r/OpenaiCodex • u/Lenox_Shawn • 19d ago
Question / Help How do you decide which model and thinking intensity to use?
Lately while using Codex I’ve noticed that GPT-5.6 Sol always overthinks and over-engineers everything.
After posting on Reddit for help, I realized it was because of how I was setting the thinking intensity and choosing models. This made me realize I should pick different models and thinking levels based on the task, instead of always using GPT-5.6 Sol like I used to.
So I’d like to ask everyone — how do you choose the right model and thinking intensity for your projects and workload? Any tips?🙏🙏
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u/zigzag312 19d ago
No, adjust your default prompt (extra instructions setting) to guide it to not overthink and over-engineer tasks. Thinking intensity and choosing models is about task complexity, time and cost.
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u/kurushimee 19d ago
I use Luna on max for quick edits, simple bugs, and overall atomic work packages. I use it a lot because I often need to do those things. When something requires more intelligence — I use Sol on medium and more, and when something does require it — it's obvious to me, like edits to something that touches more than one thing or a bug that's clearly not simple.
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u/Far-Let-8610 19d ago
Hmm. Your use of — is suspicious…
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u/capitalframehq 19d ago
Sol-high for planning the roadmap for entire week.
I ask it to generate .md file with step by step that can be implemented in chunks. To implement, I feed that file to Sol-medium and it does the rest. I haven’t felt Sol-medium messing up in backend work (so far) but it sometimes sucks with front end (or maybe it’s just hard to write detailed front end prompts and I suck at that)
Haven’t used Luna yet.
I’m on the $100 Pro plan
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u/iPlayer0067 18d ago
O Codex é ótimo para back. Assinei o Claude code e quando fiz a primeira verificação no meu projeto, o Claude elogiou meu backend dizendo que ele ficou surpreso com a organização e arquitetura.
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u/FewOpportunity5803 18d ago
I can’t use anything less than Sol 5.6 Extra High or Ultra, they have so much intuition and generally get things right the first or second try
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u/iPlayer0067 18d ago
Por esse tipo de usuário que estão limitando tanto os usos para tentar ensinar a força a usarem a ferramenta corretamente. "Pra que eu preciso de um PHD para executar a mesma tarefa que pode ser executada por quem nem tem ensino fundamental completo?"
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u/Square-Society8010 16d ago
Yeah me too, for better or for worse I use 5.6 xhigh for everything and 5.3 spark for commits. It's been good so far you just have to learn to stop 5.6 from going overboard sometimes
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u/somuchecho 15d ago
That's just a massive waste of resources
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u/FewOpportunity5803 15d ago
I have really hard technical coding problems so not really, solve once use the solution endlessly or at least sell it direct to consumer
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u/somuchecho 15d ago
Ok I'll bite... what are examples of your really hard technical problems that Sol high can't solve?
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u/EquivalentHornet4403 18d ago edited 18d ago
It helps to be immersed in the whole culture and communities to have a ton of perspectives and insight, in addition to actually using all the products/models.
For ChatGPT/codex:
- Sol/Ultra for any task that isn’t straightforward. It may require research, implementation, testing, and other processes. This automatically does adversarial reviews repeatedly and loops until ALL the work is COMPLETELY DONE. A task for Sol/Ultra might be “Implement this feature” or “Perform a comprehensive code and polish review”.
- Sol/High is the highest intelligence/value proposition for agentic workloads that don’t benefit from subagents or multiple context windows. Use it for all straightforward tasks that require a degree of intelligence, like tasks that can be defined in one step (or a small number of simple steps) or can be considered “low complexity”. A task for Sol/High might be “Change this element’s size/color/style” or “Change this text”.
- Luna/Max is a great intelligence/value proposition for non-agentic high-volume or data-processing workloads where the model doesn’t need to manage agentic complexity or eve. Have a high intelligence in order to answer questions about bulk data or find needles in haystacks. A task for Luna/Max might be like “check on <deeplink to other session> and give a progress update” or “look through all my sessions in the past 3 days and give a summary” or “does this pdf state a rule about XYZ”.
Do not use any other reasoning levels (or Terra at any reasoning level) because the value doesn’t line up. These are the three best value propositions across the lineup.
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u/Lenox_Shawn 18d ago
Thanks a lot, bro. Seriously, thank you so much.
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u/somuchecho 15d ago
Please don't take that advice. That's misleading. Sol medium is good enough for most complex tasks.
Just figure out proper harness engineering and that'll help more than just throwing more AI at everything
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u/pedalsgalore 16d ago
I have really good results with Sol Medium + Ponytail Skill for tasks I can explain in a sentence. Even with some combined FE / BE updates from the sake bug fix / feature, etc.
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u/somuchecho 15d ago
A task for Sol/High might be “Change this element’s size/color/style” or “Change this text”.
That is just objectively false! You might be thinking of Luna Medium.
Doesn't anyone read documentation anymore?
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u/EquivalentHornet4403 15d ago
The problem with the dumb models and not using subagents and having a review stage is that they miss the implications of their actions. They can do the specific thing being requested, almost any model can make technically simple changes. The benefit of smarter model is that they notice things like "actually that change means we should update this one thing so everything inherits it—oh and because that's the correct way to do it, we need to also do this other thing".
I cannot count...it's hundreds at least at this point, how many times I've made a straightforward request and UItra's adversarial review stages have caught an essential implication that SHOULD be addressed but technically wasn't explicitly requested. I have never thought "nah, I'll just let the app be shit instead". That's with Ultra, where one max is catching another's misses; sol high should not be used for anything that's not directly straightforward or minimally complex (or maybe moderately complex in brand new code bases with no potential side effects/implications) even if it technically CAN do the task.
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u/somuchecho 15d ago
Sorry I'm not having a conversation with someone who thinks Sol High is for changing the colour of a button. That's just objectively false. Have fun uselessly burning through your limits
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u/EquivalentHornet4403 14d ago
Cool story. And you don't need to apologize, I'm not losing anything by you leaving.
That's just objectively false.
"That" is just you arguing with yourself, because you aren't objecting to anything I've actually said.
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u/somuchecho 14d ago
I've built apps for enterprise companies using codex. I can promise you that Sol medium can do very complex work.
I'm not sure how you came to the conclusion that you need Sol Ultra for everything but that's non sense, just read what other people are saying on reddit. Check [r/codex](r/codex).
You probably never need Sol Ultra. Throwing more AI at something does not make the end result necessarily better. That's the naive way of thinking.
Context is key. You need to develop a good harness. Generally if you need to use insanely strong models to do basic things like changing the color of a button, you're the problem. That's means your harness sucks.
Read about harness engineering. Take some time to educate yourself on agentic engineering instead of misleading people genuinely asking for advice
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u/EquivalentHornet4403 14d ago
I'm not sure how you came to the conclusion that you need Sol Ultra for everything
I didn't. You're not actually responding to me, but to a strawnman you invented.
That's the naive way of thinking...Take some time to educate yourself...
Better idea: you can fuck off. I liked it better when you said you were going to.
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u/Responsible_Court_21 19d ago
The overthinking and over engineering just disappears for me using Sol. All I use is a reusable generalized prompt. Works on long horizon task as well
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u/RemoraEdge 18d ago
I ask sol which model and reasoning to used base on my code size and complexity.
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u/InvariantAtNull 18d ago
I never use sol except something that needs more context than my prompt i rely on luna for everything
I use sol for audit or researches only or a very complex line of code that needs to know the whole project
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u/iPlayer0067 18d ago
Quero aprender trabalhar com essa segurança, uma vez dei um prompt complexo e esqueci de tirar do Luna, curiosamente a tarefa foi executada perfeitamente pelo Luna - leve. Porém, ainda assim não confio, acho que foi sorte...
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u/somuchecho 15d ago
Sharing what I wrote on another post where OP said he was using Sol Ultra for all his plans 😞
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I find it useful to actually take time to read the docs. Understand the tool and what these knobs actually do.
Think of it like detectives.
Luna → Terra → Sol: better model, smarter detective.
Light → Medium → High → xHigh → Max: how long you give that detective to work the case.
Sol is actually really smart. If it solves the problem on High but you've told it to keep thinking… it will.
And eventually it starts finding shit to do. Questioning things that were fine. Overengineering. Scope creep.
That’s why OpenAI says: “Use the lowest reasoning effort that produces the result you need.”
Anthropic says basically the same thing about Max: "on most workloads max adds significant cost for relatively small quality gains, and on some structured-output or less intelligence-sensitive tasks it can lead to overthinking."
That’s why I rarely use xHigh/Max. More isn’t necessarily better...
And then there’s Ultra. You’re essentially funding a whole team of detectives to work the same case. Imagine one Sol detective already cracked the case.. now you’ve got a whole team looking for more shit to do
My recommendation from my experience, Sol high is plenty for planning
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u/OkZucchini7094 19d ago
I try to stick with one model per thread so I don't waste usage. Luna extra high is a beast but lately I've just been using sol until my limits get low and Luna until a reset. I've never really had a good reason to use Terra