ChatGPT-auth WebSocket transport always falls back to HTTPS on Linux (0.106.0 + 0.107.0-alpha.8)

Summary

ChatGPT-auth websocket transport fails consistently on Linux, then Codex falls back to HTTPS.

Reproduces on:

• codex-cli 0.106.0
• codex-cli 0.107.0-alpha.8

Environment

• OS: Arch Linux
• Shell: zsh
• Terminal: tmux 3.6a
• Auth mode: Logged in using ChatGPT

Expected behavior

Codex keeps websocket transport for streaming responses.

Actual behavior

On startup/user turn:

• websocket prewarm fails
• sampling retries 5 times
• transport falls back to HTTP/HTTPS

Observed log patterns in ~/.codex/log/codex-tui.log:

startup websocket prewarm setup failed: stream disconnected before completion: failed to send websocket request: Connection closed normally
stream disconnected - retrying sampling request (1/5 ...)
...
codex_core::client: falling back to HTTP

Also observed:

startup websocket prewarm setup failed: stream disconnected before completion: websocket closed by server before response.completed

Minimal repro

1. codex login status returns Logged in using ChatGPT
2. Start codex
3. Enter test
4. See banner: Falling back from WebSockets to HTTPS transport...

WS feature-flag variants tested

• responses_websockets=true, responses_websockets_v2=true
• responses_websockets=false, responses_websockets_v2=true
• responses_websockets=true, responses_websockets_v2=false

All combinations still fall back.

Diagnostics already done

• Unset proxy env vars (HTTP_PROXY, HTTPS_PROXY, ALL_PROXY, plus lowercase variants)
• Relogin ChatGPT auth (codex logout, codex login --device-auth)
• Tested stable and alpha side-by-side binaries
• Tested both IPv4 and IPv6 reachability to chatgpt.com
• Raw curl websocket-upgrade probes to https://chatgpt.com/backend-api/codex/responses over IPv4 and IPv6 both return HTTP 500 (connectivity/TLS works, but no successful upgrade in this unauthenticated probe)

Versions

$ codex --version
codex-cli 0.106.0

$ ~/codex-test/0.107.0-alpha.8/codex --version
codex-cli 0.107.0-alpha.8

$ codex login status
Logged in using ChatGPT

Hypothesis

Issue appears specific to ChatGPT-auth websocket path (not resolved by version bump to current alpha in this environment).