Custom GPT Action no longer invoked on mobile clients since ChatGPT app 1.2026.139 — regression?

GPT builders
1

Since the May 25 release of ChatGPT mobile app 1.2026.139, my custom GPT’s configured Action stops being invoked on mobile clients. The model just replies in natural language saying it can’t access the verification endpoint. Same GPT, same account, works perfectly on desktop web.

Also reproducible from chatgpt opened on mobile browsers, not only the native app — so this looks like a regression in how Actions are handled on mobile clients in general, not just an app bug.

Setup

  • Custom GPT with an Action calling an external auth gateway (custom email/OTP, not OAuth).

  • Action domain confirmed healthy: direct call returns 200 OK.

  • Failures started exactly on May 25, 2026 (same day as 1.2026.139 rollout).

Confirmed failing

  • ChatGPT Android app 1.2026.139 (Android 16) — 100% reproducible

  • chatgpt on Android mobile browsers — 100% reproducible

Confirmed working

  • ChatGPT desktop web — Action invoked normally

Already ruled out

  • GPT config (unchanged, works on desktop)

  • Auth provider (gateway returns 200)

  • Device, network, VPN, cache, reinstall, multiple accounts

Support ticket open for over a week, circling without reaching engineering, so trying the community route.

Questions

  1. Anyone else with a custom GPT Action seeing this regression on mobile since May 25?

  2. iOS users — can you confirm or deny the same behavior on the iOS app?

  3. Any workaround beyond “use desktop”?

Thanks, Onefra.

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