1# Claude API — Java
2 
3> **Note:** The Java SDK supports the Claude API and beta tool use with annotated classes. Agent SDK is not yet available for Java.
4 
5## Package Reference
6 
7Types are organized by package. If a class you need isn't shown in an example below, locate it via this table first — don't block on fetching SDK source over the network.
8 
9| `import` prefix | Contains |
10|---|---|
11| `com.anthropic.client` / `com.anthropic.client.okhttp` | `AnthropicClient`, `AnthropicOkHttpClient` |
12| `com.anthropic.models.messages` | non-beta request/response types — `MessageCreateParams`, `Model`, `Message`, `TextBlockParam`, `ContentBlockParam`, `ToolUseBlockParam`, `ToolResultBlockParam`, `CacheControlEphemeral`, `Tool*` (e.g. `ToolBash20250124`, `ToolTextEditor20250728`), `StopReason`, `StructuredMessage*` |
13| `com.anthropic.models.messages.batches` | Batch API — `BatchResultsParams`, `MessageBatchIndividualResponse` |
14| `com.anthropic.models.beta` | `AnthropicBeta` (beta-flag constants) |
15| `com.anthropic.models.beta.messages` | beta-endpoint types — `MessageCreateParams`, `BetaMessage`, `BetaStopReason`, `BetaContextManagementConfig`, `BetaMcpToolset`, `BetaRequestMcpServerUrlDefinition`, `BetaTool*` |
16| `com.anthropic.core` | `JsonValue`, `JsonField`, `JsonSchemaLocalValidation`, `com.anthropic.core.http.StreamResponse` |
17| `com.anthropic.errors` | typed exceptions — `AnthropicServiceException`, `RateLimitException`, `NotFoundException`, etc. (see `shared/error-codes.md`) |
18 
19`client.messages()` uses `com.anthropic.models.messages.*`; `client.beta().messages()` uses `com.anthropic.models.beta.messages.*`. Both packages define a `MessageCreateParams` — import the one matching the client path you call.
20 
21### Key types per feature
22 
23Write from this table instead of `javap`/jar inspection. Endpoint column tells you whether to use `client.messages()` or `client.beta().messages()`.
24 
25| Feature | Endpoint | Key Java types / builder calls |
26|---|---|---|
27| User profiles | beta | `client.beta().userProfiles().create(...)` / `.retrieve(id)` / `.list()`. Pass the returned profile id on the beta `MessageCreateParams`. Requires a beta header — check the SDK's beta-headers reference for the current flag. |
28| Agent Skills | beta | `BetaContainerParams`, `BetaSkillParams`, `BetaCodeExecutionTool20250825`. `.addBeta("code-execution-2025-08-25").addBeta("skills-2025-10-02")`. Download the output via `client.beta().files().download(fileId)`. |
29| Cache diagnostics | beta | `BetaDiagnosticsParam`, `BetaCacheControlEphemeral` |
30| Context editing | beta | `.contextManagement(BetaContextManagementConfig.builder()…)`. The edit strategy is a `BetaClearToolUses20250919Edit` (or `BetaClearThinking20251015Edit`); its trigger is a `BetaInputTokensTrigger` built separately and passed to the edit's builder — there is no direct `.inputTokensTrigger(N)` shortcut on the edit builder. `javap` the edit and trigger classes for the exact setter names. |
31| Memory tool | non-beta | `.addTool(MemoryTool20250818.builder().build())` from `com.anthropic.models.messages` |
32| Programmatic tool calling | non-beta | `CodeExecutionTool20260120`, `Tool`, `ContentBlockParam` |
33| Strict tool use | non-beta | `Tool`, `Tool.InputSchema` |
34| Task budgets | beta | `.outputConfig(BetaOutputConfig.builder().taskBudget(BetaTokenTaskBudget.builder()...))` |
35| Tool search | non-beta | `.addTool(ToolSearchToolRegex20251119.builder()...)` from `com.anthropic.models.messages` |
36| Web search | non-beta | `WebSearchTool20260209` from `com.anthropic.models.messages` — the latest variant with dynamic filtering (Opus 4.8/4.7/4.6 + Sonnet 4.6). For older models or Vertex, use `WebSearchTool20250305` |
37 
38### Discovering type and member names
39 
40If a class or builder method you need isn't in the tables above, `jar tf <anthropic-java-core jar> | grep -i <term>` or `javap -classpath <jar> com.anthropic.models.…` is fast enough to locate names. **Do not compile and run a separate reflection program** to enumerate members — the first build is slow enough to be backgrounded in many environments, trapping you in a polling loop. Write the script with the names you found and let the compiler error (`cannot find symbol`) point at any wrong member.
41 
42## Installation
43 
44Maven:
45 
46```xml
47<dependency>
48    <groupId>com.anthropic</groupId>
49    <artifactId>anthropic-java</artifactId>
50    <version>2.34.0</version>
51</dependency>
52```
53 
54Gradle:
55 
56```groovy
57implementation("com.anthropic:anthropic-java:2.34.0")
58```
59 
60## Client Initialization
61 
62```java
63import com.anthropic.client.AnthropicClient;
64import com.anthropic.client.okhttp.AnthropicOkHttpClient;
65 
66// Default (reads ANTHROPIC_API_KEY from environment)
67AnthropicClient client = AnthropicOkHttpClient.fromEnv();
68 
69// Explicit API key
70AnthropicClient client = AnthropicOkHttpClient.builder()
71    .apiKey("your-api-key")
72    .build();
73```
74 
75---
76 
77## Basic Message Request
78 
79```java
80import com.anthropic.models.messages.MessageCreateParams;
81import com.anthropic.models.messages.Message;
82import com.anthropic.models.messages.Model;
83 
84MessageCreateParams params = MessageCreateParams.builder()
85    .model(Model.CLAUDE_OPUS_4_8)
86    .maxTokens(16000L)
87    .addUserMessage("What is the capital of France?")
88    .build();
89 
90Message response = client.messages().create(params);
91response.content().stream()
92    .flatMap(block -> block.text().stream())
93    .forEach(textBlock -> System.out.println(textBlock.text()));
94```
95 
96---
97 
98## Thinking
99 
100**Adaptive thinking is the recommended mode for Claude 4.6+ models.** Claude decides dynamically when and how much to think. The builder has a direct `.thinking(ThinkingConfigAdaptive)` overload — no manual union wrapping.
101 
102> **Fable 5, Opus 4.8, Opus 4.7, Opus 4.6, and Sonnet 4.6:** Use adaptive thinking (below). `ThinkingConfigEnabled.builder().budgetTokens(N)` is removed on Fable 5, Opus 4.8, and 4.7 (400 if sent); deprecated on Opus 4.6 and Sonnet 4.6.
103> **Older models:** Use `.thinking(ThinkingConfigEnabled.builder().budgetTokens(N).build())` (budget must be < `maxTokens`, min 1024).
104 
105```java
106import com.anthropic.models.messages.ContentBlock;
107import com.anthropic.models.messages.MessageCreateParams;
108import com.anthropic.models.messages.Model;
109import com.anthropic.models.messages.ThinkingConfigAdaptive;
110 
111MessageCreateParams params = MessageCreateParams.builder()
112    .model(Model.CLAUDE_SONNET_4_6)
113    .maxTokens(16000L)
114    .thinking(ThinkingConfigAdaptive.builder().build())
115    .addUserMessage("Solve this step by step: 27 * 453")
116    .build();
117 
118for (ContentBlock block : client.messages().create(params).content()) {
119    block.thinking().ifPresent(t -> System.out.println("[thinking] " + t.thinking()));
120    block.text().ifPresent(t -> System.out.println(t.text()));
121}
122```
123 
124`ContentBlock` narrowing: `.thinking()` / `.text()` return `Optional<T>` — use `.ifPresent(...)` or `.stream().flatMap(...)`. Alternative: `isThinking()` / `asThinking()` boolean+unwrap pairs (throws on wrong variant).
125 
126---
127 
128## Effort Parameter
129 
130Effort is nested inside `OutputConfig` — there is NO `.effort()` directly on `MessageCreateParams.Builder`.
131 
132```java
133import com.anthropic.models.messages.OutputConfig;
134 
135.outputConfig(OutputConfig.builder()
136    .effort(OutputConfig.Effort.HIGH)  // or LOW, MEDIUM, MAX
137    .build())
138```
139 
140Combine with `Thinking = ThinkingConfigAdaptive` for cost-quality control.
141 
142---
143 
144## Prompt Caching
145 
146System message as a list of `TextBlockParam` with `CacheControlEphemeral`. Use `.systemOfTextBlockParams(...)` — the plain `.system(String)` overload can't carry cache control. For placement patterns and the silent-invalidator audit checklist, see `shared/prompt-caching.md`.
147 
148```java
149import com.anthropic.models.messages.TextBlockParam;
150import com.anthropic.models.messages.CacheControlEphemeral;
151 
152.systemOfTextBlockParams(List.of(
153    TextBlockParam.builder()
154        .text(longSystemPrompt)
155        .cacheControl(CacheControlEphemeral.builder()
156            .ttl(CacheControlEphemeral.Ttl.TTL_1H)  // optional; also TTL_5M
157            .build())
158        .build()))
159```
160 
161There's also a top-level `.cacheControl(CacheControlEphemeral)` on `MessageCreateParams.Builder` and on `Tool.builder()`.
162 
163Verify hits via `response.usage().cacheCreationInputTokens()` / `response.usage().cacheReadInputTokens()`.
164 
165---
166 
167## Token Counting
168 
169```java
170import com.anthropic.models.messages.MessageCountTokensParams;
171 
172long tokens = client.messages().countTokens(
173    MessageCountTokensParams.builder()
174        .model(Model.CLAUDE_SONNET_4_6)
175        .addUserMessage("Hello")
176        .build()
177).inputTokens();
178```
179 
180---
181 
182## PDF / Document Input
183 
184`DocumentBlockParam` builder has source shortcuts. Wrap in `ContentBlockParam.ofDocument()` and pass via `.addUserMessageOfBlockParams()`.
185 
186```java
187import com.anthropic.models.messages.DocumentBlockParam;
188import com.anthropic.models.messages.ContentBlockParam;
189import com.anthropic.models.messages.TextBlockParam;
190 
191DocumentBlockParam doc = DocumentBlockParam.builder()
192    .source(Base64PdfSource.builder().data(base64String).build())
193    // or .source(UrlPdfSource.builder().url("https://...").build())
194    .title("My Document")        // optional
195    .build();
196```
197 
198For **Files API** document references, use the beta path and beta types — see `files-api.md`: `BetaRequestDocumentBlock.builder().source(BetaFileDocumentSource.builder().fileId(id).build())`.
199 
200```java
201.addUserMessageOfBlockParams(List.of(
202    ContentBlockParam.ofDocument(doc),
203    ContentBlockParam.ofText(TextBlockParam.builder().text("Summarize this").build())))
204```
205 
206---
207 
208## Stop Details
209 
210When `stopReason()` is `"refusal"`, the response includes structured `stopDetails()`:
211 
212```java
213response.stopDetails().ifPresent(details -> {
214    System.out.println("Category: " + details.category());
215    System.out.println("Explanation: " + details.explanation());
216});
217```
218 
219**Refusal fallbacks (Claude Fable 5) — opt in by default.** Fallbacks are opt-in: without them a refused request simply stops. New `claude-fable-5` code should include the server-side `fallbacks` parameter (beta header `server-side-fallback-2026-06-01`, fallback model `claude-opus-4-8`, on the beta messages call) by default. The exact Java builder methods (and the client-side middleware for providers without server-side support) are not documented here — WebFetch the Java SDK repo's `examples/` from `shared/live-sources.md`; full semantics in `shared/model-migration.md` → Migrating to Claude Fable 5 → `refusal` stop reason.
220 
221---
222 
223## Error Type
224 
225`AnthropicServiceException` exposes `.errorType()` returning `Optional<ErrorType>` for programmatic error classification:
226 
227```java
228try {
229    client.messages().create(params);
230} catch (AnthropicServiceException e) {
231    e.errorType().ifPresent(type ->
232        System.out.println("Error type: " + type)  // RATE_LIMIT_ERROR, OVERLOADED_ERROR, etc.
233    );
234}
235```
236 
237---
238 
239