diff --git a/denops/@denops-private/denops.ts b/denops/@denops-private/denops.ts
index dc305af4..a7c073bd 100644
--- a/denops/@denops-private/denops.ts
+++ b/denops/@denops-private/denops.ts
@@ -5,11 +5,14 @@ import {
   type Dispatcher,
   type Meta,
 } from "jsr:@denops/core@^7.0.0";
-import { ensure, is } from "jsr:@core/unknownutil@^3.18.1";
+import { ensure } from "jsr:@core/unknownutil@^4.0.0/ensure";
+import { isTupleOf } from "jsr:@core/unknownutil@^4.0.0/is/tuple-of";
+import { isArray } from "jsr:@core/unknownutil@^4.0.0/is/array";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
 import type { Host as HostOrigin } from "./host.ts";
 import type { Service as ServiceOrigin } from "./service.ts";
 
-const isBatchReturn = is.TupleOf([is.Array, is.String] as const);
+const isBatchReturn = isTupleOf([isArray, isString] as const);
 
 export type Host = Pick<HostOrigin, "redraw" | "call" | "batch">;
 
diff --git a/denops/@denops-private/error.ts b/denops/@denops-private/error.ts
index 96cc0fbb..e8e2cc04 100644
--- a/denops/@denops-private/error.ts
+++ b/denops/@denops-private/error.ts
@@ -1,4 +1,4 @@
-import { is } from "jsr:@core/unknownutil@^3.18.1";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
 import {
   fromErrorObject,
   isErrorObject,
@@ -16,7 +16,7 @@ export function errorSerializer(err: unknown): unknown {
 }
 
 export function errorDeserializer(err: unknown): unknown {
-  if (is.String(err)) {
+  if (isString(err)) {
     const obj = tryOr(() => JSON.parse(err), undefined);
     if (isErrorObject(obj)) {
       return fromErrorObject(obj);
diff --git a/denops/@denops-private/error_test.ts b/denops/@denops-private/error_test.ts
index bef58402..1e9e2508 100644
--- a/denops/@denops-private/error_test.ts
+++ b/denops/@denops-private/error_test.ts
@@ -1,12 +1,12 @@
 import { assert, assertEquals, assertInstanceOf } from "jsr:@std/assert@^1.0.1";
-import { is } from "jsr:@core/unknownutil@^3.18.1";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
 import { errorDeserializer, errorSerializer } from "./error.ts";
 
 Deno.test("errorSerializer", async (t) => {
   await t.step("serializes Error", () => {
     const err = new Error("error message");
     const ret = errorSerializer(err);
-    assert(is.String(ret));
+    assert(isString(ret));
     assertEquals({ ...JSON.parse(ret), stack: "stack" }, {
       attributes: {},
       message: "error message",
@@ -19,7 +19,7 @@ Deno.test("errorSerializer", async (t) => {
   await t.step("serializes String", () => {
     const err = "error message";
     const ret = errorSerializer(err);
-    assert(is.String(ret));
+    assert(isString(ret));
     assertEquals(ret, "error message");
   });
 
@@ -29,7 +29,7 @@ Deno.test("errorSerializer", async (t) => {
       message: "error message",
     };
     const ret = errorSerializer(err);
-    assert(is.String(ret));
+    assert(isString(ret));
     assertEquals(JSON.parse(ret), {
       type: "error",
       message: "error message",
diff --git a/denops/@denops-private/host.ts b/denops/@denops-private/host.ts
index c2ff268d..6ee00434 100644
--- a/denops/@denops-private/host.ts
+++ b/denops/@denops-private/host.ts
@@ -1,4 +1,10 @@
-import { ensure, is, type Predicate } from "jsr:@core/unknownutil@^3.18.1";
+import type { Predicate } from "jsr:@core/unknownutil@^4.0.0/type";
+import { ensure } from "jsr:@core/unknownutil@^4.0.0/ensure";
+import { asOptional } from "jsr:@core/unknownutil@^4.0.0/as/optional";
+import { isArray } from "jsr:@core/unknownutil@^4.0.0/is/array";
+import { isParametersOf } from "jsr:@core/unknownutil@^4.0.0/is/parameters-of";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
+import { isUnknown } from "jsr:@core/unknownutil@^4.0.0/is/unknown";
 
 /**
  * Host (Vim/Neovim) which is visible from Service
@@ -94,15 +100,15 @@ export function invoke(
 }
 
 const serviceMethodArgs = {
-  load: is.ParametersOf([is.String, is.String] as const),
-  unload: is.ParametersOf([is.String] as const),
-  reload: is.ParametersOf([is.String] as const),
-  interrupt: is.ParametersOf([is.OptionalOf(is.Unknown)] as const),
-  dispatch: is.ParametersOf([is.String, is.String, is.Array] as const),
-  dispatchAsync: is.ParametersOf(
-    [is.String, is.String, is.Array, is.String, is.String] as const,
+  load: isParametersOf([isString, isString] as const),
+  unload: isParametersOf([isString] as const),
+  reload: isParametersOf([isString] as const),
+  interrupt: isParametersOf([asOptional(isUnknown)] as const),
+  dispatch: isParametersOf([isString, isString, isArray] as const),
+  dispatchAsync: isParametersOf(
+    [isString, isString, isArray, isString, isString] as const,
   ),
-  close: is.ParametersOf([] as const),
+  close: isParametersOf([] as const),
 } as const satisfies {
   [K in keyof ServiceForInvoke]: Predicate<Parameters<ServiceForInvoke[K]>>;
 };
diff --git a/denops/@denops-private/host/nvim.ts b/denops/@denops-private/host/nvim.ts
index 89f88422..4c70475d 100644
--- a/denops/@denops-private/host/nvim.ts
+++ b/denops/@denops-private/host/nvim.ts
@@ -1,4 +1,10 @@
-import { ensure, is } from "jsr:@core/unknownutil@^3.18.1";
+import { ensure } from "jsr:@core/unknownutil@^4.0.0/ensure";
+import { isArray } from "jsr:@core/unknownutil@^4.0.0/is/array";
+import { isNull } from "jsr:@core/unknownutil@^4.0.0/is/null";
+import { isNumber } from "jsr:@core/unknownutil@^4.0.0/is/number";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
+import { isTupleOf } from "jsr:@core/unknownutil@^4.0.0/is/tuple-of";
+import { isUnionOf } from "jsr:@core/unknownutil@^4.0.0/is/union-of";
 import { Client, Session } from "jsr:@lambdalisue/messagepack-rpc@^2.4.0";
 import { errorDeserializer, errorSerializer } from "../error.ts";
 import { getVersionOr } from "../version.ts";
@@ -27,8 +33,8 @@ export class Neovim implements Host {
         }
         return invoke(
           this.#service,
-          ensure(method, is.String),
-          ensure(args, is.Array),
+          ensure(method, isString),
+          ensure(args, isArray),
         );
       },
 
@@ -130,16 +136,16 @@ export class Neovim implements Host {
 // nvim_call_function throws a special error object
 // https://github.com/neovim/neovim/blob/5dc0bdfe98b59bb03226167ed541d17cc5af30b1/src/nvim/api/vimscript.c#L260
 // https://github.com/neovim/neovim/blob/5dc0bdfe98b59bb03226167ed541d17cc5af30b1/src/nvim/api/private/defs.h#L63-L66
-const isNvimErrorObject = is.TupleOf([is.Number, is.String] as const);
+const isNvimErrorObject = isTupleOf([isNumber, isString] as const);
 
 // nvim_call_atomics returns a tuple of [return values, error details]
-const isNvimCallAtomicReturn = is.TupleOf(
+const isNvimCallAtomicReturn = isTupleOf(
   [
-    is.Array,
-    is.OneOf([
-      is.Null,
+    isArray,
+    isUnionOf([
+      isNull,
       // the index, the error type, the error message
-      is.TupleOf([is.Number, is.Number, is.String] as const),
+      isTupleOf([isNumber, isNumber, isString] as const),
     ]),
   ] as const,
 );
diff --git a/denops/@denops-private/host/vim.ts b/denops/@denops-private/host/vim.ts
index 52d059a8..3c2626a6 100644
--- a/denops/@denops-private/host/vim.ts
+++ b/denops/@denops-private/host/vim.ts
@@ -1,4 +1,9 @@
-import { ensure, is } from "jsr:@core/unknownutil@^3.18.1";
+import { ensure } from "jsr:@core/unknownutil@^4.0.0/ensure";
+import { isArray } from "jsr:@core/unknownutil@^4.0.0/is/array";
+import { isLiteralOf } from "jsr:@core/unknownutil@^4.0.0/is/literal-of";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
+import { isTupleOf } from "jsr:@core/unknownutil@^4.0.0/is/tuple-of";
+import { isUnknown } from "jsr:@core/unknownutil@^4.0.0/is/unknown";
 import {
   Client,
   type Message,
@@ -120,16 +125,16 @@ export class Vim implements Host {
   }
 }
 
-const isCallReturn = is.TupleOf([is.Unknown, is.String] as const);
+const isCallReturn = isTupleOf([isUnknown, isString] as const);
 
-const isBatchReturn = is.TupleOf([is.Array, is.String] as const);
+const isBatchReturn = isTupleOf([isArray, isString] as const);
 
-const isVoidMessage = is.TupleOf([is.LiteralOf("void")] as const);
+const isVoidMessage = isTupleOf([isLiteralOf("void")] as const);
 
-const isInvokeMessage = is.TupleOf(
+const isInvokeMessage = isTupleOf(
   [
-    is.LiteralOf("invoke"),
-    is.String,
-    is.Array,
+    isLiteralOf("invoke"),
+    isString,
+    isArray,
   ] as const,
 );
diff --git a/denops/@denops-private/host_test.ts b/denops/@denops-private/host_test.ts
index 050d9b8d..ea2f644e 100644
--- a/denops/@denops-private/host_test.ts
+++ b/denops/@denops-private/host_test.ts
@@ -4,7 +4,7 @@ import {
   assertSpyCalls,
   stub,
 } from "jsr:@std/testing@^1.0.0-rc.5/mock";
-import { AssertError } from "jsr:@core/unknownutil@^3.18.1";
+import { AssertError } from "jsr:@core/unknownutil@^4.0.0/assert";
 import { unimplemented } from "jsr:@lambdalisue/errorutil@^1.1.0";
 import { invoke, type Service } from "./host.ts";
 
diff --git a/denops/@denops-private/util.ts b/denops/@denops-private/util.ts
index 1e12b1b3..fb407e27 100644
--- a/denops/@denops-private/util.ts
+++ b/denops/@denops-private/util.ts
@@ -1,9 +1,12 @@
 import type { Meta } from "jsr:@denops/core@^7.0.0";
-import { is, type Predicate } from "jsr:@core/unknownutil@^3.18.1";
+import type { Predicate } from "jsr:@core/unknownutil@^4.0.0/type";
+import { isLiteralOneOf } from "jsr:@core/unknownutil@^4.0.0/is/literal-one-of";
+import { isObjectOf } from "jsr:@core/unknownutil@^4.0.0/is/object-of";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
 
-export const isMeta: Predicate<Meta> = is.ObjectOf({
-  mode: is.LiteralOneOf(["release", "debug", "test"] as const),
-  host: is.LiteralOneOf(["vim", "nvim"] as const),
-  version: is.String,
-  platform: is.LiteralOneOf(["windows", "mac", "linux"] as const),
+export const isMeta: Predicate<Meta> = isObjectOf({
+  mode: isLiteralOneOf(["release", "debug", "test"] as const),
+  host: isLiteralOneOf(["vim", "nvim"] as const),
+  version: isString,
+  platform: isLiteralOneOf(["windows", "mac", "linux"] as const),
 });
diff --git a/denops/@denops-private/version_test.ts b/denops/@denops-private/version_test.ts
index 53195019..621fcadb 100644
--- a/denops/@denops-private/version_test.ts
+++ b/denops/@denops-private/version_test.ts
@@ -1,7 +1,12 @@
 import { assert, assertEquals } from "jsr:@std/assert@^1.0.1";
 import { resolvesNext, stub } from "jsr:@std/testing@^1.0.0-rc.5/mock";
 import type { SemVer } from "jsr:@std/semver@^0.224.3/types";
-import { is, type Predicate } from "jsr:@core/unknownutil@^3.18.1";
+import type { Predicate } from "jsr:@core/unknownutil@^4.0.0/type";
+import { isArrayOf } from "jsr:@core/unknownutil@^4.0.0/is/array-of";
+import { isNumber } from "jsr:@core/unknownutil@^4.0.0/is/number";
+import { isObjectOf } from "jsr:@core/unknownutil@^4.0.0/is/object-of";
+import { isString } from "jsr:@core/unknownutil@^4.0.0/is/string";
+import { isUnionOf } from "jsr:@core/unknownutil@^4.0.0/is/union-of";
 import { getVersionOr } from "./version.ts";
 
 Deno.test("getVersionOr()", async (t) => {
@@ -53,12 +58,12 @@ Deno.test("getVersionOr()", async (t) => {
   });
 });
 
-const isSemVer = is.ObjectOf({
-  major: is.Number,
-  minor: is.Number,
-  patch: is.Number,
-  prerelease: is.ArrayOf(is.UnionOf([is.String, is.Number])),
-  build: is.ArrayOf(is.String),
+const isSemVer = isObjectOf({
+  major: isNumber,
+  minor: isNumber,
+  patch: isNumber,
+  prerelease: isArrayOf(isUnionOf([isString, isNumber])),
+  build: isArrayOf(isString),
 }) satisfies Predicate<SemVer>;
 
 async function isInsideWorkTree(): Promise<boolean> {
diff --git a/denops/@denops-private/worker.ts b/denops/@denops-private/worker.ts
index 5902655a..4902ba97 100644
--- a/denops/@denops-private/worker.ts
+++ b/denops/@denops-private/worker.ts
@@ -5,7 +5,7 @@ import {
   readableStreamFromWorker,
   writableStreamFromWorker,
 } from "jsr:@lambdalisue/workerio@^4.0.1";
-import { ensure } from "jsr:@core/unknownutil@^3.18.1";
+import { ensure } from "jsr:@core/unknownutil@^4.0.0/ensure";
 import { pop } from "jsr:@lambdalisue/streamtools@^1.0.0";
 import { asyncSignal } from "jsr:@milly/async-signal@^1.0.0";
 import type { Meta } from "jsr:@denops/core@^7.0.0";