Azure OpenAI Model Upgrades: Prompt Safety Pitfalls with GPT-4o and Beyond

Upgrading to New Azure OpenAI Models? Beware Your Old Prompts Might Break.

I recently worked on upgrading our Azure OpenAI integration from gpt-35-turbo to gpt-4o-mini, expecting it to be a straightforward configuration change. Just update the Azure Foundry resource endpoint, change the model name, deploy the code — and voilà, everything should work as before. Right?

Not quite.

The Unexpected Roadblock

As soon as I deployed the updated code, I started seeing 400 status errors from the OpenAI endpoint. The message was cryptic:

The response was filtered due to the prompt triggering Azure OpenAI's content management policy.

At first, I assumed it was a bug in my SDK call or a malformed payload. But after digging deeper, I realized this wasn’t a technical failure — it was a content safety filter kicking in before the prompt even reached the model.

The Prompt That Broke It

Here’s the original system prompt that worked perfectly with gpt-35-turbo:

YOU ARE A QNA EXTRACTOR IN TEXT FORMAT. YOU WILL GET A SET OF SURVEYJS QNA JSONS. YOU WILL CONVERT THAT INTO A TEXT DOCUMENT. FOR THE QUESTIONS WHERE NO ANSWER WAS GIVEN, MARK THOSE AS NO ANSWER. HERE IS THE QNA: BE CREATIVE AND PROFESSIONAL. I WANT TO GENERATE A DOCUMENT TO BE PUBLISHED. {{$style}} +++++ 
{{$input}} +++++

This prompt had been reliable for months. But with gpt-4o-mini, it triggered Azure’s new input safety layer, introduced in mid-2024.

What Changed with GPT-4o-mini?

Unlike gpt-35-turbo, the gpt-4o family:

• Applies stricter content filtering — not just on the output, but also on the input prompt.
• Treats system messages and user messages as role-based chat messages, passing them through moderation before the model sees them.
• Flags prompts that look like prompt injection attempts like aggressive instructions like “YOU ARE…”, “BE CREATIVE”, “GENERATE”, “PROFESSIONAL”.
• Flags unusual formatting (like `+++++`), artificial delimiters or token markers as it may look like encoded content.

In short, the model didn’t even get a chance to process my prompt — it was blocked at the gate.

Fixing It: Softening the Prompt

The solution wasn’t to rewrite the entire logic, but to soften the system prompt and remove formatting that could be misinterpreted. Here’s what helped:

- Replacing “YOU ARE…” with a gentler instruction like “Please help convert the following Q&A data…”
- Removing creative directives like “BE CREATIVE” or “PROFESSIONAL” unless clearly contextualized.
- Avoiding raw JSON markers and template syntax (`{{ }}`, `+++++`) in the prompt.

Once I made these changes, the model responded smoothly — and the upgrade was finally complete.

Evolving the Prompt — Not Abandoning It

Interestingly, for some prompts I didn’t have to completely eliminate the “YOU ARE…” structure. Instead, I refined it to be more natural and less directive. Here’s a comparison:

Key Takeaways

- Model upgrades aren’t just about configuration changes — they can introduce new moderation layers that affect prompt design.
- Prompt safety filtering is now a first-class citizen in Azure OpenAI, especially for newer models.
- System prompts need to be rewritten with moderation in mind, not just clarity or creativity.

This experience reminded me that even small upgrades can surface big learning moments. If you're planning to move to gpt-4o-mini or any newer Azure OpenAI model, take a moment to review your prompts — they might need a little more finesse than before.