Can LongCat Flash Chat run on Mac Studio M5 Ultra 512GB?
What this means
LongCat Flash Chat fits on the Mac Studio M5 Ultra · 512GB at IQ1_S. We estimate it uses 159.8GB of the conservative 504GB working budget.
Estimated decode speed is 109.5–153.3 tokens/s. A roughly 300-word answer may take around 3 seconds.
See how fast it feels
Using the midpoint of our 109.5–153.3 tokens/s estimate for this demo.
Where the memory goes
| Component | Detail | GB |
|---|---|---|
| Model weights | IQ1_S GGUF (114 GB) + mmap overhead | 119.7 |
| KV cache | 4K context window | 39.3 |
| Runtime | macOS inference app + compute buffers | 0.8 |
| Total needed | at IQ1_S, 4K context | 159.8 |
| Working budget | 512 GB unified memory − conservative macOS reserve | 504 |
| Headroom | remaining inside the working budget | 344.2 |
Pick your quant
| Quant | Download | Memory | Estimated speed | Verdict |
|---|---|---|---|---|
| IQ1_S ★ | 114 GB | 159.8 GB | ~109.5–153.3 tok/s | ✓ Runs great |
Get it running on this Mac
Recommended app: LM Studio. Follow the point-and-click steps below.
Download LM Studio from its official site and drag it to Applications. Open it once and allow macOS to launch it. This route uses the graphical app; you do not need its CLI or local-server features.
Search for ggml-org/LongCat-Flash-Chat-GGUF. Use the publisher name shown on this page—or paste its full Hugging Face URL. Similarly named community uploads may contain different files.
Open the GGUF download options and select the row containing IQ1_S. The download should be about 114 GB. Do not select vision-projector or mmproj helper files for a text-only chat.
Choose the downloaded model in the model selector and click Load if prompted. Keep the default local runtime and start with a 4K (4096-token) context. Close memory-heavy apps for the first load.
Try “Explain why the sky is blue in three sentences.” This page estimates 109.5–153.3 tokens/s; it is not an LM Studio measurement unless marked ✓ Verified.
A second reply while offline confirms that the model is running on this Mac.
This report names an exact Hugging Face repository and GGUF quant. LM Studio lets you search that exact source, choose the matching quant, download it, and chat without using Terminal.
An open-source GGUF alternative with friendly hardware-fit hints.
Its MLX engine is experimental, and support for new model architectures can lag.A trusted Ollama catalog model, or later use with coding tools and a local API.
An Ollama package may use different weights or a different quant from this report.One interface for GGUF, MLX, Ollama, documents, and knowledge workflows.
It exposes more choices than the first-chat path and its free license is for personal use.- Model not listed: paste the exact repository ggml-org/LongCat-Flash-Chat-GGUF, not only the model nickname.
- Download stalls: confirm there is enough free storage, reconnect to Wi-Fi, and restart the download inside the app.
- Load fails or the app closes: quit memory-heavy apps. In LM Studio, confirm IQ1_S is the model currently loaded. Otherwise use a smaller model from this Mac's results.
- No reply while offline: make sure the downloaded local model—not a remote or cloud model—is selected in the chat.
Your anonymous feedback helps us prioritize which Mac and model paths to retest.
Other models on this Mac
LongCat Flash Chat on other Mac Studio M5 Ultra configurations
FAQ
Can the Mac Studio M5 Ultra · 512GB run LongCat Flash Chat?
Yes at IQ1_S. We estimate about 159.8GB of working memory and 109.5–153.3 tokens/s at 4K context.
Which LongCat Flash Chat quant should I use on this Mac?
IQ1_S. It is a 114GB download and leaves about 344.2GB inside our conservative working budget.
Which app should I use for LongCat Flash Chat on this Mac?
Start with LM Studio. This page gives the complete point-and-click walkthrough.
Are these speeds measured on a Mac Studio M5 Ultra?
No. The range is a formula estimate based on memory bandwidth, model size, active parameters, cooling, and a 4K context. The app, backend, thermals, and prompt can change real performance.