We also get pretty reliable JSON output (on a smaller scale though) even without JSON mode. We usually don't use JSON mode because we often include a chain of thought part in <brainstorming> and then ask for JSON in <json> tags. With some prompt engineering, we get over 98% valid JSON in complex prompts (with long context and modestly complex JSON format). We catch the rest with json5.loads, which is only used as a fallback if json.loads fails.
4o-mini has been less reliable for us particularly with large context. The new structured output might make it possible to use mini in more situations.
We also get pretty reliable JSON output (on a smaller scale though) even without JSON mode. We usually don't use JSON mode because we often include a chain of thought part in <brainstorming> and then ask for JSON in <json> tags. With some prompt engineering, we get over 98% valid JSON in complex prompts (with long context and modestly complex JSON format). We catch the rest with json5.loads, which is only used as a fallback if json.loads fails.
4o-mini has been less reliable for us particularly with large context. The new structured output might make it possible to use mini in more situations.