[ryansolid]

Before: fallback() builds the boundary's fallback memo with runWithOwner(out._parent, () => computed(...)), beside the output and while the output's own pass is running. The memo's first pass ran at creation, under the output's owner. So the born-held check at the close of that pass read the enclosing pass's flag, not the output's. Under a mount that read a hold, the fallback was born held even though the pass creating it (the output) read nothing held. The fallback then waited with that hold.

After: the fallback is born held only when the output pass that builds it read the hold (D-27, one level: "a node it creates during that pass").

How: the fallback memo is created lazy. Its first pass runs in the output's read(b._fb) just below, in the output's context, so the born-held check asks the output. It stays owned by out._parent, so the walk over running owners for #4341 is unchanged. Lazy also releases it when its one reader, the output, stops reading it, which happens where drop disposes it or where a held swap commits. The old CONFIG_AUTO_DISPOSE clear is therefore dropped. The option is written lazy: 1 to save a byte. The seat shadow's known entry for #4428 is removed, since it could now only hide a regression.

Size vs next @ ab3d2ad, measured locally (linux): +7 B minified on bundles with a boundary, and hello world +0. Next already sits 15 B over the app: hydrating (no stores) frozen floor's recorded minified (13 B before #4463, 2 B from it), so this PR's 7 B take it to +22, past the 20 B allowance. Its cap stays at 18.74 KB and its recorded minified rises 53,585 → 53,607. page: compiled live server components goes 42.73 → 42.75 KB (recorded minified 125,518 → 125,540): it is 25 B brotli over next, and next already sits 15 B over its record.

Size-Exception: the hydrating (no stores) floor's recorded minified rises 53,585 → 53,607 (cap unchanged at 18.74 KB): 7 B are the lazy fallback memo that fixes #4428's born-held fallback, and the rest is next's own growth since the record. Correctness.

Tests: new packages/signals/tests/fallback-born-creator-4428.test.ts, which fails on next. Signals 6,026 passed after merging next. Before that merge, web 1,560 and hydrate 716 passed. Server 1,905 passed; the only failure was the known server-functions-adapter-request (#3311).

Fixes #4428

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Generated by Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 6b7da5e

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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[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	11.11 KB	0 B	0 B	+15 B	11.12 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	+18 B (+0.1%)	+7 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	32.38 KB	+17 B (+0.1%)	+7 B	+13 B	32.48 KB	✅	lazy-page.js 0.04 KB
app: CSR with Show/For/Loading/Errored/lazy	13.45 KB	+23 B (+0.2%)	+7 B	+9 B	13.47 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier (same app on the observe artifacts)	15.20 KB	+11 B (+0.1%)	+7 B	+9 B	15.20 KB	⚠️ over by 1 B, 11 B minified headroom	lazy-page.js 0.04 KB
app: CSR, observe tier + attribution engine enabled	29.78 KB	+13 B (+0.0%)	+7 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	+6 B (+0.0%)	+7 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	−67 B (−0.2%)	+7 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	+5 B (+0.0%)	+7 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)	38.80 KB	+23 B (+0.1%)	+7 B	+22 B	38.85 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	+11 B (+0.0%)	+7 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)	42.73 KB	+25 B (+0.1%)	+7 B	0 B	42.75 KB	✅	eager (counted): web.js 22.77 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	−120 B (−0.3%)	+7 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)	48.37 KB	−46 B (−0.1%)	+7 B	+22 B	48.44 KB	✅	eager (counted): client.js 27.90 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; +7 B minified over this PR's base
• app: CSR, observe tier (same app on the observe artifacts): over brotli cap by 1 B; minified 41,991 B vs 41,982 B recorded with the cap (+9 B) — 11 B of the 20 B minified allowance left; +7 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; +7 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 41089801789

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:	29.77 hits per line

---

💛 - Coveralls

[codspeed]

Merging this PR will improve performance by 8.78%

2 warnings

⚠️ 4 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	12.1 ms	11 ms	+9.84%
⚡	memo + sync render effect only (reference)	34.7 ms	32.2 ms	+7.73%

Tip

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

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_{Comparing claude/project-thread-x1ore2-4428 (6b7da5e) with next (ab3d2ad)}

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. ↩