diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog for sandwich-contexts
 
+## Unreleased
+
+* Add `postgresNixConfExtraLines` to `PostgresNixOptions`, to be able to add extra lines to `postgresql.conf`.
+
 ## 0.3.0.1
 
 * Automatically find sufficiently short Unix socket paths when the system temp ones are too long
diff --git a/lib/Test/Sandwich/Contexts/Container.hs b/lib/Test/Sandwich/Contexts/Container.hs
--- a/lib/Test/Sandwich/Contexts/Container.hs
+++ b/lib/Test/Sandwich/Contexts/Container.hs
@@ -6,7 +6,10 @@
 -}
 
 module Test.Sandwich.Contexts.Container (
-  ContainerSystem (..)
+  ContainerOptions (..)
+  , defaultContainerOptions
+
+  , ContainerSystem (..)
   , waitForHealth
 
   -- * Container/host conversions
@@ -36,8 +39,23 @@
 import UnliftIO.Process
 
 
+-- | Type to represent generic options for launching containers.
+data ContainerOptions = ContainerOptions {
+  containerOptionsSystem :: ContainerSystem
+  , containerOptionsName :: Maybe Text
+  }
+  deriving (Show, Eq)
+
+defaultContainerOptions :: ContainerOptions
+defaultContainerOptions = ContainerOptions {
+  containerOptionsSystem = ContainerSystemPodman
+  , containerOptionsName = Nothing
+  }
+
 -- | Type to represent which container system we're using.
-data ContainerSystem = ContainerSystemDocker | ContainerSystemPodman
+data ContainerSystem =
+  ContainerSystemDocker
+  | ContainerSystemPodman
   deriving (Eq)
 
 instance Show ContainerSystem where
diff --git a/lib/Test/Sandwich/Contexts/FakeSmtpServer.hs b/lib/Test/Sandwich/Contexts/FakeSmtpServer.hs
--- a/lib/Test/Sandwich/Contexts/FakeSmtpServer.hs
+++ b/lib/Test/Sandwich/Contexts/FakeSmtpServer.hs
@@ -44,7 +44,7 @@
 import Data.String.Interpolate
 import GHC.TypeLits
 import Network.HTTP.Client
-import Network.Socket (PortNumber)
+import Network.Socket (HostName, PortNumber)
 import Relude
 import System.FilePath
 import System.IO
@@ -90,8 +90,10 @@
 $(A.deriveJSON (A.defaultOptions { A.fieldLabelModifier = dropNAndCamelCase (length ("emailInfo" :: String)) }) ''EmailInfo)
 
 data FakeSmtpServer = FakeSmtpServer {
+  -- | The hostname of the fake SMTP server.
+  fakeSmtpServerHostname :: HostName
   -- | The port on which the fake SMTP server is running.
-  fakeSmtpServerSmtpPort :: PortNumber
+  , fakeSmtpServerSmtpPort :: PortNumber
   -- | Callback to retrieve the emails the server has received.
   , fakeSmtpServerGetEmails :: forall m. (MonadLoggerIO m, MonadUnliftIO m, MonadThrow m) => m [EmailInfo]
   }
@@ -181,6 +183,7 @@
               void $ liftIO (interruptProcessGroupOf p >> waitForProcess p)
           )
           (\_ -> do
+              let hostname = "localhost"
               httpPort <- waitForPortFile 120.0 httpPortFile
               smtpPort <- waitForPortFile 120.0 smtpPortFile
 
@@ -188,10 +191,14 @@
                     Just (username, password) -> [i|#{username}:#{password}@|] :: Text
                     Nothing -> ""
 
-              waitUntilStatusCodeWithTimeout (2, 0, 0) (1_000_000 * 60 * 2) YesVerify [i|http://#{authPart}localhost:#{httpPort}/api/emails|]
+              waitUntilStatusCodeWithTimeout (2, 0, 0) (1_000_000 * 60 * 2) YesVerify [i|http://#{authPart}#{hostname}:#{httpPort}/api/emails|]
 
               manager <- liftIO $ newManager defaultManagerSettings
-              void $ action $ FakeSmtpServer smtpPort (getEmails manager authPart httpPort)
+              void $ action $ FakeSmtpServer {
+                fakeSmtpServerHostname = hostname
+                , fakeSmtpServerSmtpPort = smtpPort
+                , fakeSmtpServerGetEmails = getEmails manager authPart httpPort
+                }
           )
 
 
diff --git a/lib/Test/Sandwich/Contexts/Nix.hs b/lib/Test/Sandwich/Contexts/Nix.hs
--- a/lib/Test/Sandwich/Contexts/Nix.hs
+++ b/lib/Test/Sandwich/Contexts/Nix.hs
@@ -31,6 +31,8 @@
   introduceNixContext
   , introduceNixContext'
   , introduceNixContext''
+  , makeNixContext
+  , makeNixContext'
 
   -- * Nix environments
   , introduceNixEnvironment
@@ -42,7 +44,7 @@
   , buildNixCallPackageDerivation
   , buildNixCallPackageDerivation'
 
-  -- * Nixpkgs releases
+  -- * Nixpkgs releases #releases#
   , nixpkgsReleaseDefault
   , nixpkgsRelease2405
   , nixpkgsRelease2311
@@ -176,14 +178,7 @@
   -> SpecFree (LabelValue "nixContext" NixContext :> context) m ()
   -- | Parent spec
   -> SpecFree context m ()
-introduceNixContext' nodeOptions nixpkgsDerivation = introduce' nodeOptions "Introduce Nix context" nixContext getNixContext (const $ return ())
-  where
-    getNixContext = findExecutable "nix" >>= \case
-      Nothing -> expectationFailure [i|Couldn't find "nix" binary when introducing Nix context. A Nix binary and store must already be available in the environment.|]
-      Just p -> do
-        -- TODO: make sure the Nixpkgs derivation works
-        buildCache <- newMVar mempty
-        pure (NixContext p nixpkgsDerivation buildCache)
+introduceNixContext' nodeOptions nixpkgsDerivation = introduce' nodeOptions "Introduce Nix context" nixContext (makeNixContext nixpkgsDerivation) (const $ return ())
 
 -- | Same as 'introduceNixContext'', but allows specifying the Nix binary via 'HasFile'.
 introduceNixContext'' :: (
@@ -199,19 +194,29 @@
   -> SpecFree (LabelValue "nixContext" NixContext :> context) m ()
   -- | Parent spec
   -> SpecFree context m ()
-introduceNixContext'' nodeOptions nixpkgsDerivation = introduce' nodeOptions "Introduce Nix context" nixContext getNixContext (const $ return ())
-  where
-    getNixContext = do
-      nix <- askFile @"nix"
-      -- TODO: make sure the Nixpkgs derivation works
-      buildCache <- newMVar mempty
-      pure (NixContext nix nixpkgsDerivation buildCache)
+introduceNixContext'' nodeOptions nixpkgsDerivation = introduce' nodeOptions "Introduce Nix context" nixContext (makeNixContext' nixpkgsDerivation) (const $ return ())
 
+-- | Build a 'NixContext' directly. Throws an exception if the @nix@ binary is not found.
+makeNixContext :: (MonadIO m) => NixpkgsDerivation -> m NixContext
+makeNixContext nixpkgsDerivation = findExecutable "nix" >>= \case
+  Nothing -> expectationFailure [i|Couldn't find "nix" binary when introducing Nix context. A Nix binary and store must already be available in the environment.|]
+  Just p -> do
+    -- TODO: make sure the Nixpkgs derivation works
+    buildCache <- newMVar mempty
+    pure (NixContext p nixpkgsDerivation buildCache)
+
+-- | Build a 'NixContext' directly, specifying the Nix binary via 'HasFile'.
+makeNixContext' :: (MonadIO m, MonadReader ctx m, HasFile ctx "nix") => NixpkgsDerivation -> m NixContext
+makeNixContext' nixpkgsDerivation = do
+  nix <- askFile @"nix"
+  buildCache <- newMVar mempty
+  pure (NixContext nix nixpkgsDerivation buildCache)
+
 -- | Introduce a Nix environment containing the given list of packages, using the current 'NixContext'.
 -- These packages are mashed together using the Nix @symlinkJoin@ function. Their binaries will generally
--- be found in "\<environment path\>\/bin".
+-- be found in @\<environment path\>\/bin@.
 introduceNixEnvironment :: (
-  HasBaseContextMonad context m, HasNixContext context
+  HasBaseContext context, HasNixContext context
   , MonadUnliftIO m
   )
   -- | List of package names to include in the Nix environment
@@ -222,7 +227,7 @@
 
 -- | Same as 'introduceNixEnvironment', but allows passing custom 'NodeOptions'.
 introduceNixEnvironment' :: (
-  HasBaseContextMonad context m, HasNixContext context
+  HasBaseContext context, HasNixContext context
   , MonadUnliftIO m
   )
   -- | Custom 'NodeOptions'
diff --git a/lib/Test/Sandwich/Contexts/PostgreSQL.hs b/lib/Test/Sandwich/Contexts/PostgreSQL.hs
--- a/lib/Test/Sandwich/Contexts/PostgreSQL.hs
+++ b/lib/Test/Sandwich/Contexts/PostgreSQL.hs
@@ -22,14 +22,15 @@
 -}
 
 module Test.Sandwich.Contexts.PostgreSQL (
-#ifndef mingw32_HOST_OS
   -- * Raw PostgreSQL via Nix (TCP socket)
   introducePostgresViaNix
   , withPostgresViaNix
+  , withPostgresViaNix'
 
   -- * Raw PostgreSQL via Nix (Unix socket)
   , introducePostgresUnixSocketViaNix
   , withPostgresUnixSocketViaNix
+  , withPostgresUnixSocketViaNix'
 
   -- * Containerized PostgreSQL
   , introducePostgresViaContainer
@@ -47,10 +48,8 @@
 
   -- * Re-exports
   , NetworkAddress(..)
-#endif
   ) where
 
-#ifndef mingw32_HOST_OS
 import Control.Monad.Catch (MonadMask)
 import Control.Monad.IO.Unlift
 import Control.Monad.Logger
@@ -68,8 +67,8 @@
 import Test.Sandwich.Contexts.Nix
 import Test.Sandwich.Contexts.ReverseProxy.TCP
 import Test.Sandwich.Contexts.Types.Network
-import Test.Sandwich.Contexts.Util.UUID (makeUUID)
 import Test.Sandwich.Contexts.UnixSocketPath
+import Test.Sandwich.Contexts.Util.UUID (makeUUID)
 import UnliftIO.Directory
 import UnliftIO.Environment
 import UnliftIO.Exception
@@ -96,6 +95,8 @@
   -- | Postgres default database. The @postgres@ database is always created, but you
   -- can create an additional one here. Defaults to @test@.
   , postgresNixDatabase :: Text
+  -- | Extra lines to append to `postgresql.conf`
+  , postgresNixConfExtraLines :: [Text]
   }
 defaultPostgresNixOptions :: PostgresNixOptions
 defaultPostgresNixOptions = PostgresNixOptions {
@@ -103,6 +104,7 @@
   , postgresNixUsername = "postgres"
   , postgresNixPassword = "postgres"
   , postgresNixDatabase = "test"
+  , postgresNixConfExtraLines = []
   }
 
 data PostgresContext = PostgresContext {
@@ -146,8 +148,23 @@
   => PostgresNixOptions
   -> (PostgresContext -> m a)
   -> m a
-withPostgresViaNix opts@(PostgresNixOptions {..}) action = do
-  withPostgresUnixSocketViaNix opts $ \unixSocket ->
+withPostgresViaNix opts action = do
+  nc <- getContext nixContext
+  withPostgresViaNix' nc opts action
+
+-- | Lower-level variant of 'withPostgresViaNix'.
+withPostgresViaNix' :: (
+  HasBaseContextMonad context m
+  , MonadUnliftIO m, MonadMask m, MonadFail m, MonadLogger m
+  )
+  -- | Nix context
+  => NixContext
+  -- | Options
+  -> PostgresNixOptions
+  -> (PostgresContext -> m a)
+  -> m a
+withPostgresViaNix' nc opts@(PostgresNixOptions {..}) action = do
+  withPostgresUnixSocketViaNix' nc opts $ \unixSocket ->
     withProxyToUnixSocket unixSocket $ \port ->
       action $ PostgresContext {
         postgresUsername = postgresNixUsername
@@ -189,8 +206,22 @@
   -> m a
 withPostgresUnixSocketViaNix (PostgresNixOptions {..}) action = do
   postgresBinDir <- (</> "bin") <$> buildNixSymlinkJoin [postgresNixPostgres]
-  withPostgresUnixSocket postgresBinDir postgresNixUsername postgresNixPassword postgresNixDatabase action
+  withPostgresUnixSocket postgresBinDir postgresNixUsername postgresNixPassword postgresNixDatabase postgresNixConfExtraLines action
 
+-- | Lower-level variant of 'withPostgresUnixSocket'.
+withPostgresUnixSocketViaNix' :: (
+  HasBaseContextMonad context m
+  , MonadUnliftIO m, MonadFail m, MonadMask m, MonadLogger m
+  )
+  -- | Options
+  => NixContext
+  -> PostgresNixOptions
+  -> (FilePath -> m a)
+  -> m a
+withPostgresUnixSocketViaNix' nc (PostgresNixOptions {..}) action = do
+  postgresBinDir <- (</> "bin") <$> buildNixSymlinkJoin' nc [postgresNixPostgres]
+  withPostgresUnixSocket postgresBinDir postgresNixUsername postgresNixPassword postgresNixDatabase postgresNixConfExtraLines action
+
 -- | The lowest-level raw process version.
 withPostgresUnixSocket :: (
   HasBaseContextMonad context m
@@ -204,10 +235,12 @@
   -> Text
   -- | Database
   -> Text
+  -- | Extra postgresql.conf lines
+  -> [Text]
   -- | Action callback
   -> (FilePath -> m a)
   -> m a
-withPostgresUnixSocket postgresBinDir username password database action = do
+withPostgresUnixSocket postgresBinDir username password database extraLines action = do
   Just dir <- getCurrentFolder
   baseDir <- liftIO $ createTempDirectory dir "postgres-nix"
   let dbDirName = baseDir </> "db"
@@ -243,6 +276,10 @@
           T.hPutStr h "\n"
           T.hPutStrLn h [i|listen_addresses=''|]
 
+          forM_ extraLines $ \line -> do
+            T.hPutStr h "\n"
+            T.hPutStrLn h line
+
         -- Run pg_ctl to start the DB
         createProcessWithLogging ((proc (postgresBinDir </> "pg_ctl") [
                                       "-D", dbDirName
@@ -379,5 +416,3 @@
   -- waitForSimpleQuery pc
 
   return pc
-
-#endif
diff --git a/lib/Test/Sandwich/Contexts/ReverseProxy/TCP.hs b/lib/Test/Sandwich/Contexts/ReverseProxy/TCP.hs
--- a/lib/Test/Sandwich/Contexts/ReverseProxy/TCP.hs
+++ b/lib/Test/Sandwich/Contexts/ReverseProxy/TCP.hs
@@ -6,8 +6,6 @@
 
 module Test.Sandwich.Contexts.ReverseProxy.TCP where
 
-#ifndef mingw32_HOST_OS
-
 import Control.Monad.IO.Unlift
 import Data.Conduit
 import qualified Data.Conduit.Network as DCN
@@ -39,5 +37,3 @@
       concurrently_
         (runConduit $ DCN.appSource appdata .| DCN.appSink appdataServer)
         (runConduit $ DCN.appSource appdataServer .| DCN.appSink appdata)
-
-#endif
diff --git a/sandwich-contexts.cabal b/sandwich-contexts.cabal
--- a/sandwich-contexts.cabal
+++ b/sandwich-contexts.cabal
@@ -5,12 +5,12 @@
 -- see: https://github.com/sol/hpack
 
 name:           sandwich-contexts
-version:        0.3.0.1
+version:        0.3.0.2
 synopsis:       Contexts for the Sandwich test library
 description:    Please see the <https://codedownio.github.io/sandwich documentation>.
 author:         Tom McLaughlin
 maintainer:     tom@codedown.io
-copyright:      2024 Tom McLaughlin
+copyright:      2025 Tom McLaughlin
 license:        BSD3
 build-type:     Simple
 extra-source-files:
@@ -57,7 +57,7 @@
     , aeson
     , base >=4.11 && <5
     , conduit
-    , conduit-extra
+    , conduit-extra >=1.3.7
     , containers
     , exceptions
     , filepath
@@ -73,7 +73,7 @@
     , retry
     , safe
     , sandwich >=0.3.0.0
-    , streaming-commons
+    , streaming-commons >=0.2.3.0
     , string-interpolate
     , temporary
     , text