Java API Reference - Spring AI Community

Complete API reference for the Claude Agent SDK Java, including all classes, methods, and types.

This documentation follows the structure of the official Python SDK documentation.

Installation

Maven

<dependency>
    <groupId>org.springaicommunity</groupId>
    <artifactId>claude-code-sdk</artifactId>
    <version>1.0.0-SNAPSHOT</version>
</dependency>

Gradle

implementation 'org.springaicommunity:claude-code-sdk:1.0.0-SNAPSHOT'

Three-API Architecture

The Java SDK provides three ways to interact with Claude Code:

Quick Comparison

Feature	`Query`	`ClaudeSyncClient`	`ClaudeAsyncClient`
Style	Static methods	Iterator-based	Flux/Mono (Reactor)
Session	New each call	Reuses same session	Reuses same session
Conversation	Single exchange	Multi-turn	Multi-turn
Hooks	Not supported	Supported	Supported
MCP Servers	Not supported	Supported	Supported
Permission Callbacks	Not supported	Supported	Supported
Use Case	CLI tools, scripts	Traditional apps	Non-blocking apps

Both ClaudeSyncClient and ClaudeAsyncClient provide the same capabilities. They differ only in programming paradigm (blocking vs non-blocking).

When to Use `Query`

Best for:

One-off questions where you don’t need conversation history
Simple automation scripts
CLI tools and batch processing

When to Use `ClaudeSyncClient`

Best for:

Multi-turn conversations with context
Tool interception with hooks
MCP server integration
Standard Java iteration patterns

When to Use `ClaudeAsyncClient`

Best for:

Spring WebFlux applications
Server-Sent Events (SSE) streaming
Non-blocking I/O requirements
Reactive pipelines

`Query` - One-Shot API

Creates a new session for each interaction. Provides static methods for simple queries.

Methods

Method	Return Type	Description
`text(prompt)`	`String`	Simple one-liner, returns text response
`text(prompt, options)`	`String`	With configuration options
`execute(prompt)`	`QueryResult`	Full result with metadata
`execute(prompt, options)`	`QueryResult`	With configuration options
`query(prompt)`	`Iterable<Message>`	Iterate over messages
`stream(prompt)`	`Stream<Message>`	Java Stream over messages

Example - Simple query

import org.springaicommunity.claude.agent.sdk.Query;

// Simplest usage - one line
String answer = Query.text("What is 2+2?");
System.out.println(answer);  // "4"

Example - With options

import org.springaicommunity.claude.agent.sdk.Query;
import org.springaicommunity.claude.agent.sdk.QueryOptions;
import java.time.Duration;

QueryOptions options = QueryOptions.builder()
    .model("claude-sonnet-4-20250514")
    .appendSystemPrompt("Be concise")
    .timeout(Duration.ofMinutes(5))
    .build();

String response = Query.text("Explain Java", options);
System.out.println(response);

Example - Full result with metadata

import org.springaicommunity.claude.agent.sdk.Query;
import org.springaicommunity.claude.agent.sdk.types.QueryResult;

QueryResult result = Query.execute("Write a haiku about Java");

System.out.println(result.text().orElse(""));
System.out.println("Cost: $" + result.metadata().cost().calculateTotal());
System.out.println("Duration: " + result.metadata().getDuration().toMillis() + "ms");
System.out.println("Model: " + result.metadata().model());

Example - Streaming iteration

for (Message msg : Query.query("Explain recursion")) {
    if (msg instanceof AssistantMessage am) {
        am.getTextContent().ifPresent(System.out::print);
    }
}

// Or with Stream API
Query.stream("Explain recursion")
    .filter(msg -> msg instanceof AssistantMessage)
    .forEach(msg -> System.out.println(msg));

`ClaudeClient` - Factory

Factory class for creating sync and async clients.

Methods

Method	Return Type	Description
`sync()`	`ClaudeSyncClient.Builder`	Create blocking client builder
`sync(options)`	`ClaudeSyncClient.Builder`	Create builder with pre-configured CLIOptions
`async()`	`ClaudeAsyncClient.Builder`	Create reactive client builder
`async(options)`	`ClaudeAsyncClient.Builder`	Create builder with pre-configured CLIOptions

Example - Factory pattern

// Sync client with fluent builder
try (ClaudeSyncClient client = ClaudeClient.sync()
        .workingDirectory(Path.of("."))
        .model("claude-sonnet-4-20250514")
        .systemPrompt("You are helpful")
        .timeout(Duration.ofMinutes(5))
        .build()) {
    // Use client
}

// Async client
ClaudeAsyncClient client = ClaudeClient.async()
    .workingDirectory(Path.of("."))
    .permissionMode(PermissionMode.BYPASS_PERMISSIONS)
    .build();

`ClaudeSyncClient` - Blocking Client

Maintains a conversation session across multiple exchanges. Uses iterator-based message handling.

Methods

Method	Description
`connect(prompt)`	Start session with initial prompt
`query(prompt)`	Send follow-up message
`receiveResponse()`	Get iterator over response messages
`interrupt()`	Stop current operation
`close()`	End session and release resources

Example - Multi-turn conversation

import org.springaicommunity.claude.agent.sdk.ClaudeClient;
import org.springaicommunity.claude.agent.sdk.ClaudeSyncClient;
import org.springaicommunity.claude.agent.sdk.parsing.ParsedMessage;
import org.springaicommunity.claude.agent.sdk.types.AssistantMessage;
import java.util.Iterator;

try (ClaudeSyncClient client = ClaudeClient.sync()
        .workingDirectory(Path.of("."))
        .build()) {

    // First turn
    client.connect("My favorite color is blue. Remember this.");
    Iterator<ParsedMessage> response = client.receiveResponse();
    while (response.hasNext()) {
        ParsedMessage msg = response.next();
        if (msg.isRegularMessage() && msg.asMessage() instanceof AssistantMessage am) {
            am.getTextContent().ifPresent(System.out::println);
        }
    }

    // Second turn - Claude remembers context
    client.query("What is my favorite color?");
    response = client.receiveResponse();
    while (response.hasNext()) {
        ParsedMessage msg = response.next();
        if (msg.isRegularMessage() && msg.asMessage() instanceof AssistantMessage am) {
            am.getTextContent().ifPresent(System.out::println);  // "blue"
        }
    }
}

Example - With hooks

import org.springaicommunity.claude.agent.sdk.hooks.HookRegistry;
import org.springaicommunity.claude.agent.sdk.hooks.HookInput;
import org.springaicommunity.claude.agent.sdk.hooks.HookOutput;

HookRegistry hookRegistry = new HookRegistry();

// Block dangerous commands
hookRegistry.registerPreToolUse("Bash", input -> {
    if (input instanceof HookInput.PreToolUseInput preToolUse) {
        String cmd = preToolUse.getArgument("command", String.class).orElse("");
        if (cmd.contains("rm -rf")) {
            return HookOutput.block("Dangerous command blocked");
        }
    }
    return HookOutput.allow();
});

// Log all tool results
hookRegistry.registerPostToolUse(input -> {
    if (input instanceof HookInput.PostToolUseInput postToolUse) {
        System.out.println("Tool completed: " + postToolUse.toolName());
    }
    return HookOutput.allow();
});

try (ClaudeSyncClient client = ClaudeClient.sync()
        .workingDirectory(Path.of("."))
        .permissionMode(PermissionMode.DEFAULT)
        .hookRegistry(hookRegistry)
        .build()) {
    // Hooks intercept tool calls
}

Example - With MCP servers

import org.springaicommunity.claude.agent.sdk.mcp.McpServerConfig;

// External MCP server (subprocess)
McpServerConfig npmServer = McpServerConfig.command("npx")
    .args("-y", "@anthropic/mcp-server-filesystem")
    .env("HOME", System.getProperty("user.home"))
    .build();

// In-process SDK MCP server
McpServerConfig sdkServer = McpServerConfig.sdk(myMcpServer);

try (ClaudeSyncClient client = ClaudeClient.sync()
        .workingDirectory(Path.of("."))
        .mcpServer("filesystem", npmServer)
        .mcpServer("custom", sdkServer)
        .build()) {
    // MCP tools available to Claude
}

`ClaudeAsyncClient` - Reactive Client

Non-blocking reactive API using Project Reactor. Use when you need composable, non-blocking chains.

Methods

Method	Return Type	Description
`connect(prompt)`	`TurnSpec`	Start session with prompt
`query(prompt)`	`TurnSpec`	Send follow-up message
`onMessage(handler)`	`ClaudeAsyncClient`	Register message handler
`onResult(handler)`	`ClaudeAsyncClient`	Register result handler
`close()`	`Mono<Void>`	End session

TurnSpec Methods

Method	Return Type	Description
`.text()`	`Mono<String>`	Collected text, enables flatMap chaining
`.textStream()`	`Flux<String>`	Streaming text
`.messages()`	`Flux<Message>`	All message types

Example - Text response with TurnSpec

ClaudeAsyncClient client = ClaudeClient.async()
    .workingDirectory(Path.of("."))
    .permissionMode(PermissionMode.BYPASS_PERMISSIONS)
    .build();

// Simple text response
client.connect("Hello!").text()
    .doOnSuccess(System.out::println)
    .subscribe();  // Non-blocking

Example - Multi-turn with flatMap chaining

// Elegant multi-turn via flatMap
client.connect("My favorite color is blue.").text()
    .flatMap(r1 -> client.query("What is my favorite color?").text())
    .doOnSuccess(System.out::println)  // "blue"
    .subscribe();

Example - Text streaming

// Stream text as it arrives
client.query("Explain recursion").textStream()
    .doOnNext(System.out::print)
    .subscribe();

Example - Full message access

// Access all message types for metadata
client.query("List files").messages()
    .doOnNext(msg -> {
        if (msg instanceof AssistantMessage am) {
            am.text().ifPresent(System.out::println);
        } else if (msg instanceof ResultMessage rm) {
            System.out.printf("Cost: $%.6f%n", rm.totalCostUsd());
        }
    })
    .subscribe();

Example - Spring WebFlux SSE endpoint

import org.springframework.web.bind.annotation.*;
import org.springframework.http.MediaType;
import reactor.core.publisher.Flux;

@RestController
public class ChatController {
    private final ClaudeAsyncClient client;

    public ChatController() {
        this.client = ClaudeClient.async()
            .workingDirectory(Path.of("."))
            .permissionMode(PermissionMode.BYPASS_PERMISSIONS)
            .build();
    }

    @GetMapping(value = "/chat", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
    public Flux<String> chat(@RequestParam String message) {
        return client.query(message).textStream();
    }
}

Example - Cross-turn handlers

ClaudeAsyncClient client = ClaudeClient.async()
    .workingDirectory(Path.of("."))
    .build();

// Register handlers (cross-turn concerns)
client.onMessage(msg -> logger.info("Message: {}", msg.getClass().getSimpleName()))
      .onResult(result -> logger.info("Turn complete, tokens: {}",
          result.usage().inputTokens() + result.usage().outputTokens()));

// Handlers are called for ALL turns
client.queryAndReceive("First question").subscribe();
client.queryAndReceive("Second question").subscribe();  // Handlers still fire

Flux vs Handlers

If you are…	Use
Printing or streaming output to a user	Flux
Building a WebFlux/SSE endpoint	Flux
Doing per-turn filtering or transformation	Flux
Logging tool usage across all turns	Handlers
Collecting metrics or tracing	Handlers
Running a long-lived agent loop	Handlers

“If the logic belongs to a single turn, use Flux. If the logic applies to the entire session, use handlers.”

Types

`QueryOptions`

Configuration for Query operations.

QueryOptions.builder()
    .model("claude-sonnet-4-20250514")      // Model selection
    .systemPrompt("Custom system prompt")    // Replace default
    .appendSystemPrompt("Additional instructions")  // Append to default
    .timeout(Duration.ofMinutes(5))          // Query timeout
    .allowedTools(List.of("Read", "Write"))  // Restrict tools
    .disallowedTools(List.of("Bash"))        // Block tools
    .maxTurns(10)                            // Limit agentic turns
    .maxBudgetUsd(1.0)                       // Cost limit
    .workingDirectory(Path.of("/project"))   // Working directory
    .build();

`CLIOptions`

Lower-level configuration for CLI transport. Use with ClaudeClient.sync(options) or ClaudeClient.async(options).

CLIOptions options = CLIOptions.builder()
    .model("claude-sonnet-4-20250514")
    .systemPrompt("You are helpful")
    .allowedTools(List.of("Read", "Write"))
    .maxTurns(10)
    .build();

// When using pre-built CLIOptions, only session config is available on builder
try (ClaudeSyncClient client = ClaudeClient.sync(options)
        .workingDirectory(Path.of("."))
        .timeout(Duration.ofMinutes(5))
        .build()) {
    // .model() NOT available here - already in options
}

`PermissionMode`

public enum PermissionMode {
    DEFAULT,           // Standard permission behavior
    ACCEPT_EDITS,      // Auto-accept file edits
    PLAN,              // Planning mode - read-only
    BYPASS_PERMISSIONS // Bypass all checks (use with caution)
}

`HookRegistry`

HookRegistry registry = new HookRegistry();

// Pre-tool hook - runs before tool executes
registry.registerPreToolUse("Bash", input -> {
    // Return HookOutput.allow() or HookOutput.block("reason")
    return HookOutput.allow();
});

// Post-tool hook - runs after tool completes
registry.registerPostToolUse(input -> {
    // Log, trace, or modify behavior
    return HookOutput.allow();
});

`McpServerConfig`

Configure MCP servers for tool integration.

// External process (npx, docker, etc.)
McpServerConfig external = McpServerConfig.command("npx")
    .args("-y", "@anthropic/mcp-server-filesystem")
    .env("HOME", System.getProperty("user.home"))
    .build();

// In-process SDK server
McpServerConfig inProcess = McpServerConfig.sdk(myMcpServer);

Message Types

`ParsedMessage`

Sealed interface wrapping messages from the CLI.

public sealed interface ParsedMessage permits
    ParsedMessage.RegularMessage,
    ParsedMessage.Control,
    ParsedMessage.ControlResponseMessage,
    ParsedMessage.EndOfStream {

    boolean isRegularMessage();   // User, Assistant, System, Result
    boolean isControlRequest();   // Control protocol request
    boolean isControlResponse();  // Control protocol response

    Message asMessage();          // Get as Message, or null
    ControlRequest asControlRequest();
}

Processing Messages

Iterator<ParsedMessage> response = client.receiveResponse();
while (response.hasNext()) {
    ParsedMessage parsed = response.next();
    if (parsed.isRegularMessage()) {
        Message message = parsed.asMessage();
        if (message instanceof AssistantMessage am) {
            System.out.println(am.getTextContent().orElse(""));
        } else if (message instanceof ResultMessage result) {
            System.out.println("Done. Cost: $" + result.totalCostUsd());
        }
    }
}

`Message`

Base interface for regular messages.

public sealed interface Message permits UserMessage, AssistantMessage, ResultMessage

`AssistantMessage`

public record AssistantMessage(
    List<ContentBlock> content,
    String model
) implements Message {
    public Optional<String> getTextContent();
}

`ResultMessage`

public record ResultMessage(
    String subtype,
    long durationMs,
    long durationApiMs,
    boolean isError,
    int numTurns,
    String sessionId,
    Double totalCostUsd,
    Usage usage,
    String result
) implements Message

Content Block Types

public sealed interface ContentBlock permits TextBlock, ThinkingBlock, ToolUseBlock, ToolResultBlock

`TextBlock`

public record TextBlock(String text) implements ContentBlock

`ToolUseBlock`

public record ToolUseBlock(
    String id,
    String name,
    Map<String, Object> input
) implements ContentBlock

Error Types

public class ClaudeSDKException extends RuntimeException {
    // Base exception for all SDK errors
}

public class TransportException extends ClaudeSDKException {
    // Raised when CLI transport fails
}

public class SessionClosedException extends ClaudeSDKException {
    // Raised when operating on a closed session
}

public class MessageParseException extends ClaudeSDKException {
    // Raised when message parsing fails
}

Community

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Documentation Index

​Installation

​Maven

​Gradle

​Three-API Architecture

​Quick Comparison

​When to Use Query

​When to Use ClaudeSyncClient

​When to Use ClaudeAsyncClient

​Query - One-Shot API

​Methods

​Example - Simple query

​Example - With options

​Example - Full result with metadata

​Example - Streaming iteration

​ClaudeClient - Factory

​Methods

​Example - Factory pattern

​ClaudeSyncClient - Blocking Client

​Methods

​Example - Multi-turn conversation

​Example - With hooks

​Example - With MCP servers

​ClaudeAsyncClient - Reactive Client

​Methods

​TurnSpec Methods

​Example - Text response with TurnSpec

​Example - Multi-turn with flatMap chaining

​Example - Text streaming

​Example - Full message access

​Example - Spring WebFlux SSE endpoint

​Example - Cross-turn handlers

​Flux vs Handlers

​Types

​QueryOptions

​CLIOptions

​PermissionMode

​HookRegistry

​McpServerConfig

​Message Types

​ParsedMessage

​Processing Messages

​Message

​AssistantMessage

​ResultMessage

​Content Block Types

​TextBlock

​ToolUseBlock

​Error Types

​See also

Installation

Maven

Gradle

Three-API Architecture

Quick Comparison

When to Use `Query`

When to Use `ClaudeSyncClient`

When to Use `ClaudeAsyncClient`

`Query` - One-Shot API

Methods

Example - Simple query

Example - With options

Example - Full result with metadata

Example - Streaming iteration

`ClaudeClient` - Factory

Methods

Example - Factory pattern

`ClaudeSyncClient` - Blocking Client

Methods

Example - Multi-turn conversation

Example - With hooks

Example - With MCP servers

`ClaudeAsyncClient` - Reactive Client

Methods

TurnSpec Methods

Example - Text response with TurnSpec

Example - Multi-turn with flatMap chaining

Example - Text streaming

Example - Full message access

Example - Spring WebFlux SSE endpoint

Example - Cross-turn handlers

Flux vs Handlers

Types

`QueryOptions`

`CLIOptions`

`PermissionMode`

`HookRegistry`

`McpServerConfig`

Message Types

`ParsedMessage`

Processing Messages

`Message`

`AssistantMessage`

`ResultMessage`

Content Block Types

`TextBlock`

`ToolUseBlock`

Error Types

See also