diff --git a/apps/desktop/scripts/vite-workspace-packages.test.mjs b/apps/desktop/scripts/vite-workspace-packages.test.mjs
index 6b54f44fe2..ed7c711fb1 100644
--- a/apps/desktop/scripts/vite-workspace-packages.test.mjs
+++ b/apps/desktop/scripts/vite-workspace-packages.test.mjs
@@ -79,3 +79,28 @@ test('renderer loads a newly exported workspace module after its manifest change
   }
   throw failure;
 });
+
+test('renderer-facing Runtime Host protocol does not load Node crypto', async (t) => {
+  const repoRoot = await realpath(new URL('../../..', import.meta.url));
+  const root = join(repoRoot, 'apps/desktop/src/renderer');
+  const server = await createServer({
+    configFile: false,
+    root,
+    logLevel: 'silent',
+    server: { host: '127.0.0.1', port: 0 },
+    optimizeDeps: { noDiscovery: true, include: [] },
+    plugins: [workspacePackagesPlugin(repoRoot)],
+  });
+  t.after(() => server.close());
+  await server.listen();
+
+  const protocolModule = join(
+    repoRoot,
+    'packages/runtime-host/dist/protocol/client-capability.js',
+  );
+  const response = await fetch(`${server.resolvedUrls.local[0]}@fs/${protocolModule}`);
+  const transformed = await response.text();
+
+  assert.equal(response.status, 200, transformed);
+  assert.doesNotMatch(transformed, /vite-browser-external:node:crypto/u);
+});
diff --git a/apps/desktop/src/main/runtime-host-boot.ts b/apps/desktop/src/main/runtime-host-boot.ts
index 69c98b496c..8c49cf8813 100644
--- a/apps/desktop/src/main/runtime-host-boot.ts
+++ b/apps/desktop/src/main/runtime-host-boot.ts
@@ -64,7 +64,8 @@ import {
   openRuntimeHostPeerEndpointOwner,
   type RuntimeHostPeerEndpointOwner,
 } from '@maka/runtime-host/peer-reachability';
-import { clientCapabilityEntityId, type WorkspaceTarget } from "@maka/runtime-host/protocol";
+import { clientCapabilityEntityId } from "@maka/runtime-host/client-capability-entity-id";
+import type { WorkspaceTarget } from "@maka/runtime-host/protocol";
 import { runtimeHostProfileUsesHostWorkspace } from "@maka/runtime-host/profile-kind";
 import { createCredentialMcpOAuthStorage, McpClientManager } from "@maka/mcp";
 import { createWorkBoardStore } from "@maka/storage/work-board-store";
diff --git a/apps/desktop/src/main/runtime-host-native-capabilities.ts b/apps/desktop/src/main/runtime-host-native-capabilities.ts
index ad6698a2b9..a4df30f0f1 100644
--- a/apps/desktop/src/main/runtime-host-native-capabilities.ts
+++ b/apps/desktop/src/main/runtime-host-native-capabilities.ts
@@ -30,7 +30,6 @@ import {
   CLIENT_CAPABILITY_MAX_OFFERS,
   CLIENT_CAPABILITY_MAX_TOOLS,
   CLIENT_CAPABILITY_MAX_TOOLS_PER_OFFER,
-  clientCapabilityEntityId,
   decodeClientCapabilityReplaceInput,
   decodeClientCapabilityToolDescriptor,
   type ClientCapabilityCallFrame,
@@ -42,6 +41,7 @@ import {
   type ClientCapabilityServiceOffer,
   type ClientCapabilityToolDescriptor,
 } from "@maka/runtime-host/protocol";
+import { clientCapabilityEntityId } from "@maka/runtime-host/client-capability-entity-id";
 import { toJSONSchema, z } from "zod";
 import { withBrowserOriginAdmission } from './browser/browser-origin-admission.js';
 import type { DesktopTargetScope } from '../shared/runtime-host-identity.js';
diff --git a/packages/cli/src/mcp-capability-provider.ts b/packages/cli/src/mcp-capability-provider.ts
index 99c2fae840..92f331fd58 100644
--- a/packages/cli/src/mcp-capability-provider.ts
+++ b/packages/cli/src/mcp-capability-provider.ts
@@ -21,10 +21,10 @@ import { createHash } from 'node:crypto';
 import type { McpBoundTool, McpToolBinding } from '@maka/core/mcp';
 import type { McpClientManager } from '@maka/mcp';
 import type { ClientCapabilityProvider } from '@maka/runtime-host/client';
+import { clientCapabilityEntityId } from '@maka/runtime-host/client-capability-entity-id';
 import {
   CLIENT_CAPABILITY_MAX_TOOLS,
   CLIENT_CAPABILITY_MAX_TOOLS_PER_OFFER,
-  clientCapabilityEntityId,
   decodeClientCapabilityReplaceInput,
   type ClientCapabilityCallResult,
   type ClientCapabilityOffer,
diff --git a/packages/runtime-host/package.json b/packages/runtime-host/package.json
index 75a7a3f099..bd2aa832a2 100644
--- a/packages/runtime-host/package.json
+++ b/packages/runtime-host/package.json
@@ -9,6 +9,7 @@
     "./adapter": "./dist/adapter/index.js",
     "./protocol": "./dist/protocol/index.js",
     "./client": "./dist/client/index.js",
+    "./client-capability-entity-id": "./dist/client-capability-entity-id.js",
     "./webrtc-stun-policy": "./dist/webrtc-stun-policy.js",
     "./peer-reachability": "./dist/peer-reachability/index.js",
     "./peer-mesh": "./dist/peer-mesh/index.js",
diff --git a/packages/runtime-host/protocol-compatible-changes/client-capability-entity-id-boundary.json b/packages/runtime-host/protocol-compatible-changes/client-capability-entity-id-boundary.json
new file mode 100644
index 0000000000..64d35cacb5
--- /dev/null
+++ b/packages/runtime-host/protocol-compatible-changes/client-capability-entity-id-boundary.json
@@ -0,0 +1,5 @@
+{
+  "epoch": 109,
+  "files": ["packages/runtime-host/src/protocol/client-capability.ts"],
+  "reason": "Moves the Node-only clientCapabilityEntityId helper out of the browser-facing protocol module (#4700). Wire shape, validation limits, and error behavior are unchanged; older and newer peers decode identical frames."
+}
diff --git a/packages/runtime-host/src/client-capability-entity-id.ts b/packages/runtime-host/src/client-capability-entity-id.ts
new file mode 100644
index 0000000000..12460fe4ef
--- /dev/null
+++ b/packages/runtime-host/src/client-capability-entity-id.ts
@@ -0,0 +1,28 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { createHash } from 'node:crypto';
+
+/** Normalize an arbitrary Client Capability identity into a wire-safe entity id. */
+export function clientCapabilityEntityId(value: string, maxLength = 128): string {
+  if (/^[A-Za-z0-9_-]+$/u.test(value) && value.length <= maxLength) return value;
+  const label = value.replace(/[^A-Za-z0-9_-]+/gu, '_').slice(0, maxLength - 25) || 'mcp';
+  const digest = createHash('sha256').update(value).digest('hex').slice(0, 24);
+  return `${label}_${digest}`;
+}
diff --git a/packages/runtime-host/src/protocol/client-capability.ts b/packages/runtime-host/src/protocol/client-capability.ts
index 9e9c43c535..924cf66462 100644
--- a/packages/runtime-host/src/protocol/client-capability.ts
+++ b/packages/runtime-host/src/protocol/client-capability.ts
@@ -17,7 +17,6 @@
  * under the License.
  */
 
-import { createHash } from 'node:crypto';
 import { TOOL_ACTIVITY_KINDS, type ToolActivityKind } from '@maka/core/events';
 import {
   decodeInteractionAnswer,
@@ -85,18 +84,6 @@ export const CLIENT_CAPABILITY_MAX_OFFERS = 32;
 export const CLIENT_CAPABILITY_MAX_SERVICES = 32;
 export const CLIENT_CAPABILITY_MAX_TOOLS_PER_OFFER = 64;
 
-/**
- * Normalize an arbitrary Client Capability identity (an MCP server id or tool
- * name from user configuration) into a wire-safe entity id: identities that
- * already fit pass through unchanged, anything else becomes a readable label
- * plus a collision-proof digest of the original value.
- */
-export function clientCapabilityEntityId(value: string, maxLength = 128): string {
-  if (/^[A-Za-z0-9_-]+$/u.test(value) && value.length <= maxLength) return value;
-  const label = value.replace(/[^A-Za-z0-9_-]+/gu, '_').slice(0, maxLength - 25) || 'mcp';
-  const digest = createHash('sha256').update(value).digest('hex').slice(0, 24);
-  return `${label}_${digest}`;
-}
 export const CLIENT_CAPABILITY_MAX_TOOLS = 256;
 export const CLIENT_CAPABILITY_MAX_MANIFEST_BYTES = 56 * 1024;
 export const CLIENT_CAPABILITY_MAX_RESULT_BYTES = 24 * 1024 * 1024;