Server names containing "/" (all official-registry names) are not percent-encoded → registry Add returns HTTP 400 and server-detail UI 404s #598

Summary

Official MCP Registry server names are reverse-DNS identifiers that always contain a / (e.g. io.github.evidai/polymarket-guard). mcpproxy uses this name raw — un-percent-encoded — as (1) a URL path segment in the registry "add" API call, (2) a route segment in the web UI server-detail page, and (3) a filesystem path for the per-server log. Each breaks:

1. Adding from a registry fails with HTTP 400.
2. The server-detail page renders "404 Page Not Found".
3. The per-server log file is written into an unintended nested directory.

The UI also displays the raw name instead of the registry's human-readable title.

Spec background

Per the official MCP Registry schema (2025-12-11), the server name is a reverse-DNS identifier — "Must contain exactly one forward slash separating namespace from server name" (^[a-zA-Z0-9.-]+/[a-zA-Z0-9._-]+$). Every official-registry name therefore contains a /. The Registry Aggregators guide states explicitly:

URL path parameters such as serverName … must be URL-encoded. For example, io.modelcontextprotocol/everything must be encoded as io.modelcontextprotocol%2Feverything.

There is also an optional title field that the schema says clients "MAY choose to use … for display purposes." So name is an identifier (not URL/path safe, not a label); title is the display string.

Refs: server.schema.json 2025-12-11; modelcontextprotocol.io/registry/registry-aggregators; modelcontextprotocol.io/registry/about

Symptom 1 — Add → HTTP 400

Clicking "Add to MCP" for any Official MCP Registry server issues (from the web UI, captured in http.log):

POST /api/v1/registries/Official MCP Registry/servers/io.github.evidai/polymarket-guard/add  → 400  (x3)

Both path params are interpolated raw: the registry name Official MCP Registry (spaces) and the server name io.github.evidai/polymarket-guard (slash). The unencoded / adds an extra path segment so the route can't match …/servers/{serverName}/add → 400. Because every official-registry name contains a /, this affects adding any of them.

Symptom 2 — server-detail UI → 404

Verified with a real browser (Playwright driving Chrome) against the three URL variants:

The server (index.html) is served for all /ui/* paths (200), but the front-end router treats the unencoded / as an extra segment and falls through to the generic 404 page. Encoding the slash as %2F makes the route match. Fix: encodeURIComponent(name) when building detail links / routes (and decode on read).

Symptom 3 — filesystem

The per-server log for this server is written to:

~/Library/Logs/mcpproxy/server-io.github.evidai/polymarket-guard.log

i.e. the / in the name created a nested server-io.github.evidai/ directory rather than a single server-<name>.log file. The name should be sanitized/encoded when used as a filename key.

Expected

• Percent-encode path parameters (both the registry name and the server name) in the registry add API call.
• encodeURIComponent the server name in web-UI routes and links; decode when reading the route param.
• Sanitize/encode the name when used as a filesystem key for logs.
• Display the registry-provided title (fall back to name when absent) rather than rendering the raw identifier.

Environment

• mcpproxy-go macOS app v0.37.0 (tray + web UI at 127.0.0.1:8080)
• Source registry: "Official MCP Registry" (registry.modelcontextprotocol.io)
• Example server: io.github.evidai/polymarket-guard

Repro

1. In the web UI → Registries → Official MCP Registry, search any server and click "Add to MCP" → toast shows HTTP 400: bad request.
2. With a server whose name contains / present, open …/ui/servers/<namespace>/<name> → "404 Page Not Found".