DESIGN: OS Vietnamese helps AI Agent write Vietnamese as a Vietnamese person would, rather than as a translation from English. The set includes 10 skills, a verified knowledge base, and an automatic testing toolset. Completely FREE: no paid packages, no accounts, no data sent anywhere.

Why we did it

After many years of creating products for Vietnamese users, and recently using AI to generate interfaces and content, we encountered the same set of recurring errors:

• Word-for-word translations: "Please enter your password", "As a user, I want...".
• Stacked diacritical marks like Ấ, Ệ, Ữ, Ợ are cut off due to low line-height; buttons break layout because Vietnamese words are longer than English.
• NFD Unicode strings copied from macOS corrupt search functions; amounts are written as 1,500,000 instead of 1.500.000.
• Claims like "best", "number 1" in advertising lack evidence; refer to outdated circulars.

What the set can do

• Checks by rules, not guesses: over 90 checking rules with unique codes (like CAL001 for machine translation, NFC001 for Unicode, NUM001 for number formatting, LAW001 for advertising terms needing proof). Each error comes with a correction suggestion, includes a mode for auto-correcting Unicode and punctuation style (hoà/hòa).
• Typography and interface: thresholds for line-height of stacked diacritics, character limits for buttons, tabs, badges, toasts; checks if font contains all Vietnamese characters; cross-verifies en.json and vi.json files, catches plural ICU errors.
• 24 domains of address, from UX microcopy to academic text.
• 339 pairs of evaluation samples for comparative standards.
• 12 verified knowledge modules with 53 SHA-256 checkpoints, able to run tests directly on your machine.
• No telemetry, no external libraries required (only Python 3.9+).

10 specialized skills

1. UX Writing, Design Tokens, and i18n for design systems.
2. SaaS landing pages, e-commerce, real estate (according to Advertising Law 75/2025).
3. Technical documentation: API, Runbook, Changelog, ADR, surveys.
4. B2B emails, Zalo OA/ZNS, official letters according to Decree 30/2020; data consent according to Decree 13/2023.
5. Finance, banking, electronic invoices: Circular 99/2025, Decree 70/2025, VietQR/Napas.
6. Education at 7 levels, from Kindergarten to Doctorate and professor/associate professor titles.
7. Healthcare: electronic medical records, prescriptions, mandatory declarations for functional foods (Decree 15/2018).
8. Civil, commercial, labor contracts; penalty caps for violations at 8% (Commercial Law 2005).
9. Hotels, tourism, airlines: transparent pricing, no ambiguous "++" prices.
10. Recruitment and HR: non-discriminatory JDs, minimum probation salary at 85% (Labor Code 2019).

For whom

Designers, PMs, developers, content writers, and legal teams using AI Agent to create products for Vietnamese users, wanting the first draft to be correct in Vietnamese and adhere to the law.

Free. Downloadable from GitHub and ready to use immediately.