docs(smoke): document the throwaway-catalog invariant and fix the label JSDoc

Addresses the two review comments that still applied to HEAD (the third, the
stop() race, was already fixed in a8022138).

- AGENTS.md still described the prod-web-server helper as shared by only
  smoke:web and smoke:web:browser, and said nothing about catalog isolation.
  It is the source of truth for these smoke mechanics, so record the invariant
  there: the temp catalog per run and why, that only the catalog (not HOME) is
  redirected, that teardown needs both halves of child-cleanup.mjs and is
  therefore async for every caller, and where the contract is unit-tested.

- The `label` JSDoc claimed the option prefixes the temp dir. It does not —
  that prefix is fixed at `smoke-web-catalog-` (deliberately, so every run's
  dir is greppable); `label` only prefixes teardown warnings.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HDdo1rNRVQnVRRdsqSrvG3
Signed-off-by: cliffhall <cliff@futurescale.com>

AGENTS.md

@@ -657,7 +657,9 @@ The ⚠️ option-deletion hazard, the snapshot rule, and the recovery recipe ab
   - **`npm run coverage`** is the per-file ≥90 gate and is now part of `npm run ci` — never treat it as optional before a push. It supersedes the old standalone `test:integration` step: web's `test:coverage` runs the `unit` **and** `integration` projects under v8 instrumentation, so `coverage` both enforces the ≥90 gate and exercises the same web integration paths CI covers.
 - **`smoke` is NOT part of `validate`** — it is included in `npm run ci`. It runs `smoke:launcher` (`--help` dispatch) plus the prod `smoke:cli` / `smoke:tui` / `smoke:web` / `smoke:web:browser` / `smoke:web:app`, and contains **no build commands** — it assumes the cli/tui/launcher bundles already exist (a full `validate` builds them; `smoke:web` builds `clients/web/dist` on demand). CI runs `validate`, then the `coverage` gate (which also covers the web integration project), then `verify:build-gate` (the #1769 build gate — see below), then `smoke` (with Playwright chromium installed just before it, since `smoke:web:browser` needs it). GitHub CI runs this same chain as separate workflow steps, with the Storybook play-function tests last (see below).
 - `smoke:launcher` (`scripts/smoke-launcher.mjs`) runs the built launcher with `--help`, `--cli --help`, and `--tui --help`, asserting each exits 0 and prints that mode's usage banner (which also proves the launcher resolved and loaded the right client build). It's the cheap dispatch check before the heavier prod smokes below.
-- `smoke:web` (`scripts/smoke-web.mjs`) starts `mcp-inspector --web` (prod, no `--dev`) against the built `clients/web/dist` and asserts `GET /` serves the SPA (HTTP 200) with the injected `__INSPECTOR_API_TOKEN__`. Prod `--web` serves from `clients/web/dist`, which ships in the published package but is absent in a fresh checkout — the runner builds it on demand (`build:client` = `vite build`) on first launch, or exits with an actionable error if that build can't run (see `clients/web/server/ensure-web-build.ts` and the launcher README). `--dev` runs Vite directly and never needs `dist`. It shares the spawn/readiness/teardown helper (`scripts/lib/prod-web-server.mjs`) with `smoke:web:browser`, so the two can't drift.
+- `smoke:web` (`scripts/smoke-web.mjs`) starts `mcp-inspector --web` (prod, no `--dev`) against the built `clients/web/dist` and asserts `GET /` serves the SPA (HTTP 200) with the injected `__INSPECTOR_API_TOKEN__`. Prod `--web` serves from `clients/web/dist`, which ships in the published package but is absent in a fresh checkout — the runner builds it on demand (`build:client` = `vite build`) on first launch, or exits with an actionable error if that build can't run (see `clients/web/server/ensure-web-build.ts` and the launcher README). `--dev` runs Vite directly and never needs `dist`. It shares the spawn/readiness/teardown helper (`scripts/lib/prod-web-server.mjs`) with **`smoke:web:browser` and `smoke:web:app`**, so the three can't drift.
+
+  **Every web smoke runs against a throwaway catalog (#1977).** The helper mints a temp dir per run and passes it as `MCP_CATALOG_PATH`; without it the web backend falls back to the developer's real `~/.mcp-inspector/mcp.json`, which made these smokes both destructive and non-deterministic — `smoke:web:app`'s deep link persists a `deep-link` server row, so a *second* run found it already on disk, raced hydration, and drew a spurious (swallowed, non-fatal) 409 that was really just residue from the previous run. CI never saw it: a fresh `HOME` per run made every CI run look like a first run. This matches `smoke:cli` / `smoke:tui`, which have always driven a temp `--catalog`. Only the **catalog** is redirected — other per-user state under `~/.mcp-inspector` (OAuth tokens, `storage/`) stays shared, because isolating it means redirecting `HOME` wholesale, which would also move the npx and Playwright caches these smokes depend on. Teardown uses **both** halves of `scripts/lib/child-cleanup.mjs` (`stopChild` to await the child's exit, then `removeSafe` to delete the dir) — a bare `kill()` only *delivers* the signal, so removing synchronously re-enters the #1801 ENOTEMPTY race. That makes `stop()` **async**, so every caller must `await` it (and a caller's own `fail()`/`shutdown()` becomes async in turn, or execution runs past the intended exit). The isolation contract's pure halves — `createTempCatalog` and `buildWebServerEnv` — are unit-tested in `scripts/lib/prod-web-server.test.mjs` via `test:scripts`, since the smokes exit immediately after teardown and so cannot detect a regression that silently reshared the catalog.
 - `smoke:web:browser` (`scripts/smoke-web-browser.mjs`, #1615) goes a step further than `smoke:web`: it boots the same prod `--web` server and then actually **runs** the bundle in headless Chromium (Playwright — already a `clients/web` devDependency for the Storybook tests), asserting the app renders its first meaningful frame (the "Add Servers" control) with **no uncaught error**. `smoke:web` only checks the served HTML, so a Node built-in reaching the browser bundle slipped through it; this smoke catches that regression as a _class_ (e.g. #1612). The mechanism is the uncaught error, not a magic string: under Vite the excluded module becomes an empty stub and the first _call_ into it (e.g. `fs.readFileSync(...)` during a transitive module's init) throws a `TypeError` that aborts app mount. A _synchronous_ such throw fires `pageerror`; its _async_ twin (the same `TypeError` via `await`/`.then()`, or a failed dynamic import) is logged on the console channel as `Uncaught (in promise) …` / `Failed to fetch dynamically imported module` — the smoke hard-fails on both. The literal `Module "…" has been externalized` text is, **in a prod build**, a build-time warning (`vite build` / `npm run build`), not a runtime message, so the browser never sees it (under `npm run dev` Vite's stub is instead a `Proxy` that `console.warn`s that string at runtime); and an externalized import that is never _called_ ships a harmless `{}` and is invisible here by design. Every _other_ console error is printed as a diagnostic, not a failure (so a benign font-CDN or React-warning `console.error` doesn't flake CI). Playwright is resolved via `createRequire` based at `clients/web/package.json` — a bare `import("playwright")` would resolve relative to `scripts/`, not the cwd, so it can't be reached that way (it only appears to work when an ancestor `node_modules` carries playwright, and fails in CI, which has none). The npm script's `cd clients/web` exists only so `npx playwright install chromium` finds the local playwright bin (a no-op when already installed).
 - `smoke:web:app` (`scripts/smoke-web-app.mjs`, #1859) goes one step further again: `smoke:web:browser` stops at first paint and never connects to a server, so the Apps tab, the sandbox controller, and the UI-protocol bridge were unexercised by any smoke. This one boots the same prod `--web` server, spawns the `mcp-app-http.json` composable test server (the `mcp_app_demo` tool + its `mcp_app_demo_widget` UI resource), and drives the whole **connect → open app → widget ready** chain through a single deep-link navigate (`?serverUrl=…&autoConnect=<token>&openApp=…&appArgs=…&autoOpen=<token>`). The assertion is the `data-app-status="ready"` contract from [clients/web/README.md](clients/web/README.md) — the renderer reports `ready` only once the widget has loaded inside the sandbox iframe _and_ fired `notifications/initialized` back through the bridge, so one attribute covers the sandbox proxy being served, the UI resource loading, and the handshake completing. Two mechanics are load-bearing and easy to get wrong: the test server announces readiness on **stderr** (`console.error` in `server-composable.ts`), so both child streams are piped and scanned — watching stdout alone times out with an empty diagnostic; and its bound port is **not** the config's, because `createTestServerHttp` resolves through `findAvailablePort()`, which walks upward when the configured port is taken — so the smoke parses the announced URL rather than assuming `3130`. **Scope note:** this runs against the repo build tree like every other smoke, so it would _not_ have caught #1859 itself (a packaging failure — the file is always present in-repo); `pack:verify` owns that dimension. It does carry a cheap structural pre-check that the proxy page exists at the path `sandbox-controller.ts` resolves, so a move/rename fails fast with a clear cause instead of an opaque render timeout.
 - **The build gate for the browser-externalized-builtin class (#1769)** is the earlier, more complete companion to `smoke:web:browser`. A Vite plugin in `clients/web/vite.config.ts` (logic in `clients/web/server/browser-externalized-builtin-gate.ts`, unit-tested) turns Vite 8's _browser-externalization warning_ (`Module "node:*" has been externalized for browser compatibility`) into a hard `vite build` error, so a Node built-in in the browser graph now **fails `npm run build` / `validate`** instead of shipping a `{}` stub. This catches **both** the _called-at-init_ case (which `smoke:web:browser` also catches, but later/at runtime) **and** the _imported-but-never-called_ case (the `{}` stub that is invisible to the runtime smoke "by design" — see above). Because rolldown **swallows a throw inside `onLog`** (the one hook where a thrown error doesn't abort — verified against vite@8.0.0), the plugin _records_ the warning in `onLog` and re-throws in `buildEnd`. There is **no stable log `code`**, so the gate keys off the documented message phrasing; `npm run verify:build-gate` (`scripts/verify-build-gate.mjs`, in `npm run ci` and the GitHub workflow) runs a real build with a `node:fs` probe forced into `src/main.tsx` and asserts the build fails via the gate — the only check that catches the message phrasing **drifting** in a future Vite bump and silently disabling the gate. The gate is scoped to `vite build` (`apply: 'build'`) — never `vite dev` or the vitest projects — **and** to the browser (`client`) environment (`applyToEnvironment`), so a future SSR/node environment built from this config isn't failed for a legitimate `node:*` import; the Node runner build (tsup, `build:runner`) is a separate config where built-ins are legitimate. `smoke:web:browser` stays as the runtime backstop for crashes the build can't reason about.

scripts/lib/prod-web-server.mjs

@@ -103,7 +103,8 @@ export function buildWebServerEnv({
  * @param {string} opts.host
  * @param {string} opts.port
  * @param {string} opts.token  value injected as MCP_INSPECTOR_API_TOKEN
- * @param {string} [opts.label]  prefix for the temp dir + cleanup warnings
+ * @param {string} [opts.label]  prefix for teardown warnings (the temp dir's own
+ *   prefix is fixed, so every run's dir is greppable as `smoke-web-catalog-*`)
  */
 export function startProdWebServer({ host, port, token, label = "smoke:web" }) {
   const baseUrl = `http://${host}:${port}`;