/**
 * Resolves the latest user-friendly activity snippet from a coding-harness runtime log.
 *
 * The Agents Server local agent runner streams the answering harness output (for example
 * Claude Code `--output-format stream-json`) into a live runtime log file next to the queued
 * message. This helper extracts the most recent natural-language assistant narration so the
 * durable chat can show what the agent is doing right now instead of a generic thinking
 * placeholder. Only concrete, safe activity is surfaced; raw tool payloads, JSON envelopes,
 * and private reasoning are intentionally ignored. When no concrete activity is known, this
 * resolves to `null` so the caller keeps the browser's rotating generic thinking state.
 *
 * @param logText - Raw runtime log content.
 * @returns Latest human-readable activity snippet, or `null` when none can be resolved.
 * @private internal utility of the agent-message runtime
 */
export declare function resolveAgentMessageRuntimeActivity(logText: string | null | undefined): string | null;