/**
 * The documented contract: one path segment. `isUnsafePathInput` is a
 * traversal guard only and ADMITS `a/b`, so the separator axes are
 * checked here as well. The session dir is ONE directory name under
 * `_runtime/`.
 *
 * EXPORTED because the session id is the last caller-supplied segment of
 * more than one session-scoped path: the runtime dir here, and the dispatch
 * ledger's dir under `.peaks/_sub_agents/` (read by
 * `src/services/dispatch/dispatch-ledger-reader.ts`). One predicate, two
 * users, so the two cannot drift apart.
 */
export declare function isSinglePathSegment(sessionId: string): boolean;
export declare function getSessionDir(projectRoot: string, sessionId: string): string;
/**
 * The TOTAL entry to the same axis. Same predicate, same path; the only
 * difference is that this one is total — it never throws.
 *
 * WHY TWO ENTRIES RATHER THAN ONE. The partial entry above is correct
 * for a caller that cannot proceed without a session dir: a throw is
 * the one failure a caller cannot forget to handle. It is the WRONG
 * shape for a frame whose own doc promises never to throw — the
 * statusline, the fire-and-forget telemetry writer, the best-effort
 * probe. Each of those frames had to wrap the partial entry in a
 * `try { } catch { return null }`, and that swallow cannot be told
 * apart from a real "there is nothing here" answer. Measured on the
 * compact backoff (`auto-compact-lifecycle.ts`), the conflation turned
 * an unresolvable id into the ADMIT branch and re-opened a dispatch
 * that the open run should have suppressed.
 *
 * The split does NOT make a swallow unwriteable — TypeScript has no
 * checked exceptions, so nothing here can. It makes the swallow
 * UNNECESSARY at a named place, and it gives every checker a stable
 * name to key on: a frame that degrades must say so by calling this
 * function, and the degrading branch (`ok: false`) is then a value the
 * caller has to handle rather than a `catch` nobody reads.
 *
 * `reason` is a single-line English sentence fit for an envelope — no
 * stack traces, no CLI verbs (see `human-nl-choice-only-tenet`).
 */
export declare function tryGetSessionDir(projectRoot: string, sessionId: string): {
    readonly ok: true;
    readonly dir: string;
} | {
    readonly ok: false;
    readonly reason: string;
};