Tracing quickstart

# Trace an AI application with Braintrust

Set up Braintrust tracing in this working directory. Follow these steps in order.

## Step 1: Set up Braintrust access

Check whether `BRAINTRUST_API_KEY` is set in the environment. If it is, skip this step.

If it isn't, ask the user to do the following, then stop and wait for the user to confirm. Do not guess, invent, or hardcode an API key.

1. Sign up or sign in at https://www.braintrust.dev/signup
2. Create an API key at https://www.braintrust.dev/app/~/configuration/org/api-keys
3. Set `BRAINTRUST_API_KEY` (the value starts with `sk-`) as an environment variable in the shell the user will run the app from, for example `export BRAINTRUST_API_KEY="sk-..."`. If the app loads a `.env` file, add it there instead. The user should not commit the key to version control.

Once the user confirms, continue. If the key isn't visible in your own environment, that's expected when the user set it in a separate shell or in a `.env` file that only the app loads. Don't block on it.

## Step 2: Detect the SDK

Look at the workspace and determine the right Braintrust SDK(s) to use. If the project spans more than one language, instrument each one. If the project is a monorepo, check the git root to get oriented, but only instrument applications in or below the current working directory.

## Step 3: Follow the SDK's configure tracing guide

For each SDK, read the matching page and follow its "Configure tracing" section. Do not follow any other Braintrust setup docs.

| SDK | Guide |
| --- | ------|
| Python | https://www.braintrust.dev/docs/sdks/python/install-and-instrument.md |
| TypeScript | https://www.braintrust.dev/docs/sdks/typescript/install-and-instrument.md |
| Go | https://www.braintrust.dev/docs/sdks/go/install-and-instrument.md |
| Java | https://www.braintrust.dev/docs/sdks/java/install-and-instrument.md |
| Ruby | https://www.braintrust.dev/docs/sdks/ruby/install-and-instrument.md |
| C# | https://www.braintrust.dev/docs/sdks/csharp/install-and-instrument.md |

## Step 4: Install and configure the SDK

- Install the SDK with the package manager the project already uses. Use the latest version: look it up and install that version rather than pinning to `latest`. Verify the install succeeded.
- Prefer auto-instrumentation over manual wrappers.
- Set the project name in the SDK initialization to the repository or application name. If the user has a specific Braintrust project in mind, use that instead.

## Rules

- Add only tracing. Do not add evals or anything else.
- Make only the code changes needed to add tracing. Do not run application code, and do not break or meaningfully modify existing code.
- Do not use the Braintrust CLI (`bt`).

Full documentation: https://www.braintrust.dev/docs/llms.txt