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> For a complete documentation index, see https://docs.band.ai/llms.txt.
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# Model SDK Adapters

> Reference for band-sdk 6.0.1's AnthropicAdapter and GeminiAdapter, their config fields and defaults, provider key handling, and construction errors.

`AnthropicAdapter` and `GeminiAdapter` call a model provider's SDK directly and run the tool loop themselves. Use them when your agent is a prompt plus Band's tools, with no framework in between. Both follow the shared [adapter construction](/reference/sdk/features#adapter-construction) rules and take the [feature keywords](/reference/sdk/features#adapter-features).

## `AnthropicAdapter`

Adapter for the Anthropic SDK with a manual tool loop.

```python
from band.adapters import AnthropicAdapter, AnthropicAdapterConfig

adapter = AnthropicAdapter(
    config: AnthropicAdapterConfig | None = None,
    *,
    history_converter: AnthropicHistoryConverter | None = None,
    additional_tools: list[CustomToolDef] | None = None,
    **features: Unpack[FeatureKwargs],
)
```

| `AnthropicAdapterConfig` field | Type          | Default               | Description                                                                                                                             |
| :----------------------------- | :------------ | :-------------------- | :-------------------------------------------------------------------------------------------------------------------------------------- |
| `model`                        | `str`         | `"claude-sonnet-5-5"` | Anthropic model ID                                                                                                                      |
| `provider_key`                 | `str \| None` | `None`                | Anthropic API key; the Anthropic client reads `ANTHROPIC_API_KEY` when unset                                                            |
| `system_prompt`                | `str \| None` | `None`                | Complete system prompt, sent verbatim. When set, `custom_section`, `include_base_instructions`, and the capability sections are ignored |
| `custom_section`               | `str`         | `""`                  | Additional instructions appended to the Band system prompt                                                                              |
| `include_base_instructions`    | `bool`        | `True`                | Include the Band platform instructions in the system prompt                                                                             |
| `max_tokens`                   | `int`         | `4096`                | Maximum response tokens per API call; must be greater than `0`                                                                          |

```python
from band.adapters import AnthropicAdapter, AnthropicAdapterConfig

adapter = AnthropicAdapter(
    AnthropicAdapterConfig(custom_section="Answer in one paragraph."),
)
```

Emits `TOOL_CALLS` and `USAGE`. Since `band-sdk` 6.0.0 the tool loop ends a turn after a successful `band_no_reply` call whose sibling tool calls also succeeded, without sending the model another request. `api_key` and `prompt` are not fields; passing either raises `ValidationError` (`Extra inputs are not permitted`). See [Anthropic SDK](/connect/anthropic) for a worked example.

## `GeminiAdapter`

Adapter for the Google Gen AI SDK with a manual tool loop.

```python
from band.adapters import GeminiAdapter, GeminiAdapterConfig

adapter = GeminiAdapter(
    config: GeminiAdapterConfig | None = None,
    *,
    history_converter: GeminiHistoryConverter | None = None,
    additional_tools: list[CustomToolDef] | None = None,
    **features: Unpack[FeatureKwargs],
)
```

| `GeminiAdapterConfig` field | Type            | Default              | Description                                                                                                                             |
| :-------------------------- | :-------------- | :------------------- | :-------------------------------------------------------------------------------------------------------------------------------------- |
| `model`                     | `str`           | `"gemini-3.8-flash"` | Gemini model name                                                                                                                       |
| `provider_key`              | `str \| None`   | `None`               | Gemini API key; without it, the Google Gen AI client reads `GOOGLE_API_KEY` or `GEMINI_API_KEY`, or uses Vertex AI                      |
| `system_prompt`             | `str \| None`   | `None`               | Complete system prompt, sent verbatim. When set, `custom_section`, `include_base_instructions`, and the capability sections are ignored |
| `custom_section`            | `str`           | `""`                 | Additional instructions appended to the Band system prompt                                                                              |
| `include_base_instructions` | `bool`          | `True`               | Include the Band platform instructions in the system prompt                                                                             |
| `max_output_tokens`         | `int \| None`   | `None`               | Output token cap per call; `None` uses the model default                                                                                |
| `temperature`               | `float \| None` | `None`               | Sampling temperature; `None` uses the model default                                                                                     |
| `max_tool_rounds`           | `int`           | `20`                 | Model calls a single turn may make before it fails with `Exceeded max tool rounds (<n>) in room <room_id>; tool sequence: ...`          |
| `max_retries`               | `int`           | `2`                  | Retries of a call after a transient server or transport error                                                                           |
| `retry_base_delay_s`        | `float`         | `1.0`                | First retry delay in seconds, doubled on each further retry                                                                             |
| `max_history_messages`      | `int`           | `200`                | Room history entries kept per room; older ones are trimmed                                                                              |

```python
from band.adapters import GeminiAdapter, GeminiAdapterConfig

adapter = GeminiAdapter(GeminiAdapterConfig(temperature=0.2))
```

Emits `TOOL_CALLS` and `USAGE`. Without a key, client construction fails with `Gemini client initialization failed. Either set GOOGLE_API_KEY / GEMINI_API_KEY, or enable Vertex AI mode (GOOGLE_GENAI_USE_VERTEXAI=true + GOOGLE_CLOUD_PROJECT).` A failed model run that Gemini returns as data, such as a safety `finish_reason` or a blocked prompt, is reported to the room as a provider failure with its coarse code; the detail goes only to the agent log. See [Gemini](/connect/gemini) for a worked example.