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docs(smoke): retract the #2132 mechanism claim; state that it is unknown

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An isolated repro of the mechanism I described — a server writing three
SSE frames then going silent with the connection held open, read via
fetch + getReader — delivers every frame in all three engines, WebKit
included. So 'the SSE stream's last message is not delivered' is not a
supported description of the failure.

The keep-alive experiment that appeared to confirm it was one
observation, and the failure is not even stable in shape: two consecutive
webkit runs failed at different stages (ready wait vs connect wait),
which a deterministic buffering bug would not do.

What is unchanged: the App smokes really do fail under Playwright's
WebKit, which is why the engine stays out of the matrix; that reason
never depended on the mechanism. The parseSSE cross-chunk defect also
stands, being read off the code rather than inferred from an experiment.

No behavior change.

Signed-off-by: cliffhall <cliff@futurescale.com>
This commit is contained in:
cliffhall 2026-08-25 23:02:43 -04:00
commit d493b232b3
1 changed files with 16 additions and 14 deletions
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@ -481,7 +481,7 @@ SMOKE_BROWSER=firefox npm run smoke:web:engine # all three smokes, one engine
Unset, the engine is `chromium` — so `npm run ci` and `npm run smoke` are unchanged. CI runs Chromium inside the `build` job's `npm run smoke`, and every other gated engine in a separate `Sandbox smokes (<engine>)` matrix job — today that matrix holds **Firefox alone**; see the paragraph below for where WebKit stands. Splitting it that way, rather than running the whole `build` job once per engine, is deliberate: validate, the coverage gate, the two verify gates and Storybook are all engine-independent. An unrecognized value is an error, not a fallback: a silent fallback would report a green Chromium run under a job labelled `webkit`. A missing browser binary fails naming the engine and its `npx playwright install --with-deps <engine>`.
**CI green today: Chromium and Firefox.** WebKit is supported by the tooling and worth running locally, but it is **not yet in the CI matrix** — the two App smokes fail there, tracked in [#2132](https://github.com/modelcontextprotocol/inspector/issues/2132): the SSE stream's last message is not delivered, so an App never leaves "loading". **This has not been reproduced in real Safari** — an MCP App opens there normally — so on current evidence it is a property of Playwright's WebKit build (whose network stack is not Safari's) rather than a browser bug users hit. It still blocks gating the engine, and it is worth understanding before WebKit joins the matrix. An engine is either green in CI or absent from it — a `continue-on-error` job would report coverage nobody is held to.
**CI green today: Chromium and Firefox.** WebKit is supported by the tooling and worth running locally, but it is **not yet in the CI matrix** — the two App smokes fail there, tracked in [#2132](https://github.com/modelcontextprotocol/inspector/issues/2132). **This has not been reproduced in real Safari** — an MCP App opens there normally — so on current evidence it is a property of Playwright's WebKit build rather than a browser bug users hit. The mechanism is not yet identified; see the issue, whose first diagnosis was retracted after an isolated repro failed to reproduce it. It still blocks gating the engine, and it is worth understanding before WebKit joins the matrix. An engine is either green in CI or absent from it — a `continue-on-error` job would report coverage nobody is held to.
**Why these smokes specifically.** Most of the web client's behavior is React and Mantine, where a second engine buys little. The MCP Apps sandbox is the exception — it is built out of the primitives that genuinely diverge between engines: a CSP `<meta>` injected as the first `<head>` child of a `srcdoc` document, a nested sandboxed iframe, a `Permissions-Policy` `allow` attribute, and `postMessage` origin discipline across those two frames. Nothing else covers that: `sandbox-csp.test.ts` asserts which policy _string_ is built, which passes identically on an engine that ignores `<meta>` CSP entirely, and no Storybook story reaches the sandbox at all (all three App stories point the iframe at a `data:` placeholder and hand the renderer a mock bridge). Storybook itself remains Chromium-only — broadening it covers a much larger and differently-shaped surface, and is a separate decision.