diff --git a/.github/workflows/test-pg-real.yml b/.github/workflows/test-pg-real.yml
new file mode 100644
index 00000000..c54ce984
--- /dev/null
+++ b/.github/workflows/test-pg-real.yml
@@ -0,0 +1,66 @@
+name: pg-real tests
+
+on: [pull_request]
+
+concurrency:
+  group: pg-real-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  pg-real:
+    runs-on: ubuntu-latest
+
+    services:
+      postgres:
+        # Supabase image ships the auth schema, auth.uid(), and the extensions
+        # (uuid-ossp, pg_cron, btree_gist, vector) this repo's migrations need.
+        # Plain postgres:15 would require manual bootstrap SQL.
+        image: supabase/postgres:15.8.1.060
+        env:
+          POSTGRES_PASSWORD: postgres
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd "pg_isready -U postgres"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 20
+
+    env:
+      DATABASE_URL: postgresql://postgres:postgres@localhost:5432/postgres
+      PGPASSWORD: postgres
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+
+      - run: npm ci
+
+      - name: Install psql client
+        run: sudo apt-get update && sudo apt-get install -y --no-install-recommends postgresql-client
+
+      - name: Bootstrap storage schema
+        # The supabase/postgres image ships a partial storage schema; the rest
+        # is provisioned by the storage-api service at runtime, which we do
+        # not run in CI. This aligns the schema with what migrations expect.
+        run: psql "$DATABASE_URL" -v ON_ERROR_STOP=1 -q -f tests/pg/bootstrap.sql
+
+      - name: Apply migrations
+        run: |
+          set -euo pipefail
+          shopt -s nullglob
+          files=(supabase/migrations/*.sql)
+          if [ ${#files[@]} -eq 0 ]; then
+            echo "No migration files found"
+            exit 1
+          fi
+          for f in "${files[@]}"; do
+            echo "Applying $f"
+            psql "$DATABASE_URL" -v ON_ERROR_STOP=1 -q -f "$f"
+          done
+
+      - run: npm run test:pg
diff --git a/CLAUDE.md b/CLAUDE.md
index 76def15f..e6b1c483 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -355,6 +355,16 @@ export async function POST(request: Request) {
 
 **Patterns**: Always mock `@/lib/supabase/server`. Use `vi.clearAllMocks()` and `eventBus.clear()` in `beforeEach`. API route tests: mock `@/lib/init` and lib functions, test auth (401), validation (400), not found (404), errors (500), happy path.
 
+### Testing database-level logic (pg-real)
+
+Mocked Supabase clients cannot exercise Postgres triggers, RPCs, or RLS policies. A parallel Vitest project `pg-real` runs against a real Postgres instance in CI (GitHub Actions `supabase/postgres:15` service container, migrations replayed from `supabase/migrations/` before the suite runs). Locally: `npm run test:pg` against a DATABASE_URL pointing at any Postgres with the Supabase `auth` schema and migrations applied.
+
+**File convention**: `*.pg.test.ts`. The `unit` project excludes this suffix; only `pg-real` picks it up.
+
+**Helpers**: `tests/pg/setup.ts` exposes `getPool()` and `withUserContext(userId, fn)` (sets `ROLE authenticated` + `request.jwt.claims` for RLS tests). `tests/pg/fixtures.ts` has `seedCompany()`, `insertDraftJournalEntry()`, `insertBalancedLines()`, etc.
+
+**When to add a pg-real test**: any PR that creates or modifies a trigger, RPC, RLS policy, or DEFERRABLE constraint must include or extend a `*.pg.test.ts` test covering the new behavior. Mock coverage is not sufficient — it will pass on a broken migration. The suite is intentionally small (compliance gate, not a rewrite of the mock suite); add only smoke-level tests for new DB-layer constructs.
+
 ---
 
 ## Database & Migrations
diff --git a/app/api/audit-trail/__tests__/audit-log.pg.test.ts b/app/api/audit-trail/__tests__/audit-log.pg.test.ts
new file mode 100644
index 00000000..bc5d6e3f
--- /dev/null
+++ b/app/api/audit-trail/__tests__/audit-log.pg.test.ts
@@ -0,0 +1,37 @@
+import { randomUUID } from 'node:crypto'
+import { describe, expect, it } from 'vitest'
+import { getPool } from '@/tests/pg/setup'
+import { insertAuthUser } from '@/tests/pg/fixtures'
+
+describe('audit-log.pg — append-only immutability', () => {
+  it('rejects UPDATE on audit_log rows', async () => {
+    const userId = await insertAuthUser()
+    const auditId = randomUUID()
+    await getPool().query(
+      `INSERT INTO public.audit_log (id, user_id, action, description)
+       VALUES ($1, $2, 'SECURITY_EVENT', 'pg-real seed')`,
+      [auditId, userId],
+    )
+
+    await expect(
+      getPool().query(
+        `UPDATE public.audit_log SET description = 'tampered' WHERE id = $1`,
+        [auditId],
+      ),
+    ).rejects.toThrow(/cannot be modified or deleted/i)
+  })
+
+  it('rejects DELETE on audit_log rows', async () => {
+    const userId = await insertAuthUser()
+    const auditId = randomUUID()
+    await getPool().query(
+      `INSERT INTO public.audit_log (id, user_id, action, description)
+       VALUES ($1, $2, 'SECURITY_EVENT', 'pg-real seed')`,
+      [auditId, userId],
+    )
+
+    await expect(
+      getPool().query(`DELETE FROM public.audit_log WHERE id = $1`, [auditId]),
+    ).rejects.toThrow(/cannot be modified or deleted/i)
+  })
+})
diff --git a/lib/bookkeeping/__tests__/engine.pg.test.ts b/lib/bookkeeping/__tests__/engine.pg.test.ts
new file mode 100644
index 00000000..b5de22b5
--- /dev/null
+++ b/lib/bookkeeping/__tests__/engine.pg.test.ts
@@ -0,0 +1,72 @@
+import { describe, expect, it } from 'vitest'
+import { getPool } from '@/tests/pg/setup'
+import {
+  insertBalancedLines,
+  insertDraftJournalEntry,
+  seedCompany,
+} from '@/tests/pg/fixtures'
+
+describe('engine.pg — triggers & RPCs that mocks cannot catch', () => {
+  it('rejects INSERT into journal_entries when the fiscal period is closed', async () => {
+    const { userId, companyId, fiscalPeriodId } = await seedCompany({ isClosed: true })
+
+    await expect(
+      insertDraftJournalEntry({ userId, companyId, fiscalPeriodId }),
+    ).rejects.toThrow(/locked\/closed fiscal period/i)
+  })
+
+  it('commit_journal_entry assigns sequential voucher numbers under concurrency', async () => {
+    const { userId, companyId, fiscalPeriodId } = await seedCompany()
+
+    const entryA = await insertDraftJournalEntry({ userId, companyId, fiscalPeriodId })
+    const entryB = await insertDraftJournalEntry({ userId, companyId, fiscalPeriodId })
+    await insertBalancedLines(entryA)
+    await insertBalancedLines(entryB)
+
+    // Two dedicated clients so the row-level lock on voucher_sequences is
+    // actually exercised — not just a single connection serialising calls.
+    const clientA = await getPool().connect()
+    const clientB = await getPool().connect()
+    try {
+      const [resA, resB] = await Promise.all([
+        clientA.query<{ voucher_number: number }>(
+          `SELECT voucher_number FROM public.commit_journal_entry($1::uuid, $2::uuid)`,
+          [companyId, entryA],
+        ),
+        clientB.query<{ voucher_number: number }>(
+          `SELECT voucher_number FROM public.commit_journal_entry($1::uuid, $2::uuid)`,
+          [companyId, entryB],
+        ),
+      ])
+      const numbers = [resA.rows[0]!.voucher_number, resB.rows[0]!.voucher_number].sort(
+        (a, b) => a - b,
+      )
+      expect(numbers).toEqual([1, 2])
+    } finally {
+      clientA.release()
+      clientB.release()
+    }
+  })
+
+  it('rejects UPDATE to a posted journal entry (committed immutability)', async () => {
+    const { userId, companyId, fiscalPeriodId } = await seedCompany()
+
+    // Bypass commit_journal_entry by inserting directly as 'posted'. The
+    // immutability trigger fires on UPDATE, not INSERT, so this is legal
+    // setup on the superuser connection.
+    const entryId = await insertDraftJournalEntry({
+      userId,
+      companyId,
+      fiscalPeriodId,
+      status: 'posted',
+      voucherNumber: 1,
+    })
+
+    await expect(
+      getPool().query(
+        `UPDATE public.journal_entries SET description = 'tampered' WHERE id = $1`,
+        [entryId],
+      ),
+    ).rejects.toThrow(/Cannot modify a posted journal entry/i)
+  })
+})
diff --git a/lib/supabase/__tests__/rls.pg.test.ts b/lib/supabase/__tests__/rls.pg.test.ts
new file mode 100644
index 00000000..743c2e27
--- /dev/null
+++ b/lib/supabase/__tests__/rls.pg.test.ts
@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest'
+import { insertDraftJournalEntry, seedCompany } from '@/tests/pg/fixtures'
+import { withUserContext } from '@/tests/pg/setup'
+
+describe('rls.pg — tenant isolation on journal_entries', () => {
+  it('returns only the authenticated user\'s company rows', async () => {
+    const a = await seedCompany()
+    const b = await seedCompany()
+
+    // One entry in each tenant.
+    const entryA = await insertDraftJournalEntry({
+      userId: a.userId,
+      companyId: a.companyId,
+      fiscalPeriodId: a.fiscalPeriodId,
+    })
+    await insertDraftJournalEntry({
+      userId: b.userId,
+      companyId: b.companyId,
+      fiscalPeriodId: b.fiscalPeriodId,
+    })
+
+    // user A should see exactly entryA and nothing from tenant B.
+    const rows = await withUserContext(a.userId, async (client) => {
+      const res = await client.query<{ id: string; company_id: string }>(
+        `SELECT id, company_id FROM public.journal_entries`,
+      )
+      return res.rows
+    })
+
+    expect(rows).toHaveLength(1)
+    expect(rows[0]!.id).toBe(entryA)
+    expect(rows[0]!.company_id).toBe(a.companyId)
+  })
+})
diff --git a/package-lock.json b/package-lock.json
index b83c9d9d..f8496b7b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -59,6 +59,7 @@
       "devDependencies": {
         "@tailwindcss/postcss": "^4",
         "@types/node": "^20",
+        "@types/pg": "^8.20.0",
         "@types/react": "^19",
         "@types/react-dom": "^19",
         "@types/sharp": "^0.31.1",
@@ -66,6 +67,7 @@
         "dotenv": "^17.2.3",
         "eslint": "^9",
         "eslint-config-next": "16.1.5",
+        "pg": "^8.20.0",
         "tailwindcss": "^4",
         "typescript": "^5",
         "vitest": "^4.0.18"
@@ -5548,6 +5550,18 @@
         "undici-types": "~6.21.0"
       }
     },
+    "node_modules/@types/pg": {
+      "version": "8.20.0",
+      "resolved": "https://registry.npmjs.org/@types/pg/-/pg-8.20.0.tgz",
+      "integrity": "sha512-bEPFOaMAHTEP1EzpvHTbmwR8UsFyHSKsRisLIHVMXnpNefSbGA1bD6CVy+qKjGSqmZqNqBDV2azOBo8TgkcVow==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/node": "*",
+        "pg-protocol": "*",
+        "pg-types": "^2.2.0"
+      }
+    },
     "node_modules/@types/phoenix": {
       "version": "1.6.7",
       "resolved": "https://registry.npmjs.org/@types/phoenix/-/phoenix-1.6.7.tgz",
@@ -11593,6 +11607,103 @@
         "url": "https://ko-fi.com/killymxi"
       }
     },
+    "node_modules/pg": {
+      "version": "8.20.0",
+      "resolved": "https://registry.npmjs.org/pg/-/pg-8.20.0.tgz",
+      "integrity": "sha512-ldhMxz2r8fl/6QkXnBD3CR9/xg694oT6DZQ2s6c/RI28OjtSOpxnPrUCGOBJ46RCUxcWdx3p6kw/xnDHjKvaRA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "pg-connection-string": "^2.12.0",
+        "pg-pool": "^3.13.0",
+        "pg-protocol": "^1.13.0",
+        "pg-types": "2.2.0",
+        "pgpass": "1.0.5"
+      },
+      "engines": {
+        "node": ">= 16.0.0"
+      },
+      "optionalDependencies": {
+        "pg-cloudflare": "^1.3.0"
+      },
+      "peerDependencies": {
+        "pg-native": ">=3.0.1"
+      },
+      "peerDependenciesMeta": {
+        "pg-native": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/pg-cloudflare": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/pg-cloudflare/-/pg-cloudflare-1.3.0.tgz",
+      "integrity": "sha512-6lswVVSztmHiRtD6I8hw4qP/nDm1EJbKMRhf3HCYaqud7frGysPv7FYJ5noZQdhQtN2xJnimfMtvQq21pdbzyQ==",
+      "dev": true,
+      "license": "MIT",
+      "optional": true
+    },
+    "node_modules/pg-connection-string": {
+      "version": "2.12.0",
+      "resolved": "https://registry.npmjs.org/pg-connection-string/-/pg-connection-string-2.12.0.tgz",
+      "integrity": "sha512-U7qg+bpswf3Cs5xLzRqbXbQl85ng0mfSV/J0nnA31MCLgvEaAo7CIhmeyrmJpOr7o+zm0rXK+hNnT5l9RHkCkQ==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/pg-int8": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/pg-int8/-/pg-int8-1.0.1.tgz",
+      "integrity": "sha512-WCtabS6t3c8SkpDBUlb1kjOs7l66xsGdKpIPZsg4wR+B3+u9UAum2odSsF9tnvxg80h4ZxLWMy4pRjOsFIqQpw==",
+      "dev": true,
+      "license": "ISC",
+      "engines": {
+        "node": ">=4.0.0"
+      }
+    },
+    "node_modules/pg-pool": {
+      "version": "3.13.0",
+      "resolved": "https://registry.npmjs.org/pg-pool/-/pg-pool-3.13.0.tgz",
+      "integrity": "sha512-gB+R+Xud1gLFuRD/QgOIgGOBE2KCQPaPwkzBBGC9oG69pHTkhQeIuejVIk3/cnDyX39av2AxomQiyPT13WKHQA==",
+      "dev": true,
+      "license": "MIT",
+      "peerDependencies": {
+        "pg": ">=8.0"
+      }
+    },
+    "node_modules/pg-protocol": {
+      "version": "1.13.0",
+      "resolved": "https://registry.npmjs.org/pg-protocol/-/pg-protocol-1.13.0.tgz",
+      "integrity": "sha512-zzdvXfS6v89r6v7OcFCHfHlyG/wvry1ALxZo4LqgUoy7W9xhBDMaqOuMiF3qEV45VqsN6rdlcehHrfDtlCPc8w==",
+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/pg-types": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/pg-types/-/pg-types-2.2.0.tgz",
+      "integrity": "sha512-qTAAlrEsl8s4OiEQY69wDvcMIdQN6wdz5ojQiOy6YRMuynxenON0O5oCpJI6lshc6scgAY8qvJ2On/p+CXY0GA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "pg-int8": "1.0.1",
+        "postgres-array": "~2.0.0",
+        "postgres-bytea": "~1.0.0",
+        "postgres-date": "~1.0.4",
+        "postgres-interval": "^1.1.0"
+      },
+      "engines": {
+        "node": ">=4"
+      }
+    },
+    "node_modules/pgpass": {
+      "version": "1.0.5",
+      "resolved": "https://registry.npmjs.org/pgpass/-/pgpass-1.0.5.tgz",
+      "integrity": "sha512-FdW9r/jQZhSeohs1Z3sI1yxFQNFvMcnmfuj4WBMUTxOrAyLMaTcE1aAMBiTlbMNaXvBCQuVi0R7hd8udDSP7ug==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "split2": "^4.1.0"
+      }
+    },
     "node_modules/picocolors": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/picocolors/-/picocolors-1.1.1.tgz",
@@ -11679,6 +11790,49 @@
       "integrity": "sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==",
       "license": "MIT"
     },
+    "node_modules/postgres-array": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/postgres-array/-/postgres-array-2.0.0.tgz",
+      "integrity": "sha512-VpZrUqU5A69eQyW2c5CA1jtLecCsN2U/bD6VilrFDWq5+5UIEVO7nazS3TEcHf1zuPYO/sqGvUvW62g86RXZuA==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=4"
+      }
+    },
+    "node_modules/postgres-bytea": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/postgres-bytea/-/postgres-bytea-1.0.1.tgz",
+      "integrity": "sha512-5+5HqXnsZPE65IJZSMkZtURARZelel2oXUEO8rH83VS/hxH5vv1uHquPg5wZs8yMAfdv971IU+kcPUczi7NVBQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
+    "node_modules/postgres-date": {
+      "version": "1.0.7",
+      "resolved": "https://registry.npmjs.org/postgres-date/-/postgres-date-1.0.7.tgz",
+      "integrity": "sha512-suDmjLVQg78nMK2UZ454hAG+OAW+HQPZ6n++TNDUX+L0+uUlLywnoxJKDou51Zm+zTCjrCl0Nq6J9C5hP9vK/Q==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
+    "node_modules/postgres-interval": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/postgres-interval/-/postgres-interval-1.2.0.tgz",
+      "integrity": "sha512-9ZhXKM/rw350N1ovuWHbGxnGh/SNJ4cnxHiM0rxE4VN41wsg8P8zWn9hv/buK00RP4WvlOyr/RBDiptyxVbkZQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "xtend": "^4.0.0"
+      },
+      "engines": {
+        "node": ">=0.10.0"
+      }
+    },
     "node_modules/prelude-ls": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.2.1.tgz",
@@ -12668,6 +12822,16 @@
         "url": "https://github.com/sponsors/wooorm"
       }
     },
+    "node_modules/split2": {
+      "version": "4.2.0",
+      "resolved": "https://registry.npmjs.org/split2/-/split2-4.2.0.tgz",
+      "integrity": "sha512-UcjcJOWknrNkF6PLX83qcHM6KHgVKNkV62Y8a5uYDVv9ydGQVwAHMKqHdJje1VTWpljG0WYpCDhrCdAOYH4TWg==",
+      "dev": true,
+      "license": "ISC",
+      "engines": {
+        "node": ">= 10.x"
+      }
+    },
     "node_modules/ssf": {
       "version": "0.11.2",
       "resolved": "https://registry.npmjs.org/ssf/-/ssf-0.11.2.tgz",
@@ -14157,6 +14321,16 @@
         "node": ">=0.8"
       }
     },
+    "node_modules/xtend": {
+      "version": "4.0.2",
+      "resolved": "https://registry.npmjs.org/xtend/-/xtend-4.0.2.tgz",
+      "integrity": "sha512-LKYU1iAXJXUgAXn9URjiu+MWhyUXHsvfp7mcuYm9dSUKK0/CjtrUwFAxD82/mCWbtLsGjFIad0wIsod4zrTAEQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=0.4"
+      }
+    },
     "node_modules/y18n": {
       "version": "4.0.3",
       "resolved": "https://registry.npmjs.org/y18n/-/y18n-4.0.3.tgz",
diff --git a/package.json b/package.json
index 6712f19d..3372e0c2 100644
--- a/package.json
+++ b/package.json
@@ -11,7 +11,8 @@
     "build": "next build",
     "start": "next start",
     "lint": "eslint",
-    "test": "vitest run"
+    "test": "vitest run --project unit",
+    "test:pg": "vitest run --project pg-real"
   },
   "dependencies": {
     "@aws-sdk/client-bedrock-runtime": "^3.1022.0",
@@ -64,6 +65,7 @@
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
     "@types/node": "^20",
+    "@types/pg": "^8.20.0",
     "@types/react": "^19",
     "@types/react-dom": "^19",
     "@types/sharp": "^0.31.1",
@@ -71,6 +73,7 @@
     "dotenv": "^17.2.3",
     "eslint": "^9",
     "eslint-config-next": "16.1.5",
+    "pg": "^8.20.0",
     "tailwindcss": "^4",
     "typescript": "^5",
     "vitest": "^4.0.18"
diff --git a/tests/pg/bootstrap.sql b/tests/pg/bootstrap.sql
new file mode 100644
index 00000000..cbbfa480
--- /dev/null
+++ b/tests/pg/bootstrap.sql
@@ -0,0 +1,48 @@
+-- pg-real CI bootstrap.
+--
+-- The Supabase Postgres image ships a partial `storage` schema; the remaining
+-- columns and functions are provisioned at runtime by the storage-api
+-- service, which we do not run in CI. This bootstrap aligns the schema with
+-- what our migrations expect so the replay loop succeeds. It is idempotent
+-- and safe to run against a freshly-initialised container.
+
+CREATE SCHEMA IF NOT EXISTS storage;
+
+CREATE TABLE IF NOT EXISTS storage.buckets (
+  id          text PRIMARY KEY,
+  name        text NOT NULL,
+  owner       uuid,
+  created_at  timestamptz DEFAULT now(),
+  updated_at  timestamptz DEFAULT now()
+);
+
+ALTER TABLE storage.buckets
+  ADD COLUMN IF NOT EXISTS public              boolean DEFAULT false,
+  ADD COLUMN IF NOT EXISTS file_size_limit     bigint,
+  ADD COLUMN IF NOT EXISTS allowed_mime_types  text[];
+
+CREATE TABLE IF NOT EXISTS storage.objects (
+  id                uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  bucket_id         text REFERENCES storage.buckets(id) ON DELETE CASCADE,
+  name              text,
+  owner             uuid,
+  created_at        timestamptz DEFAULT now(),
+  updated_at        timestamptz DEFAULT now(),
+  last_accessed_at  timestamptz DEFAULT now(),
+  metadata          jsonb,
+  version           text,
+  owner_id          text
+);
+
+ALTER TABLE storage.objects ENABLE ROW LEVEL SECURITY;
+
+-- storage.foldername(): splits a slash-delimited object name into segments.
+-- Migrations use `(storage.foldername(name))[n]` to derive tenant scoping
+-- from the object path.
+CREATE OR REPLACE FUNCTION storage.foldername(name text)
+  RETURNS text[]
+  LANGUAGE sql
+  IMMUTABLE
+AS $$
+  SELECT string_to_array(name, '/');
+$$;
diff --git a/tests/pg/fixtures.ts b/tests/pg/fixtures.ts
new file mode 100644
index 00000000..bdff2e0f
--- /dev/null
+++ b/tests/pg/fixtures.ts
@@ -0,0 +1,139 @@
+import { randomUUID } from 'node:crypto'
+import { getPool } from './setup'
+
+// Minimal fixture inserters for pg-real tests. All inserts go through the
+// pool (superuser `postgres`), which bypasses RLS — that is intentional for
+// seeding. RLS is exercised only where a test explicitly opens a user
+// context via withUserContext().
+
+export async function insertAuthUser(id: string = randomUUID()): Promise<string> {
+  // auth.users has many columns but most default. We only need `id` and a
+  // non-conflicting `email`. Everything else (role, aud, timestamps, etc.)
+  // has a default or is nullable in the supabase/postgres image.
+  await getPool().query(
+    `INSERT INTO auth.users (id, email, instance_id)
+     VALUES ($1, $2, '00000000-0000-0000-0000-000000000000'::uuid)`,
+    [id, `pg-real-${id}@test.invalid`],
+  )
+  return id
+}
+
+export async function insertCompany(params: {
+  createdBy: string
+  name?: string
+  entityType?: 'enskild_firma' | 'aktiebolag'
+}): Promise<string> {
+  const id = randomUUID()
+  await getPool().query(
+    `INSERT INTO public.companies (id, name, entity_type, created_by)
+     VALUES ($1, $2, $3, $4)`,
+    [id, params.name ?? 'Test AB', params.entityType ?? 'aktiebolag', params.createdBy],
+  )
+  return id
+}
+
+export async function insertCompanyMember(params: {
+  companyId: string
+  userId: string
+  role?: 'owner' | 'admin' | 'member' | 'viewer'
+}): Promise<void> {
+  await getPool().query(
+    `INSERT INTO public.company_members (company_id, user_id, role)
+     VALUES ($1, $2, $3)`,
+    [params.companyId, params.userId, params.role ?? 'owner'],
+  )
+}
+
+export async function insertFiscalPeriod(params: {
+  userId: string
+  companyId: string
+  isClosed?: boolean
+  periodStart?: string
+  periodEnd?: string
+  name?: string
+}): Promise<string> {
+  const id = randomUUID()
+  await getPool().query(
+    `INSERT INTO public.fiscal_periods
+       (id, user_id, company_id, name, period_start, period_end, is_closed, closed_at)
+     VALUES ($1, $2, $3, $4, $5, $6, $7, $8)`,
+    [
+      id,
+      params.userId,
+      params.companyId,
+      params.name ?? '2026',
+      params.periodStart ?? '2026-01-01',
+      params.periodEnd ?? '2026-12-31',
+      params.isClosed ?? false,
+      params.isClosed ? new Date() : null,
+    ],
+  )
+  return id
+}
+
+// One-call helper: creates user + company + owner membership + open fiscal
+// period. Returns the IDs tests need.
+export async function seedCompany(overrides: { isClosed?: boolean } = {}): Promise<{
+  userId: string
+  companyId: string
+  fiscalPeriodId: string
+}> {
+  const userId = await insertAuthUser()
+  const companyId = await insertCompany({ createdBy: userId })
+  await insertCompanyMember({ companyId, userId, role: 'owner' })
+  const fiscalPeriodId = await insertFiscalPeriod({
+    userId,
+    companyId,
+    isClosed: overrides.isClosed,
+  })
+  return { userId, companyId, fiscalPeriodId }
+}
+
+// Insert a draft journal entry and return its id. Uses a placeholder
+// voucher_number=0 which commit_journal_entry() will overwrite on commit.
+export async function insertDraftJournalEntry(params: {
+  userId: string
+  companyId: string
+  fiscalPeriodId: string
+  entryDate?: string
+  description?: string
+  voucherSeries?: string
+  status?: 'draft' | 'posted'
+  voucherNumber?: number
+}): Promise<string> {
+  const id = randomUUID()
+  await getPool().query(
+    `INSERT INTO public.journal_entries
+       (id, user_id, company_id, fiscal_period_id, voucher_number, voucher_series,
+        entry_date, description, source_type, status)
+     VALUES ($1, $2, $3, $4, $5, $6, $7, $8, 'manual', $9)`,
+    [
+      id,
+      params.userId,
+      params.companyId,
+      params.fiscalPeriodId,
+      params.voucherNumber ?? 0,
+      params.voucherSeries ?? 'A',
+      params.entryDate ?? '2026-06-01',
+      params.description ?? 'Test entry',
+      params.status ?? 'draft',
+    ],
+  )
+  return id
+}
+
+// Insert a balanced pair of journal entry lines (1 debit row + 1 credit row
+// at the given amount). Needed before commit_journal_entry() because the
+// balance constraint trigger fires on draft→posted.
+export async function insertBalancedLines(
+  journalEntryId: string,
+  amount: number = 1000,
+): Promise<void> {
+  await getPool().query(
+    `INSERT INTO public.journal_entry_lines
+       (journal_entry_id, account_number, debit_amount, credit_amount)
+     VALUES ($1, '1930', $2, 0),
+            ($1, '3001', 0, $2)`,
+    [journalEntryId, amount],
+  )
+}
diff --git a/tests/pg/setup.ts b/tests/pg/setup.ts
new file mode 100644
index 00000000..3dba5468
--- /dev/null
+++ b/tests/pg/setup.ts
@@ -0,0 +1,116 @@
+import { Pool, type PoolClient } from 'pg'
+import { afterAll, beforeAll } from 'vitest'
+
+// Shared pool for the pg-real project. DATABASE_URL must point at a Postgres
+// instance that already has every migration from supabase/migrations/ applied
+// and that includes the Supabase `auth` schema (supabase/postgres image).
+const databaseUrl =
+  process.env.DATABASE_URL ?? 'postgresql://postgres:postgres@localhost:5432/postgres'
+
+let pool: Pool | null = null
+
+export function getPool(): Pool {
+  if (!pool) {
+    pool = new Pool({ connectionString: databaseUrl, max: 8 })
+  }
+  return pool
+}
+
+// Acquire a fresh client. Caller must always .release().
+export async function getClient(): Promise<PoolClient> {
+  return getPool().connect()
+}
+
+// Run `fn` inside a role/JWT context that auth.uid() / user_company_ids() will
+// observe. Uses SET LOCAL inside a transaction so the role reverts on commit
+// or rollback. Always rolls back so the test's writes do not persist — tests
+// that need to seed data must do that on the superuser connection first.
+export async function withUserContext<T>(
+  userId: string,
+  fn: (client: PoolClient) => Promise<T>,
+): Promise<T> {
+  const client = await getClient()
+  try {
+    await client.query('BEGIN')
+    // Set JWT claims BEFORE switching role: non-superuser set_config on a
+    // namespaced GUC is fine, but keeping order explicit avoids surprises.
+    // Set both the whole-claims object and the individual `sub` claim —
+    // different versions of Supabase's auth.uid() read one or the other.
+    await client.query(`SELECT set_config('request.jwt.claims', $1, true)`, [
+      JSON.stringify({ sub: userId, role: 'authenticated' }),
+    ])
+    await client.query(`SELECT set_config('request.jwt.claim.sub', $1, true)`, [userId])
+    await client.query(`SET LOCAL ROLE authenticated`)
+    // Fail loudly and early if the JWT context did not land the way we
+    // expect — otherwise RLS policies return empty and the real test
+    // failure points at an unrelated assertion.
+    const authCheck = await client.query<{ uid: string | null }>(
+      `SELECT auth.uid()::text AS uid`,
+    )
+    if (authCheck.rows[0]?.uid !== userId) {
+      throw new Error(
+        `withUserContext: auth.uid() resolved to ${authCheck.rows[0]?.uid ?? 'NULL'}, ` +
+          `expected ${userId}. Check request.jwt.claims setup.`,
+      )
+    }
+    const result = await fn(client)
+    await client.query('ROLLBACK')
+    return result
+  } catch (err) {
+    await client.query('ROLLBACK').catch(() => {})
+    throw err
+  } finally {
+    client.release()
+  }
+}
+
+// Schema sanity: fail loud if migrations did not apply, rather than letting
+// every test fail with a cryptic "relation does not exist". Runs once per
+// test file (vitest invokes setupFiles per worker).
+beforeAll(async () => {
+  const client = await getClient()
+  try {
+    const result = await client.query<{ name: string; kind: 'trigger' | 'function' | 'table' }>(`
+      SELECT 'trigger'::text AS kind, tgname AS name FROM pg_trigger
+        WHERE tgname IN ('enforce_period_lock', 'audit_log_no_update')
+      UNION ALL
+      SELECT 'function'::text, proname FROM pg_proc
+        WHERE proname IN ('commit_journal_entry', 'user_company_ids', 'audit_log_immutable')
+      UNION ALL
+      SELECT 'table'::text, tablename FROM pg_tables
+        WHERE schemaname = 'public'
+          AND tablename IN ('journal_entries', 'companies', 'company_members',
+                            'fiscal_periods', 'audit_log', 'voucher_sequences')
+    `)
+    const found = new Set(result.rows.map((r) => `${r.kind}:${r.name}`))
+    const required = [
+      'trigger:enforce_period_lock',
+      'trigger:audit_log_no_update',
+      'function:commit_journal_entry',
+      'function:user_company_ids',
+      'function:audit_log_immutable',
+      'table:journal_entries',
+      'table:companies',
+      'table:company_members',
+      'table:fiscal_periods',
+      'table:audit_log',
+      'table:voucher_sequences',
+    ]
+    const missing = required.filter((r) => !found.has(r))
+    if (missing.length > 0) {
+      throw new Error(
+        `pg-real schema sanity check failed. Missing: ${missing.join(', ')}. ` +
+          `Did every migration in supabase/migrations/ apply cleanly to ${databaseUrl}?`,
+      )
+    }
+  } finally {
+    client.release()
+  }
+})
+
+afterAll(async () => {
+  if (pool) {
+    await pool.end()
+    pool = null
+  }
+})
diff --git a/vitest.config.ts b/vitest.config.ts
index 6accecdb..949970ba 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -1,14 +1,46 @@
 import { defineConfig } from 'vitest/config'
 import path from 'path'
 
+const alias = { '@': path.resolve(__dirname, '.') }
+
+const unitProject = {
+  resolve: { alias },
+  test: {
+    name: 'unit',
+    globals: true,
+    environment: 'node' as const,
+    include: ['**/*.test.ts'],
+    exclude: ['**/node_modules/**', '**/*.pg.test.ts'],
+  },
+}
+
+const pgRealProject = {
+  resolve: { alias },
+  test: {
+    name: 'pg-real',
+    globals: true,
+    environment: 'node' as const,
+    include: ['**/*.pg.test.ts'],
+    exclude: ['**/node_modules/**'],
+    setupFiles: ['tests/pg/setup.ts'],
+    // One-connection-at-a-time to avoid cross-file DB contention.
+    fileParallelism: false,
+    testTimeout: 15000,
+  },
+}
+
+// Only register the pg-real project when DATABASE_URL is set. Local devs
+// running a bare `vitest run` would otherwise hit the schema sanity check
+// against a non-existent DB. `npm run test:pg` is the opt-in entry point.
+const projects = process.env.DATABASE_URL
+  ? [unitProject, pgRealProject]
+  : [unitProject]
+
 export default defineConfig({
+  resolve: { alias },
   test: {
     globals: true,
     environment: 'node',
-  },
-  resolve: {
-    alias: {
-      '@': path.resolve(__dirname, '.'),
-    },
+    projects,
   },
 })