English is the default interface language. Turkish is available in Settings → Language and is remembered in the current browser. Switching language preserves the current editor and unsaved values. Open tabs observe preference changes. This preference is separate from portable project definitions and does not grant project-write permission.
The Turkish catalog loads only when requested; English messages remain their source strings. There is no translation service, remote request or new runtime dependency. Failed loading preserves the current interface and offers an error rather than changing to an incomplete language. Unknown third-party diagnostics fall back to their original text.
Project/source/skill names, imported descriptions, commands, file paths, document bodies and authored guidance retain their original language. Interface localization must never rewrite snapshots or generated project instructions. Dates and counts use the selected locale; Turkish count labels use an uninflected noun after a number.
Technical terminology
Preserve established technical vocabulary across interface languages: Skill/Skills, Plugin/Plugins, MCP, Agent, Harness, Preset, Snapshot, Provider, Hook, CLI, API and transport names such as stdio. Product type labels retain their standard names, including Skills, MCP servers and Plugins. Translate surrounding actions, explanations and ordinary navigation; Settings and Library still have localized labels. Turkish sentences may use normal Turkish suffixes on a preserved technical noun, such as snapshot’ı kaydet or skill’leri bul, and counts use 2 skill.
Do not replace a Skill with a translated word meaning an ability, a Plugin with a generic extension, or a Snapshot with a word that could mean a screenshot. Keep capitalization of acronyms, product names, identifiers and commands. Terminology changes belong in reviewed catalog messages; never transform user-authored content or apply a runtime word-replacement pass.
Catalog maintenance
web/locales/en.json is the canonical message inventory. Its values equal the English source keys. web/locales/tr.json contains matching translations. New UI copy uses t('English source', { name: value }) with named {{name}} interpolation. Keep a complete sentence together when word order matters. Render results as React text, never HTML.
bun run check:locales checks both inventories and literal UI translation calls. Unit tests verify nonempty translations, matching placeholders, fallback behavior, inherited-property handling, preserved inserted names and localized count grammar. bun run test:ui includes language switching, persisted choice, multiple tabs, preserved drafts, unchanged authored names, seven translated pages and desktop/mobile accessibility checks.
When adding a locale, register its native display name, loader and supported identifier in web/i18n.ts; add a complete catalog and locale-specific number/plural behavior, then extend browser checks. Do not expose a language with a partially populated catalog as supported.
Adding languages
English and Turkish are available. More languages are welcome: a new locale needs a complete catalog that passes the same coverage, interpolation and layout checks before it appears in the selector. Vendor messages and your own Library content stay in their original language.