[bot] Instrument Cartesia (60,223 weekly downloads)

[braintrust-bot]

Summary

Cartesia publishes an official TypeScript/JavaScript SDK, @cartesia/cartesia-js on npm (Stainless-generated, currently v3.x), providing execution APIs for real-time and batch text-to-speech generation using its Sonic model family. This repository has zero instrumentation for any Cartesia SDK surface — no wrapper, no diagnostics channel, no plugin, no auto-instrumentation config, no e2e scenario.

What's missing

Execution surfaces exposed by @cartesia/cartesia-js that are not instrumented:

SDK Method	Description
client.tts.generate({ modelId, transcript, voice, outputFormat })	Batch text-to-speech generation, returns synthesized audio bytes
client.tts.sse({ modelId, transcript, ... })	Server-Sent-Events streaming text-to-speech generation
client.tts.websocket(...) / ws.send({ transcript, ... })	Low-latency WebSocket streaming TTS generation, the SDK's primary realtime execution path
client.voices.clone(...) / client.voices.localize(...)	Voice generation/transformation execution surfaces

The SDK ships its own REST/WebSocket client (ws as a peer dependency in Node.js) — it does not depend on openai or the Vercel ai package, so none of it is picked up by existing OpenAI/AI-SDK auto-instrumentation.

No coverage in any instrumentation layer:

• No wrapper function (e.g. wrapCartesia()) in js/src/wrappers/ (52 files checked)
• No channel definitions or plugin in js/src/instrumentation/plugins/ (108 files checked)
• No auto-instrumentation config in js/src/auto-instrumentations/configs/ (34 files checked, including all.ts)
• No e2e test scenario under e2e/scenarios/
• Repo-wide case-insensitive grep for cartesia returns zero matches anywhere in the repo

Weekly downloads

Weekly downloads: 60,223 (as of 2026-09-07; window 2026-08-31 to 2026-09-06; https://api.npmjs.org/downloads/point/last-week/@cartesia/cartesia-js)

Braintrust docs status

not_found. Cartesia does not appear anywhere on the Braintrust tracing-integrations index — https://www.braintrust.dev/docs/guides/tracing/integrations — which enumerates Tracing integrations (OpenTelemetry, Vercel AI SDK, LangChain, LlamaIndex, Cloudflare Workers AI, etc.), Agent frameworks (LiveKit Agents, Mastra, Pipecat, etc.), Eval frameworks, and Testing frameworks. Cartesia is also absent from https://www.braintrust.dev/docs/integrations. The only path to Braintrust tracing for Cartesia calls made through the Vercel AI SDK (a different, generic provider) is unrelated to Cartesia's own native SDK, which this issue is about.

Upstream references

• npm package: https://www.npmjs.com/package/@cartesia/cartesia-js
• Official SDK GitHub: https://github.com/cartesia-ai/cartesia-js
• Realtime TTS quickstart: https://docs.cartesia.ai/get-started/realtime-text-to-speech-quickstart

Braintrust docs sources checked

• https://www.braintrust.dev/docs/guides/tracing/integrations
• https://www.braintrust.dev/docs/integrations

Local files inspected

• Repo-wide case-insensitive grep for cartesia — zero matches
• js/src/wrappers/*.ts — full directory listing (52 files) — no cartesia.ts wrapper
• js/src/instrumentation/plugins/*.ts — full directory listing (108 files) — no Cartesia channels or plugin file
• js/src/auto-instrumentations/configs/*.ts — full directory listing (34 files, including all.ts) — no Cartesia config entry
• js/src/instrumentation/plugins/instrumentation-names.test.ts — canonical INSTRUMENTATION_NAMES list has no Cartesia entry
• e2e/scenarios/ — no Cartesia test scenario