ElevenLabs Local Dev Loop

Overview

Set up a fast, cost-effective local development workflow for ElevenLabs audio projects. The loop centers on three moves — mock the SDK so unit tests never burn character quota, gate real API calls behind an explicit ELEVENLABS_INTEGRATION=1 flag, and select a cheaper model in dev while keeping the high-quality model for production — with tsx watch hot reload and a quota checker to round out the cycle.

Follow the high-level flow below to scaffold the project, then drill into references/implementation.md for the full code of every step and references/examples.md for worked end-to-end runs.

Prerequisites

Before starting, confirm your environment is ready:

• The elevenlabs-install-auth setup is complete, so the SDK (@elevenlabs/elevenlabs-js) is installed and ELEVENLABS_API_KEY is available in .env.local.
• Node.js 18+ with npm or pnpm.
• vitest installed as the test runner (recommended) — it powers the mock layer and the integration-test guard.

Instructions

Work through the six steps in order. Each is summarized here; the full code for every step lives in references/implementation.md.

1. Project structure — lay out src/elevenlabs/ (client, config, tts), tests/__mocks__/ and tests/fixtures/sample.mp3, a git-ignored output/, and .env.local / .env.example. Full tree in the reference.
2. Environment configuration — write an environment-aware config.ts that picks the model and output format by NODE_ENV. This is the essential skeleton:

   // src/elevenlabs/config.ts
   export function loadConfig() {
     const env = process.env.NODE_ENV || "development";
     return {
       apiKey: process.env.ELEVENLABS_API_KEY || "",
       // cheaper/faster in dev, best quality in prod
       modelId: env === "production"
         ? "eleven_multilingual_v2"   // 1.0 credits/char
         : "eleven_flash_v2_5",       // 0.5 credits/char, ~75ms
       defaultVoiceId: process.env.ELEVENLABS_VOICE_ID || "21m00Tcm4TlvDq8ikWAM",
       outputFormat: "mp3_22050_32",  // smaller files for dev
     };
   }

1. Mock the SDK — write tests/__mocks__/elevenlabs.ts that returns the sample.mp3 fixture from textToSpeech.convert/stream and stubs voices.getAll and user.get, so unit tests cost nothing.
2. Development scripts — add dev (tsx watch), test, test:watch, test:integration, generate, and quota scripts to package.json.
3. Quota-aware development — add src/check-quota.ts that reads user.subscription and exits non-zero when fewer than 1000 characters remain, so a low balance fails fast.
4. Integration test guard — write tests/tts.test.ts where the real-API test is it.skipIf(!useRealApi) and only runs under ELEVENLABS_INTEGRATION=1; the mocked test always runs.

See references/implementation.md for the complete, copy-pasteable code for each step.

Output

• Working development environment with hot reload via tsx watch
• Mock layer that avoids API calls and character charges during dev
• Quota checker to prevent surprise billing
• Integration test guard pattern (ELEVENLABS_INTEGRATION=1)
• Environment-aware model selection (cheap in dev, quality in prod)

Error Handling

Examples

Four worked runs of the loop — full walkthroughs in references/examples.md:

• Zero-cost unit tests — npm run test drives the service through the mock client, passes offline, and never touches the API or your quota.
• Quota preflight — npm run quota prints Characters: 500 / 10,000 (5.0% used) and exits 1 when fewer than 1000 characters remain, blocking a paid run before it starts.
• Opt-in integration run — npm run test:integration sets ELEVENLABS_INTEGRATION=1, flipping the it.skipIf(!useRealApi) test on so the real API is hit only when you ask for it.
• Hot-reload iteration — npm run dev (tsx watch) restarts on save; with the dev model (eleven_flash_v2_5) and mocks, each loop stays fast and free.

Resources

• ElevenLabs JS SDK
• Vitest Mocking
• tsx (TypeScript Execute)

Next Steps

Once the dev loop is running, move on to production-ready code: see the elevenlabs-sdk-patterns skill for streaming, retries, and voice-management patterns you can layer on top of this environment.