@@ -132,6 +132,18 @@ export const SYNC_EMBEDDING_SEARCH_FUNCTION = `CREATE OR REPLACE FUNCTION sync_e
   END;
   $$`
 
+const comparableSource = (source: string) => source.replace(/\s+/g, ' ').trim()
+
+/**
+ * Whether a live `pg_proc.prosrc` is {@link SYNC_EMBEDDING_SEARCH_FUNCTION}'s body, ignoring
+ * whitespace: PostgreSQL stores the body between the `$$` quotes verbatim.
+ */
+export function isCurrentSyncEmbeddingSearchSource(prosrc: string): boolean {
+  return (
+    comparableSource(prosrc) === comparableSource(SYNC_EMBEDDING_SEARCH_FUNCTION.split('$$')[1])
+  )
+}
+
 export type KnowledgeProjection = 'embedding_search'
 
 /** Active vector projections that mirror document access for legacy synchronous writers. */
 
@@ -1,5 +1,5 @@
 import { readFileSync } from 'node:fs'
-import { SYNC_EMBEDDING_SEARCH_FUNCTION } from '@sim/db/knowledge-projection'
+import { isCurrentSyncEmbeddingSearchSource } from '@sim/db/knowledge-projection'
 import { backfillEmbeddingSearch } from '@sim/db/script-migrations/0015_backfill_embedding_search'
 import {
   backfillSearchVectors,
@@ -364,9 +364,6 @@ describe('search projection upgrade in PostgreSQL', () => {
     const [installed] = await sql<{ body: string }[]>`
       SELECT prosrc AS body FROM pg_proc
       WHERE oid = ${`"${schemaName}".sync_embedding_search`}::regproc`
-    const normalized = (text: string) => text.replace(/\s+/g, ' ').trim()
-    expect(normalized(installed.body)).toBe(
-      normalized(SYNC_EMBEDDING_SEARCH_FUNCTION.split('$$')[1])
-    )
+    expect(isCurrentSyncEmbeddingSearchSource(installed.body)).toBe(true)
   })
 })
@@ -1,7 +1,7 @@
 import { spawnSync } from 'node:child_process'
 import { readFile } from 'node:fs/promises'
 import { fileURLToPath } from 'node:url'
-import { SYNC_EMBEDDING_SEARCH_FUNCTION } from '@sim/db/knowledge-projection'
+import { isCurrentSyncEmbeddingSearchSource } from '@sim/db/knowledge-projection'
 import {
   inspectSearchProjection,
   purgeSearchProjection,
@@ -47,6 +47,19 @@ describe('Search candidate retirement in PostgreSQL', () => {
       FROM pg_proc p WHERE p.oid = 'public.sync_embedding_search'::regproc`
   }
 
+  /** Applies migration 0449 as the migrator does, in one transaction. */
+  async function applyMigration() {
+    const migration = await readFile(
+      new URL('../migrations/0449_retire_search_projection_writes.sql', import.meta.url),
+      'utf8'
+    )
+    await sql.begin(async (tx) => {
+      for (const statement of migration.split('--> statement-breakpoint')) {
+        if (statement.trim()) await tx.unsafe(statement)
+      }
+    })
+  }
+
   async function control<T>(run: (admin: Sql) => Promise<T>): Promise<T> {
     const url = new URL(databaseUrl)
     url.pathname = '/postgres'
@@ -91,17 +104,7 @@ describe('Search candidate retirement in PostgreSQL', () => {
     expect(provision.status, provision.stdout + provision.stderr).toBe(0)
     ;[provisioned] = await definitions()
     // Every behaviour below runs on the function the versioned migration installs, replayed twice.
-    const migration = await readFile(
-      new URL('../migrations/0449_retire_search_projection_writes.sql', import.meta.url),
-      'utf8'
-    )
-    for (let replay = 0; replay < 2; replay++) {
-      await sql.begin(async (tx) => {
-        for (const statement of migration.split('--> statement-breakpoint')) {
-          if (statement.trim()) await tx.unsafe(statement)
-        }
-      })
-    }
+    for (let replay = 0; replay < 2; replay++) await applyMigration()
     await sql`INSERT INTO "user" (id, name, email, email_verified, created_at, updated_at)
       VALUES ('reader', 'Synthetic reader', 'reader@example.test', true, now(), now())`
     await sql`INSERT INTO project (id, name, owner_id) VALUES ('project', 'Synthetic project', 'reader')`
@@ -159,14 +162,10 @@ describe('Search candidate retirement in PostgreSQL', () => {
     return row.n
   }
 
-  const normalized = (text: string) => text.replace(/\s+/g, ' ').trim()
-
   it('installs the provisioning function and leaves both triggers as they were', async () => {
     const [migrated] = await definitions()
-    expect(normalized(migrated.body)).toBe(normalized(provisioned.body))
-    expect(normalized(migrated.body)).toBe(
-      normalized(SYNC_EMBEDDING_SEARCH_FUNCTION.split('$$')[1])
-    )
+    expect(isCurrentSyncEmbeddingSearchSource(provisioned.body)).toBe(true)
+    expect(isCurrentSyncEmbeddingSearchSource(migrated.body)).toBe(true)
     expect(migrated.sync).toBe(provisioned.sync)
     expect(migrated.sync).toContain("current_setting('sim.projection_mode'")
     expect(migrated.acl).toBe(provisioned.acl)
@@ -368,17 +367,47 @@ describe('Search candidate retirement in PostgreSQL', () => {
     })
   })
 
+  function runPurge(...args: string[]) {
+    return spawnSync('bun', ['--no-env-file', './scripts/purge-search-projection.ts', ...args], {
+      cwd: packageRoot,
+      env: { ...process.env, MIGRATION_DATABASE_URL: fixtureUrl.toString() },
+      encoding: 'utf8',
+      timeout: 30_000,
+    })
+  }
+
+  it('refuses --execute until migration 0449 is live, and the dry run reports it', async () => {
+    await seedBase({ id: 'search', width: 1536, model: 'text-embedding-3-small', chunks: 3 }, true)
+    await sql.unsafe(`CREATE OR REPLACE FUNCTION public.sync_embedding_search()
+      RETURNS trigger LANGUAGE plpgsql AS $$ BEGIN RETURN NEW; END; $$`)
+    try {
+      const dryRun = runPurge()
+      expect(dryRun.status, dryRun.stdout + dryRun.stderr).toBe(0)
+      expect(dryRun.stdout).toContain('"projectionRetired":false')
+      const stale = runPurge('--execute', '--pause-ms', '0')
+      expect(stale.status).toBe(1)
+      expect(stale.stdout + stale.stderr).toContain('Migration 0449 is not live')
+      expect(await candidateCount('search')).toBe(3)
+
+      await applyMigration()
+      await sql`ALTER TABLE embedding DISABLE TRIGGER embedding_search_sync`
+      expect(runPurge('--execute', '--pause-ms', '0').status).toBe(1)
+      expect(await candidateCount('search')).toBe(3)
+    } finally {
+      await sql`ALTER TABLE embedding ENABLE TRIGGER embedding_search_sync`
+      await applyMigration()
+    }
+    const dryRun = runPurge()
+    expect(dryRun.stdout).toContain('"projectionRetired":true')
+    const execute = runPurge('--execute', '--pause-ms', '0')
+    expect(execute.status, execute.stdout + execute.stderr).toBe(0)
+    expect(await candidateCount('search')).toBe(0)
+  })
+
   it('runs as an operator command: dry run by default, deletes only with --execute', async () => {
     await seedBase({ id: 'search', width: 1536, model: 'text-embedding-3-small', chunks: 3 }, true)
     await seedBase({ id: 'ordinary', width: 1536, model: 'text-embedding-3-small', chunks: 2 })
-    const run = (...args: string[]) => {
-      return spawnSync('bun', ['--no-env-file', './scripts/purge-search-projection.ts', ...args], {
-        cwd: packageRoot,
-        env: { ...process.env, MIGRATION_DATABASE_URL: fixtureUrl.toString() },
-        encoding: 'utf8',
-        timeout: 30_000,
-      })
-    }
+    const run = runPurge
     const help = run('--help')
     expect(help.status).toBe(0)
     expect(help.stdout).toContain('REINDEX INDEX CONCURRENTLY embedding_search_512_cosine_hnsw_idx')
@@ -401,16 +430,7 @@ describe('Search candidate retirement in PostgreSQL', () => {
     await sql`CREATE TABLE shadow.knowledge_base (id text, is_search_index boolean)`
     await sql.unsafe(`ALTER DATABASE "${database}" SET search_path = shadow, public`)
     try {
-      const execute = spawnSync(
-        'bun',
-        ['--no-env-file', './scripts/purge-search-projection.ts', '--execute', '--pause-ms', '0'],
-        {
-          cwd: packageRoot,
-          env: { ...process.env, MIGRATION_DATABASE_URL: fixtureUrl.toString() },
-          encoding: 'utf8',
-          timeout: 30_000,
-        }
-      )
+      const execute = runPurge('--execute', '--pause-ms', '0')
       expect(execute.status, execute.stdout + execute.stderr).toBe(0)
     } finally {
       await sql.unsafe(`ALTER DATABASE "${database}" RESET search_path`)
 
@@ -1,4 +1,5 @@
 import { parseArgs } from 'node:util'
+import { isCurrentSyncEmbeddingSearchSource } from '@sim/db/knowledge-projection'
 import { createLogger, LogLevel } from '@sim/logger'
 import { getPostgresErrorCode } from '@sim/utils/errors'
 import { sleep } from '@sim/utils/helpers'
@@ -35,8 +36,9 @@ bases (knowledge_base.is_search_index). Canonical embedding and document rows ar
 
 MIGRATION_DATABASE_URL=... bun --no-env-file packages/db/scripts/purge-search-projection.ts [--execute] [options]
 
-Without --execute, prints each Search knowledge base's planner row estimate (≈) and whether any
-candidate row remains, and changes nothing.
+Without --execute, prints whether migration 0449 is live (projectionRetired), each Search knowledge
+base's planner row estimate (≈) and whether any candidate row remains, and changes nothing.
+--execute refuses until migration 0449 is live: wait for the deploy's migrate job to finish.
   --execute         Delete in batches, each its own short transaction; any error stops the run.
   --batch-size N    Rows per batch, 1–${MAX_BATCH_SIZE} (default ${DEFAULT_BATCH_SIZE}).
   --pause-ms N      Pause after each batch, 0–${MAX_PAUSE_MS} (default ${DEFAULT_PAUSE_MS}).
@@ -45,9 +47,13 @@ candidate row remains, and changes nothing.
 MIGRATION_DATABASE_URL must be a direct PlanetScale primary (port 5432, sslmode=verify-full,
 sslrootcert=system); poolers are refused. Rerun until the dry run reports none remaining, then,
 from a direct primary session outside peak traffic (this script never runs them):
+  -- wait while pg_stat_activity shows an anti-wraparound autovacuum of embedding_search
+  SET maintenance_work_mem = '2GB'; SET statement_timeout = 0;
   REINDEX INDEX CONCURRENTLY embedding_search_512_cosine_hnsw_idx;
+  -- if it fails: DROP INDEX CONCURRENTLY embedding_search_512_cosine_hnsw_idx_ccnew; then retry
   VACUUM (ANALYZE) embedding_search;
-The full runbook is in the pull request that added this script.`
+Rebuild each HNSW index a purged Search knowledge base used: text-embedding-3-small and -large
+bases use only the 512 one. The full runbook is in the pull request that added this script.`
 
 /** Deliberate operator messages never include database values, credentials or statement text. */
 export class SearchProjectionPurgeError extends Error {
@@ -145,6 +151,24 @@ export function connectOperatorDatabase(rawUrl: string | undefined): Sql {
   })
 }
 
+/**
+ * Whether migration 0449 is live: `public.sync_embedding_search` has the body that deletes a
+ * Search chunk's candidate row, and its `embedding_search_sync` trigger is enabled. Before that,
+ * chunk writes keep projecting the rows a purge deletes.
+ */
+async function isProjectionRetired(sql: Sql): Promise<boolean> {
+  const [live] = await sql<{ source: string | null; trigger_enabled: boolean }[]>`
+    SELECT (SELECT prosrc FROM pg_proc WHERE oid = to_regproc('public.sync_embedding_search')) AS source,
+      EXISTS (
+        SELECT 1 FROM pg_trigger
+        WHERE tgrelid = to_regclass('public.embedding') AND tgname = 'embedding_search_sync'
+          AND tgenabled <> 'D'
+      ) AS trigger_enabled`
+  return (
+    live.trigger_enabled && live.source !== null && isCurrentSyncEmbeddingSearchSource(live.source)
+  )
+}
+
 /** Search knowledge bases in id order; the table is small and read once per run. */
 async function searchKnowledgeBases(sql: Sql): Promise<string[]> {
   const rows = await sql<{ id: string }[]>`
@@ -317,6 +341,7 @@ async function main(): Promise<void> {
     if (!values.execute) {
       const states = await inspectSearchProjection(sql)
       logger.info('Search candidate rows (dry run; nothing deleted; estimatedRows is ≈)', {
+        projectionRetired: await isProjectionRetired(sql),
         knowledgeBases: states,
         remaining: states.some((state) => state.remaining),
       })
@@ -327,6 +352,10 @@ async function main(): Promise<void> {
         to_regclass('public.search_retirement_state') IS NOT NULL AS retirement_installed`
     if (!session.writable)
       throw new SearchProjectionPurgeError('The purge requires a writable primary connection')
+    if (!(await isProjectionRetired(sql)))
+      throw new SearchProjectionPurgeError(
+        'Migration 0449 is not live (sync_embedding_search() is not the retiring body, or its trigger is disabled); wait for the migrate job to finish'
+      )
     if (session.retirement_installed)
       throw new SearchProjectionPurgeError(
         'A shadow-copy Search retirement job is still installed; abort it with the release that shipped it first'