Who it is forA performance-minded developer who wants to check whether DSpark speculative decoding helps on their own Mac and workload.
The problemThe README gives projections, not end-to-end results for every machine, so the developer needs to measure the difference locally.
The outcomeTwo server runs, one with the default DSpark draft and one with target-only generation, with timings recorded for the same prompt.
What you need first
- An Apple silicon Mac running macOS 26 or later
- Enough unified memory for the target model, draft model, and context (the README tests Qwen models on a 40-core M5 Max with 48 GB)
- Homebrew, or Xcode Command Line Tools and Python 3.12 for a source build
- Client tools such as opencode, claude, codex, or hermes installed separately, if you use the launchers
Steps
- Install the package with
brew install lithos-ai/tap/lithos-metal. - Start the default server with
lithos-metal serve --model nvidia/Qwen3.8-27B-NVFP4and time a fixed prompt with the curl call from the README. - Stop the server and restart it with
lithos-metal serve --model nvidia/Qwen3.8-27B-NVFP4 --no-draft. (inferred, check the README) - Repeat the same timed prompt and record the tokens per second for both runs.
Prompt for your agent
Using the lithos-metal repo at https://github.com/lithos-ai/lithos-metal, run the same fixed prompt against `lithos-metal serve --model nvidia/Qwen3.8-27B-NVFP4` and again with `--no-draft`. Report wall-clock time and generated token count for each run in a two-row table. Verify both runs used the same prompt and max_completion_tokens before comparing.
Caveat. The README warns that its own speed figures exclude drafting and rewind and are not end-to-end comparisons, so your timings only apply to your machine, model, and prompt.
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