/**
 * Graph upload-session path for outbound attachments above the inline limit.
 * Shared by every tool that attaches a file; `tool` names the caller for the
 * Graph call tag and the error prefixes, so a stalled session is greppable back
 * to the tool that started it.
 *
 * Two steps, distinct in auth and host:
 *   1. `POST /me/messages/{draftId}/attachments/createUploadSession` — through
 *      the Graph SDK (auth handled by `postGraph`), returns a pre-authenticated
 *      `uploadUrl`.
 *   2. Chunked `PUT` to that `uploadUrl` — a plain fetch to a non-Graph host
 *      with NO bearer token (the URL itself is the credential). Each chunk is a
 *      multiple of 320 KiB except the last, per Graph's contract, and carries a
 *      `Content-Range` header. Graph returns 200 for an intermediate chunk and
 *      201 for the final one.
 *
 * Every non-2xx PUT throws with the response status and body preserved, so a
 * session that stalls mid-chunk is diagnosable rather than silent.
 */
import type { GraphClientConfig } from "./graph-client.js";
import type { OutboundAttachment } from "./outbound-attachments.js";
/** Chunk size for the upload PUT: 3.125 MiB, a whole multiple of 320 KiB as
 *  Graph requires for every chunk except the final remainder. */
export declare const UPLOAD_CHUNK_BYTES: number;
/**
 * Upload one large attachment to an existing draft via a Graph upload session.
 * Returns the number of chunks PUT (for observability). The draft must already
 * exist; the attachment must have passed `resolveOutboundAttachments`. `tool`
 * names the calling tool for the Graph call tag and the error prefixes.
 */
export declare function uploadAttachmentSession(config: GraphClientConfig, draftId: string, att: OutboundAttachment, tool: string): Promise<number>;
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