inspector/clients/launcher/README.md
Cliff Hall 5efe9ddc7b
refactor: self-validating clients, fast validate + separate coverage/smoke (#1504) (#1505)
* refactor(launcher): self-contained validate; split smokes into top-level step (#1504)

Previously `validate:launcher` built cli/tui/web and ran the cross-client
smokes, so the launcher's "validation" depended on every other client
being built — and the launcher had no lint/format/coverage of its own.

- clients/launcher: add a web-style `validate` (format:check && lint &&
  build && test:coverage) with a Node-only eslint flat config, prettier,
  and a per-file coverage gate (parse-launcher-argv.ts covered;
  src/index.ts excluded as binary bootstrap). 100% on the gated file.
- Root `validate:launcher` now just delegates: `cd clients/launcher &&
  npm run validate` — no dependency on the other clients.
- New top-level `smoke` step (smoke:launcher + smoke:cli + smoke:tui +
  smoke:web) with NO build commands; `validate` runs it last. Each
  client's own validation builds its bundle first, so nothing builds
  twice (cli/tui via test:coverage, launcher via its validate;
  smoke:web builds dist on demand).
- clients/tui test:coverage now builds the TUI bundle (mirroring cli) so
  the build-free smoke has it available.
- CI: replace the standalone cli/tui/launcher build step with a
  "Validate launcher" step. Docs updated (AGENTS.md, launcher README).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* refactor(cli,tui,root): every client self-validates; smoke separate from validate

Extends the launcher self-validate work to the CLI and TUI, and makes the
top-level `validate` nothing but the per-client validations — smokes are
now a separate top-level target.

- clients/cli, clients/tui: add a web-style `validate` with a Node flat
  eslint config + prettier. CLI lint/format pass as-is. TUI registers
  eslint-plugin-react-hooks for the classic rules only (rules-of-hooks +
  exhaustive-deps, which the source already references); the stricter
  react-hooks@7 rules are not enforced on the interim component surface
  (#1501).
- Avoid double builds:
  - CLI's e2e spawns the built binary, so its `test:coverage` builds first;
    `validate` folds that in (`format:check && lint && test:coverage`, no
    separate `build`).
  - TUI tests don't spawn a bundle, so `validate` keeps an explicit
    `build` (for the smoke) and `test:coverage` is pure.
- Root: `validate` = validate:web && validate:cli && validate:tui &&
  validate:launcher (each delegates to the client's own validate). `smoke`
  is no longer part of `validate` — it's a separate top-level target run
  after a build/validate, with no build commands of its own.
- CI: per-client "Validate X" steps + a single "Run cross-client smokes"
  (npm run smoke). Docs updated (AGENTS.md, cli/tui READMEs).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore(root): drop redundant test aggregator scripts

Now that every client self-validates and the top-level `validate` chains
the per-client validations, the root `test` / `test:web` / `test:cli` /
`test:tui` / `test:coverage` aggregators are redundant — run
`npm run validate` (all) or `cd clients/<name> && npm run validate` (one).
`test:storybook` stays (it's the one check not part of validate). CI was
already using each client's own scripts, so it's unaffected. Docs updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(web): silence happy-dom infra noise in unit runs

Passing unit runs printed dozens of alarming-but-expected lines that made
green runs look broken — all from happy-dom performing real I/O with no
server behind it:
- `<iframe src="/sandbox.html">` (MCP Apps sandbox) made happy-dom fetch
  and later unload that URL, emitting ~40 `DOMException [NetworkError/
  AbortError]` + `AsyncTaskManager destroyed` lines. Disable child-frame
  navigation in the unit project (the tests only assert on the iframe
  element/attributes, not its document), removing the noise with no
  coverage loss.
- App-level renders read `GET /api/config` via useSandboxUrl /
  useServerListWritable, 404-ing ~76x. Add a benign default `fetch` (empty
  200) in the unit setup; tests that exercise fetch still override it.

Negative tests that assert on errors already suppress their own console
output (e.g. jsonUtils/schemaUtils); CLI, TUI, and the web integration
suite were already clean. Unit suite is now noise-free; 2424 web tests
pass and the coverage gate is unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* refactor(scripts): make validate fast (test), split coverage into its own target

Each client's `validate` now runs `test` instead of `test:coverage`, so
the everyday pre-push check skips v8 instrumentation (and, for web, the
slower integration project). The per-file coverage gate moves to a
dedicated top-level `coverage` script:

  coverage = coverage:web && coverage:cli && coverage:tui && coverage:launcher
  coverage:<name> = cd clients/<name> && npm run test:coverage

`validate` still builds each client's bundle (cli via its test `pretest`,
the others via an explicit `build`), so `npm run validate && npm run
smoke` works unchanged. CI now runs `validate` (fast checks + builds),
then `coverage` (the gate), then `smoke` — collapsing the old per-client
steps. Docs updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* ci: drop the coverage gate from CI; keep web integration as its own step

CI no longer runs `npm run coverage` — the per-file coverage gate is now a
local/manual check (`npm run coverage` before pushing). To avoid silently
dropping the web integration suite (it only ran via test:coverage, and
`validate` runs the unit project only), CI gains a standalone
`clients/web` `test:integration` step that exercises the real
stdio/HTTP/OAuth/storage paths without coverage instrumentation.

CI is now: validate (fast) → web integration → smoke → storybook. Docs
updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* refactor(smoke): give smoke:launcher its own script like the others

smoke:launcher was the odd one out — an inline chain of three
`node clients/launcher/build/index.js ... --help` commands while smoke:cli
/ smoke:tui / smoke:web each run a `scripts/smoke-*.mjs`. Extract it to
`scripts/smoke-launcher.mjs`, which runs the same `--help` / `--cli --help`
/ `--tui --help` dispatch checks but now also asserts each prints that
mode's usage banner (proving the launcher resolved the right client build)
and verifies the required builds exist up front with a clear error. Prints
a `smoke:launcher OK — ...` summary in the same style as the rest. Docs
updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: reorder package.json scripts for readability

Move frequently-run scripts toward the top and rarely-run-by-hand ones
(pretest hooks, lint/format internals, etc.) toward the end, consistently
across the root and client manifests. Pure reordering — no script names or
values changed, and no other manifest content is touched.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs: drop references to removed root inspector / test:storybook scripts

The reordering dropped the root `inspector` and `test:storybook`
aggregators (intentional — `inspector` is redundant with `web`, and
storybook is run from clients/web in CI). Update AGENTS.md so it no longer
points at `npm run inspector`, and run `test:storybook` from `clients/web/`.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: address PR #1505 review (format glob gap, fetch-baseline comment)

- TUI format/format:check now also cover the client-root source files
  (index.ts, tui.tsx, dev.ts) that live outside src/ — `eslint .` already
  lints them, so they were linted but not format-checked. (cli/launcher
  have no source outside src/; their root .ts are single-quoted configs
  intentionally left out of prettier, matching web.)
- Reword the setup.ts default-fetch comment: it overstated auto-restore
  (the unit project sets no restoreMocks/unstubGlobals), and now also
  flags that the permissive 200 default means a test asserting on a fetch
  FAILURE must install its own rejecting stub.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: remove redundant root install:clients script

`install:clients` ran the same `node scripts/install-clients.mjs` as
`postinstall`, which fires automatically on `npm install` — so the manual
alias was redundant. Drop it and the doc references (AGENTS.md, spec).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(ci): skip smoke:tui in CI (Ink needs a real TTY)

This PR made CI run the full `npm run smoke`, which surfaced that
smoke:tui fails in headless CI: the Ink TUI throws "Raw mode is not
supported" on mount (no TTY) and exits before rendering its first frame.
The old CI never ran smoke:tui, so this was latent.

smoke-tui.mjs now self-skips when `process.env.CI` is set — the boot/
render check is inherently local-only (a TUI needs a terminal). The TUI is
still built and unit-tested in CI; `npm run smoke` stays the single
command everywhere (full locally, tui-skipped in CI). Verified
`CI=true npm run smoke` is green (launcher/cli OK, tui SKIPPED, web OK).
Docs + CI comment updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-21 11:41:33 -04:00

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# MCP Inspector Launcher
The launcher is the package that provides the global `mcp-inspector` binary (e.g. when users run `npx @modelcontextprotocol/inspector`). It is not a separate user-facing app—it is the single entrypoint that selects and runs one of the clients (web, CLI, or TUI).
## Responsibility
- Parse mode from a leading prefix of `--web` (default), `--cli`, or `--tui` immediately after the script name.
- Forward all following arguments unchanged (including tokens that look like mode flags).
- Dynamically import that app’s runner from `clients/{web,cli,tui}/build/index.js` (relative to the launcher build output) and call it **in-process** (no `spawn()`).
All configuration parsing, config-file loading, and server setup are handled by the app runners and by **core**; the launcher does not interpret config or env vars.
## Web server-list flags (`--web`)
`mcp-inspector --web` chooses which server list the UI shows and whether it is
editable (see [specification/v2_catalog_launch_config.md](../../specification/v2_catalog_launch_config.md)):
| Invocation | Server list | Editable in UI? |
| ---------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- | --------------- |
| `mcp-inspector --web` | Default catalog `~/.mcp-inspector/mcp.json` | Yes |
| `mcp-inspector --web --catalog <path>` (or `MCP_CATALOG_PATH=<path>`) | That file as the active catalog (created/seeded if missing) | Yes |
| `mcp-inspector --web --config <path>` | That file as a **read-only session** — shown but never written, seeded, or migrated (safe for a foreign config) | No |
| `mcp-inspector --web --server-url <url> --transport http --header "Name: Value"` (or a positional command) | One ad-hoc server held in memory, connectable with the given `--header`s | No |
Rules: `--catalog` and `--config` are mutually exclusive; neither combines with
an ad-hoc target or `--header`; `--header` requires an ad-hoc HTTP/SSE server
and is applied to that connection (it is no longer a warn-only no-op).
## CLI and TUI server-list flags (`--cli` / `--tui`)
The CLI and TUI use the same `--catalog` / `--config` vocabulary as `--web`,
resolved by the shared `core/mcp/node/config.ts` helpers:
| Invocation | Server list source |
| ------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------- |
| `mcp-inspector --cli` / `--tui` (no source flag, no ad-hoc target) | Default writable catalog `~/.mcp-inspector/mcp.json` (created/seeded empty if missing) |
| `--catalog <path>` (or `MCP_CATALOG_PATH=<path>`) | That file as a **writable catalog** — seeded empty if missing |
| `--config <path>` | That file as a **read-only session** — served as-is, never written or seeded; **errors if absent** |
| positional command / `--server-url <url>` | One ad-hoc server |
Rules (shared `serverSourceConflict`): `--catalog` and `--config` are mutually
exclusive, and neither combines with an ad-hoc command/URL target. The CLI/TUI
do not perform catalog CRUD yet — they are read consumers — so the
writable/read-only split currently surfaces only as **seed-if-missing**
(`--catalog`/default) vs **error-if-missing** (`--config`). Full writable
persistence is tracked in #1482 / #1432.
### Production web build (`--web`, no `--dev`)
Prod `--web` serves static assets from `clients/web/dist/`, which only exists
after a build. In the published package `dist/` always ships. In a fresh dev
checkout it is absent, so the runner **builds it on demand** the first time you
launch (`vite build` via `npm run build:client`, run in `clients/web`) instead
of serving a broken page (#1486). If that build can't run — e.g. dev
dependencies are missing — the launcher exits with an actionable error telling
you to run `npm run build` (from `clients/web`) or relaunch with `--dev` to use
the Vite dev server. `--dev` never needs `dist/`; it runs Vite directly.
CI and `npm run validate` (via the top-level `smoke` step) exercise this prod
path end-to-end with `npm run smoke:web` (`scripts/smoke-web.mjs`): it starts
`mcp-inspector --web` against the built `dist/` and asserts `GET /` returns the
SPA (HTTP 200) with the injected `__INSPECTOR_API_TOKEN__`.
### CLI and TUI smokes
The top-level `smoke` step also runs end-to-end smokes for the other two modes
through the built launcher artifact (beyond the `--help` checks in
`smoke:launcher`):
- `npm run smoke:cli` (`scripts/smoke-cli.mjs`) — runs `mcp-inspector --cli`
against the bundled stdio test server via a temp `--catalog` and asserts
`tools/list` returns the server's tools, plus the `--catalog`/`--config`
resolution paths (default-catalog seed-on-missing, read-only `--config`
error-without-seed, `--catalog`/`--config` conflict).
- `npm run smoke:tui` (`scripts/smoke-tui.mjs`) — launches
`mcp-inspector --tui --catalog <temp>` and asserts the Ink app renders its
first frame within a timeout, then shuts it down (a shallow boot/render
check, not full interaction).
Both build `test-servers/build` on demand if it is missing.
## Development
Like the web client, the launcher self-validates from its own folder:
```bash
npm run validate # format:check && lint && build && test:coverage
```
This has **no** dependency on the other clients being built — it only checks the
launcher's own source. `eslint.config.js` is a Node-only flat config (the web
client's React/Storybook plugins stripped out), and the per-file coverage gate
covers `parse-launcher-argv.ts` (the pure arg-parsing logic); `src/index.ts` is
excluded as binary bootstrap and is instead exercised by the smokes above. The
repo-root `validate:launcher` simply delegates here (`cd clients/launcher && npm run validate`).
## Publishing
The root `@modelcontextprotocol/inspector` package ships as one fat tarball: `npm run build` at the repo root builds all clients, then `prepack` runs before `npm publish`. Runtime dependencies are declared on the root `package.json`; client builds bundle `@inspector/core` and externalize npm packages resolved from the root install.
## Architecture
For how the launcher fits with the shared config processor and app runners, see the [Launcher and config consolidation](../../docs/launcher-config-consolidation-plan.md) document in the repo root `docs/` folder.