aal?.currentLevel === 'aal1') {
-        return NextResponse.json({ error: 'MFA-verifiering krävs.' }, { status: 403 })
+        const response = NextResponse.json(
+          { error: 'MFA-verifiering krävs.' },
+          { status: 403 },
+        )
+        copyResponseCookies(supabaseResponse, response)
+        return response
       }
     }
     return supabaseResponse
@@ -352,14 +357,17 @@ async function updateSessionInner(
       const destination = carriesDestination
         ? safeReturnTo(request.nextUrl.searchParams.get('next'), '/')
         : '/'
-      return NextResponse.redirect(new URL(destination, request.url))
+      return redirectWithAuthCookies(
+        supabaseResponse,
+        new URL(destination, request.url),
+      )
     }
     return supabaseResponse
   }
 
   // Protected routes - require authentication
   if (!user) {
-    return bounceToAuth(request, '/login')
+    return bounceToAuth(request, supabaseResponse, '/login')
   }
 
   // ── Home-domain affinity (WL, founder call 2026-08-05) ──────────────────
@@ -380,7 +388,7 @@ async function updateSessionInner(
     request,
   )
   if (homeOutcome.redirectTo) {
-    return NextResponse.redirect(homeOutcome.redirectTo)
+    return redirectWithAuthCookies(supabaseResponse, homeOutcome.redirectTo)
   }
   if (homeOutcome.cacheOk) {
     supabaseResponse.cookies.set(
@@ -408,7 +416,8 @@ async function updateSessionInner(
       const mfaTarget = `/mfa/enroll${
         innerReturnTo ? `?returnTo=${encodeURIComponent(innerReturnTo)}` : ''
       }`
-      return NextResponse.redirect(
+      return redirectWithAuthCookies(
+        supabaseResponse,
         new URL(
           `/account/set-password?returnTo=${encodeURIComponent(mfaTarget)}`,
           request.url,
@@ -452,7 +461,7 @@ async function updateSessionInner(
 
     // User has MFA enrolled but hasn't verified this session → redirect to verify
     if (aal?.nextLevel === 'aal2' && aal?.currentLevel === 'aal1') {
-      return bounceToAuth(request, '/mfa/verify')
+      return bounceToAuth(request, supabaseResponse, '/mfa/verify')
     }
 
     // MFA required but user has no factor enrolled yet → force enrollment
@@ -476,7 +485,7 @@ async function updateSessionInner(
         const hasVerifiedFactor = factors?.totp?.some(f => f.status === 'verified')
 
         if (!hasVerifiedFactor) {
-          return bounceToAuth(request, '/mfa/enroll')
+          return bounceToAuth(request, supabaseResponse, '/mfa/enroll')
         }
       }
     }
@@ -568,7 +577,7 @@ async function updateSessionInner(
       if (isByraNoCompanyAllowed) {
         return supabaseResponse
       }
-      return NextResponse.redirect(new URL('/byra', request.url))
+      return redirectWithAuthCookies(supabaseResponse, new URL('/byra', request.url))
     }
 
     // Multi-user seat gate: memberships exist but every one is frozen for
@@ -593,7 +602,10 @@ async function updateSessionInner(
       .maybeSingle()
 
     const destination = enrichmentRow ? '/select-company' : '/onboarding'
-    return NextResponse.redirect(new URL(destination, request.url))
+    return redirectWithAuthCookies(
+      supabaseResponse,
+      new URL(destination, request.url),
+    )
   }
 
   // Set company cookie on the response so downstream requests have it
@@ -674,6 +686,28 @@ function copyResponseCookies(from: NextResponse, to: NextResponse): void {
   }
 }
 
+/**
+ * Redirect that carries the auth cookies queued on `authResponse`.
+ *
+ * auth-js writes through the `setAll` callback while `getUser()` runs: a
+ * successful refresh puts the ROTATED tokens on the response, a dead session
+ * puts the cookie DELETIONS there. A bare `NextResponse.redirect()` throws
+ * both away, so the browser replays the old cookie on the very next request:
+ * a consumed refresh token on the happy path, and a dead one on the expiry
+ * path, where production showed the bounce and the following /login each
+ * spending their own GoTrue 400 about 100 ms apart. Every response that
+ * replaces `supabaseResponse` has to go through here (or through
+ * `copyResponseCookies`, for the non-redirect ones).
+ */
+function redirectWithAuthCookies(
+  authResponse: NextResponse,
+  url: URL | string,
+): NextResponse {
+  const response = NextResponse.redirect(url)
+  copyResponseCookies(authResponse, response)
+  return response
+}
+
 function sessionTimeoutResponse(
   request: NextRequest,
   authResponse: NextResponse,
@@ -755,9 +789,14 @@ const AUTH_DESTINATION_PARAM = {
  * that was going to happen anyway, on exactly the same conditions. The auth
  * pages navigate to the destination only after the step-up succeeds, and the
  * next request re-runs this same gate regardless.
+ *
+ * The bounce also has to carry the cookies auth-js queued on the response
+ * while `getUser()` ran, hence `authResponse`: see
+ * `redirectWithAuthCookies`.
  */
 function bounceToAuth(
   request: NextRequest,
+  authResponse: NextResponse,
   target: keyof typeof AUTH_DESTINATION_PARAM,
 ) {
   // Absolute-path reference: replaces path AND clears query/fragment.
@@ -769,7 +808,7 @@ function bounceToAuth(
   if (destination !== '/') {
     url.search = `${AUTH_DESTINATION_PARAM[target]}=${encodeURIComponent(destination)}`
   }
-  return NextResponse.redirect(url)
+  return redirectWithAuthCookies(authResponse, url)
 }
 
 /**