diff --git a/codex-cli/build.mjs b/codex-cli/build.mjs
index 465e8b92..16664d76 100644
--- a/codex-cli/build.mjs
+++ b/codex-cli/build.mjs
@@ -72,6 +72,9 @@ if (isDevBuild) {
 esbuild
   .build({
     entryPoints: ["src/cli.tsx"],
+    // Do not bundle the contents of package.json at build time: always read it
+    // at runtime.
+    external: ["../package.json"],
     bundle: true,
     format: "esm",
     platform: "node",
diff --git a/codex-cli/src/app.tsx b/codex-cli/src/app.tsx
index 5d859db5..3f84935c 100644
--- a/codex-cli/src/app.tsx
+++ b/codex-cli/src/app.tsx
@@ -1,12 +1,13 @@
 import type { ApprovalPolicy } from "./approvals";
 import type { AppConfig } from "./utils/config";
+import type { TerminalChatSession } from "./utils/session.js";
 import type { ResponseItem } from "openai/resources/responses/responses";
 
 import TerminalChat from "./components/chat/terminal-chat";
 import TerminalChatPastRollout from "./components/chat/terminal-chat-past-rollout";
 import { checkInGit } from "./utils/check-in-git";
-import { CLI_VERSION, type TerminalChatSession } from "./utils/session.js";
 import { onExit } from "./utils/terminal";
+import { CLI_VERSION } from "./version";
 import { ConfirmInput } from "@inkjs/ui";
 import { Box, Text, useApp, useStdin } from "ink";
 import React, { useMemo, useState } from "react";
diff --git a/codex-cli/src/components/chat/terminal-chat-input.tsx b/codex-cli/src/components/chat/terminal-chat-input.tsx
index 819b8ea3..e22ec82e 100644
--- a/codex-cli/src/components/chat/terminal-chat-input.tsx
+++ b/codex-cli/src/components/chat/terminal-chat-input.tsx
@@ -584,7 +584,7 @@ export default function TerminalChatInput({
 
         try {
           const os = await import("node:os");
-          const { CLI_VERSION } = await import("../../utils/session.js");
+          const { CLI_VERSION } = await import("../../version.js");
           const { buildBugReportUrl } = await import(
             "../../utils/bug-report.js"
           );
diff --git a/codex-cli/src/components/chat/terminal-chat.tsx b/codex-cli/src/components/chat/terminal-chat.tsx
index 998a190c..f34ab792 100644
--- a/codex-cli/src/components/chat/terminal-chat.tsx
+++ b/codex-cli/src/components/chat/terminal-chat.tsx
@@ -24,9 +24,9 @@ import {
   uniqueById,
 } from "../../utils/model-utils.js";
 import { createOpenAIClient } from "../../utils/openai-client.js";
-import { CLI_VERSION } from "../../utils/session.js";
 import { shortCwd } from "../../utils/short-path.js";
 import { saveRollout } from "../../utils/storage/save-rollout.js";
+import { CLI_VERSION } from "../../version.js";
 import ApprovalModeOverlay from "../approval-mode-overlay.js";
 import DiffOverlay from "../diff-overlay.js";
 import HelpOverlay from "../help-overlay.js";
diff --git a/codex-cli/src/utils/agent/agent-loop.ts b/codex-cli/src/utils/agent/agent-loop.ts
index 60749a23..97041def 100644
--- a/codex-cli/src/utils/agent/agent-loop.ts
+++ b/codex-cli/src/utils/agent/agent-loop.ts
@@ -11,6 +11,7 @@ import type {
 } from "openai/resources/responses/responses.mjs";
 import type { Reasoning } from "openai/resources.mjs";
 
+import { CLI_VERSION } from "../../version.js";
 import {
   OPENAI_TIMEOUT_MS,
   OPENAI_ORGANIZATION,
@@ -24,7 +25,6 @@ import { parseToolCallArguments } from "../parsers.js";
 import { responsesCreateViaChatCompletions } from "../responses.js";
 import {
   ORIGIN,
-  CLI_VERSION,
   getSessionId,
   setCurrentModel,
   setSessionId,
diff --git a/codex-cli/src/utils/check-updates.ts b/codex-cli/src/utils/check-updates.ts
index 5e326c1c..6999c90c 100644
--- a/codex-cli/src/utils/check-updates.ts
+++ b/codex-cli/src/utils/check-updates.ts
@@ -1,7 +1,7 @@
 import type { AgentName } from "package-manager-detector";
 
 import { detectInstallerByPath } from "./package-manager-detector";
-import { CLI_VERSION } from "./session";
+import { CLI_VERSION } from "../version";
 import boxen from "boxen";
 import chalk from "chalk";
 import { getLatestVersion } from "fast-npm-meta";
diff --git a/codex-cli/src/utils/session.ts b/codex-cli/src/utils/session.ts
index 19867220..201929f6 100644
--- a/codex-cli/src/utils/session.ts
+++ b/codex-cli/src/utils/session.ts
@@ -1,9 +1,3 @@
-// Node ESM supports JSON imports behind an assertion. TypeScript's
-// `resolveJsonModule` takes care of the typings.
-import pkg from "../../package.json" assert { type: "json" };
-
-// Read the version directly from package.json.
-export const CLI_VERSION: string = (pkg as { version: string }).version;
 export const ORIGIN = "codex_cli_ts";
 
 export type TerminalChatSession = {
diff --git a/codex-cli/src/version.ts b/codex-cli/src/version.ts
new file mode 100644
index 00000000..89f638df
--- /dev/null
+++ b/codex-cli/src/version.ts
@@ -0,0 +1,8 @@
+// Note that "../package.json" is marked external in build.mjs. This ensures
+// that the contents of package.json will always be read at runtime, which is
+// preferable so we do not have to make a temporary change to package.json in
+// the source tree to update the version number in the code.
+import pkg from "../package.json" with { type: "json" };
+
+// Read the version directly from package.json.
+export const CLI_VERSION: string = (pkg as { version: string }).version;
diff --git a/codex-cli/tests/check-updates.test.ts b/codex-cli/tests/check-updates.test.ts
index 75ec8aaf..4f77fc51 100644
--- a/codex-cli/tests/check-updates.test.ts
+++ b/codex-cli/tests/check-updates.test.ts
@@ -9,7 +9,7 @@ import {
   renderUpdateCommand,
 } from "../src/utils/check-updates";
 import { detectInstallerByPath } from "../src/utils/package-manager-detector";
-import { CLI_VERSION } from "../src/utils/session";
+import { CLI_VERSION } from "../src/version";
 
 // In-memory FS mock
 let memfs: Record<string, string> = {};
@@ -37,8 +37,8 @@ vi.mock("node:fs/promises", async (importOriginal) => {
 
 // Mock package name & CLI version
 const MOCK_PKG = "my-pkg";
+vi.mock("../src/version", () => ({ CLI_VERSION: "1.0.0" }));
 vi.mock("../package.json", () => ({ name: MOCK_PKG }));
-vi.mock("../src/utils/session", () => ({ CLI_VERSION: "1.0.0" }));
 vi.mock("../src/utils/package-manager-detector", async (importOriginal) => {
   return {
     ...(await importOriginal()),
diff --git a/codex-cli/vite.config.ts b/codex-cli/vite.config.ts
deleted file mode 100644
index 669a10f2..00000000
--- a/codex-cli/vite.config.ts
+++ /dev/null
@@ -1,4 +0,0 @@
-import { defineConfig } from 'vite';
-
-// Provide a stub Vite config in the CLI package to avoid resolving a parent-level vite.config.js
-export default defineConfig({});
\ No newline at end of file
diff --git a/codex-cli/vitest.config.ts b/codex-cli/vitest.config.ts
new file mode 100644
index 00000000..97af07fc
--- /dev/null
+++ b/codex-cli/vitest.config.ts
@@ -0,0 +1,12 @@
+import { defineConfig } from "vitest/config";
+
+/**
+ * Vitest configuration for the CLI package.
+ * Disables worker threads to avoid pool recursion issues in sandbox.
+ */
+export default defineConfig({
+  test: {
+    threads: false,
+    environment: "node",
+  },
+});