/**
 * Layer 4 (v1.7.5): persistence for resolved embedding metadata.
 *
 * Reads / writes the schema-v7 columns on `embedder_capability`
 * (`dim`, `query_prefix`, `document_prefix`, `prefix_source`, `base_model`,
 * `size_bytes`, `fetched_at`).
 *
 * **Cache lifetime: forever, until explicit invalidation.** v1.7.5 originally
 * shipped a 90-day TTL with stale-while-revalidate; that was reverted before
 * promotion in favour of "cache once, never auto-refetch" semantics. Reasoning:
 * the fields we cache (dim, model_type, hidden_size, ONNX sizes) are immutable
 * for a given HF model id — HF doesn't allow rewriting a published revision.
 * The fields that CAN change post-publish (tokenizer_config corrections,
 * retroactively-added prompts) change rarely, and silently auto-refetching
 * burns HF API quota across the whole user base for negligible benefit.
 * Users invalidate explicitly when they need to via the
 * `obsidian-brain models refresh-cache` CLI command.
 *
 * SQL-only — does not call HF, does not load JSON, does not consult seed.
 * All higher-level orchestration lives in `metadata-resolver.ts` (Layer 3).
 */
import type { DatabaseHandle } from '../store/db.js';
/** Source markers persisted into `prefix_source`. */
export type CachedPrefixSource = 'override' | 'seed' | 'metadata' | 'metadata-base' | 'readme' | 'fallback' | 'none';
/** Shape stored in / loaded from the `embedder_capability` v7 columns. */
export interface CachedMetadata {
    modelId: string;
    dim: number | null;
    /** Resolved max tokens (from advertised_max_tokens column for v6 compat). */
    maxTokens: number | null;
    queryPrefix: string | null;
    documentPrefix: string | null;
    prefixSource: CachedPrefixSource;
    baseModel: string | null;
    sizeBytes: number | null;
    fetchedAt: number | null;
}
/**
 * Load cached metadata for `modelId`, or null if absent / has no v7 columns
 * populated yet.
 */
export declare function loadCachedMetadata(db: DatabaseHandle, modelId: string): CachedMetadata | null;
/**
 * Persist metadata for `modelId`. Writes to v7 columns; preserves any
 * existing `discovered_max_tokens` / `discovered_at` / `method` from the v6
 * adaptive-capacity flow (we only INSERT-or-UPDATE the v7 fields).
 */
export declare function upsertCachedMetadata(db: DatabaseHandle, meta: CachedMetadata): void;
/**
 * Invalidate cached metadata so the next resolver pass refetches from the
 * seed → HF chain. NULLs the v7 columns (dim, query_prefix, etc.) on the
 * matching row(s) but preserves v6 capacity columns (`advertised_max_tokens`,
 * `discovered_max_tokens`, `method`) — those track adaptive-capacity drift,
 * not metadata, and shouldn't be reset by a metadata refresh.
 *
 * Returns the number of rows touched. When `modelId` is omitted, clears
 * every entry; otherwise only the row for that exact `embedder_id`.
 *
 * Called by `obsidian-brain models refresh-cache [--model <id>]`.
 */
export declare function clearMetadataCache(db: DatabaseHandle, modelId?: string): number;