diff --git a/CHANGELOG.md b/CHANGELOG.md
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+# Changelog
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.0.0] - 2026-04-25
+
+Initial release. Streamly adapter for
+[`valiant`](https://hackage.haskell.org/package/valiant). Exposes
+`selectStreamly` (cursor-based) and `foldStreamly` (single-shot
+extended-protocol) as `Stream IO r` values from
+[`streamly-core`](https://hackage.haskell.org/package/streamly-core).
+
+[0.1.0.0]: https://github.com/joshburgess/valiant/releases/tag/v0.1.0.0
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
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+Copyright (c) 2026 Josh Burgess
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice,
+   this list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from this
+   software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
diff --git a/README.md b/README.md
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+++ b/README.md
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+# valiant-streamly
+
+[Streamly](https://hackage.haskell.org/package/streamly-core) adapter
+for [`valiant`](https://hackage.haskell.org/package/valiant).
+
+Produces `Stream IO r` values from query results.
+
+## Quick start
+
+```haskell
+import Valiant
+import Valiant.Streamly
+import Streamly.Data.Stream qualified as Stream
+import Streamly.Data.Fold qualified as Fold
+
+countUsers :: Pool -> IO Int
+countUsers pool =
+  withTransaction pool $ \tx ->
+    Stream.fold Fold.length $
+      selectStreamly (txConn tx) listAllUsers () 500
+```
+
+## Two streaming strategies
+
+- `selectStreamly conn stmt params batchSize` — cursor-based. Must run
+  inside a transaction.
+- `foldStreamly conn stmt params` — single-shot extended-protocol
+  query. No transaction required.
+
+Both functions accumulate one result set at a time before yielding.
+For truly incremental memory use, drive `Valiant.withCursor` /
+`Valiant.fetchBatch` directly.
+
+See the [valiant tutorial](https://github.com/joshburgess/valiant/blob/main/docs/TUTORIAL.md)
+for `Statement` definitions and the `valiant prepare` workflow.
diff --git a/src/Valiant/Streamly.hs b/src/Valiant/Streamly.hs
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+++ b/src/Valiant/Streamly.hs
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+{-# OPTIONS_GHC -fno-full-laziness #-}
+
+-- | Streamly streaming adapter for valiant.
+--
+-- Produces @Stream IO r@ values from query results, enabling
+-- high-performance composable stream processing with streamly.
+--
+-- @
+-- import Valiant
+-- import Valiant.Streamly
+-- import Streamly.Data.Stream qualified as Stream
+-- import Streamly.Data.Fold qualified as Fold
+--
+-- withTransaction pool $ \\tx -> do
+--   count <- Stream.fold Fold.length $
+--     selectStreamly (txConn tx) listAllUsers () 500
+--   print count
+-- @
+module Valiant.Streamly
+  ( -- * Cursor-based streaming (requires transaction)
+    selectStreamly
+    -- * Fold-based streaming (no transaction required)
+  , foldStreamly
+  ) where
+
+import Streamly.Data.Stream (Stream)
+import Streamly.Data.Stream qualified as Stream
+import Valiant (Connection, Statement, fetchAll, fetchAllCursor)
+
+-- | Stream query results using a server-side cursor.
+--
+-- Must be called inside a transaction. Fetches rows in batches and
+-- yields decoded rows one at a time.
+--
+-- Note: rows are accumulated in memory before yielding (see
+-- 'Valiant.Conduit.selectSource' for the same caveat).
+selectStreamly
+  :: Connection
+  -> Statement p r
+  -> p
+  -> Int
+  -- ^ Batch size
+  -> Stream IO r
+selectStreamly conn stmt params batchSize =
+  Stream.concatEffect (Stream.fromList <$> fetchAllCursor conn stmt params batchSize)
+
+-- | Stream query results using single-shot extended-protocol execution.
+--
+-- Does not require a transaction.
+foldStreamly
+  :: Connection
+  -> Statement p r
+  -> p
+  -> Stream IO r
+foldStreamly conn stmt params =
+  Stream.concatEffect (Stream.fromList <$> fetchAll conn stmt params)
diff --git a/test/Main.hs b/test/Main.hs
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--- /dev/null
+++ b/test/Main.hs
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+module Main where
+
+import Data.Int (Int32)
+import Data.Text (Text)
+import Valiant
+import Valiant.Streamly (foldStreamly, selectStreamly)
+import Streamly.Data.Fold qualified as Fold
+import Streamly.Data.Stream qualified as Stream
+import Test.Hspec
+import TestSupport
+
+main :: IO ()
+main = hspec $ do
+  describe "Valiant.Streamly" $ do
+    describe "selectStreamly (cursor-based)" $ do
+      it "streams all rows from a cursor" $ do
+        withTestConnection $ \conn -> withSchema conn $ do
+          insertTestUsers conn
+          withTransactionConn conn $ \tx -> do
+            rows <- Stream.fold Fold.toList $
+              selectStreamly (txConn tx) stmtListAll () 2
+            length rows `shouldBe` 5
+
+      it "returns empty for no rows" $ do
+        withTestConnection $ \conn -> withSchema conn $ do
+          withTransactionConn conn $ \tx -> do
+            rows <- Stream.fold Fold.toList $
+              selectStreamly (txConn tx) stmtListAll () 10
+            rows `shouldBe` ([] :: [(Int32, Text)])
+
+      it "works with small batch size" $ do
+        withTestConnection $ \conn -> withSchema conn $ do
+          insertTestUsers conn
+          withTransactionConn conn $ \tx -> do
+            rows <- Stream.fold Fold.toList $
+              selectStreamly (txConn tx) stmtListAll () 1
+            length rows `shouldBe` 5
+
+    describe "foldStreamly (no transaction)" $ do
+      it "streams all rows without a transaction" $ do
+        withTestConnection $ \conn -> withSchema conn $ do
+          insertTestUsers conn
+          rows <- Stream.fold Fold.toList $
+            foldStreamly conn stmtListAll ()
+          length rows `shouldBe` 5
+
+      it "returns empty for no rows" $ do
+        withTestConnection $ \conn -> withSchema conn $ do
+          rows <- Stream.fold Fold.toList $
+            foldStreamly conn stmtListAll ()
+          rows `shouldBe` ([] :: [(Int32, Text)])
+
+      it "composes with streamly combinators" $ do
+        withTestConnection $ \conn -> withSchema conn $ do
+          insertTestUsers conn
+          count <- Stream.fold Fold.length $
+            foldStreamly conn stmtListAll ()
+          count `shouldBe` 5
diff --git a/test/TestSupport.hs b/test/TestSupport.hs
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--- /dev/null
+++ b/test/TestSupport.hs
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+module TestSupport
+  ( withTestConnection
+  , withSchema
+  , insertTestUsers
+  , stmtListAll
+  , stmtSelectOne
+  ) where
+
+import Data.ByteString (ByteString)
+import Data.ByteString.Char8 qualified as BS8
+import Data.Int (Int32)
+import Data.Text (Text)
+import Valiant
+import System.Environment (lookupEnv)
+
+requireDatabaseUrl :: IO ByteString
+requireDatabaseUrl = do
+  mUrl <- lookupEnv "DATABASE_URL"
+  case mUrl of
+    Just url -> pure (BS8.pack url)
+    Nothing -> error "DATABASE_URL is not set."
+
+withTestConnection :: (Connection -> IO a) -> IO a
+withTestConnection action = do
+  url <- requireDatabaseUrl
+  conn <- connectString url
+  result <- action conn
+  close conn
+  pure result
+
+withSchema :: Connection -> IO a -> IO a
+withSchema conn action = do
+  _ <- simpleQuery conn "DROP TABLE IF EXISTS users_streamly CASCADE"
+  _ <- simpleQuery conn
+    "CREATE TABLE users_streamly (\
+    \  id SERIAL PRIMARY KEY,\
+    \  name TEXT NOT NULL,\
+    \  email TEXT\
+    \)"
+  result <- action
+  _ <- simpleQuery conn "DROP TABLE IF EXISTS users_streamly CASCADE"
+  pure result
+
+insertTestUsers :: Connection -> IO ()
+insertTestUsers conn = do
+  _ <- simpleQuery conn
+    "INSERT INTO users_streamly (name, email) VALUES \
+    \('Alice', 'alice@example.com'),\
+    \('Bob', 'bob@example.com'),\
+    \('Carol', NULL),\
+    \('Dave', 'dave@example.com'),\
+    \('Eve', 'eve@example.com')"
+  pure ()
+
+stmtListAll :: Statement () (Int32, Text)
+stmtListAll = mkStatement
+  "SELECT id, name FROM users_streamly ORDER BY id"
+  [] ["id", "name"] "<test>"
+
+stmtSelectOne :: Statement Int32 (Int32, Text, Maybe Text)
+stmtSelectOne = mkStatement
+  "SELECT id, name, email FROM users_streamly WHERE id = $1"
+  [23] ["id", "name", "email"] "<test>"
diff --git a/valiant-streamly.cabal b/valiant-streamly.cabal
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+++ b/valiant-streamly.cabal
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+cabal-version:   3.0
+name:            valiant-streamly
+version:         0.1.0.0
+synopsis:        Streamly streaming adapter for valiant
+description:
+  Stream PostgreSQL query results using the @streamly@ library.
+  Provides cursor-based and fold-based producers as @Stream IO r@
+  values, enabling high-performance composable stream processing.
+license:         BSD-3-Clause
+license-file:    LICENSE
+author:          Josh Burgess
+maintainer:      joshburgess.webdev@gmail.com
+category:        Database
+homepage:        https://github.com/joshburgess/valiant
+bug-reports:     https://github.com/joshburgess/valiant/issues
+build-type:      Simple
+extra-doc-files:
+  README.md
+  CHANGELOG.md
+tested-with:     GHC ==9.10.3
+
+source-repository head
+  type:     git
+  location: https://github.com/joshburgess/valiant
+  subdir:   adapters/valiant-streamly
+
+flag werror
+  description: Enable -Werror for development builds.
+  default:     False
+  manual:      True
+
+common warnings
+  ghc-options: -Wall -Wcompat -Wno-unticked-promoted-constructors -funbox-strict-fields -fspecialise-aggressively
+  if flag(werror)
+    ghc-options: -Werror
+
+library
+  import:           warnings
+  hs-source-dirs:   src
+  default-language: GHC2021
+  default-extensions:
+    DerivingStrategies
+    OverloadedStrings
+    StrictData
+
+  exposed-modules:
+    Valiant.Streamly
+
+  build-depends:
+    , base            >=4.17 && <5
+    , valiant         >=0.1  && <0.2
+    , streamly-core   >=0.2  && <0.4
+
+test-suite valiant-streamly-test
+  import:           warnings
+  type:             exitcode-stdio-1.0
+  hs-source-dirs:   test
+  main-is:          Main.hs
+  default-language: GHC2021
+  default-extensions:
+    OverloadedStrings
+
+  ghc-options: -rtsopts "-with-rtsopts=-K8K"
+
+  other-modules:
+    TestSupport
+
+  build-depends:
+    , base            >=4.17 && <5
+    , bytestring      >=0.11 && <0.13
+    , hspec           >=2.11 && <2.13
+    , valiant
+    , valiant-streamly
+    , pg-wire
+    , streamly-core   >=0.2  && <0.4
+    , text            >=2.0  && <2.2