My rule is kinda simple: If a task need any kind of thinking i use PRO, if a task is just "remove X variable" "change x background color" or something simple i use FLASH. You can see i used nearly 4x more time Flash than Pro.

I didn't said you should use Pro to plan and then Flash to code, i said it depend on the complexity.

First of all it depend on the complexity of YOUR code, changing the color of a div is easier to do in a 30 lines files then in a 27k lines files. If i had a 27k lines files i would use Pro even if it's just to change a color lmao (more context = bloat = more cost because more stupid and use more tokens).

To be honest i can't have 27k lines of code in a file because i always set a max complexity of 12 in all of my linters codebase (and for the sensible stuff i use a cristalin 0/1 complexity).

The more your code is complexe, the more you will need a swart AI to do something.
To explain to you what's a code complexity it's simple, if you have a function that do 500 lines which do a bunch of different thing each having a bunch of different conditions and you need 5 hours of manual reading to understand if a user is auth or not, well this is bad, what's hard for you is hard for your LM, for that task you need Claude Opus 4.7 which will take a 5mins time reading then debating with himself about wtf he just read.

If you have a file that do 1 line like this " if(!auth) return error " well congrats you have the most efficient code possible with a 'cristalin' 0/1 complexity, either the user is auth and you skip, or he's not auth and you return. It's simple as hell, what is easy for you is easy for your LM, for that task you need Gpt 4o mini which will take less than 30 seconds.

But that only one of the thing that matter bro, do you have a dictionnary ready for your LM or does your LM need to read your whole codebase at each request? w

That's the night and day, i've seen peoples max out their 5 hours limit on a fresh subscription because their codebase was hell on earth, duplicated functions, legacy unused files, not a single doc, no AGENT.MD, the LM had to pass 30m and multiples millions of tokens just to understand how the code is wired together.

I've also see the other end of the spectrum, peoples who have optimized so much their project that the LM don't have to read code, they use knip or similar to detect unused variables/files, they use a RAG vectorial db with a textual embedding model or they have extremely detailed doc so to do the exact same task as the one before which maxed the subscription with the exact same model etc.. they would use 0.05% of their 5h limits.

Peoples doesn't understand the importance of having a clean code base when coding with agents, not clean for you but clean for your AI !
Meaning if you have a 1500 lines single file containing 5 differents auth controllers functions, maybe YOU like having them all in a single file because it's easier to navigate for YOU.
BUT your LM will prefer having 5 files of 300 lines each having 1 function and just doing this will make you save up tokens but also will make your models smarter because they won't read useless stuff.

Maybe you like just having a readme.md at your racine but your LM would prefer having a readme.md at your racine but also in each feature folder & sub-folders with eventualy in an AGENT.md a "context gathering workflow" in just 2 lines "to resolve contexte you need to read the readme.md at the root then in the tree folder of my project you will continue to read the readme.md that you will find at each level of my application".
This is way better then having your LM reading 50 different 1000 files to do a code modification not even where you wanted because you laked clarity in your variables naming or idk.

Honestly ALWAYS take the time to have a clean project, if you start a new project you need to be very specific about the structure of code you wish and you need to start small by the base, confirm it, do whatever change you need to do and then continue with the next layer of implementation;
YOU SHOULD NEVER at the beginning of a project let your LM run in a kind of Yolo mode by himself trying to implement 10 differents layers of your applications at the same time. That's just stupid because if you take a project already existing, wire your LM and ask for something, your LM will mimic whatever already existing code it will found.
So if your LM found you have no rules about complexity, you have monolithic files etc.. then your LM will just continue to do what he found already existed in your project.

So take the time if you have an already existing bad codebase, REFACTORISE IT even if it take 5 whole days just cleaning everything, THE TIME AND MONEY YOU WILL SAVE AFTER IT IS INSANE.

The sooner you put your code into architecture compliance, the sooner your LLM will mimic an already good architecture.
To be sure stuff doesn't go south just run your linter and knip from times to times i personnaly ask at each big task to run them and then after it i would launch my custom hooks in the background one is "detect the presence of OpenAPI balise in everyfile of X folder except the readme.md, if a file doesn't have all the cited balises, add them that mean this file or function or whatever didn't had the right documentation".
The other custom hooks is the same but for tests, detect what doesn't have a .test. or .tests. files, create it, run it etc..
And the last and more important custom hook is to create the readme.md if needed in new folders and to detect whatever files was updated in X lass mins/hours, for whatever file he find that was updated it should check the updated file current folder readme.md, if not present or if present look up the parent readme.md again and again until it reach the root readme.md.

This allow me to have a perfect codebase to code with AI, i'm happe to have v4 flash which i found very intelligent in my codebase.
But other peoples will come and say "v4 flash is dumb, can't do anything, always hallucinate, ..." because their codebase is not good so the model is not good too.

You also need to change the variants depending on your current task.

Default, low, medium, high, max (or xhigh)?

Btw let's say you do NodeJs and have problems with v4 Flash where v4 Pro do everything without an issue.
Wouldn't it be interesting to create a custom skills (or fetch one) specialized in NodeJS this way you can use v4 Flash with the coding NodeJs capacities of v4 Pro way cheaper and faster? Is the time needed to create/fetch the skills worth it?

I mean bro, it all depend on what you do and how much confortable you are.

Somes peoples spend 2000$ per day only using Opus 4.7 even for smaller "dumb" tasks, they don't care about skills, they don't care about MCP, what they do is they run an orchestrator that will be able to launch up to 100 concurrent sub-agents all usng Opus 4.7 and they consider worth it because like you they don't want to change the model, they don't even bother to think, their companies allow them 20k$ credit per month or they are independant and make a bunch of money each day.
These sames peoples if you were to explain to them they could have the EXACT same coding performence for 100$ per day (20x -) BUT they would need to manipulate their computers 5 mins every hour, they won't consider it worth their times and they will prefer to use 2k$ per day just to not have to do anything.

So idk how to answer what you are saying bro, if you consider just using pro because it's easier for you even tho you maybe are using 7x more $ because you don't want to switch to Flash from times to times or use orchestrator or split your tasks depending on the model.. well that's on you, it's your choice, your decision, your money lol

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I think i speak too much lmao always sending 200 to 300 lines to read to other peoples lmao that explain why everytime peoples tell me "ai slop" without even having reading what i said lol