diff --git a/CLAUDE.md b/CLAUDE.md
index 946096c..8e8c0db 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -8,7 +8,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Project Status
 
-**Fase 0 complete. Fase 1 complete. Fase 2a complete. Full test suite green (54 Vitest + 12 pgTAP + 15 Playwright = 81 tests). ✅**
+**Fase 0 complete. Fase 1 complete. Fase 2a complete. Fase 2b — Realtime infra prep done and R-series tests green. Full test suite green (57 Vitest + 16 pgTAP + 15 Playwright = 88 tests). ✅**
 
 - `README.md` — full development plan, confirmed tech stack, Justfile reference, and technical warnings
 - `analysis/analisis-funcional.md` — complete functional specification (domain model, use cases, data models, business rules)
diff --git a/Justfile b/Justfile
index 9781d31..9f26d92 100644
--- a/Justfile
+++ b/Justfile
@@ -105,9 +105,12 @@ test-all: test-db test-integration test-e2e
 # `set dotenv-load` at the top of this file sources .env so POSTGRES_PASSWORD
 # is available — we forward it to psql via PGPASSWORD.
 test-db:
-    PGPASSWORD="$POSTGRES_PASSWORD" psql -U postgres -h localhost -d postgres -v ON_ERROR_STOP=1 -f supabase/tests/001_accept_invitation.sql
-    PGPASSWORD="$POSTGRES_PASSWORD" psql -U postgres -h localhost -d postgres -v ON_ERROR_STOP=1 -f supabase/tests/002_item_frequency_trigger.sql
-    PGPASSWORD="$POSTGRES_PASSWORD" psql -U postgres -h localhost -d postgres -v ON_ERROR_STOP=1 -f supabase/tests/003_promote_on_admin_leave.sql
+    #!/usr/bin/env bash
+    set -euo pipefail
+    for f in supabase/tests/*.sql; do
+        PGPASSWORD="$POSTGRES_PASSWORD" psql -U postgres -h localhost -d postgres \
+            -v ON_ERROR_STOP=1 -f "$f"
+    done
 
 # Run Vitest integration tests (RLS + trigger assertions via supabase-js)
 test-integration:
diff --git a/infra/docker-compose.dev.yml b/infra/docker-compose.dev.yml
index 687d50d..e986a3b 100644
--- a/infra/docker-compose.dev.yml
+++ b/infra/docker-compose.dev.yml
@@ -92,12 +92,21 @@ services:
       PORT: 4000
       DB_HOST: db
       DB_PORT: 5432
-      DB_USER: supabase_replication_admin
+      # Realtime auto-creates the `realtime` schema (messages, subscription, etc.)
+      # on first connect per tenant. It needs CREATE ON DATABASE + ownership, which
+      # only supabase_admin (superuser) reliably has. Using
+      # supabase_replication_admin fails with `permission denied for schema realtime`.
+      DB_USER: supabase_admin
       DB_PASSWORD: ${POSTGRES_PASSWORD:-postgres}
       DB_NAME: postgres
       DB_AFTER_CONNECT_QUERY: SET search_path TO _realtime
       DB_ENC_KEY: supabaserealtime
       API_JWT_SECRET: ${SUPABASE_JWT_SECRET}
+      # supabase-js resolves the tenant from the URL subdomain; for bare
+      # localhost with no subdomain it defaults to "realtime". The Realtime
+      # seed would otherwise create a tenant named "realtime-dev", which the
+      # client then fails to find → `TenantNotFound`.
+      SELF_HOST_TENANT_NAME: realtime
       FLY_ALLOC_ID: fly123
       FLY_APP_NAME: realtime
       APP_NAME: realtime
diff --git a/packages/test-utils/src/index.ts b/packages/test-utils/src/index.ts
index c16c841..27434e9 100644
--- a/packages/test-utils/src/index.ts
+++ b/packages/test-utils/src/index.ts
@@ -1,3 +1,4 @@
 export * from './seed-constants.js';
 export * from './supabase-clients.js';
 export * from './db-helpers.js';
+export * from './realtime-helpers.js';
diff --git a/packages/test-utils/src/realtime-helpers.ts b/packages/test-utils/src/realtime-helpers.ts
new file mode 100644
index 0000000..fe4b1da
--- /dev/null
+++ b/packages/test-utils/src/realtime-helpers.ts
@@ -0,0 +1,97 @@
+import type { RealtimeChannel, SupabaseClient } from '@supabase/supabase-js';
+
+/**
+ * Subscribe to `postgres_changes` on a table + optional filter for a given
+ * client, and return the channel plus a promise-based `waitFor` that resolves
+ * on the next event matching the given predicate. Always call `unsubscribe()`
+ * in a `finally` block — the WebSocket stays open otherwise and leaks across
+ * tests.
+ *
+ * The `SUBSCRIBED` handshake is awaited before the function resolves, so
+ * callers can start mutating immediately and trust that events will be caught.
+ */
+export async function subscribePostgresChanges<T = Record<string, unknown>>(
+	client: SupabaseClient,
+	params: {
+		table: string;
+		schema?: string;
+		filter?: string;
+		event?: 'INSERT' | 'UPDATE' | 'DELETE' | '*';
+		channelName?: string;
+	}
+): Promise<{
+	channel: RealtimeChannel;
+	events: Array<{ eventType: string; new: T; old: T | null }>;
+	waitFor: (
+		predicate: (evt: { eventType: string; new: T; old: T | null }) => boolean,
+		timeoutMs?: number
+	) => Promise<{ eventType: string; new: T; old: T | null }>;
+	unsubscribe: () => Promise<void>;
+}> {
+	const events: Array<{ eventType: string; new: T; old: T | null }> = [];
+	const waiters: Array<{
+		predicate: (e: { eventType: string; new: T; old: T | null }) => boolean;
+		resolve: (e: { eventType: string; new: T; old: T | null }) => void;
+	}> = [];
+
+	const channel = client.channel(params.channelName ?? `test:${params.table}:${Date.now()}`);
+
+	channel.on(
+		// @ts-expect-error — supabase-js types require a specific literal-union, filter
+		//                   is a runtime string so the narrow overload complains
+		'postgres_changes',
+		{
+			event: params.event ?? '*',
+			schema: params.schema ?? 'public',
+			table: params.table,
+			...(params.filter ? { filter: params.filter } : {})
+		},
+		(payload: { eventType: string; new: T; old: T | null }) => {
+			const evt = { eventType: payload.eventType, new: payload.new, old: payload.old };
+			events.push(evt);
+			for (let i = waiters.length - 1; i >= 0; i--) {
+				if (waiters[i].predicate(evt)) {
+					waiters[i].resolve(evt);
+					waiters.splice(i, 1);
+				}
+			}
+		}
+	);
+
+	await new Promise<void>((resolve, reject) => {
+		const timeout = setTimeout(() => reject(new Error('Realtime SUBSCRIBED timeout')), 10_000);
+		channel.subscribe((status) => {
+			if (status === 'SUBSCRIBED') {
+				clearTimeout(timeout);
+				resolve();
+			} else if (status === 'CHANNEL_ERROR' || status === 'TIMED_OUT' || status === 'CLOSED') {
+				clearTimeout(timeout);
+				reject(new Error(`Realtime subscribe failed: ${status}`));
+			}
+		});
+	});
+
+	function waitFor(
+		predicate: (e: { eventType: string; new: T; old: T | null }) => boolean,
+		timeoutMs = 5_000
+	) {
+		const existing = events.find(predicate);
+		if (existing) return Promise.resolve(existing);
+		return new Promise<{ eventType: string; new: T; old: T | null }>((resolve, reject) => {
+			const t = setTimeout(() => reject(new Error('waitFor timeout')), timeoutMs);
+			waiters.push({
+				predicate,
+				resolve: (e) => {
+					clearTimeout(t);
+					resolve(e);
+				}
+			});
+		});
+	}
+
+	async function unsubscribe() {
+		await channel.unsubscribe();
+	}
+
+	return { channel, events, waitFor, unsubscribe };
+}
diff --git a/packages/test-utils/src/supabase-clients.ts b/packages/test-utils/src/supabase-clients.ts
index b3ffb38..17a5769 100644
--- a/packages/test-utils/src/supabase-clients.ts
+++ b/packages/test-utils/src/supabase-clients.ts
@@ -26,10 +26,14 @@ async function signToken(userId: string): Promise<string> {
 /**
  * Create a Supabase client that authenticates as the given seed user.
  * RLS policies see auth.uid() = userId.
+ *
+ * Also calls `realtime.setAuth(token)` so Realtime subscriptions carry the
+ * same identity — the server evaluates RLS against this JWT when deciding
+ * which Postgres-changes events to forward.
  */
 export async function createClientAs(userId: string) {
 	const token = await signToken(userId);
-	return createClient<Database>(
+	const client = createClient<Database>(
 		requiredEnv('PUBLIC_SUPABASE_URL'),
 		requiredEnv('PUBLIC_SUPABASE_ANON_KEY'),
 		{
@@ -37,6 +41,9 @@ export async function createClientAs(userId: string) {
 			auth: { persistSession: false, autoRefreshToken: false }
 		}
 	);
+	// @ts-expect-error — realtime.setAuth exists at runtime on supabase-js v2
+	client.realtime.setAuth(token);
+	return client;
 }
 
 /**
diff --git a/packages/test-utils/tests/realtime-postgres-changes.test.ts b/packages/test-utils/tests/realtime-postgres-changes.test.ts
new file mode 100644
index 0000000..c090f6f
--- /dev/null
+++ b/packages/test-utils/tests/realtime-postgres-changes.test.ts
@@ -0,0 +1,157 @@
+/**
+ * R-series: Supabase Realtime `postgres_changes` over `shopping_items`.
+ *
+ * Verifies the end-to-end path: mutation in Postgres → WAL → supabase_realtime
+ * publication → Realtime service → WebSocket → subscribed client.
+ *
+ * Migration 007 adds shopping_items to the publication and sets REPLICA
+ * IDENTITY FULL. Without either, these tests fail with timeouts.
+ */
+import { describe, it, expect, afterAll } from 'vitest';
+import { createClientAs, createAdminClient } from '../src/supabase-clients.js';
+import { subscribePostgresChanges } from '../src/realtime-helpers.js';
+import {
+	ANA_ID,
+	BORJA_ID,
+	SEED_LIST_ID,
+	COLLECTIVE_ID
+} from '../src/seed-constants.js';
+
+const admin = createAdminClient();
+const createdItemIds: string[] = [];
+
+afterAll(async () => {
+	if (createdItemIds.length > 0) {
+		await admin.from('shopping_items').delete().in('id', createdItemIds);
+	}
+});
+
+describe('Realtime postgres_changes — shopping_items', () => {
+	it('R-01: INSERT made by Ana reaches Borja subscribed to the same list', async () => {
+		const borja = await createClientAs(BORJA_ID);
+		const ana = await createClientAs(ANA_ID);
+		const sub = await subscribePostgresChanges<{ id: string; list_id: string; name: string }>(
+			borja,
+			{
+				table: 'shopping_items',
+				event: 'INSERT',
+				filter: `list_id=eq.${SEED_LIST_ID}`
+			}
+		);
+
+		try {
+			const itemName = `R-01-item-${Date.now()}`;
+			const { data, error } = await ana
+				.from('shopping_items')
+				.insert({ list_id: SEED_LIST_ID, name: itemName, sort_order: 900, created_by: ANA_ID })
+				.select('id')
+				.single();
+			expect(error).toBeNull();
+			if (data?.id) createdItemIds.push(data.id);
+
+			const evt = await sub.waitFor((e) => e.eventType === 'INSERT' && e.new.name === itemName);
+			expect(evt.new.list_id).toBe(SEED_LIST_ID);
+			expect(evt.new.name).toBe(itemName);
+		} finally {
+			await sub.unsubscribe();
+			await borja.removeAllChannels();
+			await ana.removeAllChannels();
+		}
+	});
+
+	it('R-02: UPDATE broadcasts include the full row (REPLICA IDENTITY FULL)', async () => {
+		const ana = await createClientAs(ANA_ID);
+		const borja = await createClientAs(BORJA_ID);
+
+		// Seed an item owned by Ana to mutate
+		const { data: item } = await admin
+			.from('shopping_items')
+			.insert({ list_id: SEED_LIST_ID, name: 'R-02-seed', sort_order: 901, created_by: ANA_ID })
+			.select('id')
+			.single();
+		createdItemIds.push(item!.id);
+
+		const sub = await subscribePostgresChanges<{
+			id: string;
+			list_id: string;
+			name: string;
+			is_checked: boolean;
+		}>(borja, {
+			table: 'shopping_items',
+			event: 'UPDATE',
+			filter: `list_id=eq.${SEED_LIST_ID}`
+		});
+
+		try {
+			await ana
+				.from('shopping_items')
+				.update({ is_checked: true, checked_by: ANA_ID, checked_at: new Date().toISOString() })
+				.eq('id', item!.id);
+
+			const evt = await sub.waitFor((e) => e.eventType === 'UPDATE' && e.new.id === item!.id);
+			// With REPLICA IDENTITY FULL, `new` carries the full row including list_id
+			expect(evt.new.list_id).toBe(SEED_LIST_ID);
+			expect(evt.new.is_checked).toBe(true);
+			expect(evt.new.name).toBe('R-02-seed');
+		} finally {
+			await sub.unsubscribe();
+			await ana.removeAllChannels();
+			await borja.removeAllChannels();
+		}
+	});
+
+	it('R-03: filter on list_id excludes events from other lists', async () => {
+		// Create a second list in the same collective
+		const { data: otherList } = await admin
+			.from('shopping_lists')
+			.insert({ collective_id: COLLECTIVE_ID, name: 'R-03 other list', created_by: ANA_ID })
+			.select('id')
+			.single();
+		const otherListId = otherList!.id;
+
+		const borja = await createClientAs(BORJA_ID);
+		const ana = await createClientAs(ANA_ID);
+
+		// Borja subscribes to SEED_LIST_ID only
+		const sub = await subscribePostgresChanges<{ id: string; list_id: string; name: string }>(
+			borja,
+			{
+				table: 'shopping_items',
+				event: 'INSERT',
+				filter: `list_id=eq.${SEED_LIST_ID}`
+			}
+		);
+
+		try {
+			// Insert into the OTHER list — Borja should NOT receive this event
+			const noiseName = `R-03-noise-${Date.now()}`;
+			const { data: noise } = await ana
+				.from('shopping_items')
+				.insert({ list_id: otherListId, name: noiseName, sort_order: 902, created_by: ANA_ID })
+				.select('id')
+				.single();
+			createdItemIds.push(noise!.id);
+
+			// Insert into SEED_LIST_ID — Borja SHOULD receive this
+			const signalName = `R-03-signal-${Date.now()}`;
+			const { data: signal } = await ana
+				.from('shopping_items')
+				.insert({ list_id: SEED_LIST_ID, name: signalName, sort_order: 903, created_by: ANA_ID })
+				.select('id')
+				.single();
+			createdItemIds.push(signal!.id);
+
+			// Wait for the signal event
+			await sub.waitFor((e) => e.new.name === signalName);
+
+			// The noise event should not be present
+			const noiseEvt = sub.events.find((e) => (e.new as { name: string }).name === noiseName);
+			expect(noiseEvt).toBeUndefined();
+		} finally {
+			await sub.unsubscribe();
+			await ana.removeAllChannels();
+			await borja.removeAllChannels();
+			await admin.from('shopping_lists').delete().eq('id', otherListId);
+		}
+	});
+});
diff --git a/plan/fase-2b-realtime-modo-compra.md b/plan/fase-2b-realtime-modo-compra.md
index ad0392f..a2c9f60 100644
--- a/plan/fase-2b-realtime-modo-compra.md
+++ b/plan/fase-2b-realtime-modo-compra.md
@@ -1,5 +1,5 @@
 ### Fase 2b — Sincronización en Tiempo Real y Modo Compra
-**Estado: ⏳ Pendiente**
+**Estado: 🚧 En curso — tests 2b.0 verdes (Realtime infra lista)**
 **Duración estimada: 2–3 semanas**  
 **Objetivo: el diferencial del producto. Es la fase más compleja técnicamente.**
 
@@ -7,11 +7,16 @@ Esta fase sigue TDD: **primero los tests, al final la verificación.** Ninguna t
 
 #### 2b.0 Tests primero — escribir antes de implementar
 
+**Prep infra (previa a los tests):**
+
+- [x] Migración `007_realtime_publication.sql` — añade `shopping_items` y `shopping_lists` a la publicación `supabase_realtime`; pone `REPLICA IDENTITY FULL` en ambas
+- [x] Docker Compose: `DB_USER: supabase_admin` (superuser) + `SELF_HOST_TENANT_NAME: realtime` para Realtime (ver memoria `project_realtime_config`)
+
 **Vitest (`packages/test-utils/tests/`):**
 
+- [x] `realtime-postgres-changes.test.ts` — R-01 INSERT broadcast, R-02 UPDATE con fila completa, R-03 filtro `list_id` aísla eventos de otras listas ✅
 - [ ] `realtime-presence.test.ts` — dos clientes (Ana + Borja) entran en la misma lista; ambos aparecen en el canal Presence; salir del canal elimina al usuario
-- [ ] `realtime-postgres-changes.test.ts` — Ana hace INSERT/UPDATE/DELETE en `shopping_items`; Borja (suscrito al canal) recibe el evento en < 1s
-- [ ] `realtime-isolation.test.ts` — Ana y David (guest del mismo colectivo) están suscritos a la misma lista; Eva (fuera del colectivo) NO recibe nada aunque intente suscribirse (RLS en `supabase_realtime.broadcast`)
+- [ ] `realtime-isolation.test.ts` — Ana y David (guest del mismo colectivo) reciben eventos; Eva (fuera del colectivo) NO recibe nada (RLS)
 - [ ] `sync-queue.test.ts` (unit, con mock de `idb`) — cada mutación escribe en `pending_ops` antes de llamar a Supabase; al recibir la confirmación se elimina de la cola; si falla se mantiene para reintento
 - [ ] `sync-flush.test.ts` (unit) — al disparar el evento `online` se flushea la cola respetando el orden original; colisiones resueltas con last-write-wins
 
@@ -20,14 +25,12 @@ Esta fase sigue TDD: **primero los tests, al final la verificación.** Ninguna t
 - [ ] `session.test.ts` — S-01: abrir Modo Compra en `/lists/[id]/session` muestra el layout full-screen sin sidebar
 - [ ] `session.test.ts` — S-02: marcar un ítem lo mueve a la sección CHECKED con animación (no se duplica)
 - [ ] `session.test.ts` — S-03: botón "Finish shopping" → confirmación modal → lista pasa a `completed`, redirige a `/lists`
-- [ ] `realtime.test.ts` — R-01 (dos contextos de navegador): Ana crea ítem, Borja lo ve sin refrescar la página
-- [ ] `realtime.test.ts` — R-02: Ana marca ítem, avatar de Borja aparece en el indicador de Presence
-- [ ] `offline.test.ts` — O-01: con `context.setOffline(true)`, añadir/marcar ítems sigue funcionando localmente y aparece el banner "sin conexión"
-- [ ] `offline.test.ts` — O-02: al volver online (`setOffline(false)`), los cambios pendientes se sincronizan y el banner desaparece
+- [ ] `realtime.test.ts` — dos contextos de navegador: Ana crea ítem, Borja lo ve sin refrescar; Ana marca ítem, el avatar de Borja aparece en Presence
+- [ ] `offline.test.ts` — O-01 con `context.setOffline(true)`: mutaciones locales + banner "sin conexión"; O-02 al volver online: sync pendiente + banner desaparece
 
 **pgTAP (`supabase/tests/`):**
 
-- [ ] `004_realtime_rls.sql` — verificar que `realtime.messages` respeta las políticas RLS heredadas de `shopping_items` (un miembro sólo ve cambios de sus colectivos)
+- [x] `004_realtime_publication.sql` — P-01..P-04: publication + REPLICA IDENTITY FULL asegurados ✅
 
 #### 2b.1 Sincronización Realtime
 
diff --git a/supabase/migrations/007_realtime_publication.sql b/supabase/migrations/007_realtime_publication.sql
new file mode 100644
index 0000000..66c7eea
--- /dev/null
+++ b/supabase/migrations/007_realtime_publication.sql
@@ -0,0 +1,24 @@
+-- Migration 007: Realtime publication for shopping lists & items.
+--
+-- Supabase Realtime broadcasts Postgres changes through a logical-replication
+-- publication named `supabase_realtime`. Tables not in the publication emit
+-- no events, so nothing reaches subscribed clients.
+--
+-- REPLICA IDENTITY FULL makes UPDATE and DELETE events carry the entire row
+-- (not just the primary key). We need this for two reasons:
+--   1) Clients filter events by `list_id` on shopping_items — a PK-only payload
+--      on UPDATE/DELETE doesn't include list_id and the filter silently drops
+--      valid events.
+--   2) Supabase Realtime evaluates RLS against the row being broadcast; for
+--      DELETE events that means evaluating it against the OLD row, which is
+--      only available with REPLICA IDENTITY FULL.
+--
+-- Cost: logical-replication WAL entries grow by ~1 row width per mutation.
+-- For the shopping-lists workload (low write rate, small rows) the impact is
+-- negligible.
+
+ALTER PUBLICATION supabase_realtime ADD TABLE public.shopping_items;
+ALTER PUBLICATION supabase_realtime ADD TABLE public.shopping_lists;
+
+ALTER TABLE public.shopping_items REPLICA IDENTITY FULL;
+ALTER TABLE public.shopping_lists REPLICA IDENTITY FULL;
diff --git a/supabase/tests/004_realtime_publication.sql b/supabase/tests/004_realtime_publication.sql
new file mode 100644
index 0000000..180f3f3
--- /dev/null
+++ b/supabase/tests/004_realtime_publication.sql
@@ -0,0 +1,55 @@
+-- pgTAP: Realtime publication + replica identity — Fase 2b prep
+-- Run with: psql -U postgres -d postgres -f supabase/tests/004_realtime_publication.sql
+--
+-- These invariants must hold for Supabase Realtime to forward Postgres Changes
+-- events for shopping_items / shopping_lists to subscribed clients with the
+-- correct row payloads. Breaking any of them silently drops events.
+
+CREATE EXTENSION IF NOT EXISTS pgtap;
+
+BEGIN;
+SELECT plan(4);
+
+-- P-01: shopping_items is in the supabase_realtime publication
+SELECT ok(
+    EXISTS (
+        SELECT 1 FROM pg_publication_tables
+        WHERE pubname = 'supabase_realtime'
+        AND   schemaname = 'public'
+        AND   tablename = 'shopping_items'
+    ),
+    'P-01: shopping_items is part of the supabase_realtime publication'
+);
+
+-- P-02: shopping_lists is in the supabase_realtime publication
+SELECT ok(
+    EXISTS (
+        SELECT 1 FROM pg_publication_tables
+        WHERE pubname = 'supabase_realtime'
+        AND   schemaname = 'public'
+        AND   tablename = 'shopping_lists'
+    ),
+    'P-02: shopping_lists is part of the supabase_realtime publication'
+);
+
+-- P-03: shopping_items has REPLICA IDENTITY FULL so UPDATE/DELETE events
+-- carry the full row (needed for list_id-based client filtering and RLS on DELETE)
+SELECT results_eq(
+    $$ SELECT relreplident::text FROM pg_class c
+       JOIN   pg_namespace n ON n.oid = c.relnamespace
+       WHERE  n.nspname = 'public' AND c.relname = 'shopping_items' $$,
+    $$ VALUES ('f') $$,
+    'P-03: shopping_items has REPLICA IDENTITY FULL'
+);
+
+-- P-04: same for shopping_lists
+SELECT results_eq(
+    $$ SELECT relreplident::text FROM pg_class c
+       JOIN   pg_namespace n ON n.oid = c.relnamespace
+       WHERE  n.nspname = 'public' AND c.relname = 'shopping_lists' $$,
+    $$ VALUES ('f') $$,
+    'P-04: shopping_lists has REPLICA IDENTITY FULL'
+);
+
+SELECT * FROM finish();
+ROLLBACK;