I tested GPT-5.6 and GPT-6 with Medium → Instant → Medium. Both models failed on Instant, both succeeded on Medium. Here's what I found.

I've been investigating some serious ChatGPT reliability issues over the past several days, and my latest tests revealed something particularly interesting: Both GPT-5.6 and GPT-6 showed problems under Instant, while Medium worked in every tested run. I'm a long-time ChatGPT power user, primarily working on long-form creative writing, software development, and projects requiring consistent context retention. After experiencing disappearing responses, incomplete generations, and inconsistent instruction-following, I decided to run controlled A/B/A tests. 1. GPT-5.6 – Medium → Instant → Medium Medium (Test 1): Successful. Response completed and remained visible. Instant (Test 2): Failed. Generated response disappeared. Medium (Control Test): Successful again. 2. GPT-6 – Medium → Instant → Medium Medium (Test 1): Successful. All requested story events were completed. Instant (Test 2): Failed. Response ended prematurely, leaving explicitly requested events unfinished. Medium (Control Test): Successful again. That's four successful Medium tests and two problematic Instant tests across two model generations. Important distinction: These are two different failure symptoms. GPT-5.6 lost a generated response, while GPT-6 prematurely ended a story. I'm not claiming they necessarily share the same root cause. Six runs aren't enough to establish causality, but the matching A/B/A pattern is worth investigating. 3. The technical evidence gets more interesting During my earlier investigation into disappearing GPT-5.6 Sol responses, I captured the following using Chrome Developer Tools: Endpoint: POST /backend-api/f/conversation HTTP status: 200 OK Content type: text/event-stream SSE completion indicator: complete Generated response visible during streaming Assistant message disappearing immediately afterward I also reproduced the disappearing-response behavior using GPT-5.5 in a completely new conversation. Clearing cookies didn't resolve the issue, and I've observed related symptoms across Windows, iOS, and Android. An HTTP 200 response and completed SSE stream don't prove successful message persistence, but they make the failure particularly interesting. These network diagnostics are from an earlier investigation, not from the latest A/B/A tests. 4. Did OpenAI change how Instant works? This is what I'm trying to understand. OpenAI positions Instant as the faster option for everyday tasks, while Medium provides additional reasoning effort. That's understandable. But does this mean complex, long-form creative writing is now effectively better suited to Medium? I've noticed that Medium generally completes my story prompts more reliably, but it also tends to write significantly longer responses than I actually requested. Instant often produces a more natural length, but lately it has become unreliable in my tests. I've even adjusted my custom instructions to explicitly require complete scenes without unnecessary length or invented plot developments. The differences persist. 5. Support and independent reports My investigation is already documented under OpenAI Support Case #16904787. I've submitted screenshots, conversation URLs, network diagnostics, and reproduction details. Other users have reported similar disappearing-response symptoms: https://community.openai.com/t/chatgpt-web-ui-bug-entire-responses-and-download-links-disappear-until-page-reload/1404260 And broader GPT-5.6 reliability concerns: https://community.openai.com/t/gpt-5-6-sol-has-seriously-deteriorated-the-past-week-or-so/1399353 These reports don't prove a shared technical cause, but they suggest my experience isn't entirely isolated. 6. Has anyone else tested this? I'd genuinely appreciate results from other users. If you have access to GPT-5.6 or GPT-6, could you try the same Medium → Instant → Medium sequence with a reasonably complex prompt? Please note whether: The response completes all requested instructions. The generated message remains visible after completion. Reloading the page restores any missing content. Instant and Medium produce significantly different response lengths. The selected model and reasoning level remain unchanged. Ideally, use the same prompt and comparable conversation conditions. I'm especially interested in whether this behavior is specific to my account or whether others can reproduce it. Final thoughts I understand that different reasoning levels are supposed to behave differently. But faster reasoning shouldn't mean disappearing answers, and reduced reasoning shouldn't mean abandoning explicit instructions halfway through. I'm not claiming OpenAI deliberately degraded anything. I simply want to understand whether we're seeing a regression, a configuration issue, or an intentional change in how Instant is designed to handle complex tasks. At this point, I've spent so much time documenting bugs that I'm starting to feel like an unpaid QA engineer. 😭💀 I originally just wanted to write my stories. Now I'm comparing reasoning configurations, inspecting SSE streams, collecting request IDs, and running cross-model A/B/A tests. OpenAI, I wanted a writing assistant, not a second career in software quality assurance. 😂 submitted by /u/echoabenteuer [link] [comments]

Source: r/ChatGPT | 2026-10-12

Related