Scotoma-small

Support on Ko-fi or X Money: @DJLougen

scotoma-small is the token classifier inside the Scotoma engine of Scrub N Paste, an on-device clinical PHI redaction app for macOS (Tauri + Rust). It is microsoft/deberta-v3-small (141M parameters, 98M of which are the embedding table) fine-tuned to tag 21 HIPAA Safe-Harbor-style identifier categories, then exported to ONNX and quantized to per-channel int8.

Headline (sealed evaluation 3, pre-registered, 7,108 synthetic clinical notes, scored once): rules + scotoma-small leaked 2 notes; rules + OpenMed-PII-SuperClinical-Large @0.10 leaked 26. Exact two-sided McNemar p = 8.0 × 10⁻⁷. Per note it costs about 20 ms against about 240 ms on a laptop CPU. Details and caveats are below.

_{Over-redaction shown as-is: “148/92”, “SpO2” and “Civic” were boxed — false positives on vitals and the car model; every planted identifier was covered.}

Nothing leaves the machine. In Scrub N Paste this model runs inside a local ONNX Runtime; there is no network path in the inference code.

Intended use

• Finding HIPAA Safe-Harbor identifiers in English clinical-style prose, as the learned half of a redaction system. Scrub N Paste pairs it with the deterministic Scotoma rules engine; the shipped configuration is rules + this model, with a review screen before anything is copied out.
• Direct ONNX inference in your own pipeline (see below).

Out of scope / not a substitute for:

• A guarantee of complete de-identification. It is a helper for a human who reviews the output, not an unattended compliance tool. Under 45 CFR 164.514(a) expert determination, liability is yours.
• Real clinical corpora. Every benchmark number below is on synthetic notes written by an LLM with planted identifiers. Performance on real clinical text (e.g. i2b2/n2c2) has not been measured yet.
• Non-English text; handwritten or table-heavy documents.
• Images on their own. The model reads text only. When the app redacts a screenshot, image or PDF, it runs on-device OCR first, so OCR misreads carry through.

How to use

In Scrub N Paste

Scrub N Paste (macOS) bundles this model. Hotkeys: ⌘⌥S redact selection/clipboard, ⌘⌥R restore originals, ⌘⌥D capture a screen region and redact via on-device OCR, ⌘⌥N blank note, ⌘⌥V dictate. Output renders either as [CATEGORY_N] tags or as realistic stand-ins, and a review screen shows the redacted text before you copy it. Open file… redacts an image or PDF. It writes a new image-only copy with solid black boxes, and no hidden text layer. A CLI (scotoma) exposes the same engine, including scotoma redact-file IN OUT.

Plain onnxruntime

import json
import numpy as np
import onnxruntime as ort
from tokenizers import Tokenizer

cfg = json.load(open("config.json"))
id2label = {int(k): v for k, v in cfg["id2label"].items()}
THRESH = cfg.get("scotoma_threshold", 0.02)
MAX_LEN = cfg.get("scotoma_max_len", 384)

tok = Tokenizer.from_file("tokenizer.json")
sess = ort.InferenceSession("model_quantized.onnx")

def softmax(x):
    x = x - x.max(-1, keepdims=True)
    e = np.exp(x)
    return e / e.sum(-1, keepdims=True)

def identifier_spans(text):
    enc = tok.encode(text)
    ids, attn = enc.ids[:MAX_LEN], enc.attention_mask[:MAX_LEN]
    logits = sess.run(["logits"], {
        "input_ids": np.array([ids], dtype=np.int64),
        "attention_mask": np.array([attn], dtype=np.int64),
    })[0][0]
    probs = softmax(logits)
    # identifier probability = sum over every non-O class
    n_id_classes = len(id2label) - 1                      # 42 = B-/I- × 21
    score = probs[:, 1:1 + n_id_classes].sum(-1)          # labels 1..42 are the identifiers
    spans = []
    for (s, e), p in zip(enc.offsets[:MAX_LEN], score):
        if s == e:            # special tokens have a zero-width offset
            continue
        if p >= THRESH:
            if spans and s <= spans[-1][1]:   # merge adjacent subword tokens
                spans[-1] = (spans[-1][0], e)
            else:
                spans.append((s, e))
    return spans

Raise the threshold for higher precision / lower recall; the shipped default is 0.02 because a missed identifier costs far more than an extra redaction.

Labels

BIO tags over 21 categories (43 classes total). The categories are HIPAA Safe-Harbor identifier classes; ORG is a quasi-identifier the app only redacts in strict mode:

NAME, ADDRESS, LOCATION, ZIP, DATE, AGE, PHONE, FAX, EMAIL, SSN, MRN, PLAN, ACCOUNT, LICENSE, VEHICLE, DEVICE, URL, IP, BIOMETRIC, ID, ORG

Training

Data (92,273 documents total; manifest train_v2.manifest.json, seed 0):

The previous shipped model (v1-small) used the same recipe with 4,658 planted clinical notes. Test-pool identifier values and formats are disjoint from all training pools.

Evaluation

Method, in one paragraph: identifiers are chosen first from a test-only pool (universe C, disjoint from training pools); an LLM (RedHatAI/diffusiongemma-26B-A4B-it-FP8-dynamic, Apache-2.0 — a different family from the training-data generator) writes notes around [[NAME_1]]-style placeholders; a fail-closed verifier substitutes the values so every label is exact by construction and rejects any note with missing placeholders or an unplanted-looking identifier. "Novel-format" sets re-draw the structured identifiers from 56 test-only formats never used in training. Every system is scored by the same scorer. Metric: leak-document rate — share of notes with at least one identifier left untouched — under the constraint that over-redaction (share of ordinary text redacted) stays ≤ 1%. Sealed sets are generated first and scored exactly once under a committed pre-registration.

Naming: scotoma-small was called v2-small during development. The pre-registrations and logs under bench/results/ (SEALED3_PREREG.md, SEALED3_LOG.md) use that name; it is the same file (sha256 33be2438…87e41).

Sealed evaluation 3 (7,108 notes per set; this model, scotoma-small + rules)

A powered re-match vs rules+OpenMed-large@0.1, pre-registered before scoring (exact two-sided McNemar on per-note leak indicators, α = 0.05; secondary tests listed in SEALED3_PREREG.md). Final, 2026-10-05:

• Primary verdict: significant win — rules + scotoma-small vs rules + OpenMed-large@0.1 on clin3, discordant notes 1 vs 25 (both leaked on 1), exact two-sided McNemar p = 8.0 × 10⁻⁷. All secondary comparisons are also significant wins (p ≤ 8.0 × 10⁻²⁹).
• Bootstrap CI of the difference: +0.3 percentage points, 95% CI [+0.2, +0.5].
• Over-redaction (must be ≤ 1%): ours 0.1% alone, 0.2% with rules; OpenMed-large 0.1–0.3% alone, 0.3–0.5% with rules.
• Latency: ~20 ms/note for scotoma-small vs ~240 ms/note for OpenMed-large on an M3 Max CPU; per-note CPU cost measured on a 20-core ARM Linux workstation was ~0.2 s vs ~4 s (some sealed-3 runs ran off-Mac at the same commit and sha256, with exact dev parity — see SEALED3_LOG.md).

Pre-registered dev-set selection (clin2_dev + clin2_novel_dev, rules + model @0.02): v1-small leaked 6 notes total (4 + 2), v2-small (released as scotoma-small) leaked 2 (2 + 0) with over-redaction ≤ 0.2% — so it is the "ours" candidate.

Per-category recall (clin3, ours vs OpenMed-large@0.10)

Sealed evaluation 2: the full field (860 notes per set; previous model v1-small)

(n/m = predictions were precomputed on GPU, so no comparable CPU timing.)

Verdicts (paired bootstrap 95% CI): statistically tied with OpenMed-large@0.1+rules (2 vs 5 leaked notes) and with OpenMed-small@0.02+rules on familiar formats; significantly better than everything else listed. History: sealed evaluation 1 (874 notes, v0 model) was a significant loss to OpenMed-large@0.1+rules (1.9%/1.7% vs 0.5%) — that result drove the v1 training-data work.

Limitations and bias

• All test text is synthetic. The clinical notes were written by an LLM with planted identifier values. Real-note performance (i2b2/n2c2) is unmeasured and may be worse.
• Familiar-format sets reuse the identifier format families of the training generator (the values are disjoint); novel-format sets exist to correct for that — on them the model alone degrades more (v1: 2.6% vs 0.6% alone), which is exactly what the rules engine covers.
• Trained on English clinical-style prose; other domains and languages are untested. Distribution shift (new identifier formats, OCR noise, tables) can raise the leak rate.
• Known false-positive pattern: eponymous clinical terms — e.g. "Babinski sign" can be tagged as a NAME. The review screen exists because of cases like this.
• Latency was measured on an Apple M3 Max CPU, and per-note CPU cost on a 20-core ARM Linux workstation. Other platforms are unmeasured. The app is macOS-only for now.
• A helper, not a guarantee. A human must review the output before relying on it.

Licence and attributions

• Model weights released under Apache-2.0. Base model microsoft/deberta-v3-small is MIT-licensed.
• Training data: nvidia/Nemotron-PII (CC BY 4.0, © NVIDIA); synthetic templates and planted clinical notes generated for this project (generator Qwen/Qwen3-14B-AWQ, Apache-2.0).
• Benchmark notes generated by RedHatAI/diffusiongemma-26B-A4B-it-FP8-dynamic (Apache-2.0).
• Competitor models were evaluated for benchmarking only and are not included: OpenMed models (Apache-2.0), knowledgator GLiNERs (Apache-2.0), nvidia/gliner-PII (NVIDIA Open Model License), openai/privacy-filter (Apache-2.0), StanfordAIMI de-identifier (MIT), ai4privacy (MIT), piiranha (CC-BY-NC-ND-4.0 — never redistributed), Microsoft Presidio (MIT).

Citation

@misc{scotoma-small,
  title  = {Scotoma-small: on-device clinical de-identification},
  author = {Daniel Lougen},
  year   = {2026},
  note   = {ONNX, per-channel int8; sha256 33be2438...}
}

Contact

Custom de-identification for your document types and identifier formats, new domains, on-device ML deployment, and benchmark design — the author is available for paid work: Hugging Face · Ko-fi · X @DJLougen