---
title: "2026-09-18 Histo tissue segmentation API inspection"
description: "Inspected Histo 0.0.127 tissue-head, standalone WSI, and domain-representation orchestration contracts for NanoVirDx."
image: "https://docs.virdx.dev/img/virdx-social-card.png"
---

> Documentation Index
> Fetch the complete documentation index at: https://docs.virdx.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# 2026-09-18 Histo tissue segmentation API inspection

## Work Done

- Inspected the exact `histo-v0.0.127` source tag (`b31b1223`) in the local Histo checkout.
- Documented the public box-level v2 tissue head loader and runner, including `FeatureGrid`, RGB, normalization, and output requirements.
- Compared that path with `SemanticSegPredictor` whole-slide APIs and the full `domain_representation.process_scan` orchestration.
- Recommended that NanoVirDx delegate to `process_scan` for v2 domain representations rather than rebuilding embedding, windowing, merging, or persistence.
- Confirmed that standalone semantic whole-slide prediction returns arrays and has no production persistence helper; full domain persistence belongs to Histo's internal `WsiOutputs` path.
- No source files in the target monorepo were edited.

## Lessons Learned: Pitfalls

- The local Histo checkout did not initially have the `histo-v0.0.127` tag. Searching commits by package version found a merge from another branch, not the released commit. Querying remote tags and fetching the exact tag was necessary.
- The term "tissue segmentation" can refer to the v2 shared-embedding tissue head or the older/general semantic whole-slide predictor. They have different model and input contracts and must not be treated as interchangeable.

## Lessons Learned: Improvements

- The Histo SOP should name the released tag pattern (`histo-vX.Y.Z`) and distinguish box-level head APIs, standalone semantic WSI inference, and full domain-representation orchestration.
- A concise compatibility table for loaders, input ownership, outputs, and persistence would make future NanoVirDx adapter work faster and reduce accidental orchestration duplication.

Source: https://docs.virdx.dev/knowledge/inbox/2026-09-18-histo-tissue-segmentation-api-inspection/index.mdx