Vercel AI SDK (TypeScript)
For optional help from your coding agent, use Set it up for me. It preserves your model connection and verifies a real trace after setup
Send Vercel AI SDK (TypeScript) traces to LiteLLM Lens using the runnable examples in this repository.
Prerequisites
You need Lens installed alongside LiteLLM, a key with model access, and a configured model alias. The swarm example needs a model that supports tool calls. In Lens > Traces > Set up tracing, click Generate tracing key and copy the Traces endpoint under Connection details. Ask your administrator for these if you cannot create a tracing key.
Use Node.js with built-in TypeScript support and npm. Install dependencies from the repository root so the shared npm workspaces are available.
Configuration
For a fresh checkout:
git clone https://github.com/BerriAI/litellm-lens-example.git
cd litellm-lens-example
npm install
cd vercel-ai-sdk-js
cp .env.example .env
If you already cloned the repository, run the remaining commands from vercel-ai-sdk-js/. Run npm install from the repository root if you have not installed the workspace dependencies. Copy .env.example to .env if it does not exist, then set:
| Variable | Value |
|---|---|
LITELLM_GATEWAY_URL | Your gateway’s base URL without a trailing slash or /v1, for example http://localhost:4002 |
LITELLM_API_KEY | Your LiteLLM model key |
LENS_URL | Copy Traces endpoint from Lens tracing setup and remove the final /v1/traces. Keep /lens-ingest if present. For example, http://localhost:4318 or https://gateway.example/lens-ingest |
LENS_TRACING_KEY | The dedicated tracing key from Lens tracing setup |
LITELLM_MODEL | A model alias configured on your gateway |
The checked-in values target a local development gateway. Replace them for your deployment. Keep the exporter settings from .env.example; the examples configure their trace exporters in code. They send traces to LENS_URL/v1/traces with the tracing key as a bearer token.
Leave MOCK_LITELLM_GATEWAY_URL unset unless you intend to send an additional trace copy to the local recorder.
Run an example
Simple agent
A generateText call is traced as research_agent.
node --env-file=.env simple/main.ts
See simple/main.ts for the implementation.
Agent swarm
A coordinator delegates through tools that run generateText as search_agent and writer_agent.
node --env-file=.env swarm/main.ts
See swarm/main.ts for the implementation.
Verify the trace
After the example prints its answer, open Lens > Traces on your gateway and select the new run. Look for the run associated with research_agent. Inspect the input, output, and model spans. For the swarm, inspect the specialist activity described above; its exact span layout depends on the framework.
How tracing works
The @ai-sdk/otel integration creates OpenTelemetry spans and the NodeSDK exports them to Lens. The example names agent spans from functionId. The shared gateway fetch records request attempts and gateway call IDs.
See the shared gateway transport for request-attempt and spend-correlation details.
Troubleshooting
If model calls fail, check the gateway URL, key, and model alias. If an answer appears but the trace is missing, check the terminal for exporter errors and confirm the Lens ingestion service is reachable with your tracing key. A model call succeeding does not confirm that its trace export succeeded.
Transport validation
Run the shared transport regressions from this folder:
npm test -w gateway-tracing
Validate real gateway streaming, retry, and billed response loss with:
node --env-file=.env validate-attempts.ts streaming
node --env-file=.env validate-attempts.ts retry
node --env-file=.env validate-attempts.ts response-loss
The retry scenario replaces the first real billed response with a client-side HTTP 503. The response-loss scenario consumes the real billed response and fails the client stream. Neither scenario changes gateway or provider behavior.
