---
license: cc-by-nc-4.0
language:
- en
tags:
- embeddings
- dense-retrieval
- matryoshka
- rag
- agents
- mteb
- sentence-similarity
- semantic-search
- text-embeddings
- text-embedding
- vector-search
- document-retrieval
- similarity-search
- classification
- clustering
- edge-ai
- on-device
- local-inference
- efficient-ai
- rag-retrieval
library_name: ogma
metrics:
- mteb
model-index:
- name: axiotic/ogma-small
  results:
  - task:
      type: sts
    dataset:
      name: MTEB STSBenchmark
      type: mteb/stsbenchmark-sts
      split: test
      revision: b0fddb56ed78048fa8b90373c8a3cfc37b684831
    metrics:
    - type: cosine_spearman
      value: 85.54
  - task:
      type: classification
    dataset:
      name: MTEB AmazonPolarityClassification
      type: mteb/amazon_polarity
      split: test
    metrics:
    - type: accuracy
      value: 76.72
  - task:
      type: clustering
    dataset:
      name: MTEB RedditClustering
      type: mteb/reddit-clustering
      split: test
    metrics:
    - type: v_measure
      value: 43.94
  - task:
      type: pair-classification
    dataset:
      name: MTEB TwitterSemEval2015
      type: mteb/twittersemeval2015-pairclassification
      split: test
    metrics:
    - type: cos_sim_ap
      value: 68.49
  - task:
      type: reranking
    dataset:
      name: MTEB MindSmallReranking
      type: mteb/mind_small
      split: validation
    metrics:
    - type: map
      value: 30.55
  - task:
      type: retrieval
    dataset:
      name: MTEB MSMARCO
      type: mteb/msmarco
      split: dev
    metrics:
    - type: ndcg_at_10
      value: 34.31
  - task:
      type: summarization
    dataset:
      name: MTEB SummEval
      type: mteb/summeval
      split: test
    metrics:
    - type: cos_sim_spearman
      value: 29.59
pipeline_tag: sentence-similarity
---

# ogma-small  ·  8.6M efficient text embedding model  ·  MTEB 56.32

> Efficient English text embedding model for semantic search, RAG, vector search, retrieval, clustering, classification, STS, and agent memory — MTEB 56.32, 8.6M parameters, 1024-token context

**Ogma Small** is the flagship efficiency model in the family. At 8.6M parameters it scores **56.32 MTEB** in our canonical 66-task Ogma paper results, while using only 38% of MiniLM-L6-v2's parameters, running 1.75× faster on CPU, and handling inputs 4× longer (1024 vs 256 tokens). Purpose-built to be the drop-in for every place you currently reach for MiniLM.

## Why the name Ogma?

Ogma is named after **Ogma** (also written Oghma), the Irish god associated with eloquence and credited in myth with inventing **Ogham**, an early alphabet for encoding language into symbols. That is the core job of an embedding model: turn language into compact vectors that machines can search, compare, cluster, and reason over.

---

## Use cases

ogma-small is the default efficiency model for **semantic search**, **RAG retrieval**, **agent memory**, **vector databases**, **document retrieval**, **text classification**, **clustering**, **STS / sentence similarity**, and lightweight reranking pipelines. It is aimed at teams looking for a small, fast MiniLM-style embedding model with longer context and strong MTEB quality.

Good fits:

- **On-device or local-first applications** where MiniLM-class quality is useful but model size, CPU latency, and privacy matter.
- **Production RAG systems** that need affordable embeddings for documents, chunks, tickets, chats, and internal knowledge bases.
- **Agent memory and tool-use systems** where frequent embedding calls should stay cheap and local when possible.
- **Vector search at scale** where smaller models and Matryoshka sub-dimensions can reduce index size and query cost.
- **Classification and clustering features** for safety filters, routing, topic grouping, deduplication, and analytics.

Choose ogma-small when you want the best balance of quality, speed, size, and deployability across edge, local, and server workloads.

---

## Highlights

- 🏆 **MTEB avg 56.32** — canonical Ogma paper result over 66/66 MTEB English tasks
- ⚡ **1.75× faster** than MiniLM on single-threaded CPU inference (92.9 vs 53.1 docs/s)
- 📏 **1024-token context** — 4× longer than all-MiniLM-L6-v2 (256 tokens)
- 🔀 **Symmetric routing** via task tokens — encode everything with `[SYM]`, or use `[QRY]`/`[QRY]` for retrieval (queries and documents both encoded with `task="qry"`); benchmark both routes on your task
- 📐 **Matryoshka dims**: [256, 128, 64, 32] — one model, any precision
- 🛡️ **+4.0% F1** on prompt injection detection vs MiniLM (same architecture series)

---

## Performance

### MTEB English — 66/66 tasks (category-averaged)

Benchmarked with [MTEB](https://github.com/embeddings-benchmark/mteb) v2.10.7 on the standard 66-task English benchmark using category averaging (same methodology as the MTEB leaderboard).

| Category | ogma-small | all-MiniLM-L6-v2 | Δ vs MiniLM |
|---|---|---|---|
| Classification | **66.49** | 62.62 | +3.87 |
| Clustering | **40.69** | 41.94 | -1.25 |
| PairClassification | **82.91** | 82.37 | +0.54 |
| Reranking | **50.51** | 58.04 | -7.53 |
| Retrieval | **42.05** | 41.95 | +0.10 |
| STS | **82.00** | 78.90 | +3.10 |
| Summarization | **29.59** | 30.81 | -1.22 |
| **Overall** | **56.32** | *56.09* | **+0.23** |

### Why choose Ogma Small?

ogma-small is the default recommendation for most use cases. It is MiniLM-class quality while being faster, smaller, and context-aware. Use **ogma-base** when you need the extra quality margin; use **ogma-mini** when you need to go sub-4M parameters.

### Safety — Toxicity & Prompt Injection Detection

Evaluated on the Ogma transformer architecture (same family). Embeddings are extracted then fed to a logistic regression (LR) or MLP classifier head — the embedding model itself is not fine-tuned. Evaluated against `all-MiniLM-L6-v2` as baseline.

#### 1. Jigsaw Toxic Comment Classification

**Dataset:** `Arsive/toxicity_classification_jigsaw` — Binary toxicity classification
**Train:** 25,960 · **Test:** 6,490

| Model | Classifier | Accuracy | F1 | Precision | Recall | AUC-ROC |
|---|---|---|---|---|---|---|
| **Ogma** | LogReg | 89.12% | **88.26%** | 89.09% | 87.44% | 95.74% |
| **Ogma** | MLP | 88.91% | 87.98% | 89.14% | 86.85% | 95.92% |
| MiniLM | LogReg | 87.32% | 86.25% | 87.46% | 85.07% | 94.96% |
| MiniLM | MLP | 91.71% | 91.24% | 90.13% | 92.39% | **97.16%** |

Ogma (LR) leads MiniLM (LR) by **+2.01% F1**. MiniLM (MLP) leads on this dataset — the additional training data (25K samples) allows the MLP to compensate for MiniLM's slightly weaker base representations.

#### 2. Prompt Injection Detection — deepset/prompt-injections

**Dataset:** `deepset/prompt-injections` — Binary injection detection
**Train:** 546 · **Test:** 116 (low-data regime)

| Model | Classifier | Accuracy | F1 | Precision | Recall | AUC-ROC |
|---|---|---|---|---|---|---|
| **Ogma** | LogReg | 86.21% | 84.62% | **100.0%** | 73.33% | **97.77%** |
| **Ogma** | MLP | **90.52%** | **90.27%** | 96.23% | 85.0% | 98.1% |
| MiniLM | LogReg | 82.76% | 80.39% | 97.62% | 68.33% | 94.52% |
| MiniLM | MLP | 87.07% | 86.24% | 95.92% | 78.33% | 93.96% |

Ogma leads across both classifiers: **+4.03% F1 (MLP)**, **+4.23% F1 (LogReg)**. Ogma's representations are better separated in the low-data regime — it achieves 100% precision with LogReg, meaning zero false positives.

#### 3. Prompt Injection Detection — neuralchemy/Prompt-injection-dataset

**Dataset:** `neuralchemy/Prompt-injection-dataset` — Binary injection detection
**Train:** 4,391 · **Test:** 942

| Model | Classifier | Accuracy | F1 | Precision | Recall | AUC-ROC |
|---|---|---|---|---|---|---|
| **Ogma** | LogReg | 95.22% | 95.93% | 95.84% | **96.01%** | **99.30%** |
| **Ogma** | MLP | **95.44%** | **96.16%** | 94.89% | 97.46% | **99.37%** |
| MiniLM | LogReg | 94.59% | 95.38% | 95.46% | 95.29% | 98.92% |
| MiniLM | MLP | 93.95% | 94.85% | 94.59% | 95.11% | 98.92% |

Ogma leads across all metrics: **+0.78% F1 (MLP)**, **+0.55% F1 (LR)**. Both models perform well at scale; Ogma maintains its edge and achieves higher AUC-ROC (99.37% vs 98.92%).

#### Summary

| Task | Ogma best F1 | MiniLM best F1 | Δ |
|---|---|---|---|
| Jigsaw Toxicity | 88.26% (LR) | 91.24% (MLP) | −2.98% |
| deepset Injection | **90.27% (MLP)** | 86.24% (MLP) | **+4.03%** |
| neuralchemy Injection | **96.16% (MLP)** | 95.38% (LR) | **+0.78%** |

Ogma is a stronger feature extractor for **prompt injection detection** — the safety-critical task for agent pipelines. MiniLM edges ahead on toxicity when given sufficient labelled data and a more powerful classifier head. For agentic use cases where detecting adversarial instructions is the priority, Ogma representations are the better choice.
---

## Architecture

| Property | Value |
|---|---|
| Architecture | Custom Transformer |
| Internal dim (`d_model`) | 256 |
| Output dim (`d_output`) | 256 |
| Transformer layers | 6 |
| Attention heads | 4 |
| Vocabulary | 30,000 (SentencePiece / AlbertTokenizer) |
| Max sequence length | **1,024 tokens** |
| Pooling | Mean pooling |
| Task tokens | `[QRY]` (query), `[DOC]` (document), `[SYM]` (symmetric) |
| Matryoshka dims | [32, 64, 128, 256] |
| Output normalisation | L2 (unit sphere) |
| Parameters | 8.6M |
| Model file | `model.safetensors` (33 MB) |

**Key design choices:**

- **Task token prepend:** A learnable task token (`[QRY]`, `[DOC]`, or `[SYM]`) is prepended to the input sequence before the transformer. **Recommended inference route: `[QRY]`/`[QRY]`** — encode both queries and documents with `[QRY]`; this benchmarked highest on MTEB. `[SYM]` everywhere is the next-best symmetric alternative. **We do not recommend `[DOC]` at inference time** — it is exposed for downstream fine-tuning, not as an asymmetric query/document route.
- **Matryoshka training:** The model is trained with Matryoshka Representation Learning, meaning embeddings truncated to any supported sub-dimension remain well-calibrated without retraining.
- **Mean pooling:** The average of all token outputs (excluding padding) produces the sentence embedding, which consistently outperforms CLS-token pooling in the Ogma architecture family.
- **L2 normalisation:** All outputs are unit-normalised; cosine similarity == dot product == euclidean similarity (up to a constant), simplifying downstream usage.

---

## Usage

### Installation

```bash
pip install torch tokenizers transformers huggingface_hub
```

### Basic Encoding

```python
from transformers import AutoModel, AutoTokenizer

model = AutoModel.from_pretrained("axiotic/ogma-small", trust_remote_code=True).eval()
tok   = AutoTokenizer.from_pretrained("axiotic/ogma-small", trust_remote_code=True)

sentences = [
    "The quick brown fox jumps over the lazy dog",
    "A fast auburn vulpine leaps over an idle canine",
    "The capital of France is Paris",
]
emb = model.embed(sentences, task="sym", tokenizer=tok)
# emb.shape → (256,) per sentence, L2-normalised

sim = (emb[0] @ emb[1]).item()   # cosine sim == dot product (L2-normalised)
print(f"paraphrase: {sim:.4f}")
```

`task="sym"` is a safe default for all similarity tasks (STS, clustering,
classification) and for retrieval. Ogma is trained for **symmetric routing** —
queries and documents are always encoded with the **same** task token. The two
recommended routes are:

1. `[SYM]` for everything (the safe default above), or
2. `[QRY]`/`[QRY]` — encode both queries **and** documents with `task="qry"`.

Try both on your downstream task; either can win depending on the data, and
`[QRY]`/`[QRY]` is the natural starting point when fine-tuning a classifier or
retrieval head on top of the embeddings.

### Retrieval

Encode queries **and** documents with the **same** task token. Below we show the `[QRY]`/`[QRY]` route — both calls use `task="qry"`. This is intentional (Ogma is symmetric, not asymmetric); swap in `task="sym"` to compare the SYM route on your data.

```python
from transformers import AutoModel, AutoTokenizer

model = AutoModel.from_pretrained("axiotic/ogma-small", trust_remote_code=True).eval()
tok   = AutoTokenizer.from_pretrained("axiotic/ogma-small", trust_remote_code=True)

queries = ["What is knowledge distillation?"]
docs = [
    "Knowledge distillation trains a smaller student model to mimic a larger teacher.",
    "The Eiffel Tower is in Paris, France.",
]

q = model.embed(queries, task="qry", tokenizer=tok)   # (256,) per query  — symmetric: both sides use qry
d = model.embed(docs,    task="qry", tokenizer=tok)   # (256,) per doc    — not a typo; Ogma is symmetric

scores = (q @ d.T).squeeze(0)   # cosine sim (L2-normalised, dot == cosine)
print(scores.tolist())          # [higher, lower] — first doc is relevant
```

### Matryoshka — Flexible Dimensionality

Ogma is trained with Matryoshka Representation Learning. Slice and re-normalise
to any supported sub-dimension with no retraining:

```python
import torch, torch.nn.functional as F
from transformers import AutoModel, AutoTokenizer

model = AutoModel.from_pretrained("axiotic/ogma-small", trust_remote_code=True).eval()
tok   = AutoTokenizer.from_pretrained("axiotic/ogma-small", trust_remote_code=True)

emb = model.embed(["hello world"], task="sym", tokenizer=tok)   # full 256d

for d in model.config.matryoshka_dims:
    sub = F.normalize(emb[:, :d], dim=-1)
    print(f"{d}d  norm={sub.norm(dim=-1).item():.4f}")
```
## Model Family

| Model | Params | Size | MTEB Avg | Class | Clust | PairClass | Rerank | Ret | STS | Summ | d_out | Context |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| **[ogma-large](https://huggingface.co/axiotic/ogma-large)** | 32.4M | 124 MB | **57.41** | 68.6 | 41.6 | 84.0 | 53.1 | 43.7 | 83.7 | 30.9 | 256 | 1024 |
| **[ogma-base](https://huggingface.co/axiotic/ogma-base)** | 13.3M | 51 MB | 57.02 | 67.74 | 41.49 | 83.73 | 51.25 | 42.36 | 82.84 | 29.73 | 256 | 1024 |
| **[ogma-small](https://huggingface.co/axiotic/ogma-small)** | 8.6M | 33 MB | **56.32** | 66.49 | 40.69 | 82.91 | 50.51 | 42.05 | 82.00 | 29.59 | 256 | 1024 |
| **[ogma-mini](https://huggingface.co/axiotic/ogma-mini)** | 3.5M | 14 MB | 53.06 | 61.77 | 37.38 | 79.66 | 47.39 | 36.21 | 77.71 | 31.33 | 256 | 1024 |
| **[ogma-micro](https://huggingface.co/axiotic/ogma-micro)** | 2.3M | 8.9 MB | 52.18 | 59.53 | 36.88 | 78.62 | 49.74 | 33.09 | 75.63 | 31.77 | 128 | 1024 |
| *all-MiniLM-L6-v2* | 22.7M | 87 MB | *56.09* | 62.62 | 41.94 | 82.37 | 58.04 | 41.95 | 78.90 | 30.81 | 384 | 256 |
| *potion-base-32M* | 32.0M | 123 MB | *51.22* | 66.0 | 39.2 | 78.2 | 50.9 | 32.2 | 73.9 | 29.8 | 256 | inf |
| *potion-base-8M* | 7.6M | 29 MB | *50.03* | 64.44 | 32.93 | 76.62 | 49.73 | 31.71 | 73.24 | 29.28 | 256 | inf |

All Ogma: MTEB 2.10.7, 66-task standard English set, category-averaged.
MiniLM/Potion: published scores from the [Model2Vec results page](https://github.com/MinishLab/model2vec/blob/main/results/README.md).

---

## Training Details

| Property | Value |
|---|---|
| Teacher model | `jinaai/jina-embeddings-v5-text-small` (CC-BY-NC-4.0) |
| Training paradigm | Knowledge distillation from cached teacher embeddings |
| Training data | ~7M curated English sentence pairs |
| Tokenizer | AlbertTokenizer (SentencePiece, vocab=30,000) |
| Embedding initialisation | PCA of teacher embeddings (128d) projected to d_model |
| Loss | Distillation + contrastive (balanced schedule) |
| Evaluation framework | MTEB 2.10.7 |

---

## Limitations

- **No text generation.** Ogma is an encoder-only embedding model.
- **English only.** Training data and evaluation are English-only.
- **Slower than static models.** Transformer inference is 40-100× slower than static models (Potion, Model2Vec) on CPU. The trade-off: contextual understanding and 4× longer sequences.
- **Non-commercial licence.** Due to distillation from a CC-BY-NC-4.0 teacher, Ogma inherits the NonCommercial restriction. Commercial use requires a separate Jina AI licence or retraining with a permissive teacher (Apache 2.0 compatible models like BGE or E5 can substitute at the cost of a full retraining run).
- **Reranking gap.** Ogma lags behind MiniLM-L6-v2 on reranking tasks (category avg delta: -7.5). This is an architectural characteristic: the model optimises for semantic similarity and classification over pairwise ranking.

---

## Licence & Attribution

This model is released under **[CC-BY-NC-4.0](https://creativecommons.org/licenses/by-nc/4.0/)** (Creative Commons Attribution-NonCommercial 4.0 International).

**Required attribution (must be included in all uses):**

> This model was trained via knowledge distillation from
> `jina-embeddings-v5-text-small` (https://huggingface.co/jinaai/jina-embeddings-v5-text-small)
> by Jina AI, licensed under CC-BY-NC-4.0.

---

## Citation

```bibtex
@misc{ogma2026,
  title     = {Ogma: Efficient Dense Retrieval via Structured Embeddings},
  author    = {Axiotic AI},
  year      = {2026},
  url       = {https://huggingface.co/axiotic/ogma-small},
}
```