/**
 * Slack mrkdwn ↔ GitHub-flavored markdown converters and the bare
 * `@mention` rewriter used by the outbound post pipeline. These are
 * pure string utilities — no Slack API I/O, no I/O at all — so they
 * live separately from the binding constructor and request shape code
 * in {@link ./api.ts}.
 */
/**
 * Rewrites bare `@USER_ID` tokens (the form Slack apps and humans tend
 * to type) into the `<@USER_ID>` mention syntax Slack actually renders.
 * Anything already wrapped in `<...>` is left untouched.
 */
export declare function rewriteBareMentions(text: string): string;
/**
 * Best-effort GFM → Slack mrkdwn converter used only in contexts that
 * do not support `markdown_text` (e.g. `files.completeUploadExternal`'s
 * `initial_comment` field).
 *
 * The main `{ markdown }` post path sends `markdown_text` directly
 * to `chat.postMessage` and does not go through this converter.
 */
export declare function gfmToSlackMrkdwn(input: string): string;
/**
 * Best-effort Slack mrkdwn → GFM converter applied to the text of
 * every inbound Slack message before the harness sees it.
 *
 * - `<@U123>`              → `@U123`
 * - `<#C123|name>`         → `#name` (or `#C123` when no name)
 * - `<!channel>` etc.      → `@channel`
 * - `<https://x|label>`    → `[label](https://x)`
 * - `<https://x>`          → `https://x`
 * - `*bold*` (paired)      → `**bold**`
 * - `~strike~` (paired)    → `~~strike~~`
 *
 * Inline `_italic_` and code spans pass through unchanged because both
 * formats render them identically.
 */
export declare function slackMrkdwnToGfm(input: string): string;