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feat: official SDK transport for /api/mcp — one server definition, every transport #97

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adamstankiewicz wants to merge 4 commits into from
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feat: official SDK transport for /api/mcp — one server definition, every transport #97

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12391a1
feat: the deployed MCP endpoint speaks the official SDK (closes #92)
adamstankiewicz Aug 30, 2026
fd815b4
test: the audience test follows the rename to audienceHint
adamstankiewicz Aug 30, 2026
66f5290
fix: a GET asking for the SSE stream gets the spec's 405
adamstankiewicz Aug 30, 2026
9518e82
docs: the shared server carries the arc-as-spine guidance too
adamstankiewicz Aug 31, 2026
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172 changes: 0 additions & 172 deletions mcp/app.mjs
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16 changes: 16 additions & 0 deletions mcp/build.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,22 @@ const html = `<!doctype html>
</html>
`;

// The CLI transports (stdio, local HTTP) consume the same server definition
// as the deployed route. Bundled here because they run as plain node — no
// TS, no path aliases — and a stale bundle should say so rather than drift.
const core = await build({
entryPoints: [join(root, 'src', 'lib', 'mcp', 'server.ts')],
bundle: true,
platform: 'node',
format: 'esm',
write: false,
tsconfig: join(root, 'tsconfig.json'),
alias: { 'server-only': join(root, 'test', 'stubs', 'server-only.ts') },
external: ['@modelcontextprotocol/sdk*', '@ai-sdk/*', '@openrouter/*', '@supabase/*', 'ai', 'zod', 'react', 'node:*'],
logLevel: 'error',
});
writeFileSync(join(outDir, 'server-core.mjs'), core.outputFiles[0].text);

const out = join(outDir, 'widget-shell.html');
writeFileSync(out, html);

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32 changes: 32 additions & 0 deletions mcp/core.mjs
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@@ -0,0 +1,32 @@
/**
* Loads the bundled server definition for the CLI transports.
*
* `src/lib/mcp/server.ts` is the one source of the tool surface; this file
* only adapts it to plain-node life: the bundle from `pnpm mcp:build`, the
* shell read from disk, and the API origin from env.
*/
import { existsSync, readFileSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath, pathToFileURL } from 'node:url';

const root = dirname(fileURLToPath(import.meta.url));
const API_ORIGIN = process.env.WIDGET_API_ORIGIN ?? 'http://localhost:3100';

const corePath = join(root, 'dist', 'server-core.mjs');
const shellPath = join(root, 'dist', 'widget-shell.html');

for (const [path, what] of [[corePath, 'server bundle'], [shellPath, 'widget shell']]) {
if (!existsSync(path)) {
console.error(`[mcp] ${what} missing at ${path} — run: pnpm mcp:build`);
process.exit(1);
}
}

const { buildMcpServer } = await import(pathToFileURL(corePath).href);

export function createServer() {
return buildMcpServer({
origin: API_ORIGIN,
loadShell: async () => readFileSync(shellPath, 'utf8'),
});
}
2 changes: 1 addition & 1 deletion mcp/server-http.mjs
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Expand Up @@ -18,7 +18,7 @@
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import { createServer as createHttpServer } from 'node:http';

import { createServer } from './app.mjs';
import { createServer } from './core.mjs';

const PORT = Number(process.env.MCP_HTTP_PORT ?? 3300);

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2 changes: 1 addition & 1 deletion mcp/server.mjs
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Expand Up @@ -5,6 +5,6 @@
*/
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';

import { createServer } from './app.mjs';
import { createServer } from './core.mjs';

await createServer().connect(new StdioServerTransport());
3 changes: 2 additions & 1 deletion package.json
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Expand Up @@ -20,7 +20,8 @@
"predev": "node mcp/build.mjs",
"prebuild": "node mcp/build.mjs",
"conformance": "node scripts/a2ui-conformance.mjs",
"conformance:update": "node scripts/a2ui-conformance.mjs --update"
"conformance:update": "node scripts/a2ui-conformance.mjs --update",
"mcp:inspect": "npx --yes @modelcontextprotocol/inspector@latest"
},
"dependencies": {
"@ag-ui/core": "^0.0.58",
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