The in-page file editor (<repo>/edit/<branch>/<file>) on github.com is built on CodeMirror 6 (verified via DOM: cm-editor, cm-scroller, cm-content, cm-line, cm-announced, aria-labelledby="codemirror-label" — all CM6-specific class conventions, CM5 uses CapitalCase CodeMirror-*). It bundles a curated set of language extensions but does not currently support 1C:Enterprise (BSL) / OneScript (file extensions .bsl, .os).

Status today

• Blob view (<repo>/blob/...) highlights BSL correctly via github-linguist/linguist → vendor/grammars/vsc-language-1c-bsl (TextMate) → github/treelights ✓
• Edit view (<repo>/edit/...) on the same file shows plain monochrome text, since the CM6 bundle has no BSL language extension loaded.

Reach

GitHub Code Search for lang:1C+Enterprise returns 2.6M+ files across many thousand repositories (corporate ERP/CRM forks, OneScript open-source tooling, community projects). All of them lose syntax highlighting the moment a contributor clicks the pencil icon.

What's available

We've just published a production-ready CM6 language extension that you can bundle directly:

• Package: @1c-syntax/codemirror-lang-bsl on npm
• Latest: v0.3.1
• License: MIT
• Size: 117 KB unpacked, 33 KB tarball
• Provenance: sigstore-attested via npm Trusted Publishing; verifiable with npm view @1c-syntax/codemirror-lang-bsl provenance
• Dependencies: only @codemirror/language, @lezer/{common,highlight,lr} (no runtime weight beyond what your bundle already ships)
• Source: https://github.com/1c-syntax/codemirror-lang-bsl
• Live demo: https://1c-syntax.github.io/codemirror-lang-bsl/ (with side-by-side editor + AST viewer)
• Coverage: parses 100% of syntactically valid 1C:Enterprise code across the 67 real-world .bsl/.os files we sampled from 1c-syntax/bsl-language-server and 1c-syntax/vsc-language-1c-bsl test fixtures. The handful of files the parser doesn't accept are 100% by-design malformed — intentional *ParseError* regression inputs or source-level typos (e.g. Неопределенно instead of Неопределено, Функция Имя written without parentheses). Zero hard failures (no thrown exceptions).
• Features: full BSL grammar (Russian and English keyword surfaces, preprocessor including #Если/#Область/#Использовать/#Удаление/#Вставка, regions, doc-comments, multi-line strings, date literals, async/await, labels) and an embedded SDBL query language overlay inside string literals (statement keywords, metadata-object paths, virtual-table suffixes, parameters, {...} data-composition blocks)
• Maintainer: the 1c-syntax org, which already maintains the TextMate grammar Linguist uses, the BSL language server, and the ANTLR parser

Integration shape

import { bsl } from "@1c-syntax/codemirror-lang-bsl"
// …in the language-extension map for the CM6 editor:
if (filename.endsWith(".bsl") || filename.endsWith(".os")) return bsl()

Asks

1. Could the GitHub web-editor team consider adding this extension to the CM6 bundle that powers <repo>/edit/...?
2. If there's a public process (review form, language-extension allow-list, etc.) for community-maintained CM6 grammars to land in the editor — please point us at it. We'd prefer to follow whatever the documented path is.
3. If no such process exists today, we'd be happy to collaborate on what one would look like — the 1c-syntax org has the bandwidth to keep the grammar in sync with the language as it evolves.

Happy to answer technical questions, share benchmark data, or help with the bundling step.