diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,15 @@
 # Changelog for pgmq-migration
 
+## 0.4.0.1 -- 2026-07-14
+
+### Bug Fixes
+
+* Add `SourceLedgerPolicy` and `pgmqHasqlMigrationSourceConfigWithPolicy`. Consumers whose
+  predecessor `public.schema_migrations` table is intentionally shared can select
+  `AllowUnselectedSourceRows`, inspect the adapter's unselected-row preflight, and import
+  only PGMQ history. The existing `pgmqHasqlMigrationSourceConfig` remains strict, and both
+  modes retain exact checksum and state-validator requirements for selected PGMQ rows.
+
 ## 0.4.0.0 -- 2026-07-14
 
 ### Breaking Changes
diff --git a/README.md b/README.md
new file mode 100644
--- /dev/null
+++ b/README.md
@@ -0,0 +1,28 @@
+# pgmq-migration
+
+`pgmq-migration` exposes the PGMQ schema as a native `pg-migrate` component. Applications
+compose `pgmqMigrations` into their migration plan; the package intentionally ships no
+standalone runner.
+
+Fresh databases run the two native migrations normally. Databases installed by
+`pgmq-migration` 0.3 or earlier must import their `public.schema_migrations` predecessor
+history before the first native `up`, so the PGMQ baseline is recorded rather than replayed.
+
+The existing `pgmqHasqlMigrationSourceConfig` helper requires an exclusive predecessor
+ledger. When an application deliberately shares that table with its own migrations, use the
+explicit policy-aware constructor:
+
+```haskell
+pgmqHasqlMigrationSourceConfigWithPolicy
+  provider
+  DirectFullInstallHistory
+  AllowUnselectedSourceRows
+```
+
+Call `readHasqlMigrationHistory` with that configuration first and review `unselectedRows`.
+The policy accepts but never claims or modifies those rows. It does not relax selected PGMQ
+evidence: the baseline must still reproduce its exact stored base64 MD5, and the equivalent
+two-step history still requires its state validator plus explicit equivalent-history opt-in.
+
+The repository guide at `docs/user/schema-migration.md` contains complete fresh-install,
+history-import, validation, and recovery examples.
diff --git a/pgmq-migration.cabal b/pgmq-migration.cabal
--- a/pgmq-migration.cabal
+++ b/pgmq-migration.cabal
@@ -1,6 +1,6 @@
 cabal-version:      3.4
 name:               pgmq-migration
-version:            0.4.0.0
+version:            0.4.0.1
 synopsis:           PGMQ schema migrations without PostgreSQL extension
 description:
   Installs the PGMQ schema into PostgreSQL without requiring the pgmq extension.
@@ -13,7 +13,10 @@
 maintainer:         Nadeem Bitar
 category:           Database
 build-type:         Simple
-extra-doc-files:    CHANGELOG.md
+extra-doc-files:
+  CHANGELOG.md
+  README.md
+
 extra-source-files:
   migrations/*.sql
   migrations/manifest
diff --git a/src/Pgmq/Migration/History/HasqlMigration.hs b/src/Pgmq/Migration/History/HasqlMigration.hs
--- a/src/Pgmq/Migration/History/HasqlMigration.hs
+++ b/src/Pgmq/Migration/History/HasqlMigration.hs
@@ -3,8 +3,10 @@
 -- | Explicit imports from the predecessor @hasql-migration@ ledger.
 module Pgmq.Migration.History.HasqlMigration
   ( AlternativeHistoryPolicy (..),
+    SourceLedgerPolicy (..),
     pgmqHasqlMigrationMappings,
     pgmqHasqlMigrationSourceConfig,
+    pgmqHasqlMigrationSourceConfigWithPolicy,
   )
 where
 
@@ -42,6 +44,15 @@
   | EquivalentTwoStepUpgradeHistory
   deriving stock (Eq, Show)
 
+-- | Whether the predecessor ledger may contain rows owned by other components.
+--
+-- This choice only controls unselected rows. Selected PGMQ rows always retain
+-- their exact checksum and state-validation requirements.
+data SourceLedgerPolicy
+  = RequireExclusiveSourceLedger
+  | AllowUnselectedSourceRows
+  deriving stock (Eq, Show)
+
 -- | Map the selected predecessor history shape to the native PGMQ baseline.
 pgmqHasqlMigrationMappings ::
   AlternativeHistoryPolicy ->
@@ -75,11 +86,26 @@
   AlternativeHistoryPolicy ->
   Either HasqlMigrationDefinitionError HasqlMigrationSourceConfig
 pgmqHasqlMigrationSourceConfig sourceProvider policy =
+  pgmqHasqlMigrationSourceConfigWithPolicy
+    sourceProvider
+    policy
+    RequireExclusiveSourceLedger
+
+-- | Build a source-reader configuration with an explicit ledger-ownership policy.
+--
+-- Use 'AllowUnselectedSourceRows' only when another component deliberately shares
+-- @public.schema_migrations@. The selected PGMQ rows are still verified exactly.
+pgmqHasqlMigrationSourceConfigWithPolicy ::
+  ConnectionProvider ->
+  AlternativeHistoryPolicy ->
+  SourceLedgerPolicy ->
+  Either HasqlMigrationDefinitionError HasqlMigrationSourceConfig
+pgmqHasqlMigrationSourceConfigWithPolicy sourceProvider policy sourceLedgerPolicy =
   hasqlMigrationSourceConfig
     sourceProvider
     defaultHasqlMigrationTable
     selectedFilenames
-    True
+    (sourceLedgerPolicy == RequireExclusiveSourceLedger)
     selectedPayloads
     selectedValidators
     "verified pgmq-migration cutover to native pg-migrate history"
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -34,11 +34,14 @@
     withEquivalentHistory,
   )
 import Database.PostgreSQL.Migrate.History.HasqlMigration
-  ( HasqlMigrationImportError (..),
+  ( HasqlMigrationHistory (unselectedRows),
+    HasqlMigrationImportError (..),
+    HasqlMigrationRow (filename),
     HasqlMigrationSourceConfig,
     defaultHasqlMigrationTable,
     hasqlMigrationSourceConfig,
     importHasqlMigrationHistory,
+    readHasqlMigrationHistory,
   )
 import Database.PostgreSQL.Migrate.Internal
   ( ComponentDescription (..),
@@ -61,8 +64,10 @@
 import Pgmq.Migration qualified as Migration
 import Pgmq.Migration.History.HasqlMigration
   ( AlternativeHistoryPolicy (..),
+    SourceLedgerPolicy (..),
     pgmqHasqlMigrationMappings,
     pgmqHasqlMigrationSourceConfig,
+    pgmqHasqlMigrationSourceConfigWithPolicy,
   )
 import System.Directory (doesFileExist)
 import Test.Tasty (TestTree, defaultMain, testGroup)
@@ -96,7 +101,9 @@
         ],
       testGroup
         "history import"
-        [ testCase "direct row imports without executing the target action" (testDirectHistoryImport settings conn),
+        [ testCase "strict helper rejects a shared ledger before target writes" (testStrictSharedLedger settings conn),
+          testCase "shared-ledger policy imports only PGMQ and applies the canary once" (testSharedLedgerImport settings conn),
+          testCase "direct row imports without executing the target action" (testDirectHistoryImport settings conn),
           testCase "direct import rejects altered bytes, checksum, and duplicate rows" (testDirectHistoryRejections settings conn),
           testCase "two-step history requires explicit equivalent opt-in" (testEquivalentHistoryImport settings conn),
           testCase "two-step history rejects an incomplete PGMQ contract" (testEquivalentContractRejections settings conn)
@@ -185,6 +192,37 @@
   functionExists c "pgmq.metrics_all()" >>= (@?= True)
   hasCanaryComment c >>= (@?= True)
 
+testStrictSharedLedger :: Settings.Settings -> Connection.Connection -> IO ()
+testStrictSharedLedger settings conn = withCleanDb conn $ \c -> do
+  prepareSharedDirectHistory c
+  runPolicyImportEither settings defaultImportOptions DirectFullInstallHistory
+    >>= assertImportError
+      (\case HasqlMigrationStrictSourceHasUnselected [name] -> name == unrelatedLegacyFilename; _ -> False)
+  nativeLedgerTablesAbsent c >>= (@?= True)
+
+testSharedLedgerImport :: Settings.Settings -> Connection.Connection -> IO ()
+testSharedLedgerImport settings conn = withCleanDb conn $ \c -> do
+  prepareSharedDirectHistory c
+  runSql c "DROP FUNCTION pgmq.metrics_all()"
+  let provider = connectionProviderFromSettings settings
+  config <-
+    either (assertFailure . show) pure $
+      pgmqHasqlMigrationSourceConfigWithPolicy
+        provider
+        DirectFullInstallHistory
+        AllowUnselectedSourceRows
+  history <- readHasqlMigrationHistory config >>= either (assertFailure . show) pure
+  (filename <$> unselectedRows history) @?= [unrelatedLegacyFilename]
+  sourceBefore <- legacyLedgerSnapshot c
+
+  first <- runImportWith settings defaultImportOptions DirectFullInstallHistory config >>= either (assertFailure . show) pure
+  historyOutcomes first @?= [Imported]
+  sourceAfter <- legacyLedgerSnapshot c
+  sourceAfter @?= sourceBefore
+  functionExists c "pgmq.metrics_all()" >>= (@?= False)
+
+  assertNativeCanaryLifecycle settings c
+
 testDirectHistoryImport :: Settings.Settings -> Connection.Connection -> IO ()
 testDirectHistoryImport settings conn = withCleanDb conn $ \c -> do
   prepareDirectHistory c
@@ -250,19 +288,34 @@
     runPolicyImportEither settings defaultImportOptions DirectFullInstallHistory
       >>= assertImportError (\case HasqlMigrationDuplicateLedgerFilename name -> name == directLegacyFilename; _ -> False)
 
+  withCleanDb conn $ \c -> do
+    prepareSharedDirectHistory c
+    runSql c "UPDATE public.schema_migrations SET checksum = 'altered' WHERE filename = 'pgmq_v1.11.0'"
+    runPolicyImportWithSourcePolicyEither
+      settings
+      defaultImportOptions
+      DirectFullInstallHistory
+      AllowUnselectedSourceRows
+      >>= assertImportError (\case HasqlMigrationChecksumMismatch name "altered" _ -> name == directLegacyFilename; _ -> False)
+    nativeLedgerTablesAbsent c >>= (@?= True)
+
 testEquivalentHistoryImport :: Settings.Settings -> Connection.Connection -> IO ()
 testEquivalentHistoryImport settings conn = withCleanDb conn $ \c -> do
-  prepareTwoStepHistory c
-  runPolicyImportEither settings defaultImportOptions EquivalentTwoStepUpgradeHistory
+  prepareSharedTwoStepHistory c
+  runPolicyImportWithSourcePolicyEither
+    settings
+    defaultImportOptions
+    EquivalentTwoStepUpgradeHistory
+    AllowUnselectedSourceRows
     >>= assertImportError
       ( \case
           HasqlMigrationTargetImportFailed (HistoryImportValidationFailed (HistoryEquivalentStateDisallowed _)) -> True
           _ -> False
       )
 
-  first <- runPolicyImport settings equivalentImportOptions EquivalentTwoStepUpgradeHistory
+  first <- runPolicyImportWithSourcePolicy settings equivalentImportOptions EquivalentTwoStepUpgradeHistory AllowUnselectedSourceRows
   historyOutcomes first @?= [Imported]
-  second <- runPolicyImport settings equivalentImportOptions EquivalentTwoStepUpgradeHistory
+  second <- runPolicyImportWithSourcePolicy settings equivalentImportOptions EquivalentTwoStepUpgradeHistory AllowUnselectedSourceRows
   historyOutcomes second @?= [AlreadyImported]
 
   plan <- nativePlan
@@ -334,6 +387,29 @@
   config <- either (assertFailure . show) pure (pgmqHasqlMigrationSourceConfig provider policy)
   runImportWith settings options policy config
 
+runPolicyImportWithSourcePolicy ::
+  Settings.Settings ->
+  ImportOptions ->
+  AlternativeHistoryPolicy ->
+  SourceLedgerPolicy ->
+  IO HistoryImportReport
+runPolicyImportWithSourcePolicy settings options policy sourceLedgerPolicy =
+  runPolicyImportWithSourcePolicyEither settings options policy sourceLedgerPolicy
+    >>= either (assertFailure . show) pure
+
+runPolicyImportWithSourcePolicyEither ::
+  Settings.Settings ->
+  ImportOptions ->
+  AlternativeHistoryPolicy ->
+  SourceLedgerPolicy ->
+  IO (Either HasqlMigrationImportError HistoryImportReport)
+runPolicyImportWithSourcePolicyEither settings options policy sourceLedgerPolicy = do
+  let provider = connectionProviderFromSettings settings
+  config <-
+    either (assertFailure . show) pure $
+      pgmqHasqlMigrationSourceConfigWithPolicy provider policy sourceLedgerPolicy
+  runImportWith settings options policy config
+
 runImportWith ::
   Settings.Settings ->
   ImportOptions ->
@@ -367,6 +443,11 @@
     connection
     "INSERT INTO public.schema_migrations (filename, checksum) VALUES ('pgmq_v1.11.0', '+qm4gAAF+A+99qM9BxGD0g==')"
 
+prepareSharedDirectHistory :: Connection.Connection -> IO ()
+prepareSharedDirectHistory connection = do
+  prepareDirectHistory connection
+  insertUnrelatedHistory connection
+
 prepareTwoStepHistory :: Connection.Connection -> IO ()
 prepareTwoStepHistory connection = do
   installHistoricalSchema connection
@@ -378,6 +459,20 @@
         <> "('pgmq_v1.10.1_to_v1.11.0', 'KMM7gGjkepkD1YA1hUCpEQ==')"
     )
 
+prepareSharedTwoStepHistory :: Connection.Connection -> IO ()
+prepareSharedTwoStepHistory connection = do
+  prepareTwoStepHistory connection
+  insertUnrelatedHistory connection
+
+unrelatedLegacyFilename :: FilePath
+unrelatedLegacyFilename = "application_0001.sql"
+
+insertUnrelatedHistory :: Connection.Connection -> IO ()
+insertUnrelatedHistory connection =
+  runSql
+    connection
+    "INSERT INTO public.schema_migrations (filename, checksum) VALUES ('application_0001.sql', 'application-checksum')"
+
 installHistoricalSchema :: Connection.Connection -> IO ()
 installHistoricalSchema connection = do
   path <- findFile ["pgmq-migration/migrations/0001-install-v1.11.0.sql", "migrations/0001-install-v1.11.0.sql"]
@@ -397,6 +492,39 @@
     Left err -> assertFailure ("SQL fixture failed: " <> show err)
     Right () -> pure ()
 
+legacyLedgerSnapshot :: Connection.Connection -> IO [(Text, Text)]
+legacyLedgerSnapshot connection = do
+  result <- Connection.use connection (Session.statement () legacyLedgerSnapshotStatement)
+  case result of
+    Left err -> assertFailure ("legacy ledger inspection failed: " <> show err) >> pure []
+    Right rows -> pure rows
+
+legacyLedgerSnapshotStatement :: Statement.Statement () [(Text, Text)]
+legacyLedgerSnapshotStatement =
+  preparable
+    "SELECT filename, checksum FROM public.schema_migrations ORDER BY filename"
+    Encoders.noParams
+    ( Decoders.rowList
+        ( (,)
+            <$> Decoders.column (Decoders.nonNullable Decoders.text)
+            <*> Decoders.column (Decoders.nonNullable Decoders.text)
+        )
+    )
+
+nativeLedgerTablesAbsent :: Connection.Connection -> IO Bool
+nativeLedgerTablesAbsent connection = do
+  result <- Connection.use connection (Session.statement () nativeLedgerTablesAbsentStatement)
+  case result of
+    Left err -> assertFailure ("native ledger inspection failed: " <> show err) >> pure False
+    Right absent -> pure absent
+
+nativeLedgerTablesAbsentStatement :: Statement.Statement () Bool
+nativeLedgerTablesAbsentStatement =
+  preparable
+    "SELECT to_regclass('pgmigrate.migrations') IS NULL AND to_regclass('pgmigrate.history_imports') IS NULL"
+    Encoders.noParams
+    (Decoders.singleRow (Decoders.column (Decoders.nonNullable Decoders.bool)))
+
 functionExists :: Connection.Connection -> Text -> IO Bool
 functionExists connection identity = do
   result <- Connection.use connection (Session.statement identity functionExistsStatement)
@@ -417,6 +545,24 @@
   case result of
     Left err -> assertFailure ("schema comment inspection failed: " <> show err) >> pure False
     Right matches -> pure matches
+
+assertNativeCanaryLifecycle :: Settings.Settings -> Connection.Connection -> IO ()
+assertNativeCanaryLifecycle settings connection = do
+  plan <- nativePlan
+  canaryId <- either (assertFailure . show) pure (migrationId "pgmq" "0002-schema-management-comment")
+  beforeCanary <- verifyMigrationPlan defaultRunOptions settings plan
+  case beforeCanary of
+    Left err -> assertFailure ("native verify failed after shared-ledger import: " <> show err)
+    Right (VerificationReport issues _ _ _) -> issues @?= [PendingMigration canaryId]
+  nativeRun <- runMigrationPlan defaultRunOptions settings plan
+  case nativeRun of
+    Left err -> assertFailure ("native runner failed after shared-ledger import: " <> show err)
+    Right report -> (outcome <$> toList (results report)) @?= [AlreadyApplied, AppliedNow]
+  repeated <- runMigrationPlan defaultRunOptions settings plan
+  case repeated of
+    Left err -> assertFailure ("native rerun failed after shared-ledger import: " <> show err)
+    Right report -> (outcome <$> toList (results report)) @?= [AlreadyApplied, AlreadyApplied]
+  hasCanaryComment connection >>= (@?= True)
 
 canaryCommentStatement :: Statement.Statement () Bool
 canaryCommentStatement =