diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index 357f4c8d1..5877a17f0 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -10,6 +10,22 @@ jobs:
   pr:
     name: PR
     runs-on: ubuntu-latest
+    services:
+      postgres:
+        image: postgres:17
+        env:
+          POSTGRES_USER: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_DB: builder_schema_verifier_tests
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+    env:
+      BUILDER_SCHEMA_TEST_DATABASE_URL: postgres://postgres:postgres@localhost:5432/builder_schema_verifier_tests
     steps:
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
diff --git a/scripts/verify-builder-schema.ts b/scripts/verify-builder-schema.ts
index d4005020f..8aa7259a3 100644
--- a/scripts/verify-builder-schema.ts
+++ b/scripts/verify-builder-schema.ts
@@ -56,15 +56,22 @@ const journalUrl = new URL(
 const journal = migrationJournalSchema.parse(
   JSON.parse(await readFile(journalUrl, 'utf8')),
 )
-const latestMigration = journal.entries.reduce((_, entry) => entry)
+const builderMigration = journal.entries.find(
+  (entry) => entry.tag === '0000_builder_durability',
+)
+if (!builderMigration) {
+  throw new Error(
+    'Builder migration 0000_builder_durability is missing from the journal',
+  )
+}
 const migrationSql = await readFile(
-  new URL(`../drizzle/migrations/${latestMigration.tag}.sql`, import.meta.url),
+  new URL(`../drizzle/migrations/${builderMigration.tag}.sql`, import.meta.url),
   'utf8',
 )
 const expectedMigrationHash = createHash('sha256')
   .update(migrationSql)
   .digest('hex')
-const expectedMigrationVersion = String(latestMigration.when)
+const expectedMigrationVersion = String(builderMigration.when)
 
 const databaseUrl = process.env.DATABASE_URL
 if (!databaseUrl) {
@@ -95,7 +102,8 @@ try {
   const [appliedMigration] = await sql<{ hash: string; version: string }[]>`
     select hash, created_at::text as version
     from drizzle.__drizzle_migrations
-    order by created_at desc, id desc
+    where created_at = ${expectedMigrationVersion}
+    order by id desc
     limit 1
   `
 
@@ -104,7 +112,7 @@ try {
     appliedMigration.version !== expectedMigrationVersion
   ) {
     throw new Error(
-      `Builder database migration mismatch: expected ${latestMigration.tag} (${expectedMigrationVersion}, ${expectedMigrationHash})`,
+      `Builder database migration mismatch: expected ${builderMigration.tag} (${expectedMigrationVersion}, ${expectedMigrationHash})`,
     )
   }
 
@@ -155,7 +163,7 @@ try {
   }
 
   console.info(
-    `Builder database schema matches ${latestMigration.tag} (${expectedMigrationHash})`,
+    `Builder database schema matches ${builderMigration.tag} (${expectedMigrationHash})`,
   )
 } finally {
   await sql.end()
diff --git a/tests/builder-schema-verifier.test.ts b/tests/builder-schema-verifier.test.ts
new file mode 100644
index 000000000..48a940b22
--- /dev/null
+++ b/tests/builder-schema-verifier.test.ts
@@ -0,0 +1,165 @@
+import assert from 'node:assert/strict'
+import { execFile } from 'node:child_process'
+import { createHash } from 'node:crypto'
+import { readFile } from 'node:fs/promises'
+import test from 'node:test'
+import { promisify } from 'node:util'
+import postgres from 'postgres'
+import { assertBuilderTestDatabaseUrl } from './helpers/builder-test-database'
+import {
+  BUILDER_MESSAGE_ROLES,
+  BUILDER_PROJECT_EVENT_TYPES,
+  BUILDER_RUN_STATUSES,
+} from '../src/db/types'
+
+const execute = promisify(execFile)
+const databaseUrl = process.env.BUILDER_SCHEMA_TEST_DATABASE_URL
+const tables = [
+  'builder_project_legacy_imports',
+  'builder_project_snapshots',
+  'builder_project_snapshot_reservations',
+  'builder_projects',
+  'builder_project_usage',
+  'builder_project_tombstones',
+  'builder_project_mutation_receipts',
+  'builder_project_revisions',
+  'builder_project_threads',
+  'builder_project_runs',
+  'builder_project_messages',
+  'builder_project_events',
+]
+const enums = [
+  ['builder_message_role', BUILDER_MESSAGE_ROLES],
+  ['builder_run_status', BUILDER_RUN_STATUSES],
+  ['builder_project_event_type', BUILDER_PROJECT_EVENT_TYPES],
+] as const
+
+test(
+  'Builder schema verifier accepts compatible later migrations and rejects invalid schemas',
+  { skip: databaseUrl ? false : 'Set BUILDER_SCHEMA_TEST_DATABASE_URL' },
+  async (t) => {
+    assert.ok(databaseUrl)
+    // This suite resets schemas; never accept a production database name.
+    assertBuilderTestDatabaseUrl(databaseUrl)
+    const sql = postgres(databaseUrl, { max: 1, onnotice: () => {} })
+    const journal = JSON.parse(
+      await readFile(
+        new URL('../drizzle/migrations/meta/_journal.json', import.meta.url),
+        'utf8',
+      ),
+    )
+    const migration = journal.entries.find(
+      (entry: { tag: string }) => entry.tag === '0000_builder_durability',
+    )
+    assert.ok(migration, 'Builder migration must exist in the journal')
+    const hash = createHash('sha256')
+      .update(
+        await readFile(
+          new URL(
+            `../drizzle/migrations/${migration.tag}.sql`,
+            import.meta.url,
+          ),
+        ),
+      )
+      .digest('hex')
+
+    async function reset() {
+      await sql`drop schema if exists drizzle cascade`
+      await sql`drop schema public cascade`
+      await sql`create schema public`
+      await sql`create schema drizzle`
+      await sql`create table drizzle.__drizzle_migrations (id serial primary key, hash text not null, created_at bigint not null)`
+      await sql`insert into drizzle.__drizzle_migrations (hash, created_at) values (${hash}, ${migration.when})`
+      for (const table of tables) {
+        await sql`create table ${sql(table)} (id text primary key)`
+      }
+      for (const [name, labels] of enums) {
+        // Enum labels cannot be bind parameters in CREATE TYPE.
+        await sql.unsafe(
+          `create type ${name} as enum (${labels.map((label) => `'${label}'`).join(', ')})`,
+        )
+      }
+    }
+
+    async function verify(error?: RegExp) {
+      const result = execute(
+        process.execPath,
+        ['--import', 'tsx', 'scripts/verify-builder-schema.ts'],
+        {
+          cwd: new URL('../', import.meta.url),
+          env: { ...process.env, DATABASE_URL: databaseUrl },
+          timeout: 30_000,
+        },
+      )
+      if (error) {
+        await assert.rejects(result, error)
+      } else {
+        assert.match((await result).stdout, /Builder database schema matches/)
+      }
+    }
+
+    try {
+      const [target] = await sql<
+        { database: string }[]
+      >`select current_database() as database`
+      assert.equal(target?.database, 'builder_schema_verifier_tests')
+      await t.test(
+        'accepts the required migration as the latest entry',
+        async () => {
+          await reset()
+          await verify()
+        },
+      )
+      await t.test('accepts a newer unrelated migration', async () => {
+        await reset()
+        await sql`insert into drizzle.__drizzle_migrations (hash, created_at) values ('later-chat-migration', ${migration.when + 1})`
+        await verify()
+      })
+      await t.test('rejects missing migration history', async () => {
+        await reset()
+        await sql`drop schema drizzle cascade`
+        await verify(/Drizzle migration history is missing/)
+      })
+      await t.test(
+        'rejects a newer entry without the required migration',
+        async () => {
+          await reset()
+          await sql`update drizzle.__drizzle_migrations set created_at = ${migration.when + 1}`
+          await verify(/Builder database migration mismatch/)
+        },
+      )
+      await t.test('rejects a mismatched migration hash', async () => {
+        await reset()
+        await sql`update drizzle.__drizzle_migrations set hash = 'wrong-hash'`
+        await verify(/Builder database migration mismatch/)
+      })
+      await t.test(
+        'rejects a missing required table after a later migration',
+        async () => {
+          await reset()
+          await sql`insert into drizzle.__drizzle_migrations (hash, created_at) values ('later-chat-migration', ${migration.when + 1})`
+          await sql`drop table builder_projects`
+          await verify(/invalid or missing table builder_projects/)
+        },
+      )
+      await t.test('rejects a view in place of a required table', async () => {
+        await reset()
+        await sql`drop table builder_projects`
+        await sql`create view builder_projects as select 'project'::text as id`
+        await verify(/invalid or missing table builder_projects/)
+      })
+      await t.test('rejects a missing required enum', async () => {
+        await reset()
+        await sql`drop type builder_message_role`
+        await verify(/invalid or missing enum builder_message_role/)
+      })
+      await t.test('rejects incompatible enum labels', async () => {
+        await reset()
+        await sql`alter type builder_message_role add value 'unexpected'`
+        await verify(/invalid or missing enum builder_message_role/)
+      })
+    } finally {
+      await sql.end()
+    }
+  },
+)
diff --git a/tests/builder-test-database.test.ts b/tests/builder-test-database.test.ts
new file mode 100644
index 000000000..06e09c1b7
--- /dev/null
+++ b/tests/builder-test-database.test.ts
@@ -0,0 +1,19 @@
+import assert from 'node:assert/strict'
+import test from 'node:test'
+import { assertBuilderTestDatabaseUrl } from './helpers/builder-test-database'
+
+test('Builder destructive fixture only accepts the dedicated local database without overrides', () => {
+  assert.doesNotThrow(() =>
+    assertBuilderTestDatabaseUrl(
+      'postgres://postgres@127.0.0.1:55443/builder_schema_verifier_tests',
+    ),
+  )
+  for (const url of [
+    'postgres://postgres@remote.invalid/builder_schema_verifier_tests',
+    'postgres://postgres@localhost/production',
+    'https://localhost/builder_schema_verifier_tests',
+    'postgres://postgres@localhost/builder_schema_verifier_tests?database=production',
+    'postgres://postgres@localhost/builder_schema_verifier_tests?options=-c%20search_path%3Dpublic',
+  ])
+    assert.throws(() => assertBuilderTestDatabaseUrl(url))
+})
diff --git a/tests/helpers/builder-test-database.ts b/tests/helpers/builder-test-database.ts
new file mode 100644
index 000000000..dbff109af
--- /dev/null
+++ b/tests/helpers/builder-test-database.ts
@@ -0,0 +1,13 @@
+import assert from 'node:assert/strict'
+
+export function assertBuilderTestDatabaseUrl(databaseUrl: string) {
+  const url = new URL(databaseUrl)
+  assert.ok(['postgres:', 'postgresql:'].includes(url.protocol))
+  assert.ok(['localhost', '127.0.0.1'].includes(url.hostname))
+  assert.equal(url.pathname, '/builder_schema_verifier_tests')
+  assert.equal(
+    url.search,
+    '',
+    'Test database URL must not override connection options',
+  )
+}