/**
 * @packageDocumentation
 * Vertex AI request labels.
 *
 * Vertex AI accepts a `labels` map on every generateContent request and copies it onto the matching
 * Cloud Billing export rows, which is how spend is attributed to a caller, a command or a pipeline.
 * `@langchain/google` builds the request body from a fixed set of fields and has no `labels` option,
 * so the labels are added to the built params through an `invocationParams` override, the same hook
 * {@link @gaunt-sloth/core!providers/geminiThinking.applyGeminiThoughtSummaries | applyGeminiThoughtSummaries}
 * uses. The override survives `bindTools`, which wraps this same instance.
 *
 * Vertex AI validates the keys and values (lowercase, at most 63 characters, at most 64 labels) and
 * rejects the request when they break those rules.
 */
import type { BaseChatModel } from '@langchain/core/language_models/chat_models';
/**
 * Reads the `labels` field of a `vertexai` `llm` block. Returns `undefined` when it is absent or
 * empty, and throws when it is not an object of string values.
 */
export declare function readVertexAiLabels(labels: unknown): Record<string, string> | undefined;
/**
 * Adds `labels` to every request the model builds. Returns the same model instance; a model with no
 * `invocationParams` is returned untouched.
 */
export declare function applyVertexAiLabels<T extends BaseChatModel>(model: T, labels: Record<string, string> | undefined): T;