---
title: "2026-09-18 NanoVirDx Histo v2 domain representation inference"
description: "Implemented a packaged Histo v2 inference adapter and DiffSim fine28 compatibility bridge."
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 NanoVirDx Histo v2 domain representation inference

## Work Done

- Implemented `DomainRepresentationPredictor` in NanoVirDx using Histo 0.0.127's public `load_models` and `process_scan` boundary.
- Added a flattened, packaged Histo v2.0 fine28/local configuration because the Histo wheel omits its repository-level Hydra config. Callers can still supply an existing `PipelineSettings`.
- Extended `DomainRepresentationBatch` and vxData downloads with the required nuclei segmentation artifact, and added aligned WSI/mask validation.
- Inspected `origin/cedrik/fk-fix` in DiffSim and confirmed that fine28 is the current Histo v2 taxonomy: 28 base classes plus 12 graded classes with sparse IDs 128-139.
- Ported Cedrik's nine-compartment mapping and tissue parameters into NanoVirDx. Added a narrow compatibility loader for DiffSim 0.1.100, which does not understand Histo v2 `region_ids`.
- Validated the adapter using a mocked Histo boundary. Validated a complete synthetic 40-class Histo v2 domain through T2, high-b DWI, and ADC simulation on Metal with finite outputs.
- Built the NanoVirDx wheel and confirmed that the vendored YAML is packaged. Ruff, Pyright, compileall, module boundaries, and diff checks passed.
- Committed and pushed mono commit `d78b25e8` to `origin/fk/nanovirdx`.

## Lessons Learned: Pitfalls

- DiffSim 0.1.100 validates a positional mapping against 40 region names but then indexes it with sparse labels up to 139. A 40-entry mapping therefore passes validation and fails during remapping; a 140-entry mapping fails validation.
- Histo 0.0.127 contains the domain-representation implementation but does not package its required configuration. A source-relative Hydra path is not a valid installed-package interface.
- Running Pyright from DiffSim's environment initially produced false missing-import errors. The NanoVirDx interpreter and Histo source path were needed for the relevant result.

## Lessons Learned: Improvements

- Publish Cedrik's name/`region_ids` mapping support in DiffSim, then remove NanoVirDx's `_domain_from_histo_v2` compatibility loader and return to the public `domain_from_histo` API.
- Package Histo's supported v2 settings and expose a default-settings helper, then delete NanoVirDx's vendored YAML.
- Add an Nx project and a small platform-independent adapter test target for NanoVirDx so its lazy Linux-only integrations are exercised in CI.

Source: https://docs.virdx.dev/knowledge/inbox/2026-09-18-histo-nanovirdx-domainrep-inference/index.mdx