export type FilesystemCapability = "none" | "readonly" | "persistent" | "ephemeral";
export interface AdapterCapabilities {
    /** Whether the host supports streaming responses (ReadableStream bodies). */
    streaming: boolean;
    /** Filesystem access model of the host. */
    filesystem: FilesystemCapability;
    /** Whether the host can run image transforms at request time. */
    imageRuntime: boolean;
    /** Whether the host allows background work after the response completes. */
    backgroundWork: boolean;
    /** Maximum request body size in bytes accepted by the host (if any). */
    maxBodySize?: number;
}
export interface CapabilityOptions {
    streaming?: boolean;
    filesystem?: FilesystemCapability;
    imageRuntime?: boolean;
    backgroundWork?: boolean;
    maxBodySize?: number;
}
/** Default capabilities for a full-featured long-lived Node/Bun process. */
export declare const DEFAULT_CAPABILITIES: AdapterCapabilities;
/** Default capabilities for a stateless serverless function (Vercel/Netlify). */
export declare const SERVERLESS_CAPABILITIES: AdapterCapabilities;
/** Default capabilities for an edge runtime (read-only filesystem). */
export declare const EDGE_CAPABILITIES: AdapterCapabilities;
export declare function createCapabilities(options?: CapabilityOptions): AdapterCapabilities;
/** True when the host supports streaming responses (streaming !== false). */
export declare function supportsStreaming(capabilities?: Pick<AdapterCapabilities, "streaming">): boolean;
/** True when the host can write to persistent storage (for ISR/cache/image writes). */
export declare function supportsPersistentStorage(capabilities: Pick<AdapterCapabilities, "filesystem">): boolean;
/** True when the host exposes a writable filesystem at build/runtime. */
export declare function supportsWritableFilesystem(capabilities: Pick<AdapterCapabilities, "filesystem">): boolean;
export interface CapabilityDiagnostics {
    ok: boolean;
    problems: string[];
}
/**
 * Validates a capability declaration and reports incompatible combinations.
 * Used by the build pipeline so invalid hosts fail at build time instead of
 * producing a broken runtime.
 */
export declare function validateCapabilities(capabilities: AdapterCapabilities, features?: {
    isr?: boolean;
    images?: boolean;
    streaming?: boolean;
}): CapabilityDiagnostics;