/** before_agent_start: pi hands us the assembled system prompt; returning a new
 *  `systemPrompt` replaces it for this agent run (pi rebuilds it each run, so
 *  splicing fresh every time is idempotent — never cumulative). */
interface BeforeAgentStartEventLike {
    systemPrompt: string;
}
interface BeforeAgentStartResultLike {
    systemPrompt: string;
}
/** tool_result: fired after a tool returns. `content` is the tool's output
 *  blocks; returning a new `content` replaces what the model sees. */
interface ContentBlockLike {
    type: string;
    text?: string;
}
interface ToolResultEventLike {
    toolName: string;
    isError?: boolean;
    /** The tool's resolved input. For `read` it carries the file path under
     *  `path` (or the legacy `file_path`). Typed loosely; narrowed at use. */
    input?: unknown;
    content: ContentBlockLike[];
}
interface ToolResultCtxLike {
    /** The session cwd — used to resolve a relative read path. */
    cwd?: string;
}
type ToolResultResultLike = {
    content: ContentBlockLike[];
} | void;
interface PiLike {
    on(event: 'before_agent_start', handler: (event: BeforeAgentStartEventLike) => BeforeAgentStartResultLike | void | Promise<BeforeAgentStartResultLike | void>): void;
    on(event: 'session_start', handler: (event: unknown, ctx: unknown) => void): void;
    on(event: 'tool_result', handler: (event: ToolResultEventLike, ctx: ToolResultCtxLike) => ToolResultResultLike | Promise<ToolResultResultLike>): void;
}
/**
 * Register the document substrate's pi hooks on `pi`.
 *
 * Returns immediately (inert) when CRTR_NODE_ID is absent — a non-canvas pi
 * session gets no hooks. Each handler is independently wrapped so a failure
 * degrades to a no-op (boot proceeds, the read returns) rather than bricking.
 */
export declare function registerCanvasDocSubstrate(pi: PiLike): void;
export default registerCanvasDocSubstrate;