diff --git a/frontend/app/auth/callback/route.ts b/frontend/app/auth/callback/route.ts
index 8c48ac1c..0da7f129 100644
--- a/frontend/app/auth/callback/route.ts
+++ b/frontend/app/auth/callback/route.ts
@@ -1,7 +1,10 @@
 import { NextRequest, NextResponse } from "next/server";
+import { BACKEND_ENTITLEMENT_HEADER } from "@/lib/backend-auth";
 import { createSupabaseRouteClient, hasSupabaseServerEnv } from "@/lib/supabase/server";
 import { getConfiguredSiteUrl } from "@/lib/site-url";
 
+const API_BASE = process.env.POLYWEATHER_API_BASE_URL;
+
 function normalizeNextPath(input: string | null) {
   const fallback = "/";
   const raw = String(input || "").trim();
@@ -11,6 +14,34 @@ function normalizeNextPath(input: string | null) {
   return raw;
 }
 
+async function warmSignupTrial(accessToken: string) {
+  const token = String(accessToken || "").trim();
+  if (!API_BASE || !token) return;
+
+  const headers = new Headers({
+    Accept: "application/json",
+    Authorization: `Bearer ${token}`,
+  });
+  const backendToken = process.env.POLYWEATHER_BACKEND_ENTITLEMENT_TOKEN?.trim();
+  if (backendToken) {
+    headers.set(BACKEND_ENTITLEMENT_HEADER, backendToken);
+  }
+
+  const controller = new AbortController();
+  const timeoutId = setTimeout(() => controller.abort(), 2500);
+  try {
+    await fetch(`${API_BASE}/api/auth/me`, {
+      cache: "no-store",
+      headers,
+      signal: controller.signal,
+    });
+  } catch {
+    // The account/terminal bootstrap will retry. Callback must not strand login.
+  } finally {
+    clearTimeout(timeoutId);
+  }
+}
+
 export async function GET(request: NextRequest) {
   const siteUrl = getConfiguredSiteUrl();
   if (siteUrl) {
@@ -38,7 +69,10 @@ export async function GET(request: NextRequest) {
   const supabase = createSupabaseRouteClient(request, response);
   const code = request.nextUrl.searchParams.get("code");
   if (code) {
-    await supabase.auth.exchangeCodeForSession(code);
+    const {
+      data: { session },
+    } = await supabase.auth.exchangeCodeForSession(code);
+    await warmSignupTrial(session?.access_token || "");
   }
 
   return response;
diff --git a/frontend/components/auth/__tests__/passwordReset.test.ts b/frontend/components/auth/__tests__/passwordReset.test.ts
index ff7d0c73..62ac5fad 100644
--- a/frontend/components/auth/__tests__/passwordReset.test.ts
+++ b/frontend/components/auth/__tests__/passwordReset.test.ts
@@ -26,6 +26,13 @@ export function runTests() {
     "auth",
     "ResetPasswordClient.tsx",
   );
+  const authCallbackPath = path.join(
+    projectRoot,
+    "app",
+    "auth",
+    "callback",
+    "route.ts",
+  );
 
   const loginClientSource = fs.readFileSync(loginClientPath, "utf8");
 
@@ -55,4 +62,14 @@ export function runTests() {
       resetClientSource.includes("expired"),
     "password reset client must detect an expired or invalid recovery session",
   );
+
+  const authCallbackSource = fs.readFileSync(authCallbackPath, "utf8");
+  assert(
+    authCallbackSource.includes("warmSignupTrial") &&
+      authCallbackSource.includes("exchangeCodeForSession") &&
+      authCallbackSource.includes("/api/auth/me") &&
+      authCallbackSource.includes("Authorization") &&
+      authCallbackSource.includes("Bearer"),
+    "auth callback must warm /api/auth/me with the exchanged Supabase session so new users receive the signup trial immediately",
+  );
 }
diff --git a/scripts/supabase/schema.sql b/scripts/supabase/schema.sql
index eb099789..58a927b2 100644
--- a/scripts/supabase/schema.sql
+++ b/scripts/supabase/schema.sql
@@ -46,6 +46,11 @@ create index if not exists idx_subscriptions_user_created
   on public.subscriptions(user_id, created_at desc)
   include (id, status, plan_code, source, starts_at, expires_at, updated_at);
 
+create unique index if not exists uq_subscriptions_signup_trial_user
+  on public.subscriptions(user_id)
+  where plan_code = 'signup_trial_3d'
+    and source = 'signup_trial';
+
 create table if not exists public.payments (
   id bigserial primary key,
   user_id uuid not null references auth.users(id) on delete cascade,
@@ -128,6 +133,221 @@ create table if not exists public.trial_claim_wallets (
 create unique index if not exists uq_trial_claim_wallets_address
   on public.trial_claim_wallets(lower(wallet_address));
 
+create or replace function public.claim_signup_trial(
+  p_user_id uuid,
+  p_email text default '',
+  p_telegram_user_id bigint default null,
+  p_wallet_addresses text[] default array[]::text[]
+)
+returns jsonb
+language plpgsql
+security definer
+set search_path = public, auth
+as $$
+declare
+  v_email text := lower(trim(coalesce(p_email, '')));
+  v_wallets text[] := (
+    select coalesce(array_agg(distinct lower(trim(input_wallet.value))), array[]::text[])
+    from unnest(coalesce(p_wallet_addresses, array[]::text[])) as input_wallet(value)
+    where trim(input_wallet.value) <> ''
+  );
+  v_now timestamptz := now();
+  v_expires timestamptz := v_now + interval '3 days';
+  v_claim public.trial_claims%rowtype;
+  v_claim_id bigint;
+  v_rows integer := 0;
+begin
+  if p_user_id is null then
+    return jsonb_build_object('created', false, 'reason', 'missing_user_id');
+  end if;
+
+  select tc.*
+    into v_claim
+  from public.trial_claims tc
+  where tc.user_id = p_user_id
+     or (v_email <> '' and lower(tc.email) = v_email)
+     or (p_telegram_user_id is not null and tc.telegram_user_id = p_telegram_user_id)
+     or exists (
+        select 1
+        from public.trial_claim_wallets tcw
+        where tcw.trial_claim_id = tc.id
+          and lower(tcw.wallet_address) = any(v_wallets)
+     )
+  order by
+    case when tc.user_id = p_user_id then 0 else 1 end,
+    tc.created_at asc,
+    tc.id asc
+  limit 1;
+
+  if found then
+    if v_claim.user_id <> p_user_id then
+      return jsonb_build_object('created', false, 'reason', 'already_claimed');
+    end if;
+
+    insert into public.subscriptions (
+      user_id,
+      plan_code,
+      status,
+      starts_at,
+      expires_at,
+      source,
+      created_at,
+      updated_at
+    )
+    values (
+      p_user_id,
+      'signup_trial_3d',
+      'active',
+      coalesce(v_claim.claimed_at, v_now),
+      coalesce(v_claim.claimed_at, v_now) + interval '3 days',
+      'signup_trial',
+      v_now,
+      v_now
+    )
+    on conflict (user_id)
+      where plan_code = 'signup_trial_3d'
+        and source = 'signup_trial'
+      do nothing;
+    get diagnostics v_rows = row_count;
+
+    if v_rows > 0 then
+      insert into public.entitlement_events (
+        user_id,
+        action,
+        reason,
+        actor,
+        payload,
+        created_at
+      )
+      values (
+        p_user_id,
+        'signup_trial_granted',
+        'claim_repaired',
+        'supabase_auth',
+        jsonb_build_object(
+          'plan_code', 'signup_trial_3d',
+          'expires_at', coalesce(v_claim.claimed_at, v_now) + interval '3 days'
+        ),
+        v_now
+      );
+      return jsonb_build_object(
+        'created', true,
+        'repaired', true,
+        'plan_code', 'signup_trial_3d',
+        'expires_at', coalesce(v_claim.claimed_at, v_now) + interval '3 days'
+      );
+    end if;
+
+    return jsonb_build_object('created', false, 'reason', 'already_claimed');
+  end if;
+
+  insert into public.trial_claims (
+    user_id,
+    email,
+    telegram_user_id,
+    primary_wallet_address,
+    metadata,
+    claimed_at,
+    created_at
+  )
+  values (
+    p_user_id,
+    v_email,
+    p_telegram_user_id,
+    nullif(v_wallets[1], ''),
+    jsonb_build_object('wallet_addresses', v_wallets),
+    v_now,
+    v_now
+  )
+  returning id into v_claim_id;
+
+  insert into public.trial_claim_wallets (trial_claim_id, wallet_address, created_at)
+  select v_claim_id, wallet.value, v_now
+  from unnest(v_wallets) as wallet(value)
+  on conflict do nothing;
+
+  insert into public.subscriptions (
+    user_id,
+    plan_code,
+    status,
+    starts_at,
+    expires_at,
+    source,
+    created_at,
+    updated_at
+  )
+  values (
+    p_user_id,
+    'signup_trial_3d',
+    'active',
+    v_now,
+    v_expires,
+    'signup_trial',
+    v_now,
+    v_now
+  )
+  on conflict (user_id)
+    where plan_code = 'signup_trial_3d'
+      and source = 'signup_trial'
+    do nothing;
+  get diagnostics v_rows = row_count;
+
+  insert into public.entitlement_events (
+    user_id,
+    action,
+    reason,
+    actor,
+    payload,
+    created_at
+  )
+  values
+    (
+      p_user_id,
+      'signup_trial_claimed',
+      'trial_dedupe',
+      'supabase_auth',
+      jsonb_build_object(
+        'user_id', p_user_id,
+        'email', v_email,
+        'telegram_user_id', p_telegram_user_id,
+        'wallet_addresses', v_wallets,
+        'claimed_at', v_now,
+        'storage', 'trial_claims'
+      ),
+      v_now
+    ),
+    (
+      p_user_id,
+      'signup_trial_granted',
+      'first_auth',
+      'supabase_auth',
+      jsonb_build_object(
+        'plan_code', 'signup_trial_3d',
+        'expires_at', v_expires
+      ),
+      v_now
+    );
+
+  if v_rows = 0 then
+    return jsonb_build_object('created', false, 'reason', 'already_claimed');
+  end if;
+
+  return jsonb_build_object(
+    'created', true,
+    'plan_code', 'signup_trial_3d',
+    'expires_at', v_expires
+  );
+exception
+  when unique_violation then
+    return jsonb_build_object('created', false, 'reason', 'already_claimed');
+end;
+$$;
+
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from public;
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from anon;
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from authenticated;
+grant execute on function public.claim_signup_trial(uuid, text, bigint, text[]) to service_role;
+
 create table if not exists public.referral_codes (
   id bigserial primary key,
   user_id uuid not null references auth.users(id) on delete cascade,
diff --git a/scripts/supabase/signup_trial_atomic_20260530.sql b/scripts/supabase/signup_trial_atomic_20260530.sql
new file mode 100644
index 00000000..b5be0d15
--- /dev/null
+++ b/scripts/supabase/signup_trial_atomic_20260530.sql
@@ -0,0 +1,248 @@
+-- Atomic signup-trial claim and subscription grant.
+-- Run after subscription_referral_20260529.sql.
+
+-- Keep the first real signup trial row per user and neutralize duplicate rows
+-- before adding the one-trial-per-user index.
+with ranked_signup_trials as (
+  select
+    id,
+    row_number() over (
+      partition by user_id
+      order by created_at asc, id asc
+    ) as rn
+  from public.subscriptions
+  where plan_code = 'signup_trial_3d'
+    and source = 'signup_trial'
+)
+update public.subscriptions s
+set
+  status = case when s.status = 'active' then 'expired' else s.status end,
+  source = 'signup_trial_duplicate',
+  updated_at = now()
+from ranked_signup_trials r
+where s.id = r.id
+  and r.rn > 1;
+
+create unique index if not exists uq_subscriptions_signup_trial_user
+  on public.subscriptions(user_id)
+  where plan_code = 'signup_trial_3d'
+    and source = 'signup_trial';
+
+create or replace function public.claim_signup_trial(
+  p_user_id uuid,
+  p_email text default '',
+  p_telegram_user_id bigint default null,
+  p_wallet_addresses text[] default array[]::text[]
+)
+returns jsonb
+language plpgsql
+security definer
+set search_path = public, auth
+as $$
+declare
+  v_email text := lower(trim(coalesce(p_email, '')));
+  v_wallets text[] := (
+    select coalesce(array_agg(distinct lower(trim(input_wallet.value))), array[]::text[])
+    from unnest(coalesce(p_wallet_addresses, array[]::text[])) as input_wallet(value)
+    where trim(input_wallet.value) <> ''
+  );
+  v_now timestamptz := now();
+  v_expires timestamptz := v_now + interval '3 days';
+  v_claim public.trial_claims%rowtype;
+  v_claim_id bigint;
+  v_rows integer := 0;
+begin
+  if p_user_id is null then
+    return jsonb_build_object('created', false, 'reason', 'missing_user_id');
+  end if;
+
+  select tc.*
+    into v_claim
+  from public.trial_claims tc
+  where tc.user_id = p_user_id
+     or (v_email <> '' and lower(tc.email) = v_email)
+     or (p_telegram_user_id is not null and tc.telegram_user_id = p_telegram_user_id)
+     or exists (
+        select 1
+        from public.trial_claim_wallets tcw
+        where tcw.trial_claim_id = tc.id
+          and lower(tcw.wallet_address) = any(v_wallets)
+     )
+  order by
+    case when tc.user_id = p_user_id then 0 else 1 end,
+    tc.created_at asc,
+    tc.id asc
+  limit 1;
+
+  if found then
+    if v_claim.user_id <> p_user_id then
+      return jsonb_build_object('created', false, 'reason', 'already_claimed');
+    end if;
+
+    insert into public.subscriptions (
+      user_id,
+      plan_code,
+      status,
+      starts_at,
+      expires_at,
+      source,
+      created_at,
+      updated_at
+    )
+    values (
+      p_user_id,
+      'signup_trial_3d',
+      'active',
+      coalesce(v_claim.claimed_at, v_now),
+      coalesce(v_claim.claimed_at, v_now) + interval '3 days',
+      'signup_trial',
+      v_now,
+      v_now
+    )
+    on conflict (user_id)
+      where plan_code = 'signup_trial_3d'
+        and source = 'signup_trial'
+      do nothing;
+    get diagnostics v_rows = row_count;
+
+    if v_rows > 0 then
+      insert into public.entitlement_events (
+        user_id,
+        action,
+        reason,
+        actor,
+        payload,
+        created_at
+      )
+      values (
+        p_user_id,
+        'signup_trial_granted',
+        'claim_repaired',
+        'supabase_auth',
+        jsonb_build_object(
+          'plan_code', 'signup_trial_3d',
+          'expires_at', coalesce(v_claim.claimed_at, v_now) + interval '3 days'
+        ),
+        v_now
+      );
+      return jsonb_build_object(
+        'created', true,
+        'repaired', true,
+        'plan_code', 'signup_trial_3d',
+        'expires_at', coalesce(v_claim.claimed_at, v_now) + interval '3 days'
+      );
+    end if;
+
+    return jsonb_build_object('created', false, 'reason', 'already_claimed');
+  end if;
+
+  insert into public.trial_claims (
+    user_id,
+    email,
+    telegram_user_id,
+    primary_wallet_address,
+    metadata,
+    claimed_at,
+    created_at
+  )
+  values (
+    p_user_id,
+    v_email,
+    p_telegram_user_id,
+    nullif(v_wallets[1], ''),
+    jsonb_build_object('wallet_addresses', v_wallets),
+    v_now,
+    v_now
+  )
+  returning id into v_claim_id;
+
+  insert into public.trial_claim_wallets (trial_claim_id, wallet_address, created_at)
+  select v_claim_id, wallet.value, v_now
+  from unnest(v_wallets) as wallet(value)
+  on conflict do nothing;
+
+  insert into public.subscriptions (
+    user_id,
+    plan_code,
+    status,
+    starts_at,
+    expires_at,
+    source,
+    created_at,
+    updated_at
+  )
+  values (
+    p_user_id,
+    'signup_trial_3d',
+    'active',
+    v_now,
+    v_expires,
+    'signup_trial',
+    v_now,
+    v_now
+  )
+  on conflict (user_id)
+    where plan_code = 'signup_trial_3d'
+      and source = 'signup_trial'
+    do nothing;
+  get diagnostics v_rows = row_count;
+
+  insert into public.entitlement_events (
+    user_id,
+    action,
+    reason,
+    actor,
+    payload,
+    created_at
+  )
+  values
+    (
+      p_user_id,
+      'signup_trial_claimed',
+      'trial_dedupe',
+      'supabase_auth',
+      jsonb_build_object(
+        'user_id', p_user_id,
+        'email', v_email,
+        'telegram_user_id', p_telegram_user_id,
+        'wallet_addresses', v_wallets,
+        'claimed_at', v_now,
+        'storage', 'trial_claims'
+      ),
+      v_now
+    ),
+    (
+      p_user_id,
+      'signup_trial_granted',
+      'first_auth',
+      'supabase_auth',
+      jsonb_build_object(
+        'plan_code', 'signup_trial_3d',
+        'expires_at', v_expires
+      ),
+      v_now
+    );
+
+  if v_rows = 0 then
+    return jsonb_build_object('created', false, 'reason', 'already_claimed');
+  end if;
+
+  return jsonb_build_object(
+    'created', true,
+    'plan_code', 'signup_trial_3d',
+    'expires_at', v_expires
+  );
+exception
+  when unique_violation then
+    return jsonb_build_object('created', false, 'reason', 'already_claimed');
+end;
+$$;
+
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from public;
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from anon;
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from authenticated;
+grant execute on function public.claim_signup_trial(uuid, text, bigint, text[]) to service_role;
+
+analyze public.trial_claims;
+analyze public.trial_claim_wallets;
+analyze public.subscriptions;
diff --git a/scripts/supabase/signup_trial_atomic_lockdown_20260530.sql b/scripts/supabase/signup_trial_atomic_lockdown_20260530.sql
new file mode 100644
index 00000000..1d9830ba
--- /dev/null
+++ b/scripts/supabase/signup_trial_atomic_lockdown_20260530.sql
@@ -0,0 +1,11 @@
+-- Restrict atomic signup-trial RPC to backend service-role calls only.
+
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from public;
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from anon;
+revoke all on function public.claim_signup_trial(uuid, text, bigint, text[]) from authenticated;
+grant execute on function public.claim_signup_trial(uuid, text, bigint, text[]) to service_role;
+
+select
+  has_function_privilege('anon', 'public.claim_signup_trial(uuid,text,bigint,text[])', 'execute') as anon_can_execute,
+  has_function_privilege('authenticated', 'public.claim_signup_trial(uuid,text,bigint,text[])', 'execute') as authenticated_can_execute,
+  has_function_privilege('service_role', 'public.claim_signup_trial(uuid,text,bigint,text[])', 'execute') as service_role_can_execute;
diff --git a/scripts/supabase/signup_trial_atomic_verify.sql b/scripts/supabase/signup_trial_atomic_verify.sql
new file mode 100644
index 00000000..cd51928d
--- /dev/null
+++ b/scripts/supabase/signup_trial_atomic_verify.sql
@@ -0,0 +1,38 @@
+-- Read-only verification for signup_trial_atomic_20260530.sql.
+
+select
+  exists (
+    select 1
+    from pg_indexes
+    where schemaname = 'public'
+      and tablename = 'subscriptions'
+      and indexname = 'uq_subscriptions_signup_trial_user'
+  ) as has_trial_unique_index,
+  exists (
+    select 1
+    from pg_proc p
+    join pg_namespace n on n.oid = p.pronamespace
+    where n.nspname = 'public'
+      and p.proname = 'claim_signup_trial'
+  ) as has_claim_signup_trial_rpc;
+
+select
+  count(*) as users_with_duplicate_signup_trials,
+  coalesce(sum(trial_count), 0) as total_trial_rows_in_duplicate_users
+from (
+  select user_id, count(*) as trial_count
+  from public.subscriptions
+  where plan_code = 'signup_trial_3d'
+    and source = 'signup_trial'
+  group by user_id
+  having count(*) > 1
+) d;
+
+select
+  count(*) filter (where s.id is null) as trial_claims_without_trial_subscription,
+  count(*) as total_trial_claims
+from public.trial_claims tc
+left join public.subscriptions s
+  on s.user_id = tc.user_id
+ and s.plan_code = 'signup_trial_3d'
+ and s.source = 'signup_trial';
diff --git a/src/auth/supabase_entitlement.py b/src/auth/supabase_entitlement.py
index 0de4621a..465f1a65 100644
--- a/src/auth/supabase_entitlement.py
+++ b/src/auth/supabase_entitlement.py
@@ -176,6 +176,31 @@ class SupabaseEntitlementService:
         except Exception:
             return None
 
+    def _rpc(
+        self,
+        name: str,
+        payload: Optional[Any] = None,
+        *,
+        allowed_status: Optional[List[int]] = None,
+    ) -> Any:
+        return self._rest(
+            "POST",
+            f"rpc/{name}",
+            payload=payload or {},
+            allowed_status=allowed_status or [200],
+        )
+
+    @staticmethod
+    def _looks_like_missing_rpc(exc: Exception) -> bool:
+        text = str(exc).lower()
+        return (
+            "pgrst202" in text
+            or "could not find the function" in text
+            or "function public.claim_signup_trial" in text
+            or "schema cache" in text
+            or "404" in text
+        )
+
     def _admin_user_endpoint(self, user_id: str) -> str:
         return f"{self.supabase_url}/auth/v1/admin/users/{user_id}"
 
@@ -407,6 +432,31 @@ class SupabaseEntitlementService:
         try:
             telegram_user_id = self._telegram_user_id_for(user_key)
             wallet_addresses = self._active_wallet_addresses_for(user_key)
+            try:
+                result = self._rpc(
+                    "claim_signup_trial",
+                    {
+                        "p_user_id": user_key,
+                        "p_email": normalized_email,
+                        "p_telegram_user_id": telegram_user_id,
+                        "p_wallet_addresses": wallet_addresses,
+                    },
+                    allowed_status=[200],
+                )
+                if isinstance(result, dict):
+                    self.invalidate_subscription_cache(user_key)
+                    return result
+                if isinstance(result, list) and result and isinstance(result[0], dict):
+                    self.invalidate_subscription_cache(user_key)
+                    return result[0]
+            except Exception as rpc_exc:
+                if not self._looks_like_missing_rpc(rpc_exc):
+                    raise
+                logger.warning(
+                    "signup trial rpc missing; falling back to legacy grant user_id={}: {}",
+                    user_key,
+                    rpc_exc,
+                )
             if self._trial_claim_exists(
                 user_id=user_key,
                 email=normalized_email,
@@ -437,6 +487,13 @@ class SupabaseEntitlementService:
                 if isinstance(claim_rows, list) and claim_rows and isinstance(claim_rows[0], dict):
                     claim_id = claim_rows[0].get("id")
             except Exception:
+                if self._trial_claim_exists(
+                    user_id=user_key,
+                    email=normalized_email,
+                    telegram_user_id=telegram_user_id,
+                    wallet_addresses=wallet_addresses,
+                ):
+                    return {"created": False, "reason": "already_claimed"}
                 self._record_signup_trial_claim_event(
                     user_id=user_key,
                     email=normalized_email,
diff --git a/tests/test_subscription_referral_program.py b/tests/test_subscription_referral_program.py
index 17b753fc..f4b68a46 100644
--- a/tests/test_subscription_referral_program.py
+++ b/tests/test_subscription_referral_program.py
@@ -78,6 +78,14 @@ def test_signup_trial_claim_creates_three_day_trial_once(monkeypatch):
     service = SupabaseEntitlementService()
     calls = []
 
+    monkeypatch.setattr(
+        service,
+        "_rpc",
+        lambda *args, **kwargs: (_ for _ in ()).throw(
+            RuntimeError("PGRST202 function not found")
+        ),
+    )
+
     def fake_rest(method, table, **kwargs):
         calls.append({"method": method, "table": table, **kwargs})
         if method == "GET" and table in {"trial_claims", "user_wallets"}:
@@ -99,6 +107,49 @@ def test_signup_trial_claim_creates_three_day_trial_once(monkeypatch):
     assert payload["user_id"] == "user-1"
 
 
+def test_signup_trial_uses_atomic_database_claim_rpc(monkeypatch):
+    monkeypatch.setenv("POLYWEATHER_AUTH_ENABLED", "true")
+    monkeypatch.setenv("SUPABASE_URL", "https://example.supabase.co")
+    monkeypatch.setenv("SUPABASE_ANON_KEY", "anon")
+    monkeypatch.setenv("SUPABASE_SERVICE_ROLE_KEY", "service-role")
+    service = SupabaseEntitlementService()
+    rpc_calls = []
+
+    def fake_rpc(name, payload, **kwargs):
+        rpc_calls.append({"name": name, "payload": payload, **kwargs})
+        return {
+            "created": True,
+            "plan_code": "signup_trial_3d",
+            "expires_at": "2026-06-02T00:00:00+00:00",
+        }
+
+    def fake_rest(method, table, **kwargs):
+        if method == "GET" and table == "user_wallets":
+            return [{"address": "0xabc"}]
+        raise AssertionError(
+            f"signup trial must use atomic RPC instead of legacy {method} {table}"
+        )
+
+    monkeypatch.setattr(service, "_rpc", fake_rpc, raising=False)
+    monkeypatch.setattr(service, "_rest", fake_rest)
+
+    result = service.ensure_signup_trial("user-1", "USER@example.com")
+
+    assert result["created"] is True
+    assert rpc_calls == [
+        {
+            "name": "claim_signup_trial",
+            "payload": {
+                "p_user_id": "user-1",
+                "p_email": "user@example.com",
+                "p_telegram_user_id": None,
+                "p_wallet_addresses": ["0xabc"],
+            },
+            "allowed_status": [200],
+        }
+    ]
+
+
 def test_referral_discount_applies_to_first_monthly_payment(monkeypatch, tmp_path):
     _payment_env(monkeypatch, tmp_path)
     service = PaymentContractCheckoutService()
@@ -187,6 +238,14 @@ def test_signup_trial_falls_back_to_entitlement_events_without_trial_tables(monk
     service = SupabaseEntitlementService()
     calls = []
 
+    monkeypatch.setattr(
+        service,
+        "_rpc",
+        lambda *args, **kwargs: (_ for _ in ()).throw(
+            RuntimeError("PGRST202 function not found")
+        ),
+    )
+
     def fake_rest(method, table, **kwargs):
         calls.append({"method": method, "table": table, **kwargs})
         if method == "GET" and table == "user_wallets":