diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 939a092..e26aaa9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,6 +16,7 @@ jobs:
           - '18'
           - '20'
           - '22'
+          - '24'
     steps:
     - uses: actions/checkout@v4
     - name: Setup Node.js ${{ matrix.node-version }}
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 406131c..578c615 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -19,7 +19,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v3
diff --git a/.github/workflows/fuzz.yml b/.github/workflows/fuzz.yml
index 0bcacca..79f9e5c 100644
--- a/.github/workflows/fuzz.yml
+++ b/.github/workflows/fuzz.yml
@@ -14,12 +14,12 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Setup Node.js
-      uses: actions/setup-node@v2
+      uses: actions/setup-node@v4
       with:
         cache: npm
-        node-version: "18"
+        node-version: "20"
 
     # npm@9 may fail with https://github.com/npm/cli/issues/6723
     # npm@10 may fail with "GitFetcher requires an Arborist constructor to pack a tarball"
diff --git a/eslint.config.mjs b/eslint.config.mjs
index 3d5529e..0af8fa6 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -11,112 +11,141 @@ import { FlatCompat } from "@eslint/eslintrc";
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
 const compat = new FlatCompat({
-    baseDirectory: __dirname,
-    recommendedConfig: js.configs.recommended,
-    allConfig: js.configs.all
+  baseDirectory: __dirname,
+  recommendedConfig: js.configs.recommended,
+  allConfig: js.configs.all,
 });
 
-export default [{
+export default [
+  {
     ignores: ["**/*.js", "test/deno*", "test/bun*"],
-}, ...fixupConfigRules(compat.extends(
-    "eslint:recommended",
-    "plugin:@typescript-eslint/recommended",
-    "plugin:import/recommended",
-    "plugin:import/typescript",
-    "prettier",
-)), {
+  },
+  ...fixupConfigRules(
+    compat.extends(
+      "eslint:recommended",
+      "plugin:@typescript-eslint/recommended",
+      "plugin:import/recommended",
+      "plugin:import/typescript",
+      "prettier",
+    ),
+  ),
+  {
     plugins: {
-        "@typescript-eslint": fixupPluginRules(typescriptEslintEslintPlugin),
-        tsdoc,
+      "@typescript-eslint": fixupPluginRules(typescriptEslintEslintPlugin),
+      tsdoc,
     },
 
     languageOptions: {
-        parser: tsParser,
-        ecmaVersion: 5,
-        sourceType: "script",
+      parser: tsParser,
+      ecmaVersion: 5,
+      sourceType: "script",
 
-        parserOptions: {
-            project: "./tsconfig.json",
-        },
+      parserOptions: {
+        project: "./tsconfig.json",
+      },
     },
 
     settings: {},
 
     rules: {
-        "no-constant-condition": ["warn", {
-            checkLoops: false,
-        }],
+      "no-constant-condition": [
+        "warn",
+        {
+          checkLoops: false,
+        },
+      ],
 
-        "no-useless-escape": "warn",
-        "no-console": "warn",
-        "no-var": "warn",
-        "no-return-await": "warn",
-        "prefer-const": "warn",
-        "guard-for-in": "warn",
-        curly: "warn",
-        "no-param-reassign": "warn",
-        "prefer-spread": "warn",
-        "import/no-unresolved": "off",
-        "import/no-cycle": "error",
-        "import/no-default-export": "warn",
-        "tsdoc/syntax": "warn",
-        "@typescript-eslint/await-thenable": "warn",
+      "no-useless-escape": "warn",
+      "no-console": "warn",
+      "no-var": "warn",
+      "no-return-await": "warn",
+      "prefer-const": "warn",
+      "guard-for-in": "warn",
+      curly: "warn",
+      "no-param-reassign": "warn",
+      "prefer-spread": "warn",
+      "import/no-unresolved": "off",
+      "import/no-cycle": "error",
+      "import/no-default-export": "warn",
+      "tsdoc/syntax": "warn",
+      "@typescript-eslint/await-thenable": "warn",
 
-        "@typescript-eslint/array-type": ["warn", {
-            default: "generic",
-        }],
+      "@typescript-eslint/array-type": [
+        "warn",
+        {
+          default: "generic",
+        },
+      ],
 
-        "@typescript-eslint/naming-convention": ["warn", {
-            selector: "default",
-            format: ["camelCase", "UPPER_CASE", "PascalCase"],
-            leadingUnderscore: "allow",
-        }, {
-            selector: "typeLike",
-            format: ["PascalCase"],
-            leadingUnderscore: "allow",
-        }],
+      "@typescript-eslint/naming-convention": [
+        "warn",
+        {
+          selector: "default",
+          format: ["camelCase", "UPPER_CASE", "PascalCase"],
+          leadingUnderscore: "allow",
+        },
+        {
+          selector: "typeLike",
+          format: ["PascalCase"],
+          leadingUnderscore: "allow",
+        },
+      ],
 
-        "@typescript-eslint/restrict-plus-operands": "warn",
-        //"@typescript-eslint/no-throw-literal": "warn",
-        "@typescript-eslint/unbound-method": "warn",
-        "@typescript-eslint/explicit-module-boundary-types": "warn",
-        //"@typescript-eslint/no-extra-semi": "warn",
-        "@typescript-eslint/no-extra-non-null-assertion": "warn",
+      "@typescript-eslint/restrict-plus-operands": "warn",
+      //"@typescript-eslint/no-throw-literal": "warn",
+      "@typescript-eslint/unbound-method": "warn",
+      "@typescript-eslint/explicit-module-boundary-types": "warn",
+      //"@typescript-eslint/no-extra-semi": "warn",
+      "@typescript-eslint/no-extra-non-null-assertion": "warn",
 
-        "@typescript-eslint/no-unused-vars": ["warn", {
-            argsIgnorePattern: "^_",
-        }],
+      "@typescript-eslint/no-unused-vars": [
+        "warn",
+        {
+          argsIgnorePattern: "^_",
+        },
+      ],
 
-        "@typescript-eslint/no-use-before-define": "warn",
-        "@typescript-eslint/no-for-in-array": "warn",
-        "@typescript-eslint/no-unsafe-argument": "warn",
-        "@typescript-eslint/no-unsafe-call": "warn",
+      "@typescript-eslint/no-use-before-define": "warn",
+      "@typescript-eslint/no-for-in-array": "warn",
+      "@typescript-eslint/no-unsafe-argument": "warn",
+      "@typescript-eslint/no-unsafe-call": "warn",
 
-        "@typescript-eslint/no-unnecessary-condition": ["warn", {
-            allowConstantLoopConditions: true,
-        }],
+      "@typescript-eslint/no-unnecessary-condition": [
+        "warn",
+        {
+          allowConstantLoopConditions: true,
+        },
+      ],
 
-        "@typescript-eslint/no-unnecessary-type-constraint": "warn",
-        "@typescript-eslint/no-implied-eval": "warn",
-        "@typescript-eslint/no-non-null-asserted-optional-chain": "warn",
-        "@typescript-eslint/no-invalid-void-type": "warn",
-        "@typescript-eslint/no-loss-of-precision": "warn",
-        "@typescript-eslint/no-confusing-void-expression": "warn",
-        "@typescript-eslint/no-redundant-type-constituents": "warn",
-        "@typescript-eslint/prefer-for-of": "warn",
-        "@typescript-eslint/prefer-includes": "warn",
-        "@typescript-eslint/prefer-string-starts-ends-with": "warn",
-        "@typescript-eslint/prefer-readonly": "warn",
-        "@typescript-eslint/prefer-regexp-exec": "warn",
-        "@typescript-eslint/prefer-nullish-coalescing": "warn",
-        "@typescript-eslint/prefer-optional-chain": "warn",
-        "@typescript-eslint/prefer-ts-expect-error": "warn",
-        "@typescript-eslint/indent": "off",
-        "@typescript-eslint/no-explicit-any": "off",
-        "@typescript-eslint/no-empty-interface": "off",
-        "@typescript-eslint/no-empty-function": "off",
-        "@typescript-eslint/no-var-requires": "off",
-        "@typescript-eslint/no-non-null-assertion": "off",
-        "@typescript-eslint/ban-ts-comment": "off",
+      "@typescript-eslint/no-unnecessary-type-constraint": "warn",
+      "@typescript-eslint/no-implied-eval": "warn",
+      "@typescript-eslint/no-non-null-asserted-optional-chain": "warn",
+      "@typescript-eslint/no-invalid-void-type": "warn",
+      "@typescript-eslint/no-loss-of-precision": "warn",
+      "@typescript-eslint/no-confusing-void-expression": "warn",
+      "@typescript-eslint/no-redundant-type-constituents": "warn",
+      "@typescript-eslint/prefer-for-of": "warn",
+      "@typescript-eslint/prefer-includes": "warn",
+      "@typescript-eslint/prefer-string-starts-ends-with": "warn",
+      "@typescript-eslint/prefer-readonly": "warn",
+      "@typescript-eslint/prefer-regexp-exec": "warn",
+      "@typescript-eslint/prefer-nullish-coalescing": "warn",
+      "@typescript-eslint/prefer-optional-chain": "warn",
+      "@typescript-eslint/prefer-ts-expect-error": "warn",
+      "@typescript-eslint/consistent-type-imports": [
+        "error",
+        {
+          prefer: "type-imports",
+          disallowTypeAnnotations: false,
+        },
+      ],
+      "@typescript-eslint/indent": "off",
+      "@typescript-eslint/no-explicit-any": "off",
+      "@typescript-eslint/no-empty-interface": "off",
+      "@typescript-eslint/no-empty-function": "off",
+      "@typescript-eslint/no-var-requires": "off",
+      "@typescript-eslint/no-non-null-assertion": "off",
+      "@typescript-eslint/ban-ts-comment": "off",
     },
-}];
+  },
+];
diff --git a/src/CachedKeyDecoder.ts b/src/CachedKeyDecoder.ts
index 73524f0..0de4a7d 100644
--- a/src/CachedKeyDecoder.ts
+++ b/src/CachedKeyDecoder.ts
@@ -16,8 +16,8 @@ export class CachedKeyDecoder implements KeyDecoder {
   hit = 0;
   miss = 0;
   private readonly caches: Array<Array<KeyCacheRecord>>;
-  private readonly maxKeyLength: number;
-  private readonly maxLengthPerKey: number;
+  readonly maxKeyLength: number;
+  readonly maxLengthPerKey: number;
 
   constructor(maxKeyLength = DEFAULT_MAX_KEY_LENGTH, maxLengthPerKey = DEFAULT_MAX_LENGTH_PER_KEY) {
     this.maxKeyLength = maxKeyLength;
diff --git a/src/Decoder.ts b/src/Decoder.ts
index 9239dd1..bba8804 100644
--- a/src/Decoder.ts
+++ b/src/Decoder.ts
@@ -1,11 +1,13 @@
 import { prettyByte } from "./utils/prettyByte.ts";
-import { ExtensionCodec, ExtensionCodecType } from "./ExtensionCodec.ts";
+import { ExtensionCodec } from "./ExtensionCodec.ts";
 import { getInt64, getUint64, UINT32_MAX } from "./utils/int.ts";
 import { utf8Decode } from "./utils/utf8.ts";
 import { ensureUint8Array } from "./utils/typedArrays.ts";
-import { CachedKeyDecoder, KeyDecoder } from "./CachedKeyDecoder.ts";
+import { CachedKeyDecoder } from "./CachedKeyDecoder.ts";
 import { DecodeError } from "./DecodeError.ts";
 import type { ContextOf } from "./context.ts";
+import type { ExtensionCodecType } from "./ExtensionCodec.ts";
+import type { KeyDecoder } from "./CachedKeyDecoder.ts";
 
 export type DecoderOptions<ContextType = undefined> = Readonly<
   Partial<{
@@ -70,7 +72,7 @@ export type DecoderOptions<ContextType = undefined> = Readonly<
 
     /**
      * A function to convert decoded map key to a valid JS key type.
-     * 
+     *
      * Defaults to a function that throws an error if the key is not a string or a number.
      */
     mapKeyConverter: (key: unknown) => MapKeyType;
diff --git a/src/Encoder.ts b/src/Encoder.ts
index ffb4f6b..43fcd8f 100644
--- a/src/Encoder.ts
+++ b/src/Encoder.ts
@@ -1,9 +1,10 @@
 import { utf8Count, utf8Encode } from "./utils/utf8.ts";
-import { ExtensionCodec, ExtensionCodecType } from "./ExtensionCodec.ts";
+import { ExtensionCodec } from "./ExtensionCodec.ts";
 import { setInt64, setUint64 } from "./utils/int.ts";
 import { ensureUint8Array } from "./utils/typedArrays.ts";
 import type { ExtData } from "./ExtData.ts";
 import type { ContextOf } from "./context.ts";
+import type { ExtensionCodecType } from "./ExtensionCodec.ts";
 
 export const DEFAULT_MAX_DEPTH = 100;
 export const DEFAULT_INITIAL_BUFFER_SIZE = 2048;