import type { LanguageModel, ModelMessage, SystemModelMessage, ToolSet } from "ai";
/**
 * The caching strategy to apply for one harness step.
 */
export type PromptCachePath = {
    readonly kind: "gateway-auto";
} | {
    readonly kind: "anthropic-direct";
} | {
    readonly kind: "none";
};
/**
 * Cache marker injected on the Anthropic-direct path.
 *
 * The marker carries two provider namespaces because Anthropic models are
 * reachable through providers that read different provider-options keys:
 *
 * - `anthropic.cacheControl` — read by the AI SDK Anthropic provider and by
 *   `@ai-sdk/amazon-bedrock/anthropic` and `@ai-sdk/google-vertex/anthropic`,
 *   which implement the native Anthropic Messages API.
 * - `bedrock.cachePoint` — read by the standard `@ai-sdk/amazon-bedrock`
 *   Converse provider, which does not understand `anthropic.cacheControl`.
 *
 * A provider ignores namespaces it does not own, so carrying both is safe on
 * every Anthropic-direct request regardless of which provider serves it.
 */
export interface AnthropicCacheMarker {
    readonly anthropic: {
        readonly cacheControl: {
            readonly type: "ephemeral";
        };
    };
    readonly bedrock: {
        readonly cachePoint: {
            readonly type: "default";
        };
    };
}
/**
 * Detects which prompt caching path applies to a resolved model.
 *
 * Runs once per harness step right after `resolveModel()`.
 */
export declare function detectPromptCachePath(model: LanguageModel): PromptCachePath;
/**
 * Returns the shared Anthropic cache marker used on the `anthropic-direct`
 * path. Exposed for unit tests and for the harness wiring layer.
 */
export declare function getAnthropicCacheMarker(): AnthropicCacheMarker;
/**
 * Returns a new `providerOptions` object with
 * `gateway.caching = "auto"` merged into the existing `gateway` sub-object.
 *
 * Preserves any existing author-provided `gateway` keys (such as
 * `order: ["anthropic", "bedrock"]` load balancing), and leaves an
 * explicit author override on `gateway.caching` untouched so callers can
 * opt out by setting `providerOptions.gateway.caching` to `false` or
 * another value.
 */
export declare function mergeGatewayAutoCaching(base: Readonly<Record<string, unknown>> | undefined): Record<string, unknown>;
/**
 * Returns a new ToolSet where the last tool entry carries the Anthropic
 * cache marker on `providerOptions`. Used on the `anthropic-direct` path
 * to place a stable breakpoint at the end of the tools block, caching the
 * full tool definitions across every turn.
 *
 * No-op when `tools` has no entries. Preserves existing `providerOptions`
 * on tools (merges the cache marker in via spread).
 */
export declare function applyLastToolCacheBreakpoint(tools: ToolSet, marker: AnthropicCacheMarker): ToolSet;
/**
 * Marks the last system message in an instructions array with the Anthropic
 * cache marker. This creates a cache breakpoint at the end of the system
 * prompt, preserving the system prefix when tools change between steps.
 *
 * When `instructions` is a string or undefined, returns it unchanged —
 * single-string system prompts don't support per-message providerOptions.
 * No-op when the array is empty.
 */
export declare function applySystemCacheBreakpoint(instructions: readonly SystemModelMessage[], marker: AnthropicCacheMarker): SystemModelMessage[];
/**
 * Attaches the Anthropic cache marker to the last message in `messages`
 * (whatever its role) and, as a stable mid-history anchor, to the most
 * recent `assistant` message before it. Returns a new array; does not
 * mutate the input.
 *
 * The final breakpoint must sit on the very last message so that the
 * newest content — typically a `tool` message carrying fresh tool
 * results — is written to the cache in the same request that pays for
 * it. Placing it any earlier (e.g. on the last assistant message) leaves
 * the trailing tool results outside the cached region: they get billed
 * as uncached input every turn and only enter the cache one request
 * later, capping the effective hit rate near 50%. The AI SDK Anthropic
 * provider maps a message-level marker on a `tool` message to its last
 * tool-result content block.
 *
 * The assistant anchor implements "automatic cache advancement": it
 * guarantees a breakpoint from the prior request survives into the next
 * one, so cache lookups always find the previous prefix even when a step
 * appends more content blocks than Anthropic's backward boundary scan
 * covers.
 */
export declare function applyConversationCacheControl(messages: readonly ModelMessage[], marker: AnthropicCacheMarker): ModelMessage[];