diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,16 @@
 # Revision history for pgmq-config
 
+## 0.6.1.0 -- 2026-09-16
+
+Widen the `effectful-core` bound behind the `effectful` flag to `^>=2.6 || ^>=2.7`, adding
+support for 2.7 and dropping the untested claim of support for 2.5. `Pgmq.Config.Effectful`
+uses only `Eff` and `(:>)`, both unchanged in 2.7, so no source change was required.
+
+The test suite now requires `ephemeral-pg >=0.3.1.0` and pins its temporary PostgreSQL
+clusters to `/tmp/ephpg-pgmq-hs-<uid>`, so a run killed mid-test leaves a postmaster a later
+run can reap. It therefore depends on `unix` to read the effective uid. No library
+dependency changed.
+
 ## 0.6.0.0 -- 2026-09-10
 
 Breaking: `PartitionConfig` adds `premake :: Maybe Int32`. Supply `Nothing` for the existing
diff --git a/pgmq-config.cabal b/pgmq-config.cabal
--- a/pgmq-config.cabal
+++ b/pgmq-config.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.4
 name: pgmq-config
-version: 0.6.0.0
+version: 0.6.1.0
 synopsis:
   Declarative queue configuration for PGMQ (PostgreSQL Message Queue)
 
@@ -77,7 +77,7 @@
   if flag(effectful)
     exposed-modules: Pgmq.Config.Effectful
     build-depends:
-      effectful-core ^>=2.5 || ^>=2.6,
+      effectful-core ^>=2.6 || ^>=2.7,
       pgmq-effectful >=0.6 && <0.7,
   hs-source-dirs: src
   default-language: GHC2024
@@ -114,7 +114,7 @@
     base >=4.18 && <5,
     bytestring >=0.11 && <0.13,
     directory,
-    ephemeral-pg >=0.2.1,
+    ephemeral-pg >=0.3.1.0,
     generic-lens ^>=2.2 || ^>=2.3,
     hasql,
     hasql-pool ^>=1.4,
@@ -130,6 +130,7 @@
     tasty-hunit ^>=0.10,
     text,
     time ^>=1.14,
+    unix,
 
   -- ForeignQueueSpec asserts that both reconciler backends use the lenient
   -- queue listing. The effect-backed half only exists when the library's
@@ -137,5 +138,5 @@
   if flag(effectful)
     cpp-options: -DPGMQ_EFFECTFUL
     build-depends:
-      effectful-core ^>=2.5 || ^>=2.6,
+      effectful-core ^>=2.6 || ^>=2.7,
       pgmq-effectful >=0.6 && <0.7,
diff --git a/test/EphemeralDb.hs b/test/EphemeralDb.hs
--- a/test/EphemeralDb.hs
+++ b/test/EphemeralDb.hs
@@ -12,6 +12,7 @@
 
 import Control.Monad (filterM, when)
 import Data.List.NonEmpty (NonEmpty (..))
+import Data.Monoid (Last (..))
 import Data.Text.IO qualified as TextIO
 import Database.PostgreSQL.Migrate
   ( defaultRunOptions,
@@ -19,46 +20,74 @@
     runMigrationPlan,
   )
 import EphemeralPg
-  ( StartError,
+  ( Config (temporaryRoot),
+    StartError,
     connectionSettings,
-    withCached,
+    defaultCacheConfig,
+    defaultConfig,
+    withCachedConfig,
   )
 import Hasql.Pool qualified as Pool
 import Hasql.Pool.Config qualified as PoolConfig
 import Hasql.Session qualified as Session
 import Pgmq.Migration qualified as Migration
-import System.Directory (doesFileExist)
+import System.Directory (createDirectoryIfMissing, doesFileExist)
 import System.Environment (lookupEnv)
+import System.Posix.User (getEffectiveUserID)
 
+-- | Root directory for ephemeral PostgreSQL clusters.
+--
+-- ephemeral-pg reaps abandoned clusters at startup, but only within its own
+-- temporary root. With 'temporaryRoot' unset that root is @$TMPDIR@, which
+-- @nix develop@ makes unique per shell, so a run never reclaims what an earlier
+-- session abandoned. Pinning one root across sessions keeps them reachable.
+--
+-- The path is keyed by effective uid. It is a fixed location created @0700@, so
+-- a run under a different user -- the Nix build sandbox -- must not collide with
+-- a directory it cannot write to.
+ephemeralRoot :: IO FilePath
+ephemeralRoot = do
+  uid <- getEffectiveUserID
+  pure ("/tmp/ephpg-pgmq-hs-" <> show uid)
+
+-- | Cached-startup configuration pinned to 'ephemeralRoot'.
+ephemeralConfig :: IO Config
+ephemeralConfig = do
+  root <- ephemeralRoot
+  createDirectoryIfMissing True root
+  pure defaultConfig {temporaryRoot = Last (Just root)}
+
 -- | Run an action with a temporary PostgreSQL database that has pgmq schema installed
 withPgmqDb :: (Pool.Pool -> IO a) -> IO (Either StartError a)
-withPgmqDb action = withCached $ \db -> do
-  let connSettings = connectionSettings db
-      poolConfig =
-        PoolConfig.settings
-          [ PoolConfig.size 3,
-            PoolConfig.staticConnectionSettings connSettings
-          ]
-  pool <- Pool.acquire poolConfig
-  version <- lookupEnv "PGMQ_TEST_SCHEMA_VERSION"
-  case version of
-    Just "1.12.0" -> do
-      paths <- filterM doesFileExist ["test/fixtures/pgmq-1.12.0.sql", "pgmq-config/test/fixtures/pgmq-1.12.0.sql"]
-      path <- case paths of
-        candidate : _ -> pure candidate
-        [] -> error "Missing packaged PGMQ 1.12.0 test fixture"
-      sql <- TextIO.readFile path
-      Pool.use pool (Session.script sql) >>= either (error . show) pure
-    Nothing -> installNative connSettings
-    Just "1.13.0" -> installNative connSettings
-    Just invalid -> error ("Invalid PGMQ_TEST_SCHEMA_VERSION: " <> invalid)
-  required <- (== Just "1") <$> lookupEnv "PGMQ_REQUIRE_PARTMAN"
-  -- Required runs fail for absent or unusable pg_partman, not just missing metadata.
-  partman <- Pool.use pool (Session.script "CREATE SCHEMA IF NOT EXISTS partman; CREATE EXTENSION IF NOT EXISTS pg_partman SCHEMA partman")
-  case partman of
-    Left err -> when required (error ("PGMQ_REQUIRE_PARTMAN=1: " <> show err))
-    Right () -> pure ()
-  action pool
+withPgmqDb action =
+  ephemeralConfig >>= \config ->
+    withCachedConfig config defaultCacheConfig $ \db -> do
+      let connSettings = connectionSettings db
+          poolConfig =
+            PoolConfig.settings
+              [ PoolConfig.size 3,
+                PoolConfig.staticConnectionSettings connSettings
+              ]
+      pool <- Pool.acquire poolConfig
+      version <- lookupEnv "PGMQ_TEST_SCHEMA_VERSION"
+      case version of
+        Just "1.12.0" -> do
+          paths <- filterM doesFileExist ["test/fixtures/pgmq-1.12.0.sql", "pgmq-config/test/fixtures/pgmq-1.12.0.sql"]
+          path <- case paths of
+            candidate : _ -> pure candidate
+            [] -> error "Missing packaged PGMQ 1.12.0 test fixture"
+          sql <- TextIO.readFile path
+          Pool.use pool (Session.script sql) >>= either (error . show) pure
+        Nothing -> installNative connSettings
+        Just "1.13.0" -> installNative connSettings
+        Just invalid -> error ("Invalid PGMQ_TEST_SCHEMA_VERSION: " <> invalid)
+      required <- (== Just "1") <$> lookupEnv "PGMQ_REQUIRE_PARTMAN"
+      -- Required runs fail for absent or unusable pg_partman, not just missing metadata.
+      partman <- Pool.use pool (Session.script "CREATE SCHEMA IF NOT EXISTS partman; CREATE EXTENSION IF NOT EXISTS pg_partman SCHEMA partman")
+      case partman of
+        Left err -> when required (error ("PGMQ_REQUIRE_PARTMAN=1: " <> show err))
+        Right () -> pure ()
+      action pool
   where
     installNative connSettings = do
       component <- either (error . ("Invalid PGMQ migration component: " <>) . show) pure Migration.pgmqMigrations