[ryansolid]

Summary

Before: createOptimisticStore(fn) built its derived-store family by hand and left out the projection's status hook (st: familyStatus, node.fam). When the derive read a memo that threw, the error never reached the store's readers. They kept showing the old value, and no Errored caught the error (F-12).

Separately, a derived store, createStore(fn) included, could deliver one error to an effect twice. It happened when an async derive was read beside isPending, and, once the fix above is in, when an optimistic store's derive failed while an action's guess was in flight.

After: the optimistic store builds its family through createProjectionInternal, the same path createStore(fn) uses. An upstream memo's error or pending state now reaches its readers the same way it does for a plain derived store. Each reader gets an error once, at the reveal (D-41).

How

• createProjectionInternal is exported and takes an opt flag. It also accepts a null fn, for an optimistic store that isn't derived. createOptimisticStore calls it instead of duplicating the family setup.
• errorFamily(fam, error?) skips a reader that is already errored with this exact error. This is the same check core's propagateStatus makes. The derive's own throw and its async rejection pass the error in.
  • Before the change, a derive that failed twice on the same error re-queued every reader each time. One failure came from the refresh() waiter's pull after the commit published the staged error; the other from a retried async pass rejecting again.
  • Readers showing a different error, or none, are still re-queued, including a derive that rejects with undefined.

Size vs next @ 5f07d04 (brotli / minified):

scenario	brotli	minified
compiled floor (hello world) and every frozen floor	0 B	0 B
app: hydrating + every store primitive family	−57 B	−343 B
signals: + createStore	+8 B	+16 B
app: compiled CSR	−10 B	+16 B
app: compiled hydrating	−79 B	+16 B

No caps change.

How did you test this change?

• New packages/signals/tests/optimistic-derive-memo-error-4437.test.ts. It fails on next.

• New packages/signals/tests/derived-store-error-delivered-once.test.ts covers three cases, each expecting the error once:

  • an optimistic store over a failing memo with an action's guess in flight;
  • an optimistic store's async derive read beside isPending;
  • a createStore(fn) async derive read beside isPending.

  It also has four guard cases: a sync or an async derive rejecting with undefined still reaches its reader, for both store kinds. The first three cases fail without the fix.

• Suites: signals 6,021 passed, web 195 files passed. Hydrate passes except c09-no-phantom, which also fails on next.

Fixes #4437

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Generated by Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 2146f5c

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

Not sure what this means? Click here to learn what changesets are.

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

[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	+13 B	7.43 KB	✅
signals: + createStore	14.94 KB	+8 B (+0.1%)	+16 B	+16 B	14.95 KB	✅
signals: + isPending/latest	11.08 KB	−13 B (−0.1%)	−10 B	+3 B	11.10 KB	✅
signals: + until/refresh (truth readers, no optimism)	8.04 KB	0 B	0 B	+13 B	8.06 KB	✅
app: render + one signal (the simple-app floor)	9.78 KB	0 B	0 B	+13 B	9.78 KB	✅
app: hydrating (no stores) with Show/For/Loading/Errored/lazy	18.75 KB	0 B	0 B	+13 B	18.74 KB	⚠️ over by 5 B, 7 B minified headroom	lazy-page.js 0.04 KB
app: hydrating + every store primitive family	32.37 KB	−57 B (−0.2%)	−343 B	−324 B	32.45 KB	✅	lazy-page.js 0.04 KB
app: CSR with Show/For/Loading/Errored/lazy	13.45 KB	0 B	0 B	0 B	13.47 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier (same app on the observe artifacts)	15.20 KB	0 B	0 B	+13 B	15.20 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier + attribution engine enabled	29.76 KB	0 B	0 B	0 B	29.78 KB	✅	lazy-page.js 0.04 KB
app: compiled floor (one template, one text hole, one delegated click)	9.96 KB	0 B	0 B	+13 B	9.98 KB	✅
app: compiled CSR (JSX todo app: spread/merge/omit, events, class/style, keyed For, Show, Loading + lazy, store)	26.28 KB	−10 B (−0.0%)	+16 B	+16 B	26.31 KB	✅	stats.js 0.18 KB
app: compiled hydrating (the same JSX todo app through hydrate(), compiled hydratable)	32.43 KB	−79 B (−0.2%)	+16 B	+16 B	32.52 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)	33.70 KB	0 B	0 B	+13 B	33.66 KB	⚠️ over by 45 B, 7 B minified headroom	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, trace.js 9.02 KB, wire.js 3.47 KB
page: live server components (base + live/GET + action + isPending/latest)	38.75 KB	−6 B (−0.0%)	−8 B	+80 B	38.76 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, trace.js 9.02 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)	35.63 KB	0 B	0 B	+13 B	35.66 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.06 KB, sc-comments.js 0.20 KB, trace.js 8.99 KB, wire.js 3.47 KB
page: compiled live server components (the compiled base page + live/GET + action + isPending/latest)	42.67 KB	−16 B (−0.0%)	−9 B	+4 B	42.71 KB	✅	eager (counted): web.js 22.75 KB; assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.07 KB, sc-comments.js 0.19 KB, trace.js 9.06 KB, wire.js 3.47 KB
page: base + router (base page + @solidjs/router: createRouter, two routes, preload, useNavigate)	41.20 KB	0 B	0 B	+13 B	41.23 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 9.02 KB, wire.js 3.48 KB
page: live + router (live page + @solidjs/router: createRouter, two routes, preload, useNavigate)	48.31 KB	−11 B (−0.0%)	−8 B	+5 B	48.44 KB	✅	eager (counted): client.js 27.86 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 9.01 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 5 B; minified 53,598 B vs 53,585 B recorded with the cap (+13 B) — 7 B of the 20 B minified allowance left; +0 B minified over this PR's base
• page: base server components (hydrating + dynamic + frames + sf reference): over brotli cap by 45 B; minified 101,618 B vs 101,605 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 41056290847

Warning

Build has drifted: This PR's base is out of sync with its target branch, so coverage data may include unrelated changes.
Quick fix: rebase this PR. Learn more →

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.

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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

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💛 - Coveralls

[codspeed]

Merging this PR will regress 1 benchmark

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

⚠️ 4 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

⚡ 3 improved benchmarks
❌ 1 regressed benchmark
✅ 196 untouched benchmarks
⏩ 5 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	memo + sync render effect only (reference)	30.3 ms	34.9 ms	-13.3%
⚡	build	228.5 µs	176.1 µs	+29.73%
⚡	build + consume	393.2 µs	344.1 µs	+14.26%
⚡	build + consume	744.9 µs	697.9 µs	+6.73%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing claude/project-thread-x1ore2-4437 (2146f5c) with next (9c4e4a8)}

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. ↩

[ryansolid]

I don't think either of CodSpeed's two regressions comes from this PR.

• mount-rows "memo + sync render effect only (reference)" (−12.9%): this bench uses no store. It is a known runner-type swing of ±10–20%, and CodSpeed itself warns that 5 changed benchmarks ran on different hardware for base and head.
• projection-root-write "write one NESTED field (reference)" (−12.8%): this bench flips ±13–15% on the store module's byte size alone. A V8 lazy sweep after the pre-run gc() either lands in the single measured run or misses it. We reproduced that on next earlier with a 200 B comment-only change. This PR changes only how createOptimisticStore builds its projection, not the root-write path this bench measures.

The three props-chain improvements are the same noise in the other direction. I'm not chasing any of these.

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Generated by Claude Code

[ryansolid]

CodSpeed's one regression, mount-rows "memo + sync render effect only (reference)" (−13.3%), is runner noise. This PR only changes errorFamily in projection.ts, and that bench mounts plain memos and render effects with no store or projection. That reference bench swings 10–20% between runner types, and CodSpeed flags different hardware for 4 of the changed benches here.

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Generated by Claude Code