Release the instant navs lock without clearing the whole cookie jar#94947
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The `instant()` helper in `@next/playwright` released the navigation
lock by calling `page.context().clearCookies({ name: INSTANT_COOKIE })`.
Playwright implements a filtered `clearCookies` non-atomically: it
clears the entire cookie jar and then re-adds the cookies that don't
match the filter, briefly removing the application's own cookies too.
Because Next.js reacts to the instant cookie's deletion by immediately
re-rendering (a soft refresh or a full reload), a render whose request
raced that empty window observed none of the test's cookies, so a page
reading `cookies()` rendered as if nothing was set, for example
`testCookie: not set`. Resource contention widened the clear-then-re-add
window, which is why the instant navigation suite failed intermittently
in CI.
We now release the lock by reading the instant cookie's stored entries
(Next.js may have updated the value, e.g. from `[0]` to `[1, null]`, but
preserves the domain and path) and re-adding each with a past expiry,
which deletes only those entries and leaves every other cookie
untouched. This removes the transient empty-jar window while still
firing the CookieStore deletion event that releases the lock.
To exercise the fix under the conditions that surfaced it, we want CI's
flake-detection job to replay the instant navigation suite, which only
happens when the suite's test file changes. We trigger that by
un-skipping the `renders runtime-prefetched content instantly during
navigation` test. That test had been skipped as flaky because of a real
bug in the dev runtime-prefetch decode, which #94866 has since fixed, so
it passes reliably now and no longer needs to be skipped.
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acdlite
approved these changes
Jun 23, 2026
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The
instant()helper in@next/playwrightreleased the navigation lock by callingpage.context().clearCookies({ name: INSTANT_COOKIE }). Playwright implements a filteredclearCookiesnon-atomically: it clears the entire cookie jar and then re-adds the cookies that don't match the filter, briefly removing the application's own cookies too. Because Next.js reacts to the instant cookie's deletion by immediately re-rendering (a soft refresh or a full reload), a render whose request raced that empty window observed none of the test's cookies, so a page readingcookies()rendered as if nothing was set, for exampletestCookie: not set. Resource contention widened the clear-then-re-add window, which is why the instant navigation suite failed intermittently in CI.We now release the lock by reading the instant cookie's stored entries (Next.js may have updated the value, e.g. from
[0]to[1, null], but preserves the domain and path) and re-adding each with a past expiry, which deletes only those entries and leaves every other cookie untouched. This removes the transient empty-jar window while still firing the CookieStore deletion event that releases the lock.To exercise the fix under the conditions that surfaced it, we want CI's flake-detection job to replay the instant navigation suite, which only happens when the suite's test file changes. We trigger that by un-skipping the
renders runtime-prefetched content instantly during navigationtest. That test had been skipped as flaky because of a real bug in the dev runtime-prefetch decode, which #94866 has since fixed, so it passes reliably now and no longer needs to be skipped.