README.md

---
license: gemma
base_model: google/gemma-4-31B-it-qat-q4_0-unquantized
tags:
- core-ai
- coreai
- apple
- gemma
- gemma-4
- on-device
- metal
pipeline_tag: text-generation
library_name: coreai
---

# Gemma 4 31B (dense) — Core AI

Apple **Core AI** (`.aimodel`) conversion of Google's **Gemma 4 31B** dense text decoder, ported
directly from the QAT release
[`google/gemma-4-31B-it-qat-q4_0-unquantized`](https://huggingface.co/google/gemma-4-31B-it-qat-q4_0-unquantized).
Decode-only, runs on the **stock pipelined engine** on Apple Silicon (Mac-class, ~16 GB).

> **Frontier dense, unblocked by a custom Metal kernel.** Gemma 4 31B's full (global) attention
> layers have a 32-head × 512 Q tensor that overflows MPSGraph's GPU decode scratch heap — the stock
> SDPA crashes at the first token ([apple/coreai-models#27](https://github.com/apple/coreai-models/issues/27),
> the same bug as the 12B). This bundle ships a **custom flash-decode SDPA kernel** on the full
> layers (block-GQA over the 31B's 4 global KV heads) that removes the offending op, so the model
> runs.

<!-- gen-cards:use-it begin id=gemma-4-31b (managed by scripts/gen-cards — edit cards.json / QuickStart.swift, not this block) -->
## Use it

▶️ **Run it (source)** — the [ChatDemo runner](https://github.com/john-rocky/coreai-kit/tree/main/Examples/ChatDemo)
(GUI + CLI, one app for every chat model in the catalog):

```bash
git clone https://github.com/john-rocky/coreai-kit
open coreai-kit/Examples/ChatDemo/ChatDemo.xcodeproj
# → Run, then pick "Gemma 4 31B" in the model picker

# agents / headless (macOS):
cd coreai-kit/Examples/ChatDemo
swift run chat-cli --model gemma-4-31b --prompt "What can you do, offline?"
```

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

```swift
import CoreAIKit

let chat = try await ChatSession(catalog: "gemma-4-31b")
let reply = try await chat.respond(to: prompt)
// reply: the answer, generated fully on-device
```

The take-home is [`Examples/ChatDemo/Sources/QuickStart.swift`](https://github.com/john-rocky/coreai-kit/blob/main/Examples/ChatDemo/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 `ChatSession` across turns for its transcript.
Multi-turn? Hold the `ChatSession` and call `respond(to:)` per turn — it keeps the
conversation history; `streamResponse(to:)` yields tokens as they decode.

**Integration checklist**

- SPM: `https://github.com/john-rocky/coreai-kit` → product **CoreAIKit**
- Info.plist: none needed
- Entitlements: none needed (macOS)
- First run downloads the model — 18.0 GB (Mac) — 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
<!-- gen-cards:use-it end -->

## Bundle (`gpu-pipelined/`)

| bundle | quant | size | decode (M4 Max) |
|---|---|---|---|
| `gemma4_31b_qat_decode_int4linsym_msdpa_g8` | int4 (q4_0-aligned absmax) | 19 GB | **17.2 tok/s** (prefill 22.1) |

int4 from Google's QAT checkpoint (q4_0 grid). A frontier 31B at int4 is bandwidth-bound, so decode
is in the MLX-parity range — the value is "Core AI runs a frontier dense model the stock engine
cannot." Mac-only (exceeds the iPhone memory budget). The `_g8` suffix is the higher-occupancy
flash-decode kernel (8 SIMD-groups per head split the global layers' KV scan; same numerics).

## Architecture

Clean dense `gemma4` text decoder — **no** PLE / AltUp / Laurel / MoE / KV-sharing. 60 layers,
hidden 5376, 32 heads, vocab 262144, softcap 30, tied embeddings. 5:1 sliding:full; dual head_dim
(sliding 256 / full `global_head_dim` 512); full layers use `num_global_key_value_heads` 4 with
`attention_k_eq_v` (value = raw k_proj). Both attention shapes ride one growing KV pair, so the
bundle loads on the stock `CoreAIPipelinedEngine` (2 states, no engine patch); the full layers' SDPA
runs as a custom Metal flash-decode kernel.

## Usage

```bash
huggingface-cli download mlboydaisuke/Gemma-4-31B-CoreAI \
    --include "gpu-pipelined/gemma4_31b_qat_decode_int4linsym_msdpa_g8/*" \
    --local-dir ./gemma4-31b-coreai

COREAI_CHUNK_THRESHOLD=1 llm-runner \
    --model ./gemma4-31b-coreai/gpu-pipelined/gemma4_31b_qat_decode_int4linsym_msdpa_g8 \
    --prompt "What is the capital of France?" --max-tokens 64 --chunk-size 1
```

## Conversion

Community zoo:
[github.com/john-rocky/coreai-model-zoo → `zoo/gemma4-31b.md`](https://github.com/john-rocky/coreai-model-zoo/blob/main/zoo/gemma4-31b.md).

## License

Gemma — governed by the [Gemma Terms of Use](https://ai.google.dev/gemma/terms).