feat: add max_thinking_tokens option to ClaudeAgentOptions (#298)

Add support for controlling the maximum number of tokens allocated to
extended thinking blocks via the max_thinking_tokens parameter.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

.gitignore

@@ -26,6 +26,7 @@ venv/
 ENV/
 env/
 .venv
+uv.lock
 
 # IDEs
 .vscode/

src/claude_agent_sdk/_internal/transport/subprocess_cli.py

@@ -216,6 +216,11 @@ class SubprocessCLITransport(Transport):
             # String mode: use --print with the prompt
             cmd.extend(["--print", "--", str(self._prompt)])
 
+        if self._options.max_thinking_tokens is not None:
+            cmd.extend(
+                ["--max-thinking-tokens", str(self._options.max_thinking_tokens)]
+            )
+
         # Check if command line is too long (Windows limitation)
         cmd_str = " ".join(cmd)
         if len(cmd_str) > _CMD_LENGTH_LIMIT and self._options.agents:

src/claude_agent_sdk/types.py

@@ -554,6 +554,8 @@ class ClaudeAgentOptions:
     setting_sources: list[SettingSource] | None = None
     # Plugin configurations for custom plugins
     plugins: list[SdkPluginConfig] = field(default_factory=list)
+    # Max tokens for thinking blocks
+    max_thinking_tokens: int | None = None
 
 
 # SDK Control Protocol

tests/test_transport.py

@@ -129,6 +129,17 @@ class TestSubprocessCLITransport:
         assert "--max-turns" in cmd
         assert "5" in cmd
 
+    def test_build_command_with_max_thinking_tokens(self):
+        """Test building CLI command with max_thinking_tokens option."""
+        transport = SubprocessCLITransport(
+            prompt="test",
+            options=make_options(max_thinking_tokens=5000),
+        )
+
+        cmd = transport._build_command()
+        assert "--max-thinking-tokens" in cmd
+        assert "5000" in cmd
+
     def test_build_command_with_add_dirs(self):
         """Test building CLI command with add_dirs option."""
         from pathlib import Path