@molecule/api-ai-translation-deepl

DeepL translation provider for molecule.dev.

Implements the full @molecule/api-ai-translation contract (translate, getSupportedLanguages, getUsage) over the DeepL REST API, auto-batching large inputs (50 texts per request, DeepL's limit).

Auto-generated, AI-first package reference for the molecule.dev ecosystem. It is written to be read by coding agents as much as by people, and is generated from this package's source — edit src/index.ts JSDoc, not this file.

Quick Start

import { setProvider, requireProvider } from '@molecule/api-ai-translation'
import { provider } from '@molecule/api-ai-translation-deepl'

setProvider(provider) // at startup — lazy; reads DEEPL_API_KEY on first use

const { translations } = await requireProvider().translate({
  text: 'Hello, world!',
  targetLang: 'DE',
})

Type

provider

Installation

npm install @molecule/api-ai-translation-deepl @molecule/api-ai-translation @molecule/api-secrets

API

Interfaces

`DeeplConfig`

Configuration for the DeepL translation provider.

interface DeeplConfig {
  /** DeepL API key. Defaults to DEEPL_API_KEY env var. */
  apiKey?: string
  /**
   * Base URL for the DeepL API.
   * Defaults to 'https://api-free.deepl.com' for free keys (ending in ':fx'),
   * or 'https://api.deepl.com' for pro keys.
   */
  baseUrl?: string
  /** Default formality preference. Defaults to 'default'. */
  defaultFormality?: 'default' | 'more' | 'less' | 'prefer_more' | 'prefer_less'
  /** Default model type preference. Defaults to 'latency_optimized'. */
  defaultModelType?: 'quality_optimized' | 'prefer_quality_optimized' | 'latency_optimized'
}

Functions

`createProvider(config)`

Creates a DeepL translation provider instance.

function createProvider(config?: DeeplConfig): AITranslationProvider

config — DeepL-specific configuration (API key, base URL, defaults).

Returns: An AITranslationProvider backed by the DeepL REST API.

Constants

`provider`

The provider implementation.

const provider: AITranslationProvider

`aiTranslationDeeplSecretDefinitions`

Secret definitions required by the DeepL translation bond.

const aiTranslationDeeplSecretDefinitions: SecretDefinition[]

Core Interface

Implements @molecule/api-ai-translation interface.

Bond Wiring

Setup function to register this provider with the core interface:

import { setProvider } from '@molecule/api-ai-translation'
import { provider } from '@molecule/api-ai-translation-deepl'

export function setupAiTranslationDeepl(): void {
  setProvider(provider)
}

Injection Notes

Requirements

Peer dependencies:

@molecule/api-ai-translation >=1.0.1
@molecule/api-secrets ^1.0.1

Environment Variables

DEEPL_API_KEY (required) — DeepL API key
- Setup: Copy the authentication key from your DeepL account (free keys end with ":fx").
- Get it here: https://www.deepl.com/en/your-account/keys
- Example: 279a2e9d-...:fx

Runtime Dependencies

@molecule/api-ai-translation
@molecule/api-secrets
Wiring: bond the lazy provider export once — setProvider(provider) — or setProvider(createProvider(config?)) to pass explicit config. Use the core's setProvider, NOT bond('ai-translation', …).
Config: DEEPL_API_KEY (required; free keys end in :fx and auto-route to https://api-free.deepl.com, pro keys to https://api.deepl.com); DEEPL_BASE_URL (optional) overrides the endpoint outright — it deliberately wins over the key-shape heuristic so credential brokers/gateways work with either key type.

E2E Tests

Integration checklist — drive the real UI (live preview, no mocks), adapt each item to this app's actual screens/flows, and check every box off one by one. A box you can't check is an integration bug to fix — not a skip. The sandbox has a live AI provider, so translations run for real; output is non-deterministic, so assert on the resulting LANGUAGE/meaning, never an exact string:

Translating real text to a target language through the UI returns text ACTUALLY in that language — English→Spanish produces recognizably Spanish, not the original echoed back or left in English.
Switching the target language (from the picker populated by getSupportedLanguages('target')) changes the output language for the same input — the same source re-translates into the newly chosen language.
With sourceLang omitted the provider auto-detects: a known-language input comes back with the correct detectedSourceLang, and if the UI shows a detected-language label it names the right one.
Text already in the target language is left sensible — unchanged or a valid paraphrase, never mangled, doubled, or emptied.
Empty or untranslatable input (whitespace, emoji, a bare code snippet) is handled gracefully — a clear UI state, nothing crashes.
A provider failure (bad key, quota exhausted, network drop) surfaces a visible error in the UI, not an unhandled 500 or a silently blank result.
The translate call runs server-side only — the provider key never reaches the browser (check the network panel: no key in any request).

`@molecule/api-ai-translation-deepl`

How it works

Live demos

Reference