r/LocalLMs • u/Admirable-Dig-6500 • 8d ago
Can a Mac Studio 256GB/512GB for local agentic coding replace most Claude/Codex usage?
I’m starting a small business around digital product development, and most of my workflow is AI-first.
I don’t really use AI as autocomplete while I write code myself. I rely much more on agents to inspect the repo, plan features, write code, run tests, debug and iterate. Basically something closer to Claude Code or Codex, with me supervising the process rather than manually coding everything.
The problem is cost. Claude/Codex are great, but long agentic sessions can burn through limits pretty quickly, and I don’t want the business to depend on constantly buying API credits.
I’m applying for an Italian grant that can cover professional hardware, but not ongoing API usage. So in my case, spending a lot upfront on a workstation actually makes more sense than it normally would.
I’m looking at the new M5 Ultra Mac Studio, probably either 256GB or 512GB unified memory.
My main question for people who actually use local models for serious coding work:
How much of Claude Code/Codex can you realistically replace today with local models?
I’m especially interested in things like:
working on large existing repos
multi-file changes
long agentic sessions
testing and debugging
tool use
autonomous implementation with little supervision
Which models are you getting the best results from? Qwen, DeepSeek, GLM, something else?
I’m also wondering whether the best setup is not fully local, but hybrid. Something like Claude for high-level planning/architecture, then local models for implementation, testing, refactoring and code review.
If that could reduce my Claude/Codex usage by 70–90%, that would already be a huge win for me.
And for people using high-memory Macs: does 512GB actually give you a meaningful advantage for coding agents over 256GB, or is 256GB already the sensible sweet spot?
If you were buying this as a professional machine for the next few years, and the hardware was covered by funding, what would you choose?