diff --git a/package.json b/package.json
index 92aacd9..fbcafae 100644
--- a/package.json
+++ b/package.json
@@ -11,7 +11,7 @@
   "scripts": {
     "check": "pnpm lint && pnpm test && pnpm typecheck && pnpm check:skill-assets",
     "lint": "oxlint src",
-    "test": "tsx src/rules/require-readable-spacing.test.ts && tsx src/rules/require-readable-spacing-cli.test.ts && tsx src/rules/no-array-filter-map.test.ts && tsx src/rules/no-reduce-accumulator-copy.test.ts && tsx src/rules/no-chained-type-assertions.test.ts && tsx src/rules/no-conditional-empty-object-spread.test.ts && tsx src/rules/no-unsafe-dictionary-type.test.ts && tsx src/rules/no-known-value-widening.test.ts && tsx src/rules/no-object-parameters.test.ts && tsx src/rules/no-unknown-parameters.test.ts && tsx src/rules/no-runtime-typeof.test.ts && tsx src/rules/no-shape-in-symbol-names.test.ts && tsx src/rules/no-unknown-returns.test.ts && tsx src/rules/no-unknown-type-aliases.test.ts && tsx src/rules/no-widen-then-assert.test.ts && tsx src/rules/no-reflect-get.test.ts && tsx src/rules/no-reflect-apply.test.ts && tsx src/rules/no-module-mocking.test.ts && tsx src/rules/require-safety-comment-for-type-assertion.test.ts && tsx src/effect/rules/no-service-constructor-imports.test.ts && tsx src/effect/rules/no-manual-tag-comparison.test.ts && tsx src/effect/rules/no-manual-effect-error-tag.test.ts && tsx src/effect/rules/no-manual-tagged-construction.test.ts && tsx src/effect/rules/prefer-effect-match.test.ts",
+    "test": "tsx src/rules/require-readable-spacing.test.ts && tsx src/rules/require-readable-spacing-cli.test.ts && tsx src/rules/no-array-filter-map.test.ts && tsx src/rules/no-reduce-accumulator-copy.test.ts && tsx src/rules/no-chained-type-assertions.test.ts && tsx src/rules/no-conditional-empty-object-spread.test.ts && tsx src/rules/no-unsafe-dictionary-type.test.ts && tsx src/rules/no-known-value-widening.test.ts && tsx src/rules/no-object-parameters.test.ts && tsx src/rules/no-unknown-parameters.test.ts && tsx src/rules/no-runtime-typeof.test.ts && tsx src/rules/no-shape-in-symbol-names.test.ts && tsx src/rules/no-unknown-returns.test.ts && tsx src/rules/no-unknown-type-aliases.test.ts && tsx src/rules/no-widen-then-assert.test.ts && tsx src/rules/no-widen-then-assert-cli.test.ts && tsx src/rules/no-reflect-get.test.ts && tsx src/rules/no-reflect-apply.test.ts && tsx src/rules/no-module-mocking.test.ts && tsx src/rules/require-safety-comment-for-type-assertion.test.ts && tsx src/effect/rules/no-service-constructor-imports.test.ts && tsx src/effect/rules/no-manual-tag-comparison.test.ts && tsx src/effect/rules/no-manual-effect-error-tag.test.ts && tsx src/effect/rules/no-manual-tagged-construction.test.ts && tsx src/effect/rules/prefer-effect-match.test.ts",
     "typecheck": "tsc --noEmit",
     "sync:skill-assets": "node scripts/sync-skill-assets.mjs",
     "check:skill-assets": "node scripts/sync-skill-assets.mjs --check"
diff --git a/skills/install-anti-slop/assets/anti-slop/rules/no-widen-then-assert.ts b/skills/install-anti-slop/assets/anti-slop/rules/no-widen-then-assert.ts
index c5e07f7..5b1c696 100644
--- a/skills/install-anti-slop/assets/anti-slop/rules/no-widen-then-assert.ts
+++ b/skills/install-anti-slop/assets/anti-slop/rules/no-widen-then-assert.ts
@@ -325,15 +325,16 @@ export const noWidenThenAssertRule = defineRule({
     },
   },
   createOnce(context) {
-    let scopes: Parameters<typeof resolvedVariableForIdentifier>[0] = [];
+    let scopes: Parameters<typeof resolvedVariableForIdentifier>[0] | null = null;
 
     const checkAssertion = (node: ESTree.TSAsExpression | ESTree.TSTypeAssertion) => {
       const expression = assertedExpression(node);
       if (expression.type !== "Identifier") return;
 
-      const variable = resolvedVariableForIdentifier(scopes, expression);
+      const fileScopes = (scopes ??= context.sourceCode.scopeManager.scopes);
+      const variable = resolvedVariableForIdentifier(fileScopes, expression);
       if (variable === null) return;
-      const widened = widenedBinding(variable, scopes);
+      const widened = widenedBinding(variable, fileScopes);
       if (
         widened === null ||
         node.start <= widened.declaredAt ||
@@ -357,7 +358,7 @@ export const noWidenThenAssertRule = defineRule({
 
     return {
       Program() {
-        scopes = context.sourceCode.scopeManager.scopes;
+        scopes = null;
       },
       TSAsExpression: checkAssertion,
       TSTypeAssertion: checkAssertion,
diff --git a/src/rules/no-widen-then-assert-cli.test.ts b/src/rules/no-widen-then-assert-cli.test.ts
new file mode 100644
index 0000000..42d7db9
--- /dev/null
+++ b/src/rules/no-widen-then-assert-cli.test.ts
@@ -0,0 +1,43 @@
+/// <reference types="node" />
+
+import assert from "node:assert/strict";
+import { spawnSync } from "node:child_process";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { basename, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const probeRoot = mkdtempSync(join(tmpdir(), "anti-slop-widen-"));
+const config = join(probeRoot, "oxlint.json");
+const first = join(probeRoot, "first.ts");
+const second = join(probeRoot, "second.ts");
+const violation =
+  "const source = { id: 'a' }; const widened: unknown = source; export const parsed = widened as { readonly id: string };\n";
+
+try {
+  writeFileSync(
+    config,
+    JSON.stringify({
+      jsPlugins: [
+        { name: "anti-slop", specifier: fileURLToPath(new URL("../index.ts", import.meta.url)) },
+      ],
+      rules: { "anti-slop/no-widen-then-assert": "error" },
+    }),
+  );
+  // Scopes are read lazily and cached per file; offsets differ so a stale cache cannot resolve.
+  writeFileSync(first, violation);
+  writeFileSync(second, `export const padding = 0;\n${violation}`);
+
+  const result = spawnSync(
+    "pnpm",
+    ["exec", "oxlint", "--config", config, "--threads", "1", "--format", "json", first, second],
+    { encoding: "utf8" },
+  );
+  const { diagnostics } = JSON.parse(result.stdout) as { diagnostics: { filename: string }[] };
+  assert.deepEqual(diagnostics.map(({ filename }) => basename(filename)).sort(), [
+    "first.ts",
+    "second.ts",
+  ]);
+} finally {
+  rmSync(probeRoot, { recursive: true, force: true });
+}
diff --git a/src/rules/no-widen-then-assert.ts b/src/rules/no-widen-then-assert.ts
index c5e07f7..5b1c696 100644
--- a/src/rules/no-widen-then-assert.ts
+++ b/src/rules/no-widen-then-assert.ts
@@ -325,15 +325,16 @@ export const noWidenThenAssertRule = defineRule({
     },
   },
   createOnce(context) {
-    let scopes: Parameters<typeof resolvedVariableForIdentifier>[0] = [];
+    let scopes: Parameters<typeof resolvedVariableForIdentifier>[0] | null = null;
 
     const checkAssertion = (node: ESTree.TSAsExpression | ESTree.TSTypeAssertion) => {
       const expression = assertedExpression(node);
       if (expression.type !== "Identifier") return;
 
-      const variable = resolvedVariableForIdentifier(scopes, expression);
+      const fileScopes = (scopes ??= context.sourceCode.scopeManager.scopes);
+      const variable = resolvedVariableForIdentifier(fileScopes, expression);
       if (variable === null) return;
-      const widened = widenedBinding(variable, scopes);
+      const widened = widenedBinding(variable, fileScopes);
       if (
         widened === null ||
         node.start <= widened.declaredAt ||
@@ -357,7 +358,7 @@ export const noWidenThenAssertRule = defineRule({
 
     return {
       Program() {
-        scopes = context.sourceCode.scopeManager.scopes;
+        scopes = null;
       },
       TSAsExpression: checkAssertion,
       TSTypeAssertion: checkAssertion,