---
url: >-
  https://adk.nht.io/api/@nhtio/adk/batteries/llm/openai_responses/helpers/functions/fingerprintOpenAIResponsesPrefix.md
---

# Function: fingerprintOpenAIResponsesPrefix()

```ts
function fingerprintOpenAIResponsesPrefix(input: {
  input: OpenAIResponsesInputItem[];
  instructions?: string;
  model: string;
  throughItem?: number;
  tools?: OpenAIResponsesTool[];
}): Promise<string>;
```

Defined in: [src/batteries/llm/openai\_responses/helpers.ts:610](https://github.com/NHTIO/ADK/blob/v1.20260901.0/src/src/batteries/llm/openai_responses/helpers.ts#L610)

Implements [OpenAIResponsesHelpers.fingerprintOpenAIResponsesPrefix](../../types/interfaces/OpenAIResponsesHelpers.md#property-fingerprintopenairesponsesprefix).

## Parameters

| Parameter             | Type                                                                                                                                                                                                                                                               |
| --------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `input`               | { `input`: [`OpenAIResponsesInputItem`](../../types/type-aliases/OpenAIResponsesInputItem.md)\[]; `instructions?`: `string`; `model`: `string`; `throughItem?`: `number`; `tools?`: [`OpenAIResponsesTool`](../../types/type-aliases/OpenAIResponsesTool.md)\[]; } |
| `input.input`         | [`OpenAIResponsesInputItem`](../../types/type-aliases/OpenAIResponsesInputItem.md)\[]                                                                                                                                                                               |
| `input.instructions?` | `string`                                                                                                                                                                                                                                                           |
| `input.model`         | `string`                                                                                                                                                                                                                                                           |
| `input.throughItem?`  | `number`                                                                                                                                                                                                                                                           |
| `input.tools?`        | [`OpenAIResponsesTool`](../../types/type-aliases/OpenAIResponsesTool.md)\[]                                                                                                                                                                                         |

## Returns

`Promise`<`string`>

## Remarks

Computes the fingerprint used for OpenAI Responses reasoning-item replay. The input is the exact
assembled request prefix: `model`, `instructions`, `tools`, and `input` through (but not
including) the item at `throughItem`. Assembles the Responses-shaped prefix object and delegates
canonicalisation + hashing to the shared, wire-agnostic [canonicalFingerprint](../../functions/canonicalFingerprint.md) primitive —
mirroring `fingerprintAnthropicMessagesPrefix`'s shape-and-slice pattern exactly: object keys are
recursively sorted; array order and item boundaries are preserved.