fix(signals): a staged read of a node born staged is not re-queued at the lane seam

.changeset/fix-verdict-lane-flush-loop.md

@@ -0,0 +1,5 @@
+---
+"@solidjs/signals": patch
+---
+
+Fix an infinite flush loop ("Potential Infinite Loop Detected") when a `latest()`-gated `Show` mounts a fresh `Loading` under an action hold: lane work that reads a node born staged is no longer re-queued to re-derive on a committed value it doesn't have.

packages/signals/docs/RULES-INDEX.md

@@ -73,7 +73,7 @@ Status legend: **live** stated and standing · **ruled** carries an explicit rul
 | A26 | ruled | `docs/SPEC-ASYNC-SEMANTICS.md:109` | — | action-await-contract.test.ts×2 fuzz-findings-l2.test.ts×1 posture-store-parity.test.ts×2 visibility-oracle-store.states.ts×2 visibility-oracle.states.ts×1 visibility-oracle.test.ts×1 | [ruled 2026-07-17] An ambient transaction window is one flush; parking is flush-driven — (**ruled 2026-07-17**, #2913; **enforcement hardened 2026-08-31**, #3141 — parking is flush-driven, and a trans… |
 | A27 | ruled | `docs/SPEC-ASYNC-SEMANTICS.md:299` | — | loading-value.test.ts×2 visibility-oracle.states.ts×18 visibility-oracle.test.ts×1 | [ruled 2026-08-10] The commit-#0 loading window is loading-class and verdict-quiet — (**ruled 2026-08-10**) **The commit-#0 loading window is loading-class and verdict-quiet.** A node born committed v… |
 | A28 | ruled, mechanism landed | `docs/SPEC-ASYNC-SEMANTICS.md:93` | constants.ts×1 core.ts×12 lanes.ts×2 scheduler.ts×3 types.ts×1 verdict.ts×2 store.ts×4 | createOptimistic.test.ts×5 fuzz-findings-l2.test.ts×6 held-derivation-not-a-proposal-3612.test.ts×1 issue-3800-repro.test.ts×1 latest-held-till-flush.test.ts×1 posture-store-parity.test.ts×5 question-scoped-pending.test.ts×3 snapshot-derived-store-rows.test.ts×1 createOptimisticStore.test.ts×10 optimistic-draft-visibility-3665.test.ts×5 optimistic-list-mutation-matrix.harness.ts×1 optimistic-list-mutation-matrix.test.ts×2 shallow.test.ts×1 woken-transaction-adopts-staged-bump.test.ts×1 treeshake.test.ts×2 verdict-contract.test.ts×1 visibility-oracle-store.states.ts×8 visibility-oracle.states.ts×8 | [ruled, mechanism landed 2026-09-15] A write becomes visible at flush — to every channel — (**ruled 2026-09-08**; supersedes the #2922 mid-tick pull) **A write becomes visible at flush — to every chan… |
-| A29 | amended | `docs/SPEC-ASYNC-SEMANTICS.md:117` | boundaries.ts×1 action.ts×1 async.ts×1 constants.ts×1 core.ts×13 effect.ts×1 lanes.ts×1 scheduler.ts×4 signals.ts×1 store.ts×1 | adoption-unchanged-key-read-3706.test.ts×9 body-end-supersession-visibility.test.ts×1 born-held.test.ts×3 boundary-not-born-held-3540.test.ts×4 createProjection.draft-lifetime-3585.test.ts×1 direct-commit-readers-posture.test.ts×1 fuzz-findings-l2.test.ts×6 held-conditional-memo.test.ts×1 held-frame-dependencies.test.ts×2 held-truth-lane-only.test.ts×3 l2-contract.test.ts×1 latest-held-till-flush.test.ts×2 loading-fallback-in-flush-3540.test.ts×6 loading-on-frame-following-3540.test.ts×1 mount-over-foreign-hold-3761.test.ts×1 optimistic-mount-nested-memo-3835.test.ts×1 optimistic-read-lane-not-transaction-3698.test.ts×3 posture-born-held-and-observation.test.ts×1 posture-store-parity.test.ts×6 derived-presence-async-3726.test.ts×3 optimistic-untracked-reads-f3-f5.test.ts×1 store-unchanged-read-independent-write-3688.test.ts×1 tick-scoped-pass-transaction.test.ts×2 treeshake.test.ts×3 verdict-mount-first-pass-3851.test.ts×2 visibility-oracle-store.states.ts×5 visibility-oracle-store.test.ts×1 visibility-oracle.states.ts×9 visibility-oracle.test.ts×1 write-proposals-3494.test.ts×1 | [ruled, amended in place 2026-09-13 (#3408)] A tracked read served a live transaction's staged value enters that transaction — A tracked computation served a node's staged `_pendingValue` — a value a … |
+| A29 | amended | `docs/SPEC-ASYNC-SEMANTICS.md:117` | boundaries.ts×1 action.ts×1 async.ts×1 constants.ts×1 core.ts×13 effect.ts×1 lanes.ts×1 scheduler.ts×4 signals.ts×1 store.ts×1 | adoption-unchanged-key-read-3706.test.ts×9 body-end-supersession-visibility.test.ts×1 born-held.test.ts×3 boundary-not-born-held-3540.test.ts×4 createProjection.draft-lifetime-3585.test.ts×1 direct-commit-readers-posture.test.ts×1 fuzz-findings-l2.test.ts×6 held-conditional-memo.test.ts×1 held-frame-dependencies.test.ts×2 held-truth-lane-only.test.ts×3 l2-contract.test.ts×1 latest-held-till-flush.test.ts×2 loading-fallback-in-flush-3540.test.ts×6 loading-on-frame-following-3540.test.ts×1 mount-over-foreign-hold-3761.test.ts×1 optimistic-mount-nested-memo-3835.test.ts×1 optimistic-read-lane-not-transaction-3698.test.ts×3 posture-born-held-and-observation.test.ts×1 posture-store-parity.test.ts×6 derived-presence-async-3726.test.ts×3 optimistic-untracked-reads-f3-f5.test.ts×1 store-unchanged-read-independent-write-3688.test.ts×1 tick-scoped-pass-transaction.test.ts×2 treeshake.test.ts×3 verdict-mount-first-pass-3851.test.ts×2 verdict-mount-loading-flush-loop.test.ts×2 visibility-oracle-store.states.ts×5 visibility-oracle-store.test.ts×1 visibility-oracle.states.ts×9 visibility-oracle.test.ts×1 write-proposals-3494.test.ts×1 | [ruled, amended in place 2026-09-13 (#3408)] A tracked read served a live transaction's staged value enters that transaction — A tracked computation served a node's staged `_pendingValue` — a value a … |
 | A30 | ruled | `docs/SPEC-ASYNC-SEMANTICS.md:255` | async.ts×3 attribution.ts×1 constants.ts×1 core.ts×1 effect.ts×1 lanes.ts×1 scheduler.ts×5 | async-landing-deps-3461.test.ts×3 fuzz-findings-l2.test.ts×3 held-conditional-effect.test.ts×1 held-conditional-memo.test.ts×1 held-frame-dependencies.test.ts×2 ispending-in-boundary-on-3528.test.ts×1 lane-frame-deferred-run-3662.test.ts×1 lane-frame-held-lane-3662.test.ts×1 posture-born-held-and-observation.test.ts×1 treeshake.test.ts×2 write-proposals-3494.test.ts×2 zombie-rerun-after-commit-3546.test.ts×2 | [ruled 2026-09-13 (#3410)] A memo's dependencies are the committed frame's until the frame is replaced — A pass that _staged_ its value has not replaced the committed frame, so the committed value sti… |
 | A31 | live | `docs/SPEC-ASYNC-SEMANTICS.md:129` | boundaries.ts×1 core.ts×1 lanes.ts×1 verdict.ts×2 | fuzz-findings-l2.test.ts×6 ispending-combined-atomic-3442.test.ts×1 | [live 2026-09-14 (#3442)] A memo computes under its own lane posture, never its puller's — A memo's value is one shared slot every reader sees, so its pass runs under the lane posture the memo itself … |
 | A32 | ruled | `docs/SPEC-ASYNC-SEMANTICS.md:137` | core.ts×4 lanes.ts×1 store.ts×1 | visibility-oracle-store.states.ts×8 visibility-oracle-store.test.ts×1 visibility-oracle.states.ts×9 visibility-oracle.test.ts×1 | [ruled 2026-09-14] Children-forbidden readers see the frame, not the graph — `createTrackedEffect` and `onSettled` callbacks are effect-phase code that runs after the frame is decided. They read the f… |

packages/signals/src/core/core.ts

@@ -1858,7 +1858,7 @@ export function serve(el: Signal<any> | Computed<any>, c: Computed<any> | null):
     stagedScreen(c!)
   )
     return el._value;
-  stagedRead(c!);
+  stagedRead(c!, el);
   return el._pendingValue;
 }
 
@@ -1870,10 +1870,16 @@ export function serve(el: Signal<any> | Computed<any>, c: Computed<any> | null):
  * the committed world and its lane's runs wait that round, so the held
  * write never shows through the lane. A verdict lane's work likewise: the
  * lane holds verdicts, not the frame's other stagings (#3851) — except a
- * verdict reader, which answered for itself (the lane seam, lanes.ts). */
-export function stagedRead(c: Computed<any>): void {
+ * verdict reader, which answered for itself (the lane seam, lanes.ts). Not
+ * a read of a node born staged: it has no committed value to re-derive on,
+ * and a re-run would read the same staging and re-queue every round. */
+export function stagedRead(c: Computed<any>, el?: Signal<any> | Computed<any>): void {
   c._flags |= REACTIVE_STAGED_READ;
-  if (passLane !== null) stagedReaders.push(c);
+  if (
+    passLane !== null &&
+    !((el as Computed<any> | undefined)?._statusFlags! & STATUS_UNINITIALIZED)
+  )
+    stagedReaders.push(c);
 }
 
 /** A10 for a staged node: a verdict reader (the pass entered a window) that

packages/signals/tests/verdict-mount-loading-flush-loop.test.ts

@@ -0,0 +1,105 @@
+/**
+ * A verdict reader mounts a fresh Loading under an action hold (semantic
+ * fuzzer, mount-under-hold seed 3289 cases 119 and 323).
+ *
+ * `<Show when={latest(x) > 0}>` (gated through a memo) opens while an action
+ * holds `x`, and mounts a `<Loading>` whose content reads `x` directly with
+ * no load of its own. The boundary's output is born into the held frame, so
+ * it has no committed value; the render effect inserting it is verdict-lane
+ * work that read its staging. Since #3869 the seam re-queued that effect to
+ * re-derive on the committed world every round the frame stayed parked, and
+ * each re-run read the same staging: "Potential Infinite Loop Detected".
+ */
+import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
+import {
+  action,
+  createLoadingBoundary,
+  createMemo,
+  createRenderEffect,
+  createRoot,
+  createSignal,
+  flush,
+  latest,
+  untrack
+} from "../src/index.js";
+
+beforeEach(() => vi.useFakeTimers());
+afterEach(() => vi.useRealTimers());
+
+const resolve = (v: unknown): unknown => {
+  while (typeof v === "function") v = (v as () => unknown)();
+  return v;
+};
+
+function mount(anchor: boolean) {
+  const [x, setX] = createSignal(0);
+  const screen = { x: undefined as number | undefined, slot: undefined as unknown };
+  createRoot(() => {
+    if (anchor)
+      createRenderEffect(x, v => {
+        screen.x = v;
+      });
+    const condition = createMemo(() => latest(x) > 0);
+    const children = createMemo(() =>
+      condition()
+        ? untrack(() =>
+            createLoadingBoundary(
+              () => untrack(() => () => `content ${x()}`),
+              () => "fallback"
+            )
+          )
+        : undefined
+    );
+    createRenderEffect(
+      () => resolve(children()),
+      v => {
+        screen.slot = v;
+      }
+    );
+  });
+  flush();
+  const committed = () => (anchor ? screen.x : untrack(x));
+  let release!: () => void;
+  const hold = () =>
+    action(function* () {
+      setX(1);
+      yield new Promise<void>(r => (release = r));
+    })();
+  return { screen, committed, hold, release: () => release() };
+}
+
+describe("a verdict reader mounts a fresh Loading under an action hold", () => {
+  for (const anchor of [false, true])
+    describe(anchor ? "with a reader of x on screen (case 323)" : "case 119", () => {
+      test("flush settles while held, and the commit reveals the content", async () => {
+        const m = mount(anchor);
+        expect(m.screen.slot).toBeUndefined();
+        expect(m.committed()).toBe(0);
+
+        const done = m.hold();
+        expect(() => flush()).not.toThrow();
+        await Promise.resolve();
+        expect(() => flush()).not.toThrow();
+        expect(m.committed()).toBe(0);
+
+        m.release();
+        await done;
+        flush();
+        expect(m.committed()).toBe(1);
+        expect(m.screen.slot).toBe("content 1");
+      });
+
+      // A29: a fresh, never-shown Loading over held data shows its fallback
+      // now. Pre-#3869 behavior, still open (MH1): the content shows the held
+      // value beside the committed `x = 0`.
+      test.fails("while held, the fresh boundary shows its fallback (A29)", async () => {
+        const m = mount(anchor);
+        m.hold();
+        flush();
+        await Promise.resolve();
+        flush();
+        expect(m.committed()).toBe(0);
+        expect(m.screen.slot).toBe("fallback");
+      });
+    });
+});