Voice transcription fails with 403 Cloudflare challenge on /backend-api/transcribe (Windows, 0.105.0 + 0.106.0-alpha.3)

Summary

Voice transcription in Codex fails consistently when releasing Space after dictation. The request to /backend-api/transcribe returns 403 Forbidden with a Cloudflare challenge page (Just a moment...).

Feedback Upload Correlation

Diagnostics were already uploaded via Codex /feedback.

• Thread ID: 019c96f6-c00c-76c2-a0c1-7f17c8e0a692

Environment

• OS: Windows 11 Home (10.0.26200)
• Codex stable: 0.105.0
• Codex alpha tested: 0.106.0-alpha.3
• Login: ChatGPT
• Feature flags enabled: voice_transcription=true, realtime_conversation=true

Repro

1. Open Codex TUI
2. Focus prompt
3. Hold Space, speak, release Space
4. Transcription fails

Observed

Repeated logs on 2026-02-25 show:

• ERROR codex_tui::voice: voice transcription error: transcription failed: 403 Forbidden
• Cloudflare challenge HTML in response body
• Endpoint path in payload: /backend-api/transcribe

Sample times (PT): 1:11:41 PM, 1:42:49 PM, 2:16:22 PM, 2:20:36 PM, 2:21:26 PM.

Request

Please investigate whether this is a known rollout/challenge-handling issue on the Codex voice transcription path for ChatGPT-auth sessions.