diff --git a/baikai-claude.cabal b/baikai-claude.cabal
--- a/baikai-claude.cabal
+++ b/baikai-claude.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.4
 name:          baikai-claude
-version:       0.3.0.2
+version:       0.4.0.0
 synopsis:      Anthropic Claude providers for the baikai abstraction
 description:
   Wraps the claude Haskell package as a Baikai Provider for both the Anthropic API and the
diff --git a/src/Baikai/Provider/Claude/Cli.hs b/src/Baikai/Provider/Claude/Cli.hs
--- a/src/Baikai/Provider/Claude/Cli.hs
+++ b/src/Baikai/Provider/Claude/Cli.hs
@@ -45,6 +45,7 @@
 import Baikai.Response qualified as Resp
 import Baikai.StopReason (StopReason (..))
 import Baikai.Stream (liftCompleteToStream)
+import Baikai.ThinkingLevel (ThinkingLevel (ThinkingMinimal), renderThinkingLevel)
 import Baikai.Usage (zeroUsage)
 import Control.Exception (SomeAsyncException (..), SomeException, displayException, fromException, throwIO, try)
 import Control.Lens ((^.))
@@ -138,17 +139,30 @@
 -- | Render the executable and arguments for a @claude -p@ batch call.
 -- The prompt is preceded by @--@ so dash-leading prompts and variadic
 -- flags in 'extraArgs' cannot be parsed as options.
-claudeCliCommand :: ClaudeCliConfig -> Model -> Context -> (FilePath, [String])
-claudeCliCommand cfg m ctx =
+claudeCliCommand :: ClaudeCliConfig -> Model -> Context -> Options -> (FilePath, [String])
+claudeCliCommand cfg m ctx opts =
   ( cfg ^. #executable,
     ["-p"]
       <> modelArgs m
       <> ["--output-format", "json", "--no-session-persistence"]
       <> systemPromptArgs ctx
+      <> effortArgs opts
       <> fmap Text.unpack (cfg ^. #extraArgs)
       <> ["--", Text.unpack (Internal.renderPrompt ctx)]
   )
 
+-- | Render @--effort@ from 'Options.thinking'. Claude's @--effort@ has
+-- no @minimal@, so the lowest Baikai level collapses to @low@; when
+-- 'thinking' is unset, no effort flag is emitted.
+effortArgs :: Options -> [String]
+effortArgs opts = case opts ^. #thinking of
+  Nothing -> []
+  Just lvl -> ["--effort", Text.unpack (claudeEffortValue lvl)]
+
+claudeEffortValue :: ThinkingLevel -> Text
+claudeEffortValue ThinkingMinimal = "low"
+claudeEffortValue lvl = renderThinkingLevel lvl
+
 -- | The shape of @claude -p --output-format json@ stdout.
 data ClaudeCliResult = ClaudeCliResult
   { result :: !Text,
@@ -190,8 +204,8 @@
     isResult _ = False
 
 runClaudeCli :: ClaudeCliConfig -> Model -> Context -> Options -> IO Resp.Response
-runClaudeCli cfg m ctx _opts = do
-  let (exe, args) = claudeCliCommand cfg m ctx
+runClaudeCli cfg m ctx opts = do
+  let (exe, args) = claudeCliCommand cfg m ctx opts
   start <- getCurrentTime
   executed <-
     trySync $
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -34,6 +34,7 @@
       [ commandRenderingTest,
         effortRenderingTests,
         batchCommandRenderingTest,
+        batchEffortRenderingTests,
         stderrFloodTest,
         compatDetectionTest,
         rejectsImageToolResultsTest,
@@ -174,7 +175,7 @@
           emptyContext
             & #systemPrompt .~ Just "Be terse."
             & #messages .~ Vector.singleton (user "-begin with a dash")
-    ClaudeCli.claudeCliCommand cfg model ctx
+    ClaudeCli.claudeCliCommand cfg model ctx emptyOptions
       @?= ( "/bin/claude",
             [ "-p",
               "--model",
@@ -190,6 +191,50 @@
               "-begin with a dash"
             ]
           )
+
+batchEffortRenderingTests :: TestTree
+batchEffortRenderingTests =
+  testGroup
+    "claude -p argv renders reasoning effort between the system prompt and extra args"
+    [ testCase name $ do
+        let cfg =
+              ClaudeCli.defaultClaudeCliConfig
+                { ClaudeCli.executable = "/bin/claude",
+                  ClaudeCli.extraArgs = ["--allowedTools", "Read"]
+                }
+            model =
+              emptyModel
+                & #modelId .~ "sonnet"
+                & #api .~ AnthropicMessagesCli
+                & #provider .~ "anthropic"
+            ctx =
+              emptyContext
+                & #systemPrompt .~ Just "Be terse."
+                & #messages .~ Vector.singleton (user "ping")
+            opts = emptyOptions & #thinking .~ Just level
+        ClaudeCli.claudeCliCommand cfg model ctx opts
+          @?= ( "/bin/claude",
+                [ "-p",
+                  "--model",
+                  "sonnet",
+                  "--output-format",
+                  "json",
+                  "--no-session-persistence",
+                  "--system-prompt",
+                  "Be terse.",
+                  "--effort",
+                  expected,
+                  "--allowedTools",
+                  "Read",
+                  "--",
+                  "ping"
+                ]
+              )
+    | (name, level, expected) <-
+        [ ("minimal as low", ThinkingMinimal, "low"),
+          ("max", ThinkingMax, "max")
+        ]
+    ]
 
 stderrFloodTest :: TestTree
 stderrFloodTest =