Problem: ChatGPT Windows client won't open: Unable to locate the Codex CLI binary / Codex CLI not found —— Trove problem library

What you will run into

After updating the ChatGPT Windows client it stops opening, showing:

ChatGPT failed to start.
Unable to locate the Codex CLI binary.
Set CODEX_CLI_PATH or ensure the client resources include bin/codex.

You opened ChatGPT but it complains about Codex CLI - the new ChatGPT client depends on the Codex CLI binary at startup.

Why this happens

At startup the client locates the codex binary: first PATH, then the CODEX_CLI_PATH target; if neither exists it refuses to start. Three common cases:

The client locates the CLI binary with two-level addressing: "PATH first, env-var override second" — it searches PATH for a binary named codex, and if not found, checks the path pointed to by CODEX_CLI_PATH; only when both fail does it refuse to start.

This order gives the three failure modes different semantics: not in PATH = not installed or PATH not refreshed; in PATH but CODEX_CLI_PATH pointing wrong = the variable overrode correct addressing (the variable wins over PATH, and a bad target fails everything);

wrong variable name = as if unset, falling back to PATH.

Deterministic takeaway: on "codex not found", first verify the binary directly with codex --version, then check echo $CODEX_CLI_PATH for leftovers;

before hard-coding a path in config, confirm which codex matches this machine's layout (never copy someone else's path); fix order: install/refresh PATH for ①②, unset CODEX_CLI_PATH or correct the path for ③.

Step by step

1. Check whether Codex CLI exists — Required

codex --version

'codex' not recognized -> not installed or missing from PATH, go to step 2; a version string -> installed, go to step 3.

2. Install Codex CLI — Required

powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"

Confirm with codex --version afterwards.

3. Configure CODEX_CLI_PATH (use the actual local path) — Required

where codex
setx CODEX_CLI_PATH "C:\Users\<your user>\...\codex.exe"   # use the where codex output

Do not copy a path: layouts differ across machines/installers (the article's default is %LOCALAPPDATA%\Programs\OpenAI\Codex\bin\codex.exe; locally measured %LOCALAPPDATA%\OpenAI\Codex\bin\<hash>\codex.exe).

The variable name must be exactly CODEX_CLI_PATH.

4. Reopen the client — Required

Environment variables only affect new processes: fully quit the ChatGPT client (no leftover process in Task Manager) before starting it again.

How to confirm it works

codex --version returns a version; the ChatGPT client opens normally and no longer shows Unable to locate the Codex CLI binary.

Other environments

Symptom

ChatGPT Windows client won't open: ChatGPT failed to start. Unable to locate the Codex CLI binary. Set CODEX_CLI_PATH or ensure the client resources include bin/codex.; codex --version may say 'not recognized'.

Cause

The new ChatGPT client depends on the Codex CLI binary at startup: codex is missing from PATH and CODEX_CLI_PATH is unset or wrong -> the client refuses to start.

Solution

1. codex --version to check installation;
2. Not installed -> official installer: powershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex";
3. where codex for the real path, then setx CODEX_CLI_PATH "<real path>" (exact variable name, no copied paths);
4. Fully quit the client (not minimize) and reopen.