# UAN-023 named-client and host availability probe

Date: 2026-10-03 UTC. Isolated source commit: `076b4197e49997da190389d9e247521baa3bab50`. Host: `research`, macOS 27.0 build 26A425, Node 25.9.0, npm 11.12.1. These observations do not complete UAN-023 or the v1 release matrix.

## Pinned named MCP client over HTTP

The independent client was the official [MCP Inspector CLI](https://github.com/modelcontextprotocol/inspector/blob/main/clients/cli/README.md), pinned to `@modelcontextprotocol/inspector@2.8.0`. It connected with Streamable HTTP to the packed E09 example's actual loopback server. This is a real named client and real HTTP transport; the server/data and identity policy remain local fixtures. No commercial service or external network endpoint was tested.

Reproduce from this checkout:

```sh
npm ci --ignore-scripts --no-audit --no-fund
npm run build
npm run example:e09
node test/uan023-inspector-client.mjs
```

The manual probe starts the E09 server on `127.0.0.1`, invokes the Inspector CLI four times with a 45-second per-call timeout, asserts protocol outcomes, and closes the server. It uses `npx --yes @modelcontextprotocol/inspector@2.8.0`; no credential is passed.

Observed results:

| Probe | Inspector result |
| --- | --- |
| `tools/list` | Exit 0; exactly one named album-lookup tool with input/output schemas and a `ui://uppercut/album-explorer.html` resource reference |
| `tools/call --app-info` | Exit 0; `hasApp: true`, resource MIME `text/html;profile=mcp-app` |
| `tools/call` with `{"slug":"first-light"}` | Exit 0; text and `structuredContent.result` both represent the found album |
| `tools/call` with `{"slug":"blocked-album"}` | Exit 5; `isError: true` and no successful value |

The standalone E09 packaging/build/tests also passed (3/3). The probe script is the exact assertion source. Its `.exported` E09 dependency is intentionally generated by `npm run example:e09`, not checked in. The result expands the prior SDK-only fixture evidence to a separately distributed named client CLI. Inspector CLI app metadata inspection does **not** demonstrate rendering or interaction in an MCP Apps host.

## Browser and MCP Apps host boundary

Installed Google Chrome 154.0.8037.95 was probed in a headless, no-focus session without an origin-trial token or experimental flag. `document.modelContext` and its `registerTool` member both evaluated as `undefined` on a blank page. This shows the default local Chrome session did not expose native WebMCP; it does not test a supported WebMCP agent host. Chrome's [WebMCP origin-trial notice](https://developer.chrome.com/blog/ai-webmcp-origin-trial) describes opt-in access. The package's ordinary-site fallback was covered by earlier simulated/browser fixtures, not by this blank-page probe.

The Inspector CLI read App resource metadata and called the tool, but no Inspector web UI or other MCP Apps iframe host was opened. App rendering, host-mediated UI actions, browser sandbox/CSP enforcement, and consent behavior remain unverified. No author-independent human or clean-context Astro adoption was performed. UAN-023 cannot be marked complete from this slice.

No Windows foreground UI was used. No external credential, private package, deployment, or npm publish was involved.