perf(signals): witness coarse-read machinery — one node per record subtree

[ryansolid]

What

The coarse-read stack from the create-floor isolation battery (O5–O7), landed as internal machinery with zero public API. Three pieces, one semantic unit:

1. witnessNext — the coarse read (O5)

Subscribe to ONE record's deep-witness node (dk) and serve the raw backing. No child walk, no key-set subscription, no snapshot, no leaf nodes, no wrap caches. This is the coarse-row read model: a row effect witnesses its record and reads values raw — one node + one link per record instead of one per touched leaf.

Not exported from solid-js or @solidjs/signals. The consumer is the compiler-emitted coarse-row track (the unified-For scan emission); user code never calls it. Tests import it through the internal module path.

2. Deep-witness bubbling (O6)

bumpDeep now notifies witnesses on the record AND its ancestors, so one witness covers a record subtree. Gated by a live-witness counter: apps with no deep()/witness subscribers pay one number check per change, never a chain walk. Ancestor bumps are authoritative (never lane cargo) — bisected during the battery: bubbling into an optimistic root's armed dk mid-action created an unintended override that wedged the family's generator.

3. Under-witness identity (O7) — the R18 amendment

Keyed reconcile's adoption walk threads an under-witness flag: records beneath a live deep witness keep key-matched proxy identity without materializing per-record nodes — the witness IS the subscription for its subtree. The reviewer-facing semantic surface:

• Never-wrapped records are still skipped always, even under a witness — cost stays O(wrapped), never O(store).
• Unwitnessed captures still detach (R18's "subscribing buys liveness" is unchanged where no witness exists) — narrow-subpath pruning in large store diffs is byte-for-byte today's behavior.
• Since deep() also creates dk nodes, deep() subscribers get bubbling + subtree identity too. This is a strengthening, not a break.

All three behaviors are pinned by the new reconcile-pruning-contract.test.ts (uses the __adoptVisits probe to assert exact walk-entry counts across unwitnessed / witnessed / witness-released scenarios).

Measured

Isolation battery (solo on clean next, 5 canonical fixtures, correctness gates green). Hand-compiled dbmon coarse rows vs fine-grained:

• mount 0.70x, unmount 0.61x, tick 0.90x
• deep dbmon: one witness per row replaces one per nested record
• Signal-only fixtures untouched (all of it tree-shakes out of storeless graphs; the bubble gate is one counter check)

Size

• + createStore: 14.16 → 14.30 KB (+140 B: witnessNext + bubbling + the reconcile flag)
• hydrating + store families: 26.25 → 26.31 KB (+51 B)
• Core floor, signal-only, CSR, frames: unchanged/under

Tests

signals 1472 / web 677 / solid 585, all green. Changesets included (patch, prerelease).

Made with Cursor

[changeset-bot]

🦋 Changeset detected

Latest commit: 09b52fb

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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[ryansolid]

Marked draft deliberately: this machinery is inert without its consumer (witnessNext has zero callers; bubbling/under-witness identity only activate through deep()'s dk nodes). Holding the merge until the compiler-emitted coarse-row track lands — the PR exists now so the R18-amendment semantics review can happen decoupled from the unified-For review. The one standalone behavior change if merged early: records captured under a deep() subscription keep key-matched identity through keyed reconcile instead of detaching.