diff --git a/src/app/api/login/route.ts b/src/app/api/login/route.ts
index 30c45fa..6e27c1f 100644
--- a/src/app/api/login/route.ts
+++ b/src/app/api/login/route.ts
@@ -7,15 +7,32 @@ function getSharedCookieDomain(req: NextRequest): string | undefined {
   return host.endsWith('profit-planet.partners') ? '.profit-planet.partners' : undefined
 }
 
+function splitSetCookieHeader(header: string): string[] {
+  const parts: string[] = []
+  let start = 0
+  let inExpires = false
+  for (let i = 0; i < header.length; i++) {
+    const lower = header.slice(i, i + 8).toLowerCase()
+    if (lower === 'expires=') inExpires = true
+    if (inExpires && header[i] === ';') inExpires = false
+    if (!inExpires && header[i] === ',') {
+      parts.push(header.slice(start, i).trim())
+      start = i + 1
+    }
+  }
+  const last = header.slice(start).trim()
+  if (last) parts.push(last)
+  return parts
+}
+
 function readSetCookies(res: Response): string[] {
   const anyHeaders = res.headers as any
   if (typeof anyHeaders.getSetCookie === 'function') return anyHeaders.getSetCookie()
   const single = res.headers.get('set-cookie')
-  return single ? [single] : []
+  return single ? splitSetCookieHeader(single) : []
 }
 
 function parseRefreshCookie(setCookie: string) {
-  // refreshToken=VALUE; Max-Age=...; Expires=...; SameSite=...; ...
   const m = setCookie.match(/^refreshToken=([^;]*)/i)
   if (!m) return null
   const value = m[1] ?? ''
@@ -52,7 +69,23 @@ export async function POST(req: NextRequest) {
   const refreshSetCookie = setCookies.find((c) => /^refreshToken=/i.test(c))
   if (refreshSetCookie) {
     const parsed = parseRefreshCookie(refreshSetCookie)
-    if (parsed) {
+    if (parsed?.value) {
+      // Clear host-only duplicates first.
+      out.cookies.set('refreshToken', '', {
+        path: '/',
+        httpOnly: true,
+        secure: true,
+        sameSite: 'lax',
+        maxAge: 0,
+      })
+      out.cookies.set('__Secure-refreshToken', '', {
+        path: '/',
+        httpOnly: true,
+        secure: true,
+        sameSite: 'lax',
+        maxAge: 0,
+      })
+
       out.cookies.set('refreshToken', parsed.value, {
         domain: getSharedCookieDomain(req),
         path: '/',
diff --git a/src/app/api/logout/route.ts b/src/app/api/logout/route.ts
index 17b7784..4dc70b3 100644
--- a/src/app/api/logout/route.ts
+++ b/src/app/api/logout/route.ts
@@ -28,6 +28,12 @@ export async function POST(req: NextRequest) {
   }
 
   const out = NextResponse.json(data, { status })
+
+  // Clear host-only variants
+  out.cookies.set('refreshToken', '', { path: '/', httpOnly: true, secure: true, sameSite: 'lax', maxAge: 0 })
+  out.cookies.set('__Secure-refreshToken', '', { path: '/', httpOnly: true, secure: true, sameSite: 'lax', maxAge: 0 })
+
+  // Clear shared-domain variant
   out.cookies.set('refreshToken', '', {
     domain: getSharedCookieDomain(req),
     path: '/',
@@ -36,5 +42,6 @@ export async function POST(req: NextRequest) {
     sameSite: 'lax',
     maxAge: 0,
   })
+
   return out
 }
diff --git a/src/app/api/refresh/route.ts b/src/app/api/refresh/route.ts
index fe3e35f..21e62c3 100644
--- a/src/app/api/refresh/route.ts
+++ b/src/app/api/refresh/route.ts
@@ -7,11 +7,30 @@ function getSharedCookieDomain(req: NextRequest): string | undefined {
   return host.endsWith('profit-planet.partners') ? '.profit-planet.partners' : undefined
 }
 
+function splitSetCookieHeader(header: string): string[] {
+  // Handles "Expires=Wed, 21 Oct ..." commas.
+  const parts: string[] = []
+  let start = 0
+  let inExpires = false
+  for (let i = 0; i < header.length; i++) {
+    const lower = header.slice(i, i + 8).toLowerCase()
+    if (lower === 'expires=') inExpires = true
+    if (inExpires && header[i] === ';') inExpires = false
+    if (!inExpires && header[i] === ',') {
+      parts.push(header.slice(start, i).trim())
+      start = i + 1
+    }
+  }
+  const last = header.slice(start).trim()
+  if (last) parts.push(last)
+  return parts
+}
+
 function readSetCookies(res: Response): string[] {
   const anyHeaders = res.headers as any
   if (typeof anyHeaders.getSetCookie === 'function') return anyHeaders.getSetCookie()
   const single = res.headers.get('set-cookie')
-  return single ? [single] : []
+  return single ? splitSetCookieHeader(single) : []
 }
 
 function parseRefreshCookie(setCookie: string) {
@@ -35,11 +54,24 @@ export async function POST(req: NextRequest) {
   const apiBase = process.env.NEXT_PUBLIC_API_BASE_URL
   if (!apiBase) return NextResponse.json({ message: 'Missing NEXT_PUBLIC_API_BASE_URL' }, { status: 500 })
 
-  const cookie = req.headers.get('cookie') ?? ''
+  // Prefer a single parsed cookie value to avoid "refreshToken=old; refreshToken=new" ambiguity.
+  const rt =
+    req.cookies.get('refreshToken')?.value ??
+    req.cookies.get('__Secure-refreshToken')?.value ??
+    ''
+
+  const headers: Record<string, string> = {}
+  if (rt) {
+    headers.cookie = `refreshToken=${rt}`
+  } else {
+    // fallback (best-effort)
+    const cookie = req.headers.get('cookie') ?? ''
+    if (cookie) headers.cookie = cookie
+  }
 
   const apiRes = await fetch(`${apiBase}/api/refresh`, {
     method: 'POST',
-    headers: { cookie },
+    headers,
     cache: 'no-store',
   })
 
@@ -50,7 +82,24 @@ export async function POST(req: NextRequest) {
   const refreshSetCookie = setCookies.find((c) => /^refreshToken=/i.test(c))
   if (refreshSetCookie) {
     const parsed = parseRefreshCookie(refreshSetCookie)
-    if (parsed) {
+    if (parsed?.value) {
+      // Clear any host-only variants on the frontend host to prevent duplicates.
+      out.cookies.set('refreshToken', '', {
+        path: '/',
+        httpOnly: true,
+        secure: true,
+        sameSite: 'lax',
+        maxAge: 0,
+      })
+      out.cookies.set('__Secure-refreshToken', '', {
+        path: '/',
+        httpOnly: true,
+        secure: true,
+        sameSite: 'lax',
+        maxAge: 0,
+      })
+
+      // Set the shared-domain cookie used across subdomains.
       out.cookies.set('refreshToken', parsed.value, {
         domain: getSharedCookieDomain(req),
         path: '/',