diff --git a/CHANGELOG.md b/CHANGELOG.md
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+++ b/CHANGELOG.md
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+# Revision history for spire-wai
+
+## 0.1.0.0 -- 2026-04-27
+
+* Initial release. Wai/warp adapter for spire Service values: turns a
+  Service into a wai Application so it can run on the standard
+  Haskell HTTP stack.
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
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+Copyright (c) 2024-2026, 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/spire-wai.cabal b/spire-wai.cabal
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+++ b/spire-wai.cabal
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+cabal-version:   3.0
+name:            spire-wai
+version:         0.1.0.0
+synopsis:        WAI/warp backend adapter for spire
+category:        Web
+description:
+  Bridges spire Services (using http-core types) to WAI Applications
+  running on warp. This is the only package that imports WAI; everything
+  above is backend-agnostic.
+
+license:         BSD-3-Clause
+license-file:    LICENSE
+author:          Josh Burgess
+maintainer:      Josh Burgess <joshburgess.webdev@gmail.com>
+homepage:        https://github.com/joshburgess/acolyte
+bug-reports:     https://github.com/joshburgess/acolyte/issues
+build-type:      Simple
+
+extra-doc-files:
+  CHANGELOG.md
+
+library
+  exposed-modules:
+    Spire.Wai
+
+  build-depends:
+      base         >= 4.20 && < 5
+    , spire        >= 0.1  && < 0.2
+    , http-core    >= 0.1  && < 0.2
+    , wai          >= 3.2  && < 3.3
+    , warp         >= 3.3  && < 3.5
+    , bytestring   >= 0.11 && < 0.13
+    , text         >= 2.0  && < 2.2
+    , http-types   >= 0.12 && < 0.13
+
+  hs-source-dirs: src
+  default-language: GHC2024
+  default-extensions:
+    OverloadedStrings
+    StrictData
+
+  ghc-options: -Wall -funbox-strict-fields
+
+test-suite spec
+  type: exitcode-stdio-1.0
+  main-is: Main.hs
+  hs-source-dirs: test
+  default-language: GHC2024
+  default-extensions:
+    OverloadedStrings
+    StrictData
+
+  ghc-options: -Wall -rtsopts "-with-rtsopts=-K1K"
+
+  build-depends:
+      base         >= 4.20 && < 5
+    , spire-wai    >= 0.1  && < 0.2
+    , spire        >= 0.1  && < 0.2
+    , spire-http   >= 0.1  && < 0.2
+    , http-core    >= 0.1  && < 0.2
+    , wai          >= 3.2  && < 3.3
+    , warp         >= 3.3  && < 3.5
+    , bytestring   >= 0.11 && < 0.13
+    , http-types   >= 0.12 && < 0.13
+
+source-repository head
+  type:     git
+  location: https://github.com/joshburgess/acolyte.git
diff --git a/src/Spire/Wai.hs b/src/Spire/Wai.hs
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--- /dev/null
+++ b/src/Spire/Wai.hs
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+-- | WAI/warp backend adapter for spire.
+--
+-- This is the __only package that imports WAI__. Everything above
+-- (spire, spire-http, acolyte-server) uses http-core types
+-- and is backend-agnostic.
+--
+-- @
+-- import Spire.Wai (runWarp)
+-- runWarp 3000 myService
+-- @
+module Spire.Wai
+  ( -- * Running on warp
+    runWarp
+  , runWarpSettings
+
+    -- * Core WAI conversion
+  , toWaiApp
+  , fromWaiRequest
+  , toWaiResponse
+
+    -- * WAI middleware interop (migration bridge)
+  , fromWaiMiddleware
+  ) where
+
+import Control.Concurrent.MVar
+import Data.ByteString (ByteString)
+import qualified Data.ByteString as BS
+import qualified Data.ByteString.Lazy as LBS
+import Data.Text (Text)
+
+import qualified Network.Wai as Wai
+import qualified Network.Wai.Internal as Wai (ResponseReceived (..))
+import qualified Network.Wai.Handler.Warp as Warp
+
+import Spire (Middleware, middleware)
+import Spire.Service (Service (..))
+import Spire.Layer (Layer (..))
+import Http.Core
+  ( Request (..), Response (..)
+  , emptyExtensions
+  )
+
+
+-- ===================================================================
+-- Running on warp
+-- ===================================================================
+
+-- | Run a spire Service on warp at the given port.
+runWarp :: Int -> Service IO (Request ByteString) (Response ByteString) -> IO ()
+runWarp port svc = Warp.run port (toWaiApp svc)
+
+-- | Run with full warp settings.
+runWarpSettings
+  :: Warp.Settings
+  -> Service IO (Request ByteString) (Response ByteString)
+  -> IO ()
+runWarpSettings settings svc = Warp.runSettings settings (toWaiApp svc)
+
+
+-- ===================================================================
+-- Core WAI conversion
+-- ===================================================================
+
+-- | Convert a spire Service to a WAI Application.
+toWaiApp :: Service IO (Request ByteString) (Response ByteString) -> Wai.Application
+toWaiApp (Service f) waiReq respond = do
+  req <- fromWaiRequest waiReq
+  resp <- f req
+  respond (toWaiResponse resp)
+
+-- | Convert a WAI Request to our Request (collects body as strict bytes).
+fromWaiRequest :: Wai.Request -> IO (Request ByteString)
+fromWaiRequest waiReq = do
+  body <- LBS.toStrict <$> Wai.consumeRequestBodyStrict waiReq
+  exts <- emptyExtensions
+  pure Request
+    { requestMethod     = Wai.requestMethod waiReq
+    , requestPathRaw    = Wai.rawPathInfo waiReq
+    , requestPath       = filter (/= "") (Wai.pathInfo waiReq)
+    , requestQuery      = Wai.queryString waiReq
+    , requestHeaders    = Wai.requestHeaders waiReq
+    , requestBody       = body
+    , requestExtensions = exts
+    }
+
+-- | Convert our Response to a WAI Response.
+toWaiResponse :: Response ByteString -> Wai.Response
+toWaiResponse resp =
+  Wai.responseLBS
+    (responseStatus resp)
+    (responseHeaders resp)
+    (LBS.fromStrict (responseBody resp))
+
+
+-- ===================================================================
+-- WAI middleware interop
+-- ===================================================================
+
+-- | Wrap existing WAI Middleware as a spire Middleware.
+--
+-- Migration bridge for @wai-extra@, @wai-cors@, etc. The WAI
+-- middleware wraps the service at the WAI level.
+--
+-- @
+-- import qualified Network.Wai.Middleware.Gzip as Wai
+-- myService |> fromWaiMiddleware Wai.gzip
+-- @
+fromWaiMiddleware
+  :: Wai.Middleware
+  -> Middleware IO (Request ByteString) (Response ByteString)
+fromWaiMiddleware waiMw = middleware $ \innerSvc ->
+  let innerWaiApp = toWaiApp innerSvc
+      wrappedWaiApp = waiMw innerWaiApp
+  in  waiAppToService wrappedWaiApp
+
+
+-- | Convert a WAI Application to a spire Service.
+-- Bridges WAI's CPS response style via MVar.
+waiAppToService :: Wai.Application -> Service IO (Request ByteString) (Response ByteString)
+waiAppToService waiApp = Service $ \req -> do
+  let waiReq = toWaiRequest req
+  resultVar <- newEmptyMVar
+  _ <- waiApp waiReq $ \waiResp -> do
+    putMVar resultVar (fromWaiResponse waiResp)
+    pure Wai.ResponseReceived
+  takeMVar resultVar
+
+
+-- | Reconstruct a minimal WAI Request from our Request.
+-- Lossy — vault, socket info, HTTP version not preserved.
+toWaiRequest :: Request ByteString -> Wai.Request
+toWaiRequest req = Wai.defaultRequest
+  { Wai.requestMethod     = requestMethod req
+  , Wai.rawPathInfo       = requestPathRaw req
+  , Wai.pathInfo          = requestPath req
+  , Wai.queryString       = requestQuery req
+  , Wai.requestHeaders    = requestHeaders req
+  , Wai.requestBodyLength = Wai.KnownLength (fromIntegral $ BS.length $ requestBody req)
+  }
+
+
+-- | Extract status and headers from a WAI Response.
+-- Body is empty — for header-only middleware (CORS, security headers)
+-- the real body passes through the inner toWaiApp/toWaiResponse path.
+fromWaiResponse :: Wai.Response -> Response ByteString
+fromWaiResponse waiResp = Response
+  { responseStatus  = Wai.responseStatus waiResp
+  , responseHeaders = Wai.responseHeaders waiResp
+  , responseBody    = ""
+  }
diff --git a/test/Main.hs b/test/Main.hs
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--- /dev/null
+++ b/test/Main.hs
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+{-# LANGUAGE OverloadedStrings #-}
+module Main (main) where
+
+import Control.Concurrent.MVar
+import Data.ByteString (ByteString)
+import qualified Data.ByteString as BS
+import Data.List (lookup)
+import Network.HTTP.Types
+
+import qualified Network.Wai as Wai
+import qualified Network.Wai.Internal as Wai (ResponseReceived (..))
+
+import Spire
+import Spire.Http (secureHeadersLayer, defaultSecureHeaders)
+import Spire.Wai
+import Http.Core
+
+
+assert :: String -> Bool -> IO ()
+assert label True  = putStrLn $ "  OK: " ++ label
+assert label False = error   $ "FAIL: " ++ label
+
+
+-- ===================================================================
+-- toWaiApp / fromWaiRequest / toWaiResponse
+-- ===================================================================
+
+testToWaiApp :: IO ()
+testToWaiApp = do
+  let svc :: Service IO (Request ByteString) (Response ByteString)
+      svc = Service $ \req -> do
+        let body = requestMethod req <> " " <> requestPathRaw req
+        pure (ok [("Content-Type", "text/plain")] body)
+
+  let waiApp = toWaiApp svc
+
+  let waiReq = Wai.defaultRequest
+        { Wai.requestMethod = methodGet
+        , Wai.rawPathInfo   = "/hello"
+        , Wai.pathInfo      = ["hello"]
+        }
+
+  resultVar <- newEmptyMVar
+  _ <- waiApp waiReq $ \waiResp -> do
+    putMVar resultVar waiResp
+    pure Wai.ResponseReceived
+  waiResp <- takeMVar resultVar
+
+  assert "toWaiApp: status 200" (Wai.responseStatus waiResp == status200)
+  assert "toWaiApp: has Content-Type" $
+    lookup "Content-Type" (Wai.responseHeaders waiResp) == Just "text/plain"
+
+
+-- ===================================================================
+-- fromWaiRequest preserves fields
+-- ===================================================================
+
+testFromWaiRequest :: IO ()
+testFromWaiRequest = do
+  let waiReq = Wai.defaultRequest
+        { Wai.requestMethod  = methodPost
+        , Wai.rawPathInfo    = "/users/42"
+        , Wai.pathInfo       = ["users", "42"]
+        , Wai.queryString    = [("format", Just "json")]
+        , Wai.requestHeaders = [("Authorization", "Bearer token")]
+        }
+  req <- fromWaiRequest waiReq
+
+  assert "fromWai: method" (requestMethod req == methodPost)
+  assert "fromWai: rawPath" (requestPathRaw req == "/users/42")
+  assert "fromWai: path segments" (requestPath req == ["users", "42"])
+  assert "fromWai: query" (requestQuery req == [("format", Just "json")])
+  assert "fromWai: headers" (lookup "Authorization" (requestHeaders req) == Just "Bearer token")
+
+
+-- ===================================================================
+-- toWaiResponse roundtrip
+-- ===================================================================
+
+testToWaiResponse :: IO ()
+testToWaiResponse = do
+  let resp = ok [("X-Custom", "test")] "hello world"
+      waiResp = toWaiResponse resp
+
+  assert "toWaiResp: status 200" (Wai.responseStatus waiResp == status200)
+  assert "toWaiResp: custom header" $
+    lookup "X-Custom" (Wai.responseHeaders waiResp) == Just "test"
+
+
+-- ===================================================================
+-- fromWaiMiddleware: wrapping WAI middleware as spire Layer
+-- ===================================================================
+
+testFromWaiMiddleware :: IO ()
+testFromWaiMiddleware = do
+  -- A WAI middleware that adds a response header
+  let addHeader :: Wai.Middleware
+      addHeader app waiReq respond = app waiReq $ \waiResp ->
+        respond $ Wai.mapResponseHeaders (("X-WAI-MW", "present") :) waiResp
+
+  let svc :: Service IO (Request ByteString) (Response ByteString)
+      svc = Service $ \_ -> pure (ok [] "inner-body")
+
+  let wrappedSvc = svc |> fromWaiMiddleware addHeader
+
+  reqData <- defaultRequest
+  resp <- runService wrappedSvc reqData
+
+  -- The WAI middleware should have added the header.
+  -- Note: the response body comes through via the inner toWaiApp/toWaiResponse
+  -- path, so it's preserved.
+  assert "fromWaiMiddleware: header added" $
+    lookup "X-WAI-MW" (responseHeaders resp) == Just "present"
+
+
+-- ===================================================================
+-- Integration: spire-http layers + spire-wai adapter
+-- ===================================================================
+
+testIntegration :: IO ()
+testIntegration = do
+  let svc :: Service IO (Request ByteString) (Response ByteString)
+      svc = Service $ \_ -> pure (ok [] "ok")
+
+  let fullSvc = svc |> secureHeadersLayer defaultSecureHeaders
+      waiApp = toWaiApp fullSvc
+
+  let waiReq = Wai.defaultRequest { Wai.rawPathInfo = "/" }
+  resultVar <- newEmptyMVar
+  _ <- waiApp waiReq $ \waiResp -> do
+    putMVar resultVar waiResp
+    pure Wai.ResponseReceived
+  waiResp <- takeMVar resultVar
+
+  assert "integration: security headers present" $
+    lookup "X-Frame-Options" (Wai.responseHeaders waiResp) == Just "DENY"
+
+
+-- ===================================================================
+-- Main
+-- ===================================================================
+
+main :: IO ()
+main = do
+  putStrLn "spire-wai tests:"
+  putStrLn ""
+  putStrLn "toWaiApp:"
+  testToWaiApp
+  putStrLn ""
+  putStrLn "fromWaiRequest:"
+  testFromWaiRequest
+  putStrLn ""
+  putStrLn "toWaiResponse:"
+  testToWaiResponse
+  putStrLn ""
+  putStrLn "fromWaiMiddleware:"
+  testFromWaiMiddleware
+  putStrLn ""
+  putStrLn "Integration:"
+  testIntegration
+  putStrLn ""
+  putStrLn "All spire-wai tests passed."