Route contract (AB4810) rejects a re-exported default component for a second placement of the same tool

[ScriptedAlchemy]

Summary

A project can list the same tool name on two generated MCP servers (movie-library needs search, add_to_library, download, and delete both on their primary server and on the widget-serving server, because MCP-app tools/call routes to the server that served the widget). The natural way to author the second placement is a route module that carries its own literal config (the widget-server placement differs only in _meta.ui.resourceUri) and re-exports the rest from the primary route or a shared page:

// src/mcp/movie-library-library/tools/download.tsx
import type { ToolConfig } from 'agent-bundle';
import { WIDGET_RESOURCE_URI } from '../../../widget-resource.ts';

export const config = {
  _meta: { ui: { resourceUri: WIDGET_RESOURCE_URI } },
  annotations: { readOnlyHint: true },
  description: 'Completed rTorrent payloads are published automatically by the seedbox completion timer.',
  title: 'Download',
} satisfies ToolConfig;

export { default, inputSchema, resultSchema } from '../../movie-library-public/tools/download.tsx';

agent-bundle validate rejects it:

AB4810 Route module src/mcp/movie-library-library/tools/download.tsx does not satisfy the public route contract: default export is not an async function component.
Recovery: Export const inputSchema and resultSchema, plus one async default Server Component receiving { input, signal }.

The static contract check only recognizes a locally declared export default async function. A re-exported default (export { default } from) is a legal ESM default export that resolves to exactly such a component at run time, and export const inputSchema = other.inputSchema (a member expression) is already accepted, so the default export is the odd one out.

Repro

Preview agent-bundle@43abb2db0. Two generated servers, one tool placed on both:

src/mcp/a/tools/ping.tsx      # full route: literal config, inputSchema, resultSchema, async default component
src/mcp/b/tools/ping.tsx      # literal config + `export { default, inputSchema, resultSchema } from '../../a/tools/ping.tsx';`

agent-bundle validate --json → AB4810 on src/mcp/b/tools/ping.tsx.

Expected

Either accept export { default } from '<relative module>' when the target module's default export satisfies the contract, or document that a second placement must declare its own export default async function wrapper. movie-library worked around it with src/pages/<tool>.tsx shared page components and a thin export default async function X({ input, signal }) { return <XRoute input={input} signal={signal} />; } in each placement — fine, but the diagnostic text ("default export is not an async function component") is misleading for a re-export, since it is one.

Found while re-porting ScriptedAlchemy/movie-library onto 43abb2db0.

[ScriptedAlchemy]

Re-checked on main @ 284141958: the AB4810 contract check is unchanged since 43abb2db0 (no commit touches the check between the two), so this is still present. Consumer evidence now on a PR: ScriptedAlchemy/movie-library#8 — the shared page + thin default per placement is at src/pages/search.tsx:14-19, the two placements at src/mcp/movie-library-public/tools/search.tsx and src/mcp/movie-library-library/tools/search.tsx (same for add_to_library, download, delete); PORT-NOTES § "Shared pages for the widget-support duplicates" records the constraint.