diff --git a/.changeset/trim-batch-bytes-1026.md b/.changeset/trim-batch-bytes-1026.md
new file mode 100644
index 0000000000..45f9bfe0be
--- /dev/null
+++ b/.changeset/trim-batch-bytes-1026.md
@@ -0,0 +1,6 @@
+---
+"@solidjs/signals": patch
+"solid-js": patch
+---
+
+Smaller bundles: builds without the optimistic-store, reveal-order or lane hook modules drop their dead branches, and the #4273/#4275 fixes share existing paths.
diff --git a/packages/signals/src/boundaries.ts b/packages/signals/src/boundaries.ts
index c8103258ea..7b36a765cb 100644
--- a/packages/signals/src/boundaries.ts
+++ b/packages/signals/src/boundaries.ts
@@ -148,6 +148,9 @@ export interface RevealHooks {
   _unregister(controller: object, b: Boundary): void;
   _changed(controller: object): void;
 }
+// Every call site checks the hooks themselves first (not only the slot or
+// controller, which are never set without them): a build that does not
+// import `createRevealOrder` folds the reveal-order arms away.
 export let revealHooks: RevealHooks | null = null;
 export function setRevealHooks(h: RevealHooks): void {
   revealHooks = h;
@@ -193,7 +196,7 @@ function caught(b: Boundary, node: Computed<any>, error: unknown): void {
   // nothing on screen. The fallback is instantiated once per show — a later
   // error reaches it through the `error` accessor, which is why it is one.
   if (!b._fallback) redraw(b);
-  if (b._reveal !== null) revealHooks!._changed(b._reveal);
+  if (revealHooks && b._reveal !== null) revealHooks._changed(b._reveal);
 }
 
 /** A re-armed boundary found something pending: fresh again, and the swap
@@ -206,7 +209,8 @@ function flip(b: Boundary): void {
   b._lane = b._armLane;
   const o = b._output!;
   if (!b._lane && o._config & CONFIG_HELD && txOf(o) !== flushTransaction) unhold(o);
-  if (b._lane !== null && b._output !== null) laneStageHook!(b._output, b._lane, true, false);
+  if (laneStageHook && b._lane !== null && b._output !== null)
+    laneStageHook(b._output, b._lane, true, false);
 }
 
 export function redraw(b: Boundary): void {
@@ -240,7 +244,7 @@ function catchStatus(
           b._readers.size === 0
         ) {
           if (b._fallback) redraw(b);
-          if (b._reveal !== null) revealHooks!._changed(b._reveal);
+          if (revealHooks && b._reveal !== null) revealHooks._changed(b._reveal);
         }
     return false;
   }
@@ -384,7 +388,7 @@ function boundarySeam(): void {
     if (b._readers.size === 0) {
       collecting.delete(b);
       if (b._fallback) redraw(b);
-      if (b._reveal !== null) revealHooks!._changed(b._reveal);
+      if (revealHooks && b._reveal !== null) revealHooks._changed(b._reveal);
     }
   }
 }
@@ -558,7 +562,7 @@ function createBoundary<T>(
   if (getOwner())
     cleanup(() => {
       collecting.delete(b);
-      if (controller) revealHooks!._unregister(controller, b);
+      if (revealHooks && controller) revealHooks._unregister(controller, b);
     });
   // The `on` dependencies live OUTSIDE the boundary, as the condition of a
   // `<Show>` wrapping it would: created before the owner's context names it.
@@ -598,7 +602,7 @@ function createBoundary<T>(
   b._tree = tree;
   // A slot of the reveal order in its context (reveal.ts): gated until the
   // controller releases it — before the output's first pass.
-  if (controller) revealHooks!._register(controller, b);
+  if (revealHooks && controller) revealHooks._register(controller, b);
   const output = computed<T>(
     (): T => {
       // Reveal order (reveal.ts): a gated slot shows its fallback — or, in a
@@ -612,7 +616,7 @@ function createBoundary<T>(
         // settled): the pass goes on to show it — the redraw it asks for is
         // refused mid-pass and not needed.
         link(tree, getOwner() as Computed<any>);
-        if (b._reveal !== null) revealHooks!._changed(b._reveal);
+        if (revealHooks && b._reveal !== null) revealHooks._changed(b._reveal);
         if (b._gated) {
           if (b._collapsed) {
             b._fallback = true;
@@ -717,10 +721,10 @@ function createBoundary<T>(
       release(b);
       // Shown: the slot leaves its reveal order (a later re-arm gates nobody
       // else; the frontier moves on).
-      if (b._reveal !== null) {
+      if (revealHooks && b._reveal !== null) {
         const controller = b._reveal;
         b._reveal = null;
-        revealHooks!._changed(controller);
+        revealHooks._changed(controller);
       }
       return value;
     },
diff --git a/packages/signals/src/core/core.ts b/packages/signals/src/core/core.ts
index fc84981e29..7f0b970edc 100644
--- a/packages/signals/src/core/core.ts
+++ b/packages/signals/src/core/core.ts
@@ -706,11 +706,13 @@ export function recompute(el: Computed<any>, create: boolean = false): void {
     // confirm is a landing too — the lane's end commits it) and notifies
     // only a correction: an equal truth re-runs nothing (lanes.ts). (As the
     // lane's own work the lane judged it — `laneStage`.)
+    // (The hook first: a build without lanes folds the arm away.)
     if (
+      laneOutcomeHook &&
       !create &&
       lane === null &&
       el._config & CONFIG_GUESS &&
-      laneOutcomeHook!(el, value, errored)
+      laneOutcomeHook(el, value, errored)
     ) {
       // The truth, staged under the lane's parent.
     } else if (errored) {
diff --git a/packages/signals/src/core/lanes.ts b/packages/signals/src/core/lanes.ts
index f70e0c2563..22ec77baa7 100644
--- a/packages/signals/src/core/lanes.ts
+++ b/packages/signals/src/core/lanes.ts
@@ -568,6 +568,7 @@ export function laneRead(c: Computed<any> | null, el: Signal<any> | Computed<any
   // An errored member's lane value predates its error; the error is the answer (#4106).
   if (!guess && status & STATUS_ERROR) return NOT_PENDING;
   if (c === null) return laneValueOf(el);
+  const pending = !guess && status & STATUS_PENDING;
   if (!tracking || c._config & CONFIG_CHILDREN_FORBIDDEN) {
     // An untracked read inside lane work derives from the lane like a
     // tracked one, minus the subscription — `untrack` is about
@@ -576,51 +577,41 @@ export function laneRead(c: Computed<any> | null, el: Signal<any> | Computed<any
     // lanes read by one pass link, as for tracked reads). Outside lane
     // work, the screen.
     if (passLane === null || c._config & CONFIG_CHILDREN_FORBIDDEN) return display(el);
-    enterLane(l, c);
-    if (!guess && status & STATUS_PENDING) return NOT_PENDING;
-    return laneValueOf(el);
-  }
-  // D-28: a leaf a verdict read moved into the lane still throws on a flight
-  // that has never shown — the pass leaves the lane, and its frame holds as
-  // if the read had come first (S-39, #4275).
-  if (
-    (c as any)._type === EFFECT_RENDER &&
-    passLane?._parent!._verdict === passLane &&
-    !guess &&
-    status & STATUS_PENDING &&
-    el._x!._lane === NOT_PENDING
-  )
-    setPassLane(null);
-  if ((c as any)._type === EFFECT_RENDER && (passLane === null || !sameLane(passLane, l))) {
-    if (!guess) {
-      // A flight whose value has never shown: nothing to show — the leaf
-      // waits on it, and its own frame holds (A15, #3334), not the lane's
-      // parent. The landing lands the frame: its own pass (the flush
-      // joined its transaction) reads the answer it waited on — the lane's
-      // staging, revealed at this seam.
-      if (status & STATUS_PENDING && el._x!._lane === NOT_PENDING) return NOT_PENDING;
+  } else if ((c as any)._type === EFFECT_RENDER) {
+    // A flight whose value has never shown: nothing to show — the leaf
+    // waits on it, and its own frame holds (A15, #3334), not the lane's
+    // parent. The landing lands the frame: its own pass (the flush joined
+    // its transaction) reads the answer it waited on — the lane's staging,
+    // revealed at this seam.
+    const never = pending && el._x!._lane === NOT_PENDING;
+    // D-28: a leaf a verdict read moved into the lane still throws on such
+    // a flight — the pass leaves the lane, and its frame holds as if the
+    // read had come first (S-39, #4275).
+    if (never && passLane?._parent!._verdict === passLane) setPassLane(null);
+    if (passLane === null || !sameLane(passLane, l)) {
+      if (never) return NOT_PENDING;
       if (
+        !guess &&
         el._pendingValue !== NOT_PENDING &&
         c._config & CONFIG_HELD &&
         flushTransaction !== null &&
         resolveTx(flushTransaction) === txOf(c)
       )
         return el._pendingValue;
-    }
-    if (l._held || (!guess && status & STATUS_PENDING)) {
-      if (!guess && !l._shown && status & STATUS_UNINITIALIZED) throw new NotReadyError(null);
-      // Re-derived at the reveal; once per pass (the pass may also be a stale
-      // reader of a transaction, REACTIVE_FRAME_READ — both reruns apply).
-      if (!(c._flags & REACTIVE_SCREEN_READ)) {
-        c._flags |= REACTIVE_FRAME_READ | REACTIVE_SCREEN_READ;
-        l._reruns.push(c);
+      if (l._held || pending) {
+        if (!guess && !l._shown && status & STATUS_UNINITIALIZED) throw new NotReadyError(null);
+        // Re-derived at the reveal; once per pass (the pass may also be a stale
+        // reader of a transaction, REACTIVE_FRAME_READ — both reruns apply).
+        if (!(c._flags & REACTIVE_SCREEN_READ)) {
+          c._flags |= REACTIVE_FRAME_READ | REACTIVE_SCREEN_READ;
+          l._reruns.push(c);
+        }
+        return display(el);
       }
-      return display(el);
     }
   }
   enterLane(l, c);
-  if (!guess && status & STATUS_PENDING) return NOT_PENDING;
-  return laneValueOf(el);
+  return pending ? NOT_PENDING : laneValueOf(el);
 }
 
 /** The value a guess covered: the node's committed value — a store slot's
diff --git a/packages/signals/src/core/scheduler.ts b/packages/signals/src/core/scheduler.ts
index 6ab9b4fc08..2ea0f4561c 100644
--- a/packages/signals/src/core/scheduler.ts
+++ b/packages/signals/src/core/scheduler.ts
@@ -726,12 +726,14 @@ export function schedule() {
  */
 export const ROOT_ERROR_HOOK: unique symbol = Symbol.for("solid-js/root-error-hook") as any;
 
+const HALTED = "[REACTIVITY_HALTED]";
+
 export function haltReactivity(cause?: unknown): void {
   if (halted) return;
   halted = true;
   // A cleanup error collected before the halt is dropped (owner.ts).
   rethrowCleanupError(true);
-  let message = "[REACTIVITY_HALTED]";
+  let message = HALTED;
   if (__DEV__) {
     message +=
       " An uncaught error halted the reactive system. No further updates will be processed. Handle errors with <Errored> or treat this as a crash.";
@@ -785,7 +787,7 @@ function notifyHalted(): void {
     __DEV__
       ? "[REACTIVITY_HALTED] Update ignored: the reactive system was halted by an earlier uncaught error." +
           haltedAt
-      : "[REACTIVITY_HALTED]"
+      : HALTED
   );
 }
 
@@ -1016,11 +1018,12 @@ export class GlobalQueue implements IQueue {
     // This flush's own runs, the lanes' reveals, and the landings' held runs
     // are collected apart and ordered below.
     const own = this._queues;
-    const lanes: [QueueCallback[], QueueCallback[]] = (this._queues = [[], []]);
+    const lanes: [QueueCallback[], QueueCallback[]] = [[], []];
     // The passes that read this frame's stagings as the screen read held
     // writes if it parked: the lane seam re-derives them on the committed
     // world (a lane's runs wait this round).
     if (laneSeamsHook) {
+      this._queues = lanes;
       laneSeamsHook(t !== null ? stagedReaders : null);
       if (stagedReaders.length) stagedReaders.length = 0;
     }
@@ -1179,7 +1182,7 @@ function land(u: Transaction): void {
   // (`_nodes` still lists them).
   if (__OBSERVE__ && attrHooks !== null) attrHooks.transitionSettled(u);
   const frame = reruns(u);
-  if (u._marks !== null) releaseMarksHook!(u._marks);
+  if (releaseMarksHook && u._marks !== null) releaseMarksHook(u._marks);
   // Old children die in the commits (cleanups first), then the stashed
   // effects run ahead of this flush's own. A node a lane took over since
   // (a guess written over the staged truth) is the lane's to land.
diff --git a/packages/signals/src/store/affects.ts b/packages/signals/src/store/affects.ts
index 3c701470df..7ec3246d0b 100644
--- a/packages/signals/src/store/affects.ts
+++ b/packages/signals/src/store/affects.ts
@@ -87,7 +87,7 @@ function walk(
   if (t !== undefined) {
     if (t.pb !== null) entry._scope.add(t.v);
     // The writer's view: the tick's own unflushed guesses are in motion too.
-    if (t.fam?.opt === true) raw = optHooks!.view(t, raw, true);
+    if (optHooks && t.fam?.opt === true) raw = optHooks.view(t, raw, true);
     const nodes = t.n;
     if (nodes !== null)
       for (const k of Reflect.ownKeys(nodes))
diff --git a/packages/signals/src/store/hooks.ts b/packages/signals/src/store/hooks.ts
index b3b141bdc0..a0b7a2a66e 100644
--- a/packages/signals/src/store/hooks.ts
+++ b/packages/signals/src/store/hooks.ts
@@ -35,6 +35,9 @@ export interface OptHooks {
    * into the draft. */
   reconcile(draft: any, incoming: any, keyFn: ((item: any) => any) | null): void;
 }
+// Set before any family is optimistic (`fam.opt`): a call site checks the
+// hooks first, so a build that does not import optimistic.ts folds the arm
+// away.
 export let optHooks: OptHooks | null = null;
 export function installOptHooks(hooks: OptHooks): void {
   optHooks = hooks;
diff --git a/packages/signals/src/store/reconcile.ts b/packages/signals/src/store/reconcile.ts
index 3b031aaf09..2b4a664853 100644
--- a/packages/signals/src/store/reconcile.ts
+++ b/packages/signals/src/store/reconcile.ts
@@ -57,8 +57,8 @@ export function reconcileState(
   // truth but an optimistic edit — the keyed diff is written into the draft
   // (a matched row keeps its proxy, its changed leaves become its guesses),
   // and the setter's exit turns the draft into guesses like any.
-  if (userWriting() && t.fam?.opt === true) {
-    optHooks!.reconcile(state, unwrapValue(value), keyFn);
+  if (optHooks && userWriting() && t.fam?.opt === true) {
+    optHooks.reconcile(state, unwrapValue(value), keyFn);
     return;
   }
   // Replace-mode root handed another store's proxy: chain to it (§7b).
@@ -100,7 +100,7 @@ function applyAdopt(t: StoreTarget, incoming: any, keyFn: KeyFn | null, proj = f
   // Q-D: a landing on an optimistic family is reconciled against the VIEW
   // — key matching from the arrangement the guesses made (R28), so a row
   // the guess added keeps its proxy when the server returns it.
-  const prevView = t.fam?.opt === true ? optHooks!.view(t, old) : old;
+  const prevView = optHooks && t.fam?.opt === true ? optHooks.view(t, old) : old;
   const nextArr = Array.isArray(incoming);
   const shallow = t.s === true;
   adoptPB(t, incoming, false);
diff --git a/packages/signals/src/store/store.ts b/packages/signals/src/store/store.ts
index 52d67a5bcb..0abec66c32 100644
--- a/packages/signals/src/store/store.ts
+++ b/packages/signals/src/store/store.ts
@@ -690,8 +690,8 @@ function ensurePB(target: StoreTarget): Record<PropertyKey, any> {
   // An optimistic edit composes on the view the user saw and becomes
   // guesses at the setter's exit: nothing is staged, nothing folds
   // (optimistic.ts).
-  if (userWrite && target.fam?.opt === true && !pendingNotify.has(target))
-    return (target.pb = optHooks!.draft(target));
+  if (optHooks && userWrite && target.fam?.opt === true && !pendingNotify.has(target))
+    return (target.pb = optHooks.draft(target));
   if (pb !== null && !isOwned(pb)) {
     // An adopted object awaiting its fold is the user's: the draft writes a
     // clone of it. The clone is the batch's staging — unless the adoption is
@@ -1142,12 +1142,12 @@ function notifyWrites(t: StoreTarget): void {
   // Optimistic channel: a user's writes on an optimistic family become
   // guesses on the nodes (lanes); the draft is discarded, the committed
   // backing never touched.
-  if (userWrite && t.fam?.opt === true) {
+  if (optHooks && userWrite && t.fam?.opt === true) {
     // The draft is discarded first: the diff reads the target (its nodes
     // are born from the committed frame, not the draft).
     t.pb = null;
     t.wk = null;
-    t.pb = optHooks!.writes(t, pb);
+    t.pb = optHooks.writes(t, pb);
     return;
   }
   const old = t.v;
@@ -1888,10 +1888,10 @@ function enumerationSource(target: StoreTarget): Record<PropertyKey, any> {
     // A container's arrangement guess is not a backing: the view composes
     // over the base it is shown over.
     const base = asBacking(readNode(getContainerNode(target)));
-    return target.fam?.opt === true ? optHooks!.view(target, base) : base;
+    return optHooks && target.fam?.opt === true ? optHooks.view(target, base) : base;
   }
   const src = readSource(target);
-  return optRead(target) ? optHooks!.view(target, src) : src;
+  return optHooks && optRead(target) ? optHooks.view(target, src) : src;
 }
 
 /** A read on an optimistic family that composes the lanes' values: not the
@@ -2165,8 +2165,8 @@ const traps: ProxyHandler<StoreTarget> = {
         node._value = present; // the link follows the inner store (S4)
         if (node._config & CONFIG_OVERRIDE) return !!nv;
         return present;
-      } else if (optRead(target)) {
-        const guessed = optHooks!.has(target, key);
+      } else if (optHooks && optRead(target)) {
+        const guessed = optHooks.has(target, key);
         if (guessed !== undefined) return guessed;
       }
     }
@@ -2207,8 +2207,8 @@ const traps: ProxyHandler<StoreTarget> = {
         return undefined;
     } else src = readSource(target, key, true);
     let desc: PropertyDescriptor | undefined;
-    if (!enumerating && optRead(target)) {
-      const guessed = optHooks!.descriptor(target, key);
+    if (optHooks && !enumerating && optRead(target)) {
+      const guessed = optHooks.descriptor(target, key);
       if (guessed === null) return undefined;
       desc = guessed;
     }
@@ -2412,8 +2412,8 @@ export function storeSetter<T>(proxy: T, fn: (draft: T) => T | void, guard = tru
     // A returned replacement: on an optimistic family a user's is itself an
     // optimistic edit — diffed against the view as guesses (`next` parity);
     // otherwise it is adopted as the incoming truth.
-    if (guard && target.fam?.opt === true && !writeOverride)
-      optHooks!.writes(target, unwrapValue(result));
+    if (optHooks && guard && target.fam?.opt === true && !writeOverride)
+      optHooks.writes(target, unwrapValue(result));
     else adoptPB(target, unwrapValue(result));
   }
   // A34 (3), #3612 — the derived store's twin of `setMemo`: a user write to
@@ -2614,7 +2614,7 @@ function snapshotWalk(value: any, seen: Map<object, any>, fam: StoreFamily | nul
       if (t.ovl) materializePB(t);
       backing = t.pb!;
     }
-    if (optRead(t)) backing = optHooks!.view(t, backing);
+    if (optHooks && optRead(t)) backing = optHooks.view(t, backing);
     if (backing === src) break;
     src = backing;
   }
diff --git a/packages/solid/src/client/hydration.ts b/packages/solid/src/client/hydration.ts
index 64cea3c999..73895fbe9b 100644
--- a/packages/solid/src/client/hydration.ts
+++ b/packages/solid/src/client/hydration.ts
@@ -1272,12 +1272,10 @@ function hydratedCreateErrorBoundary<T, U>(
   fn: () => T,
   fallback: (error: () => unknown, reset: () => void) => U
 ): Accessor<T | U> {
-  if (!sharedConfig.hydrating || noHydrationId()) return coreErrorBoundary(fn, fallback);
-  markTopLevelSnapshotScope();
-  const parent = getOwner()!;
-  const expectedId = peekNextChildId(parent);
-  if (sharedConfig.has!(expectedId)) {
-    const err = sharedConfig.load!(expectedId);
+  if (sharedConfig.hydrating && !noHydrationId()) {
+    markTopLevelSnapshotScope();
+    const expectedId = peekNextChildId(getOwner()!);
+    let err: unknown;
     // The server drew the fallback; the client's own run decides. The
     // content runs now with its data adopted by id but claiming no DOM —
     // the markup is the fallback's — so what it throws is the client's
@@ -1285,21 +1283,19 @@ function hydratedCreateErrorBoundary<T, U>(
     // the server's fallback up behind a hold: a render effect in the content
     // throwing the server's error until reset(), disposed with the content
     // when it re-runs (#4273).
-    if (err !== undefined) {
+    if (sharedConfig.has!(expectedId) && (err = sharedConfig.load!(expectedId)) !== undefined) {
       // The content's owner, until a fallback is built.
       let o: any;
       const read = coreErrorBoundary(
-        () => {
-          const prev = _claimOwner;
-          o = getOwner();
-          // A claim window over no owner: nothing under it claims.
-          _claimOwner = {} as Owner;
-          try {
-            return fn();
-          } finally {
-            _claimOwner = prev;
-          }
-        },
+        // While hydrating, a claim window over no owner: nothing under it
+        // claims. (`hydrateWindow` with no id or scope, hydration already on
+        // and the snapshot root marked above, only swaps the claim owner.)
+        // A later run claims nothing either way: claims are read only while
+        // hydrating.
+        () =>
+          _hydratingValue
+            ? hydrateWindow("", fn, undefined, ((o = getOwner()), {} as Owner))
+            : fn(),
         (e, reset) => ((o = 0), fallback(e, reset))
       );
       // No fallback yet: the content ran clean. Hold the server's fallback