/**
 * Crash-safe atomic write helpers for the session tracker persistence layer.
 *
 * All writes use write-to-temp + fs.rename() to ensure files are either
 * complete or nonexistent — never truncated (D-03).
 *
 * @module session-tracker/persistence/atomic-write
 */
/**
 * Atomically writes JSON data to a file.
 *
 * Writes to a temporary file (`.tmp.{timestamp}`), then renames over the
 * target path. If the process crashes mid-write, only the temp file exists —
 * the target is either complete or untouched.
 *
 * @param filePath - Absolute path to the target file.
 * @param data - Data to serialize as JSON.
 * @returns Promise that resolves when the write is complete.
 *
 * @example
 * ```typescript
 * await atomicWriteJson("/path/to/file.json", { key: "value" })
 * ```
 */
export declare function atomicWriteJson(filePath: string, data: unknown): Promise<void>;
/**
 * Atomically appends markdown content to a file.
 *
 * If the file does not exist, it is created. If it exists, the content
 * is appended with a preceding newline separator. Uses atomic rename to
 * avoid truncated files on crash.
 *
 * @param filePath - Absolute path to the target markdown file.
 * @param content - Markdown content to append.
 * @returns Promise that resolves when the append is complete.
 *
 * @example
 * ```typescript
 * await atomicAppendMarkdown("/path/to/session.md", "## USER (turn 1)\n\nHello!")
 * ```
 */
export declare function atomicAppendMarkdown(filePath: string, content: string): Promise<void>;
/**
 * Ensures a directory exists, creating it and any needed parent directories.
 *
 * @param dirPath - Absolute path to the directory.
 * @returns Promise that resolves when the directory exists.
 */
export declare function ensureDirectory(dirPath: string): Promise<void>;
/**
 * Sanitizes a session ID by stripping characters that are not alphanumeric,
 * underscore, or hyphen.
 *
 * @param sessionID - Raw session ID to sanitize.
 * @returns The sanitized session ID.
 * @throws {Error} If the sanitized ID is shorter than 3 characters.
 */
export declare function sanitizeSessionID(sessionID: string): string;
/**
 * Constructs a safe filesystem path under the session tracker root.
 *
 * Sanitizes the session ID and validates that the resolved path does not
 * escape the `.hivemind/session-tracker/` root (prevents path traversal).
 *
 * @param projectRoot - Absolute path to the project root.
 * @param sessionID - Session identifier to use as the subdirectory name.
 * @param filename - The filename within the session directory.
 * @returns Absolute, validated path under the session tracker root.
 * @throws {Error} If the resolved path escapes the tracker root.
 */
export declare function safeSessionPath(projectRoot: string, sessionID: string, filename: string): string;
/**
 * Returns the absolute path to the session tracker root for a given project.
 *
 * @param projectRoot - Absolute path to the project root.
 * @returns Absolute path to `.hivemind/session-tracker/`.
 */
export declare function sessionTrackerRoot(projectRoot: string): string;
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