[ryansolid]

Before: an optimistic guess's lane could hold a render or user effect, and that effect's transaction is the lane. When a landing settled such a reader, the settle walk joined the flush to the lane's transaction (joinFuture(txOf(node))), so the flush took the lane as its transaction. A correction later in the same flush dissolved the lane. Every node born held after that, such as the rows <For> mounted for the refreshed list, was listed on the dead lane and never committed, so those rows rendered with every hole empty.

After: a refresh that lands beside an optimistic guess mounts its rows with their content.

D-37 (RULES-DERIVED) says "A lane sees the screen plus its own guesses and never holds a sync write". Lane work never makes its node the transaction's.

How: joinFuture (core/scheduler.ts) returns when the transaction it is asked to join is a lane, gated on the lane engine (laneStageHook). Bundles without lanes pay 0 B. The guard sits in joinFuture itself, so it also covers the other held-node joinFuture(txOf(x)) calls: setSignal in core.ts, notifyContainer in store.ts, and the pending propagation in async.ts. In the signals suite only the settle walk reaches it with a lane; I couldn't build a test that reaches one of the other call sites with a lane's transaction.

Size vs next @ d0fc285 (after #4479), measured locally (linux), brotli / minified:

scenario	delta	cap
signals: + isPending/latest	+8 / +18	unchanged at 11.19 KB; recorded minified re-recorded
page: compiled live server components	+38 / +18	42.83 → 42.87 KB
page: live server components (frozen floor)	+60 / +18	unchanged at 38.91 KB (38,909 B); record unchanged
app: hydrating + every store primitive	+81 / +18	unchanged; recorded minified re-recorded
page: live + router	−5 / +18	unchanged; recorded minified re-recorded
hello world, core, simple-app, hydrating, CSR, base server components, every other scenario	0 / 0	unchanged

The brotli deltas over 20 B are layout from the same +18 B of minified code. No floor changes, so there is no Size-Exception.

How did you test this change?

• New packages/signals/tests/optimistic-lane-held-landing-4440.test.ts and packages/web/test/optimistic-guess-joins-refresh-4440.spec.tsx.

• Suites:

  suite	passed	expected fail
  signals (after merging next @ d0fc285)	6,057	17
  web (after merging next @ 663ecb0)	1,570	7

Fixes #4440.

---

🤖 Generated with Claude Code

https://claude.ai/code/session_015hPxMkC3jg3Uivh65gvaf2

[github-actions]

Size (brotli, eager entry chunk)

scenario	head	vs base	minified vs base	minified vs recorded	cap		lazy chunks (not counted)
signals: core floor (createSignal/Memo/Effect/Root/flush)	7.42 KB	0 B	0 B	+15 B	7.43 KB	✅
signals: + createStore	14.96 KB	0 B	0 B	+6 B	14.97 KB	✅
signals: + isPending/latest	11.19 KB	+8 B (+0.1%)	+18 B	0 B	11.19 KB	✅
signals: + until/refresh (truth readers, no optimism)	8.05 KB	0 B	0 B	+2 B	8.06 KB	✅
app: render + one signal (the simple-app floor)	9.78 KB	0 B	0 B	+15 B	9.78 KB	✅
app: hydrating (no stores) with Show/For/Loading/Errored/lazy	18.75 KB	0 B	0 B	0 B	18.74 KB	⚠️ over by 12 B, 20 B minified headroom	lazy-page.js 0.04 KB
app: hydrating + every store primitive family	32.47 KB	+81 B (+0.3%)	+18 B	0 B	32.48 KB	✅	lazy-page.js 0.04 KB
app: CSR with Show/For/Loading/Errored/lazy	13.45 KB	0 B	0 B	+9 B	13.47 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier (same app on the observe artifacts)	15.19 KB	0 B	0 B	+9 B	15.20 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier + attribution engine enabled	29.75 KB	0 B	0 B	+9 B	29.78 KB	✅	lazy-page.js 0.04 KB
app: compiled floor (one template, one text hole, one delegated click)	9.97 KB	0 B	0 B	+2 B	9.98 KB	✅
app: compiled CSR (JSX todo app: spread/merge/omit, events, class/style, keyed For, Show, Loading + lazy, store)	26.33 KB	0 B	0 B	+13 B	26.33 KB	⚠️ over by 3 B, 7 B minified headroom	stats.js 0.18 KB
app: compiled hydrating (the same JSX todo app through hydrate(), compiled hydratable)	32.45 KB	0 B	0 B	+7 B	32.54 KB	✅	stats.js 0.20 KB
frames: eager client consumer (frames client + transport, lazy codec)	11.75 KB	0 B	0 B	0 B	11.77 KB	✅
page: base server components (hydrating + dynamic + frames + sf reference)	33.67 KB	0 B	0 B	+9 B	33.77 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, trace.js 9.03 KB, wire.js 3.47 KB
page: live server components (base + live/GET + action + isPending/latest)	38.91 KB	+60 B (+0.2%)	+18 B	+18 B	38.91 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, trace.js 9.03 KB, wire.js 3.47 KB
page: compiled base server components (the base page as JSX: templates with class/style/attributes/events, For/Show; no spread)	35.72 KB	0 B	0 B	+9 B	35.72 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.06 KB, sc-comments.js 0.20 KB, trace.js 9.01 KB, wire.js 3.47 KB
page: compiled live server components (the compiled base page + live/GET + action + isPending/latest)	42.86 KB	+38 B (+0.1%)	+18 B	0 B	42.87 KB	✅	eager (counted): web.js 22.89 KB; assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.07 KB, sc-comments.js 0.19 KB, trace.js 9.05 KB, wire.js 3.47 KB
page: base + router (base page + @solidjs/router: createRouter, two routes, preload, useNavigate)	41.11 KB	0 B	0 B	+7 B	41.25 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, server.js 1.03 KB, serverForms.js 3.57 KB, trace.js 9.03 KB, wire.js 3.48 KB
page: live + router (live page + @solidjs/router: createRouter, two routes, preload, useNavigate)	48.49 KB	−5 B (−0.0%)	+18 B	0 B	48.51 KB	✅	eager (counted): client.js 27.98 KB; assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.07 KB, server.js 1.03 KB, serverForms.js 3.30 KB, trace.js 9.03 KB, wire.js 3.49 KB
server: floor (getRequestEvent + isServer)	1.27 KB	0 B	0 B	0 B	1.29 KB	✅
server: renderToString (the server-render floor)	22.79 KB	0 B	0 B	0 B	22.80 KB	✅

⚠️ Over the brotli cap within the minified allowance (passes)

• app: hydrating (no stores) with Show/For/Loading/Errored/lazy: over brotli cap by 12 B; minified 53,607 B vs 53,607 B recorded with the cap (+0 B) — 20 B of the 20 B minified allowance left; +0 B minified over this PR's base
• app: compiled CSR (JSX todo app: spread/merge/omit, events, class/style, keyed For, Show, Loading + lazy, store): over brotli cap by 3 B; minified 80,048 B vs 80,035 B recorded with the cap (+13 B) — 7 B of the 20 B minified allowance left; +0 B minified over this PR's base

_{Bundled with Rolldown (what Vite ships), brotli q11, decimal KB. A scenario fails only when it is over its brotli cap and its minified size is more than 20 B over the minified recorded with the cap; over the cap within that allowance is brotli layout noise and passes with a warning. Caps and their recorded minified in scripts/size/scenarios.js; the floor and page caps in floor-caps.json are frozen (lower only, or Size-Exception: in the PR body). npm run ratchet lowers caps per RC; it never raises one (scripts/size/README.md).}

[coveralls]

Coverage Report for CI Build 41105284084

Coverage remained the same at 78.1%

Details

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

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	1362
Covered Lines:	1125
Line Coverage:	82.6%
Relevant Branches:	1090
Covered Branches:	790
Branch Coverage:	72.48%
Branches in Coverage %:	Yes
Coverage Strength:	29.81 hits per line

---

💛 - Coveralls

[codspeed]

Merging this PR will improve performance by 11.24%

2 warnings

⚠️ 3 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

⚠️ 2 benchmarks with a significant change ran on different hardware

Their base and head results were measured on machines with a different CPU, core count or memory, so the changes might not come from the code. Run base and head on the same runner type.

Learn more about Macro Runners

See affected benchmarks

⚡ 2 improved benchmarks
✅ 198 untouched benchmarks
⏩ 5 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	arrow in template	12.4 ms	10.8 ms	+14.05%
⚡	memo + sync render effect only (reference)	34.8 ms	32.1 ms	+8.51%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing claude/project-thread-x1ore2-4440 (94eab76) with next (d0fc285)}

Footnotes

1. 5 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[changeset-bot]

🦋 Changeset detected

Latest commit: 94eab76

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

This PR includes changesets to release 15 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
board-example	Patch
canvas-example	Patch
server-dbmon-example	Patch
todos-server-example	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR