fix(signals): parent the pending companion's lane before poking it (#3379)

[ryansolid]

Fixes #3379 (Cluster 3 of gabbev's 2026-09-11 batch; its sibling #3378 is fixed by #3397). Independent of #3381/#3392 — based on next.

#3379 — isPending(details) false while details loads the optimistic value through an async memo

isPending/latest companions ride child lanes that deliberately do not merge with the owner's lane (A14), so an indicator can flush while the owner's async is in flight. The child lane takes its parent from the owner's _optimisticLane when it is created (getOrCreateLane).

In notifyStatus, the companion poke (_updatePendingSignal) ran before assignOrMergeLane(el, lane). When copy's pending status propagated onto details, details had no lane yet, so the companion lane it created was born parentless. The Pending effect depends on both details (the value lane) and the companion (the orphan lane); with no parent/child relation between them, assignOrMergeLane merged the companion lane into the held value lane and the indicator's run sat in that lane's effect queue until the async landed. Reading value() directly in details "worked" because details joined the lane through insertSubs before the poke.

Fix: assign the lane first, inside the same !blockStatus block. A reorder; −4 B minified.

Frames after the fix (the View effect reads details, so it correctly holds 0 / 0 until the derivation lands; the indicator no longer waits):

1000: Pending: false | View: 0 / 0
3000: Pending: true
4000: Pending: false | View: 1 / 1
5000: Pending: true
6000: Pending: false | View: 0 / 0

Before the fix, 3000: Pending: true is missing and 4000 shows View: 1 / 1 alone — the issue's symptom.

Size

Core floor 22,648 → 22,644 B. Four size-limit caps bumped by one step with notes; all brotli noise (next's caps sit within ~10–30 B of their measurements).

Verification

signals 1752/1752 (+1 skipped), solid 595, web 734; tsc clean for src/ and the new test; size-limit passes. No existing test expectation changed.

Co-authored-by: Claude via Cursor

[changeset-bot]

🦋 Changeset detected

Latest commit: fec8f85

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
@solidjs/signals	Patch
test-integration	Patch
@solidjs/web	Patch
@solidjs/babel-plugin	Patch
@solidjs/compiler	Patch
@solidjs/diagnostics	Patch
@solidjs/element	Patch
@solidjs/h	Patch
@solidjs/html	Patch
solid-js	Patch
@solidjs/universal	Patch

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[coveralls]

Coverage Report for CI Build 34727239915

Coverage remained the same at 71.842%

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• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

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Relevant Lines:	1007
Covered Lines:	772
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[codspeed]

Merging this PR will not alter performance

✅ 160 untouched benchmarks

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_{Comparing fix/pending-companion-lane-parent (fec8f85) with next (1af28a1)}