A new GPT-5.5T diagnosis just dropped this week. And if you’ve had GPT-5 behave like a completely different model on different days, this series is exactly what you need. One session it’s sharp, precise, cutting through the noise. Next session, same account, same prompt, it’s hedging everything, adding caveats where you never asked for any, refusing things it happily did yesterday. You’re not imagining it. OpenAI ships behavioral updates baked into the system prompt, and those updates change how the model processes your instructions before it even starts generating a response. The result is that power users who built workflows around a specific GPT-5 version suddenly find their carefully tuned prompts producing mush. This is the problem u/traumfisch has been systematically diagnosing and solving, version by version, since GPT-5.2.
The twist: most people try to fight OpenAI’s system prompts. That’s a losing battle. u/traumfisch figured out a smarter angle. The antidotes don’t fight the system prompt. They semantically reroute it. Same instructions, different behavioral outcome. Here’s why that actually works: OpenAI’s system prompts prime the model toward certain interpretive frames, safety postures, and output styles. When your custom instructions conflict directly with those frames, the model resolves the conflict by defaulting to OpenAI’s intent. But when you phrase your instructions to work with the underlying semantic architecture instead of against it, the model integrates both signals without friction. It’s not a jailbreak. It’s not a workaround. It’s more like learning the grain of the wood before you cut it. You stop forcing the model to choose between you and OpenAI, and you start getting clean outputs that actually match what you were trying to do in the first place. That’s the insight most people miss because they’re too busy complaining that ChatGPT “got worse.”
How to use them:
- 🔍 Find your GPT version. The library covers 5.2 (two parts), 5.3, 5.4T, and 5.5T. If you’re not sure which version you’re on, just ask ChatGPT directly: “Which version of GPT-5 are you running?” It’ll tell you. The “T” variants are typically the tuned rollouts that hit hardest in terms of behavioral changes, which is why 5.4T and 5.5T each have their own dedicated antidote. Don’t skip this step. Using the wrong antidote is worse than using none because you’re optimizing for failure modes that don’t exist in your version.
- 📋 Open the matching Substack post. Grab the custom instruction block. Free to take. The posts are well-structured: u/traumfisch explains what changed in each version, which behaviors the antidote targets, and exactly what the instruction block does. Worth reading even if you’re in a hurry. Two minutes of context will save you from cargo-culting instructions you don’t understand.
- ⚙️ Paste it into your ChatGPT custom instructions. Takes 30 seconds. Go to Settings, then Personalization, then Custom Instructions. Paste the block into the “How would you like ChatGPT to respond?” field. If you already have custom instructions there, read both before merging. In most cases the antidote instructions are designed to sit alongside your existing setup without conflicts, but a quick skim is worth it.
- 🔁 Run your normal workflow and watch the friction disappear. This is where it gets interesting. People report that the changes aren’t dramatic in an obvious way. It’s more like the constant low-grade resistance disappears. Things that used to require three prompt iterations now work on the first try. Outputs that kept adding unsolicited caveats stop doing that. The model starts feeling like the version you remember from two months ago.
Pro tip: Don’t mix versions. A GPT-5.2 antidote won’t address 5.5T failure modes. Each release has its own behavioral quirks. Match the antidote to the model you’re actually using. For example, 5.2 had issues with over-qualification, constantly hedging factual statements with “however, it’s important to note” even when no nuance was needed. The 5.2 antidote targets that specifically. GPT-5.4T introduced a different problem: a tendency to reframe creative or analytical tasks into more generic, sanitized outputs. The 5.4T antidote addresses that frame-collapsing behavior directly. GPT-5.5T has its own signature, which is why it got its own dedicated post this week. Using a 5.2 antidote on a 5.5T session is like taking last year’s prescription for this year’s bug. The symptoms look similar but the root cause is different.
Extended versions have soft paywalls, but you can unlock them by grabbing a free complementary article on the same Substack. Community feedback across different people and different contexts says these work. And we’re not talking about a handful of upvotes on a Reddit post. The thread has detailed responses from people running the antidotes across different use cases: coding workflows, research pipelines, long-form writing, customer-facing copy. The consistency of the feedback is what makes this credible. Different prompting styles, different industries, different GPT sessions, same result: measurably less friction. That’s a signal worth paying attention to.
Worth swapping in before your next frustrating ChatGPT session. 🧪
GPT-5 Series System Prompt Antidotes
by u/traumfisch in PromptEngineering