Adds the `codegraph ui [path]` command (alias `web`) and `src/ui-server/`, a
`node:http` server with no framework and no new dependency.
The command reads an index that already exists — it never creates one, so a
missing index prints the same friendly guidance the MCP tools give instead of
a stack trace, and a sensitive system directory is refused up front.
Security is the substance here, not the routing. The server binds 127.0.0.1
only, answers GET and HEAD only, and sends no CORS headers ever. The realistic
attack on a process that serves your source code from a local port is DNS
rebinding, so every request must carry a loopback `Host` (on our port) and, if
it carries an `Origin` at all, a loopback one — anything else is 403 before
the filesystem is touched. Every path resolves through the engine's existing
`validatePathWithinRoot` chokepoint, which already handles `../` traversal and
in-tree symlinks pointing out of the root (#527); `..` segments are refused
outright so a traversal attempt gets a 404 rather than the SPA shell.
`PathRefusalError` moves from `mcp/tools.ts` into the dependency-free
`errors.ts` (re-exported from its old home, so class identity and every
`instanceof` check are unchanged) — that is what lets a non-MCP read sink
enforce the same refusal without importing the MCP tool graph.
Assets come from `dist/viewer/` resolved relative to `__dirname`, the way
`db/index.ts` finds `schema.sql`. Hashed assets are cached immutably,
`index.html` never. Port 4747, or the next free one — an explicit `--port`
stays explicit rather than silently moving. `--no-open` skips the browser, and
`CODEGRAPH_BROWSER` picks one (or `none` to suppress it), which is also what
makes "did it open a browser" testable end to end.
`resolveProjectFile` and the `/api/` handler seam are the boundary CG-42's
JSON API plugs into; `/api/*` 404s as JSON so a typo'd endpoint never returns
the app shell.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Colby McHenryandClaude Opus 5
0196c2e53a