Corporate-proxy users could not connect to any remote MCP server from v2.
Two independent defects, both reported in #2067.
1. The web and TUI bundles inlined undici. It was declared in the root and
`clients/cli` manifests but named in no client's tsup `external` list, and
tsup auto-externalizes only what the *nearest* manifest declares — so
esbuild inlined 1.05MB of it into `clients/{web,tui}/build/`. undici is
CommonJS, so the emitted chunk's `require("assert")` hit esbuild's ESM
`__require` shim and threw `Dynamic require of "assert" is not supported`.
The rejected `import()` surfaced as "the `undici` package is not available",
telling users to install a package that was already present — and could not
have helped, because the specifier had been rewritten to a relative chunk at
build time.
2. `withProxyDispatcher` injected a *userland* undici `EnvHttpProxyAgent` into
Node's *built-in* fetch. That couples two different copies of undici at the
dispatcher handler interface, which is not stable across majors: Node 22
embeds undici 6, Node 24 embeds 7, Node 26 embeds 8. A userland undici 8
agent handed a built-in undici 7 handler is rejected with
`fetch failed: invalid onRequestStart method`, and the request never leaves
the process. So fixing the bundling alone would only have converted the
web/TUI failure into the CLI's.
Both halves of the pair now come from userland undici — its `fetch` and its
`EnvHttpProxyAgent` — which keeps the handler inside one copy and works
unchanged from the Node 22.19 engine floor through Node 26. Deleting the
wrapper in favor of Node's native `NODE_USE_ENV_PROXY` was not an option:
measured, it is unsupported on 22.19 (the floor) and only lands mid-22.x.
Because undici's `Response` is a different class from `globalThis.Response`,
the proxied fetch re-wraps each response as a genuine global `Response`,
streaming preserved. Without that, `res instanceof Response` is false for
callers that test it — including the SDK's OAuth error formatter, which would
degrade every message to `Raw body: [object Response]`.
The proxy now sits at the bottom of the fetch stack (`environment.fetch` for
the Node clients, and the `createTransportNode` default for the web backend,
its one caller that supplies no `fetchFn`) rather than wrapping the transport's
fetch. Proxying means *substituting* the fetch, not decorating one, so wrapping
a supplied `fetchFn` would discard it; installing it underneath lets
InspectorClient's own wrappers compose over it. A side effect worth having:
OAuth discovery and token requests go through `environment.fetch` too, and were
never proxied before.
Guarding it:
- `undici` is added to all three tsup `external` lists and removed from
`clients/cli/package.json`, so it is root-declared only, per the placement
rule in AGENTS.md. The two installs had already drifted (root 8.5.0 vs cli
8.9.0).
- New `npm run verify:bundle-externals` fails if any package a client declares
external was inlined into that client's bundle anyway. It reads the *built
output*, not the config — those two disagreed for four releases — and derives
what to check from each client's own `external` array, so a newly
externalized package is covered without editing the guard. Verified against
the real pre-fix artifact, which it flags.
- The proxy tests now drive a real forwarding proxy rather than a mock. That
matters: defect 2 was a runtime interface mismatch, which no mock can catch
because no mock ever dispatches.
AGENTS.md's must-not-bundle rule (added by #2082) is extended with why undici
slipped past it, and notes the `node -e` trap — probing the bundled chunk with
`node -e` falsely succeeds, because it exposes a global `require` that
satisfies esbuild's guard.
Closes#2067
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JTHVxSu8AUgHRLvo1ntZ8H
Signed-off-by: cliffhall <cliff@futurescale.com>
d90a955164