VoxCPM-0.5B-CoreAI

Core AI is Apple's on-device ML runtime in iOS 27 / macOS 27 and the successor to Core ML: PyTorch models are exported with Apple's coreai-torch (LLMs: coreai.llm.export) into .aimodel bundles that run on the GPU or the Neural Engine, e.g. Qwen3-8B 4-bit decodes at 94 tok/s on an M4 Max GPU, MLX 90 under the same protocol (apple-silicon-llm-bench, macOS 27 beta 26A5353q, 2026-06-11).

Mirror of mlboydaisuke/VoxCPM-0.5B-CoreAI — the canonical repo (CoreAI Model Zoo). Updates land there first.

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This model has no row on DeviceMark, the on-device LLM leaderboard.

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VoxCPM-0.5B — Core AI (on-device, iPhone + Mac)

OpenBMB's VoxCPM-0.5B converted to Apple's Core AI engine, running fully on-device — iPhone (Apple Neural Engine / GPU) and Apple-silicon Mac. No network, no server.

VoxCPM is not a classic vocoder TTS: it pairs a MiniCPM4 language-model backbone with a LocDiT flow-matching diffusion head and an AudioVAE, generating speech through a continuous (token-rate) diffusion loop. This repo ships the whole stack as Core AI model bundles plus the small host-side glue the runtime needs.

• Output: 16 kHz mono
• License: Apache-2.0 (commercial-friendly), inherited from the base model
• Quantization: weight-only int8 on the two LM backbones (the size driver); the diffusion decoder, feature encoder, and AudioVAE stay fp16 — the continuous-feedback path is quantization-sensitive (the same split mlx-community/VoxCPM2 uses).

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Earlier VoxCPM 0.5B capture on iPhone 17 Pro in the zoo's coreai-audio app. This is separate from the release's Mac entry check linked below; it does not validate that package on iPhone.

Use it

New to Core AI? Start with CoreAIKit 0.7.3. Follow its requirements and first-run steps for qwen3-0.6b, then open the same release's ChatDemo. The README records the tested OS/SDK and download size; model and device coverage is stated per example.

⚡ One line — this model is the default behind the kit's task op (import CoreAIOps; no session, no model plumbing, downloads on first use):

let audio = try await CoreAI.speak(text)

Every op, one shape — Cookbook.

▶️ Run it (source) — the Speak runner (GUI + CLI, one app for every text-to-speech model in the catalog):

git clone --branch 0.7.3 --depth 1 https://github.com/john-rocky/coreai-kit
export DEVELOPER_DIR=/Applications/Xcode-27.0.0-RC.app/Contents/Developer
open -a /Applications/Xcode-27.0.0-RC.app coreai-kit/Examples/Speak/Speak.xcodeproj
# → Run, then pick "VoxCPM 0.5B" in the model picker

# agents / headless (macOS):
cd coreai-kit/Examples/Speak
swift run -c release speak-cli --model voxcpm-0.5b --text "Hello from Core AI." --output hello.wav

Use Xcode build 27A266a from the release's .xcode-pin; adjust the app path if your installation is named differently.

💻 Build with it — complete; the glue is kit API, copy-paste runs:

import CoreAIKit

let speaker = try await KitSpeaker(catalog: "voxcpm-0.5b")
let audio = try await speaker.synthesize(text)
// audio.samples: 16 kHz mono PCM in [-1, 1] — play it or write a WAV

The take-home is Examples/Speak/Sources/QuickStart.swift — this exact code as one typed function, no UI; the CLI is an argument shell over it, and the GUI drives the same KitSpeaker(catalog:) and plays the samples. Live playback? synthesizeStreaming(_:onChunk:) hands you ~0.5 s chunks as they decode, so audio starts before the whole clip exists. The WAV container is your app's territory (the runner ships a 20-line writer).

Integration checklist

• SPM: https://github.com/john-rocky/coreai-kit (exact 0.7.3) → product CoreAIKit
• Info.plist: none needed
• Entitlements: none needed
• First run downloads the model — ~1,374 MB (Mac) / ~1,378 MB (iPhone) — then it loads from the local cache (Application Support; progress via the downloadProgress callback)
• Measure in Release — Debug is ~3× slower on per-token host work

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Contents

The JIT bundles in ios/ have not been run on an iPhone yet. The iPhone 18 Pro specialized other JIT graphs of up to 1.6 GB on its own. It refuses an h18p bundle with incompatibleCompiledAssetArchitecture (knowledge/jit-distribution.md).

A q=32 batched-prefill bundle is shipped, for fast time-to-first-audio: it seeds the KV cache in a single pass instead of looping the decode bundle once per text token (costly on the bandwidth-bound A19). Text longer than 32 tokens falls back to the bit-identical prefill-via-decode loop, so length stays unbounded.

Usage

Easiest path is the coreai-model-zoo coreai-audio app (the "Voice" tab) and CoreAIKit:

import CoreAIKit

let tts = try await VoxCPMTTS(paths: .standard(artifactsRoot: modelRoot))   // macos/ or ios/ (.aimodel)
// let tts = try await VoxCPMTTS(paths: .aot(root: modelRoot))               // ios-h18p/ (.aimodelc); from the next kit release the arch defaults to this device's
let pcm = try await tts.synthesize("On device speech synthesis, running entirely on your iPhone.")
// pcm: [Float] @ 16 kHz mono

// Or stream — get each ~0.48 s chunk as it is generated (first chunk emitted at ~0.43 s). On iPhone
// RTF sits near 1.0, so pre-roll ~2 chunks (~1 s) before playback for smooth, gapless audio
// (perceived first audio ~0.9 s — still ~5x faster than waiting ~4 s for the whole clip):
let stats = try await tts.synthesizeStreaming(text) { chunk in player.play(chunk) }

The conversion scripts and the Swift host are in the zoo (conversion/voxcpm/) and CoreAIKit.

Notes

• Plain TTS (fixed speaker). VoxCPM's voice-cloning branch is a follow-on.
• Per-step quality is fp16-equivalent (int8 LM cos > 0.999 vs the fp32 reference); whole-utterance output is natural speech.
• Community port — not an official Apple model.

Acknowledgements

OpenBMB / VoxCPM. Built on Apple's Core AI.

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More models in this format: Core AI Model Zoo — 75 models, each with the recipe that produced it.

Want a different model on-device? Open a request — free, open weights only; the export and its measured numbers get published publicly.

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