ai-translated-localization

AI-Translated Localization

When to invoke

Scope decisions:

• Starting a new App and deciding which locales to support.
• Choosing a string catalog format (.strings vs .xcstrings).
• Planning the translation flow (manual / agency / AI agent).
• User asks "are 7 locales too many", "how do translations enter git", "how to handle multi-locale App Store metadata".

Execution:

• Adding new user-facing strings (UI keys, GC titles, ASC metadata, achievement descriptions) and need to fill out their non-source locales.
• Refreshing strings whose source language changed (extractionState: stale entries in xcstrings).
• Auditing whether a release's xcstrings is complete (every key has every locale, no <TRANSLATE> placeholders shipping).

Default decisions

Default 7 locales

Locale	Code	Notes
English	en	Catalog sourceLanguage; translation source for the fan-out
Traditional Chinese	zh-Hant	Primary language — author-written alongside en, never AI-translated
Japanese	ja	Largest adjacent market outside the Chinese sphere
Simplified Chinese	zh-Hans	Converted from zh-Hant + Mainland phrasing review
Spanish	es	World's second largest native-speaker base
Thai	th	Southeast Asia representative
Korean	ko	High-penetration Asian market

• Locale codes are the script-based BCP-47 forms (zh-Hant / zh-Hans), not region forms (zh-TW / zh-CN) — matches the committed catalogs and your repo's L10n completeness gate.
• Minimum set: zh-Hant + en (every project includes at least these two).
• Per-project locale lists can be adjusted, but English and zh-Hant are always included.

Translation flow

• Handled by an AI agent, recorded as a step in plan.md: "author en + zh-Hant by hand, fan out the other 5 locales from en, write into Localizable.xcstrings" (see Execution playbook Step 1).
• Covers:
  • In-app strings
  • Game Center leaderboard / achievement names (for games)
  • App Store metadata (title / description / keywords / what's new)
  • Description text inside the Privacy Manifest
• Every time strings are added / modified, run another round of the AI translation flow; the diff lands in a PR.

Catalog format

• Use Xcode's Localizable.xcstrings (String Catalog, introduced in Xcode 15+).
• Stop using legacy .strings / .stringsdict (unless an external tool forces it).
• xcstrings is JSON-structured: PR-friendly diffs and easy for AI to manipulate.

Rationale

• 7 locales cover most of the global market while remaining a polish scope a solo developer can sustain.
• AI translation quality for App UI strings (short, clear context) is at commercial level; long marketing copy is still recommended for human review.
• xcstrings JSON structure is naturally friendly to AI / diff / version control.
• zh-Hant as primary reflects the author's native-language accuracy; en is the fan-out source because translator competence is broader from English (see Field notes).

Deviation considerations

• Focused target market: shrink to zh-Hant + en + one target-market locale.
• No budget / no time: ship zh-Hant + en first; mark others as extractionState: stale for later.
• Regulated / sensitive content (medical / financial / kids): mandatory human review after AI translation; add a review step to plan.md.
• Special scripts / RTL (Arabic / Hebrew): UI needs additional layout verification, not just translation.

Execution playbook

Use when actually performing a translation pass. The flow is source-pair seed → AI fan-out → tricky-case review → completeness check.

Step 1 — Seed source pair (en + zh-Hant)

• Source language for translation must be English (broader translator competence across all target locales than zh-Hant).
• Authors write English first; zh-Hant is the project's primary native locale and is hand-written in parallel — not AI-translated from English. Both are written by the author with intent; the other 5 locales fan out from en.
• Each new key lands in xcstrings with at minimum en + zh-Hant populated and extractionState: manual.
• Other 5 locales (ja, zh-Hans, es, th, ko) start either absent or with the placeholder string <TRANSLATE> so the fan-out pass can find them with a single grep.

Step 2 — AI fan-out pass

For each target locale, translate each key from en (source-of-truth) into the target locale. The AI doing the translation should:

• Preserve substitutions: %@, %lld, %1$@, \n, markdown markers (**, _), and any ${...} interpolation tokens are copied verbatim.
• Match plural/variation forms: if xcstrings declares plural variations for en, all forms must exist in the target locale (zero / one / two / few / many / other) per CLDR plural categories for that locale — don't blindly copy English's two forms.
• Match length budget: if source is a button label (≤ 12 chars typical), keep target short. Don't let "OK" become a 6-word phrase. UI labels lose to long translations.
• Match register / tone: derive from en's tone. Buttons are imperative, descriptions are neutral, error messages are direct. Don't add politeness markers absent in source (see locale gotchas below).
• Preserve product nouns: app name, brand terms, mode names that share visual identity across locales (e.g., "Practice" → 練習 in both zh-Hant and ja for visual consistency). Maintain a small glossary captured per-project to enforce this.

After translation, set extractionState: translated (per Apple xcstrings convention) so Xcode no longer flags the key as needing attention.

Step 3 — Tricky-case review (locale-specific gotchas)

Lessons captured from real translation passes. Apply these as a second-pass review after the bulk AI fan-out.

Japanese (ja):

• Prefer semantic over literal. "Pencil" (notes / candidate input) → メモ, NOT 鉛筆. The literal kanji confuses Japanese users; the semantic UI term is correct.
• Drop politeness markers (です / ます) in button labels and short UI strings — Japanese app UIs are typically declarative/imperative, not polite.
• 漢字 vs かな: prefer 漢字 for nouns, ひらがな for particles, カタカナ for loanwords. Don't romanize unless the source is romanized.

Thai (th):

• No politeness markers (ครับ / ค่ะ) in UI strings unless the app's voice is deliberately conversational. Calm/neutral apps drop them.
• Compound nouns: "leaderboard" → กระดานผู้นำ (no single-word equivalent). Accept the multi-word form.
• Thai has no word boundaries — sentence length affects line break behavior. UI strings >24 chars need spot-check rendering.

Korean (ko):

• Use informal-formal style (해요체) for app UI by default — neither too casual (반말) nor overly formal (합쇼체).
• 한자 should be avoided unless disambiguation is needed; pure 한글 is the modern default.
• Postpositions (조사) change based on preceding character's final consonant; AI usually handles this, but spot-check 을/를, 이/가, 은/는.

Spanish (es):

• Default to neutral Latin American Spanish unless the project explicitly targets Spain (es-ES). Avoid vosotros forms; use ustedes.
• Gender agreement: nouns referring to the user (e.g., "completed") need gender-neutral phrasing if the user's gender is unknown.

Simplified Chinese (zh-Hans):

• Convert from zh-Hant (not from en) for terminology consistency; the AI still needs to substitute Mainland-preferred terms (软件 vs 軟體, 移动 vs 行動, 视频 vs 影片).
• DON'T just run tongwen character conversion — phrase choice differs (e.g., zh-Hant 「設定」 → zh-Hans 「设置」, not 「設定 → 设定」).

English (en):

• US English by default. UK spellings (colour, centre, analyse) only if explicitly targeted.
• Sentence case for buttons and UI; Title Case only for proper nouns and app section headers.

Step 4 — Visual / glossary consistency

Beyond per-string correctness, enforce a project-level glossary so the same concept renders identically across locales and screens:

• Mode names (e.g., "Daily" / "Practice") — pick one term per locale and use it everywhere (HomeView card, hub header, navigation title, Settings labels).
• Product nouns (app name, branded features) — don't translate.
• Difficulty labels (Easy / Medium / Hard) — short, consistent.
• Action verbs (Submit / Confirm / Cancel) — match iOS native terminology in each locale (Apple has localized Human Interface Guidelines for major locales).

Maintain the glossary as either inline comments in xcstrings, or a sidecar Localization-Glossary.md in docs/ if it grows.

Step 5 — Completeness check (before PR)

Verification gates before merging a translation pass:

• <TRANSLATE> count across xcstrings = 0 (none shipped).
• extractionState: stale count = 0 (all stale entries refreshed).
• Per-key locale coverage = 100% (parse xcstrings JSON; every localizations dict has every declared locale).
• For plural keys: every locale has every plural form required by CLDR for that locale.
• Substitution token parity per key: en has N %@ → all locales have N %@ (or locale-specific reordering via %1$@ / %2$@).
• Spot-check 3-5 keys per locale visually in the simulator with Scheme → Run → Options → App Language.

L10n gate scope — and its two blind spots

Your repo's L10n completeness gate (CI-enforced) checks per-key locale completeness: every key present in a catalog has all declared locales, no <TRANSLATE>. Two things it does NOT catch — both have shipped English-fallback bugs in real projects:

1. A required key being absent entirely. The gate validates keys that exist; it cannot know a newly-activated capability needs a key that no catalog has. When an app adopts a shared feature (audio settings, ATT primer, reminders), its catalog can ship missing keys → the UI renders raw dotted keys or English literals, and the gate stays green. After wiring any shared-UI capability into a new app, diff its catalog's key set against an app that already has the feature (real-world: a new game adopted shared audio-settings UI without copying the required catalog keys; another adopted an ATT primer and the raw dotted keys appeared at runtime — both passed the gate).
2. A key referenced from shared UI code but absent from an app's catalog. Per-key completeness alone will NOT catch this — the gate only validates keys that already exist in a catalog, so a key referenced from a shared UI module that the app's own catalog never declares renders raw at runtime while the gate stays green. Build a shared-code dotted-key gate: every dotted-namespace key (e.g. leave.game.close, att.primer.title) referenced from a shared UI module (SharedUI / SettingsUI / any shared UI module) must exist in every app catalog or CI fails. Scope it to dotted keys to avoid app-conditional English-phrase false positives — English-phrase shared keys are a separate, harder case (no dotted namespace to anchor on; track them with a dedicated audit rather than this gate).

xcstrings editing footgun

When adding keys to a Localizable.xcstrings, text-splice the new entries into the file — do not round-trip the whole catalog through a Python/JSON load → dump. The round-trip reformats Xcode's style ("k" : v space-before- colon + Xcode key order) and produces a multi-thousand-line noise diff that buries the real change. Splicing keeps a clean, reviewable diff (real example: 4400-line noise diff collapsed to 192 lines after switching to splice approach).

Tooling notes

• xcstrings is JSON; parse with any JSON library. Schema: {"sourceLanguage": "en", "strings": {<key>: {"localizations": {<locale>: {"stringUnit": {"state": "translated", "value": "..."}}}}}}.
• Plural variations use {"variations": {"plural": {<cldr-form>: {"stringUnit": {...}}}}} instead of a single stringUnit.
• When fanning out via an LLM, send a single key + source + glossary in the prompt; don't batch hundreds at once (latency wins less than accuracy loses).
• For ASC metadata (App Store description, keywords, "what's new"), use the same flow but route to the ASC API endpoints rather than xcstrings. The translation principles (length budget, register, gotchas) apply identically.

Verification checklist

• Localizable.xcstrings exists and each key has 7 locale entries (2 for the minimum set).
• App Store Connect metadata is complete per locale (including screenshot captions).
• Game Center / achievement display names are complete per locale.
• PrivacyInfo.xcprivacy description itself doesn't need to be multi-locale, but the corresponding App Store privacy policy page does.

Related skills

• apple-platform-targets: xcstrings requires Xcode 15+; aligns with the deployment target's toolchain.
• spec-phase-orchestration: "translation" should be an explicit step in plan.md.

Field notes

Real translation passes have surfaced these recurring decisions:

• Source = en, primary = zh-Hant — both written by author. The other 5 fan out from en because translator competence is broader from English than from Chinese for th / ko / es.
• Glossary beats per-string correctness — visual consistency across screens matters more than the perfect translation of any single string.
• 5 locales in one pass is the sweet spot — fewer wastes the per-pass setup; more risks AI fatigue degradation on the last locales. 1 commit per locale keeps PR review tractable.