diff --git a/packages/compiler/src/frontend/lowering/expressions/object-literals.ts b/packages/compiler/src/frontend/lowering/expressions/object-literals.ts
index e5b464edc..7947f2830 100644
--- a/packages/compiler/src/frontend/lowering/expressions/object-literals.ts
+++ b/packages/compiler/src/frontend/lowering/expressions/object-literals.ts
@@ -2566,7 +2566,7 @@ export function lowerObjectLiteral(
       ) {
         throw err;
       }
-      lowerer.runtimeFences.push(...lowerer.diags.splice(propDiagsBefore));
+      for (const d of lowerer.diags.splice(propDiagsBefore)) lowerer.runtimeFences.push(d);
       droppedNames.add(name);
       continue;
     }
diff --git a/packages/compiler/src/frontend/lowering/frozen-records.test.ts b/packages/compiler/src/frontend/lowering/frozen-records.test.ts
new file mode 100644
index 000000000..47a9d7c80
--- /dev/null
+++ b/packages/compiler/src/frontend/lowering/frozen-records.test.ts
@@ -0,0 +1,58 @@
+import { describe, expect, test } from "vitest";
+import {
+  DYN,
+  STRING,
+  VOID,
+  type IrExpr,
+  type IrFunction,
+  type IrStmt,
+  type SrcLoc,
+  type IrType,
+} from "../../ir/ir.js";
+import { freezableTypes } from "./frozen-records.js";
+import type { Lowerer } from "./lowerer.js";
+
+const loc: SrcLoc = { file: "frozen.ts", start: 0, end: 1 };
+
+/** An untyped conversion of a `type`-typed value: a live-reference root. */
+function dynFrom(type: IrType, count: number): IrStmt[] {
+  const expr: IrExpr = {
+    kind: "dynFrom",
+    value: { kind: "varRef", localId: "s.0", type, loc },
+    type: DYN,
+    loc,
+  };
+  const body: IrStmt[] = [];
+  for (let i = 0; i < count; i++) body.push({ kind: "exprStmt", expr, loc });
+  return body;
+}
+
+function fn(body: IrStmt[]): IrFunction {
+  return { name: "f", params: [], returnType: VOID, locals: [], body, loc };
+}
+
+function stub(shapes: [string, unknown][] = []): Lowerer {
+  return {
+    untypedIntegrity: true,
+    classes: new Map(),
+    shapes: new Map(shapes),
+    unions: new Map(),
+  } as unknown as Lowerer;
+}
+
+describe("freezableTypes", () => {
+  test("seeds a program-sized live list without a spread argument limit", () => {
+    // A spread (`stack.push(...live)`) throws RangeError above roughly 100k
+    // arguments, which a large program's live-reference roots reach.
+    const roots = 200_000;
+    const { shapes, arrays } = freezableTypes(stub(), [fn(dynFrom(STRING, roots))]);
+    expect(shapes.size).toBe(0);
+    expect(arrays.size).toBe(0);
+  });
+
+  test("a live record type makes its shape freezable", () => {
+    const lowerer = stub([["r0", { id: "r0", fields: [] }]]);
+    const live = dynFrom({ kind: "record", shapeId: "r0" }, 1);
+    expect([...freezableTypes(lowerer, [fn(live)]).shapes]).toEqual(["r0"]);
+  });
+});
diff --git a/packages/compiler/src/frontend/lowering/frozen-records.ts b/packages/compiler/src/frontend/lowering/frozen-records.ts
index 75056b3cc..2555dfc2a 100644
--- a/packages/compiler/src/frontend/lowering/frozen-records.ts
+++ b/packages/compiler/src/frontend/lowering/frozen-records.ts
@@ -114,7 +114,7 @@ function holdsAbsentState(e: IrExpr): boolean {
 
 /** The record shapes and array types (typeKeys) whose values the program
  * may freeze. */
-function freezableTypes(
+export function freezableTypes(
   lowerer: Lowerer,
   functions: IrFunction[],
 ): { shapes: Set<string>; arrays: Set<string> } {
@@ -141,16 +141,21 @@ function freezableTypes(
     });
   if (!lowerer.untypedIntegrity && !freezesUntyped) return { shapes, arrays };
   const stack: IrType[] = [];
+  // Both seeds are program-sized (one entry per untyped conversion or check in
+  // every function), so they are pushed with loops: a spread argument list
+  // exceeds the engine's limit and throws RangeError on a large program.
   // A record checked from an untyped value copies it, frozen when the value
   // is (a fresh literal frozen in a JavaScript file included), so the shapes
   // a check builds are freezable in a program that freezes untyped values.
-  if (freezesUntyped) stack.push(...checked);
+  if (freezesUntyped) {
+    for (const type of checked) stack.push(type);
+  }
   if (lowerer.untypedIntegrity) {
     // An untyped reference to a class instance, or to a record or array
     // boxed live, reaches the values its fields and elements hold as further
     // live references. Class instances also cross into untyped code through
     // compiled callbacks, so every class is a root.
-    stack.push(...live);
+    for (const type of live) stack.push(type);
     for (const info of lowerer.classes.values())
       for (const field of info.def.fields) stack.push(field.type);
   }
diff --git a/packages/compiler/src/frontend/lowering/function-returns.ts b/packages/compiler/src/frontend/lowering/function-returns.ts
index 7378f26a7..0c09999c7 100644
--- a/packages/compiler/src/frontend/lowering/function-returns.ts
+++ b/packages/compiler/src/frontend/lowering/function-returns.ts
@@ -578,8 +578,8 @@ export function resolveInferredReturn(
       // per-statement deferral, applied to one return of an instance).
       const captured = lowerer.diags.splice(diagsBefore);
       const ice = captured.filter((d) => d.code === "SC9001");
-      if (ice.length > 0) lowerer.diags.push(...ice);
-      lowerer.runtimeFences.push(...captured.filter((d) => d.code !== "SC9001"));
+      for (const d of ice) lowerer.diags.push(d);
+      for (const d of captured) if (d.code !== "SC9001") lowerer.runtimeFences.push(d);
       const first = captured.find((d) => d.code !== "SC9001");
       // Property writes, not literal element writes: the class method
       // census reads `x["kind"] = …` as a possible write to every method
diff --git a/packages/compiler/src/frontend/lowering/lower-modules.ts b/packages/compiler/src/frontend/lowering/lower-modules.ts
index f82728c6e..00299ce58 100644
--- a/packages/compiler/src/frontend/lowering/lower-modules.ts
+++ b/packages/compiler/src/frontend/lowering/lower-modules.ts
@@ -1189,8 +1189,8 @@ function deferJsCollectionDiags(lowerer: Lowerer, sf: ts.SourceFile, diagsBefore
   if (!isJsSourceFile(sf)) return;
   const captured = lowerer.diags.splice(diagsBefore);
   const ice = captured.filter((d) => d.code === "SC9001");
-  if (ice.length > 0) lowerer.diags.push(...ice);
-  lowerer.runtimeFences.push(...captured.filter((d) => d.code !== "SC9001"));
+  for (const d of ice) lowerer.diags.push(d);
+  for (const d of captured) if (d.code !== "SC9001") lowerer.runtimeFences.push(d);
 }
 
 /** A scalar-literal expression a single-value `module.exports =` can carry
diff --git a/packages/compiler/src/frontend/lowering/lower-stmts.ts b/packages/compiler/src/frontend/lowering/lower-stmts.ts
index 2d10d56b3..729ea4b40 100644
--- a/packages/compiler/src/frontend/lowering/lower-stmts.ts
+++ b/packages/compiler/src/frontend/lowering/lower-stmts.ts
@@ -961,8 +961,8 @@ function lowerOneStatement(
   if (deferFences && lowerer.diagSink === null && lowerer.diags.length > diagsBefore) {
     const flushed = lowerer.diags.splice(diagsBefore);
     const ice = flushed.filter((d) => d.code === "SC9001");
-    lowerer.diags.push(...ice);
-    lowerer.runtimeFences.push(...flushed.filter((d) => d.code !== "SC9001"));
+    for (const d of ice) lowerer.diags.push(d);
+    for (const d of flushed) if (d.code !== "SC9001") lowerer.runtimeFences.push(d);
   }
 }
 
@@ -1222,7 +1222,10 @@ export function predeclareForwardFnDecl(lowerer: Lowerer, symbol: ts.Symbol): bo
       entry.out.push(lowerer.lowerNestedFunctionDecl(decl));
     } catch (e) {
       entry.ctx.hoistedFnDecls.delete(decl);
-      if (previousSink !== null) previousSink.push(...lowerer.diags.splice(diagsBefore));
+      if (previousSink !== null) {
+        const flushed = lowerer.diags.splice(diagsBefore);
+        for (const d of flushed) previousSink.push(d);
+      }
       throw e;
     } finally {
       lowerer.diagSink = previousSink;
diff --git a/packages/compiler/src/frontend/lowering/lowerer.ts b/packages/compiler/src/frontend/lowering/lowerer.ts
index 8b1f54763..3b370e17c 100644
--- a/packages/compiler/src/frontend/lowering/lowerer.ts
+++ b/packages/compiler/src/frontend/lowering/lowerer.ts
@@ -9644,9 +9644,9 @@ export class Lowerer {
     // array-HOF loop functions, which ride the same list), and the
     // implicit-any instances lowered eagerly at their first call sites.
     this.settleSharedHelperLocations([...functions, ...this.liftedFns, ...this.implicitFns]);
-    functions.push(...this.liftedFns);
-    functions.push(...this.implicitFns);
-    functions.push(...runtimeClassConstructs(this, functions));
+    for (const fn of this.liftedFns) functions.push(fn);
+    for (const fn of this.implicitFns) functions.push(fn);
+    for (const fn of runtimeClassConstructs(this, functions)) functions.push(fn);
 
     if (this.remainder) {
       // Deferred collection diagnostics nothing flushed — declarations no
@@ -9933,9 +9933,11 @@ export class Lowerer {
   private reportBlockedBody(decl: ts.FunctionDeclaration): void {
     const diags = blockedBodyDiagnostics(this, decl);
     const symbol = declSymbolOf(this, decl);
-    if (symbol && this.alreadyFlushed.has(symbol))
-      this.reachedBlockedBodyDiagnostics.push(...diags);
-    else for (const d of diags) this.pushDiag(d);
+    if (symbol && this.alreadyFlushed.has(symbol)) {
+      for (const d of diags) this.reachedBlockedBodyDiagnostics.push(d);
+    } else {
+      for (const d of diags) this.pushDiag(d);
+    }
   }
 
   /** Whether run() counts a signature-blocked declaration in
@@ -10647,7 +10649,7 @@ export class Lowerer {
       ...byName(this.liftedFns),
       ...byName(this.implicitFns),
     ];
-    functions.push(...runtimeClassConstructs(this, functions));
+    for (const fn of runtimeClassConstructs(this, functions)) functions.push(fn);
     if (this.regexGroupResults) for (const fn of functions) foldRegexSpanReads(this, fn);
     // The worklist can leave a virtual site with a single implementation.
     // Devirtualize after construction/override reachability has settled.
@@ -10936,10 +10938,10 @@ export class Lowerer {
     }
     const captured = this.diags.splice(diagsBefore);
     if (captured.some((d) => d.code === "SC9001")) {
-      this.diags.push(...captured);
+      for (const d of captured) this.diags.push(d);
       return null;
     }
-    this.runtimeFences.push(...captured);
+    for (const d of captured) this.runtimeFences.push(d);
 
     const fence = this.runtimeFenceStmt(captured[0], node, target.fallback, target.bareMessage);
     const loc = locOf(node);
@@ -11228,7 +11230,7 @@ export class Lowerer {
       .slice(diagsBefore)
       .filter((d) => d.rejects !== undefined || this.loweredOnceDiags.has(d));
     this.diags.length = diagsBefore;
-    this.diags.push(...kept);
+    for (const d of kept) this.diags.push(d);
   }
 
   /** A unit that still fails after its retries commits its first
@@ -11241,7 +11243,8 @@ export class Lowerer {
       d.rejects !== undefined || this.loweredOnceDiags.has(d);
     const kept = this.diags.slice(diagsBefore).filter(carried);
     this.diags.length = diagsBefore;
-    this.diags.push(...first.filter((d) => !carried(d)), ...kept);
+    for (const d of first) if (!carried(d)) this.diags.push(d);
+    for (const d of kept) this.diags.push(d);
   }
 
   /** Lowers one unit whose body-level poison skips it (a generic
diff --git a/packages/compiler/src/frontend/pipeline.ts b/packages/compiler/src/frontend/pipeline.ts
index 25af03106..28133abd5 100644
--- a/packages/compiler/src/frontend/pipeline.ts
+++ b/packages/compiler/src/frontend/pipeline.ts
@@ -455,8 +455,8 @@ function scanDroppedPackages(
       return at !== null && wanted.has(at.name);
     });
     const scanned = scanFiles(load.program, files, { userJs: false, dropped: true, edges: true });
-    into.modules.push(...scanned.modules);
-    into.edges.push(...scanned.edges);
+    for (const module of scanned.modules) into.modules.push(module);
+    for (const edge of scanned.edges) into.edges.push(edge);
   } catch {
     /* report-only detection */
   }
diff --git a/packages/compiler/src/frontend/program.ts b/packages/compiler/src/frontend/program.ts
index 2f8e4deae..56b315638 100644
--- a/packages/compiler/src/frontend/program.ts
+++ b/packages/compiler/src/frontend/program.ts
@@ -977,7 +977,7 @@ function loadProgram7(
       );
       if (extraRoots.length === 0) break;
       program.dispose();
-      programRoots.push(...extraRoots);
+      for (const root of extraRoots) programRoots.push(root);
       program = host.createProgram([...programRoots, overridesDtsPath()], options);
       if (pass === 31) throw new Error("static program-root discovery did not converge");
     }
@@ -4727,7 +4727,7 @@ function cycleReachedDeferredReferences7(
     if (symbol === undefined) continue;
     const units = unitsOfName.get(name)!;
     unitsBySymbol.set(symbol, [...(unitsBySymbol.get(symbol) ?? []), ...units]);
-    allUnits.push(...units);
+    for (const unit of units) allUnits.push(unit);
   }
   // A named class expression's inner name (`class Impl { static x =
   // Impl.m(); }`) names the class inside its own body, as the binding it
@@ -4896,7 +4896,7 @@ export function moduleEarlyBindings(
   const out: CycleEarlyBinding[] = [];
   for (const sf of order) {
     if (sf.isDeclarationFile || exact.has(sf)) continue;
-    out.push(...moduleEarlyBindingsOf7(program, sf, order));
+    for (const binding of moduleEarlyBindingsOf7(program, sf, order)) out.push(binding);
   }
   program.analysis.moduleEarlyBindings = { key, bindings: out };
   return out;