> ## Documentation Index
> Fetch the complete documentation index at: https://gomodel-refactor-provider-state.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Provider state (extra_content)

> How GoModel carries provider-specific replay state such as Gemini thought signatures and Anthropic thinking blocks through every API

Some providers attach opaque state to a reply and expect it back, unchanged,
on the next turn. Gemini 3 signs its function calls with a `thoughtSignature`
and rejects a history that replays the call without it. Anthropic requires
`thinking` blocks, signatures included, in front of a tool-use turn that
continues. Such state has no OpenAI-compatible field, so GoModel carries it in
one place: an `extra_content` object keyed by vendor.

```json theme={null}
{
  "role": "assistant",
  "tool_calls": [{
    "id": "call_1",
    "type": "function",
    "function": {"name": "lookup_weather", "arguments": "{\"city\":\"Warsaw\"}"},
    "extra_content": {"google": {"thought_signature": "EvACCu0CARFNMg..."}}
  }]
}
```

This is the shape Google's own OpenAI-compatible endpoint uses, so clients
built against it work unchanged.

## Where it appears

| API                | Location                                                                                                             |
| ------------------ | -------------------------------------------------------------------------------------------------------------------- |
| Chat Completions   | `tool_calls[].extra_content` and, for text-only turns, `message.extra_content`; also on streamed `tool_calls` deltas |
| Responses          | `function_call` output items                                                                                         |
| Anthropic Messages | `tool_use` content blocks                                                                                            |

Send the member back exactly as you received it. Clients that copy assistant
messages into the history verbatim, which is what the OpenAI, Anthropic, and
Responses SDKs do, need no changes.

## Rules

* **Every translation copies it through.** Chat, Responses, and Anthropic
  Messages ingress, streaming, and the assistant-turn echo carry
  `extra_content` without looking inside.
* **Only the owning provider sees its own vendor.** Before a request leaves
  for a provider, GoModel drops every vendor object that provider does not
  own. A Gemini signature never reaches Anthropic or OpenAI, and a history
  that moved between providers does not fail on foreign fields.
* **Only the owning adapter reads or writes inside it.** Nothing else in the
  gateway interprets the contents.

## Vendors

| Vendor      | Providers          | Members                                                                                                                                                                                                          |
| ----------- | ------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `google`    | `gemini`, `vertex` | `thought_signature`: the Gemini 3 signature of a function call or text turn. See [Gemini thought signatures](/providers/gemini#thought-signatures).                                                              |
| `anthropic` | `anthropic`        | `thinking_blocks`: the `thinking` and `redacted_thinking` blocks of an assistant turn; `is_error`: marks a tool result as failed. Set by the [Anthropic Messages API](/advanced/anthropic-messages-api) ingress. |

When a history reaches Gemini 3 without a signature, because the conversation
started on another provider or a client dropped the member, GoModel sends
Google's documented placeholder instead of surfacing the 400. Echo the real
value whenever you have it; the placeholder costs reasoning continuity for
that turn.