> ## Documentation Index
> Fetch the complete documentation index at: https://java.agentscope.io/llms.txt
> Use this file to discover all available pages before exploring further.

# DeepSeek

`agentscope-extensions-model-openai` provides first-class DeepSeek support through the OpenAI-compatible model stack. Add the OpenAI model extension module, then use `deepseek:<model>` with `ModelRegistry`.

## Add the dependency

```xml theme={null}
<dependency>
    <groupId>io.agentscope</groupId>
    <artifactId>agentscope-extensions-model-openai</artifactId>
    <version>${agentscope.version}</version>
</dependency>
```

## ModelRegistry

Set `DEEPSEEK_API_KEY`, then use the `deepseek:<model>` id:

```java theme={null}
ReActAgent agent = ReActAgent.builder()
    .name("assistant")
    .model("deepseek:deepseek-v4-flash") // Resolved internally by ModelRegistry.resolve(modelId)
    .build();
```

The provider defaults to `https://api.deepseek.com`, strips the `deepseek:` prefix before sending the model name, and uses the DeepSeek formatter from `io.agentscope.extensions.model.openai.compat.deepseek`.

## Thinking mode

Enable DeepSeek thinking mode through `ModelCreationContext` when resolving the model:

```java theme={null}
import io.agentscope.core.model.Model;
import io.agentscope.core.model.ModelCreationContext;
import io.agentscope.core.model.ModelRegistry;

Model model = ModelRegistry.resolve(
    "deepseek:deepseek-v4-flash",
    ModelCreationContext.builder()
        .enableThinking(true)
        .build());
```

Streaming callers can render `ThinkingBlockDeltaEvent` separately from `TextBlockDeltaEvent`.

## Compatibility notes

The DeepSeek formatter preserves DeepSeek-compatible message fields, including `system` roles and supported `name` fields. It also removes stale reasoning content from previous turns while preserving reasoning content needed by current tool-call context.

DeepSeek's stable endpoint does not use the tool schema `strict` field by default, so the default formatter omits `strict` even when a tool is registered with strict schema validation. Structured output uses the normal AgentScope fallback behavior unless you explicitly configure native structured output for a compatible endpoint.

For beta or compatible endpoints, pass `baseUrl`, `endpointPath`, generation options, or formatter overrides through `ModelCreationContext`.