---
base_model: google/gemma-4-E2B-it
description: Gemma 4 E2B instruction-tuned multimodal model with vision and audio
  for on-device inference.
license: apache-2.0
pipeline_tag: image-text-to-text
tags:
- vision
- audio
- completion
- tools
- apple-npu
---

# Gemma 4 E2B — Cactus engine bundle

Gemma 4 E2B instruction-tuned (vision and audio included), packaged for the
Cactus on-device engine.

A small, on-device model is fast and private, but sometimes wrong. At Cactus we
post-train models to *know when they are wrong*: we ship probes inside the
checkpoint that score every answer with a **confidence** between 0 and 1,
returned as structured data (never parsed out of the answer text). Answer
on-device when confidence is high; re-route to a bigger model when it's low:

```python
if confidence < 0.85:
    answer = ask_a_bigger_model(prompt)
```

## Benchmarks

Gemma 4 E2B Hybrid, the smallest Gemma model, matches Gemini 3.1 Flash-Lite on
most benchmarks by routing only 15–35% of queries to Flash-Lite and running the
rest itself:

| Benchmark | Handoff to match Flash-Lite (FP16) | At 4-bit | At 3-bit |
|---|---|---|---|
| ChartQA | 15–20% | 25–30% | 40–50% |
| MMBench | 30–35% | 40–45% | 50–55% |
| LibriSpeech | 25–30% | 35–40% | 55–65% |
| GigaSpeech | 30–35% | 40–45% | 50–55% |
| MMAU | 30–35% | 35–40% | 50–55% |
| MMLU-Pro | 45–55% | ~90% | n/a |

Quantisation quality is measured on
[Cactus Quants](https://github.com/cactus-compute/cactus/blob/main/docs/cactus_quants.md),
which performs well at uniform quantization; developers are encouraged to
benchmark Unsloth, GGUF, and MLX quantization independently.

## Quickstart

```python
# pip install cactus-compute
import json
from cactus.bindings.cactus import cactus_complete, cactus_init
from cactus.cli.download import download_bundle

lm = cactus_init(str(download_bundle("Cactus-Compute/gemma-4-E2B-it")))
result = cactus_complete(
    lm,
    [{"role": "user", "content": "What is the capital of France?"}],
    json.dumps({"max_tokens": 512, "auto_handoff": False}),
    None,
    lambda *_: None,
)
print(result["response"].strip())
print("confidence:", result["confidence"])
```

`"auto_handoff": false` returns the raw probe score so your app decides when to
escalate; leave it on to let the engine hand off by itself.

## Routing quality (AUROC)

AUROC measures how well the probe separates wrong answers from right ones
(higher = better, 0.5 is random, 1.0 is perfect):

| Hold-out | Modality | Cactus Hybrid | Token Entropy |
|---|---|---|---|
| MMLU | text MCQ | **0.770** | 0.697 |
| MMLU-Pro | text MCQ | **0.771** | 0.692 |
| ARC-Easy | text MCQ | **0.888** | 0.655 |
| ARC-Challenge | text MCQ | **0.834** | 0.646 |
| GSM8K (3-shot) | text gen | **0.782** | 0.731 |
| MMBench-EN-Dev | vision MCQ | **0.840** | 0.435 |
| ChartQA | vision QA | **0.779** | 0.615 |
| DocVQA | vision QA | **0.781** | 0.512 |
| MMAU | audio MCQ | **0.789** | 0.517 |
| GigaSpeech | audio | **0.876** | 0.343 |
| Earnings-22 | audio | **0.839** | 0.323 |
| LibriSpeech | audio | **0.822** | 0.427 |
| **Mean** | | **0.814** | **0.549** |

The strongest result: the probe was trained on **zero audio data**, yet achieves
0.79–0.88 AUROC on four audio benchmarks (two transcription, one audio MCQ, one
out-of-domain transcription). This rules out surface-level explanations: the
probe is reading a modality-independent correctness signal from the hidden
state, not memorizing patterns from training data.

## All formats

All Cactus Hybrid builds live in the
[Cactus Hybrid collection](https://huggingface.co/collections/Cactus-Compute/cactus-hybrid-6a60da4551074db058e8bb64):
[Transformers](https://huggingface.co/Cactus-Compute/gemma-4-e2b-it-hybrid) ·
[GGUF / llama.cpp](https://huggingface.co/Cactus-Compute/gemma-4-e2b-it-hybrid-GGUF) ·
[MLX](https://huggingface.co/Cactus-Compute/gemma-4-e2b-it-hybrid-mlx) ·
[Cactus engine](https://huggingface.co/Cactus-Compute/gemma-4-E2B-it).
Copy-paste quickstarts for every engine:
[github.com/cactus-compute/cactus-hybrid](https://github.com/cactus-compute/cactus-hybrid).

Gemma model use is subject to the Gemma terms.