TREK/server/src/plugin-mcp-tools.ts

// The seam that lets a per-session MCP server carry tools contributed by installed
// plugins, without src/nest/mcp-transport/ gaining an edge to the plugin runtime —
// the same module cycle trip-warnings.mcp.ts documents. Sibling of
// plugin-event-sink.ts and plugin-user-lifecycle.ts; the plugins layer registers
// the source at bootstrap and clears it on shutdown.

import type { McpContext, McpDynamicTool } from './nest-mcp';

/**
 * PULL rather than push, unlike setPluginEventSink: the answer depends on the
 * session's ctx, so there is nothing a push could carry ahead of time, and
 * reading it on every attach means activating or uninstalling a plugin takes
 * effect on the next session with nothing to invalidate. That is the argument
 * channel-registry.ts already makes for setPluginChannelSource.
 *
 * Unlike every sink beside it this one returns a value on the request path. An
 * unset source is not an error: it means "no plugin tools", which is the right
 * answer for any app built without the plugins runtime, and for every test that
 * never registers one.
 *
 * Deliberately NOT wrapped in try/catch here. nest-mcp's attach() contains a
 * throwing source per its own contract and logs which one failed; catching it
 * again on the way out would swallow that diagnostic and report the same
 * degraded surface less usefully.
 */
export type PluginMcpToolSource = (ctx: McpContext) => readonly McpDynamicTool[] | Promise<readonly McpDynamicTool[]>;

let source: PluginMcpToolSource | null = null;

export function setPluginMcpToolSource(fn: PluginMcpToolSource | null): void {
  source = fn;
}

export function getPluginMcpToolSource(): PluginMcpToolSource | null {
  return source;
}