`node:assert` builds its `AssertionError` eagerly, running `util.inspect`
over both operands with `depth: 1000`, `getters: true` and
`maxArrayLength: Infinity`. A React-rendered DOM element carries
`__reactFiber$*` / `__reactProps$*` as own enumerable properties, and that
fiber graph re-expands once per traversal path, so inspecting a single
rendered element allocates without bound. Measured on the Asset Library
heading: depth 6 = 1.3MB, 8 = 7.8MB, 10 = 36MB, 12 = 135MB -- at Node's
depth 1000 the worker dies before any `AssertionError` exists.
The damage is not the crash, it is the disguise. Equality assertions only
inspect their operands on failure, so these sites stayed invisible while
green and detonated exactly when the behaviour they guard regressed --
reporting as `worker exited unexpectedly` with a truncated count
(`8 passed (13)`) and no failing test named. Breaking the delete-path focus
restoration in `asset-library.tsx` reproduced it: 29.5GB anon-rss and the
system OOM killer, or a V8 heap abort in 3s under a 512MB cap. The same
regression now fails in 1.15s with `expect(element).toHaveFocus()` naming
both the expected heading and the `<body>` that took focus instead.
`expect` is not affected -- vitest prints and diffs DOM nodes through
pretty-format's DOM plugin, which reads tag/attributes/children and never
touches the fiber -- so every unsafe site converts to a matcher:
`toHaveFocus()` for the three focus comparisons, `not.toBeInTheDocument()`
for the sixteen `assert.equal(queryBy..., null)` absence checks, which are
equally lethal (proved separately: element-vs-null inspects the element).
Three layers so this cannot come back:
- the 20 live sites in asset-library/asset-picker now use matchers;
- `test-assertion-boundary/no-element-operand-equality` fails `pnpm lint`
when a DOM-element expression reaches `node:assert` equality, resolving
local bindings and exempting the forms that cannot fail with an element
in hand (`assert.notEqual(el, null)`, `el.textContent`);
- a 2048MB worker old-space ceiling in `vitest.config.ts` bounds any future
runaway to a legible `Reached heap limit` abort in seconds instead of an
OOM-killed machine (heaviest suite peaks near 1.3GB RSS).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
