Claude Code

Claude Code is Anthropic’s agentic coding tool, available from the terminal and from the Code tab in the Claude desktop app. You can connect it to Braintrust in three ways:

Trace Claude Code sessions to record session, turn, model call, tool, and subagent spans in Braintrust.
Trace with OpenTelemetry to send Claude Code’s native OpenTelemetry export to Braintrust without the tracing plugin.
Connect to Braintrust MCP to work with Braintrust projects, experiments, logs, and other data from Claude Code.

This guide covers the Claude Code CLI and local Claude Code sessions in the Code tab of the desktop app. Both interfaces use the same tracing plugin and native Claude Code MCP configuration.

Trace Claude Code sessions

The trace-claude-code plugin uses bt to trace your Claude Code sessions to Braintrust. If you can’t install Claude Code plugins, or you want to route Claude Code telemetry through an existing OpenTelemetry pipeline, trace with OpenTelemetry instead.

Set up tracing

If trace-claude-code is already installed, follow Update the tracing plugin.

Install Claude Code

If you haven’t already, install the Claude Code CLI or the Claude Code desktop app.

Install and authenticate bt

Follow the bt CLI quickstart to install bt, authenticate, and set your active context.

Enable tracing

Before starting Claude Code, run this command in a terminal:

bt trace enable claude --project <your-project>

This command:

Adds or refreshes the Braintrust plugin marketplace.
Installs (or updates) and enables trace-claude-code.
Writes a Claude-specific tracing config file, normally ~/.claude/braintrust.json, which records whether tracing is enabled and which project receives traces.

The tracing file stores settings, not credentials. These settings apply across projects during normal sessions.For more information, see bt trace enable.

Restart Claude Code

Exit any running Claude Code CLI or desktop sessions and start a new local session.

Log a test trace

Ask Claude Code to do something simple in the terminal or the Code tab in the Claude desktop app. When the session finishes, open your Braintrust project and confirm that the trace appears on the Logs page.

What Braintrust traces

Claude Code traces in Braintrust include:

Session spans with the session ID, workspace, hostname, username, operating system, Claude Code version, model, system prompt when available, Git repository metadata, and the final response of the last completed turn.
Turn spans with prompts, final responses, and the permission mode.
Model call spans with prompts, completions, token metrics, and errors.
Tool spans with inputs, outputs, approval state, and tool names.
Skill metadata when a turn loads skills.
Subagent spans nested under the turn that started the subagent.

Every span records its origin as braintrust.plugin.claude-code. Session and turn spans also record versions in context.span_origin: the plugin version in version, the bt version in bt.version, and the Claude Code version in claude-code.version. These versions are captured when each span is created, and unknown versions are null. Each turn span and every span under it, including subagent spans, records the turn’s span ID in metadata.turn_span_id. The session span also records the plugin version in trace_claude_code_version.

Common workflows

Use different tracing settings for one session

Use bt trace run to trace a single Claude Code invocation without changing the saved tracing configuration.This workflow launches Claude Code from the terminal.To change the saved destination, profile, or organization, rerun bt trace enable claude with the corresponding options. Running bt switch does not change the saved tracing configuration.To add root-span metadata, pass --additional-metadata '<JSON>' to bt trace run for one invocation or to bt trace enable for future sessions. Standard session metadata takes precedence when keys conflict.With bt v0.19.3 or later, pass --tag ci --tag release-validation to either command to tag session spans.

Trace a saved Claude Code session

Claude Code stores session transcripts locally. Use bt trace import to import a past session, even if tracing was not enabled when it ran.You can also attach an imported session to an existing span or experiment.

Resume a Claude Code session

When you resume a Claude Code session, new turns are added to its existing Braintrust trace.

Stop tracing Claude Code sessions

Use bt trace disable claude to uninstall the tracing plugin and remove its tracing configuration. Saved bt profiles and credentials are preserved. Restart Claude Code afterward.

Update the tracing plugin

To update the plugin, follow these steps:

If claude plugin list --json shows trace-claude-code earlier than v2.0.1, or bt --version shows a version earlier than v0.19.0, follow Migrate from an older plugin version.

Update bt

Follow the CLI migration guide to update bt to the latest version and complete the applicable migrations.

Update the tracing plugin

bt trace update claude

bt trace update updates the installed plugin without changing your saved tracing configuration.

Restart and verify Claude Code

Restart Claude Code, run a short local session in the CLI or desktop app, and confirm that its trace appears on the Logs page in the intended Braintrust project.

Migrate from an older plugin version

To migrate to the latest version of the trace-claude-code plugin, follow these steps:

Inspect your Claude plugins

Run this command and find trace-claude-code@braintrust-claude-plugin:

claude plugin list --json

Record the tracing plugin’s starting version before updating. If your tracing configuration file exists, also record its profile, organization, project, and any custom tracing settings you want to preserve.

If the tracing plugin is not installed, follow Set up tracing.

Install or update bt

Check whether bt is installed:

bt --version

If the command succeeds, migrate to the latest version (unless you’ve already done so).
Otherwise, install bt, authenticate, and set organization and project context.

Complete version-specific migration steps

Complete each section for a version newer than your starting trace-claude-code version, beginning with the oldest. If no sections apply, continue to the next step.

trace-claude-code v2.0.1

Complete this section if you started your migration from a tracing-plugin version earlier than v2.0.1.

Before v2.0.1, the tracing plugin read settings from Claude’s environment. Starting in v2.0.1, it reads a dedicated configuration file written by bt trace enable claude.If you don’t know which Braintrust project has been receiving your traces, find the value of the BRAINTRUST_CC_PROJECT variable.To find it, look in the env object in ~/.claude/settings.json or the project’s .claude/settings.local.json, and in your shell configuration. If it is not set, the earlier plugin used the claude-code project.

Apply your tracing settings

Run this command with your intended project, using the project you recorded earlier to preserve your destination:

bt trace enable claude --project <your-project>

Pass --profile <profile> and --org <organization> if needed to preserve your tracing account and organization. Otherwise, the command uses your active bt context, not your saved tracing settings.To preserve metadata from an older plugin’s configuration or BRAINTRUST_ADDITIONAL_METADATA, pass it explicitly with --additional-metadata '<JSON>'. Normal-session hooks do not read metadata from this environment variable.The command updates your tracing file, normally ~/.claude/braintrust.json. Check the following settings in that file:

Existing route.additional_metadata is preserved unless you pass --additional-metadata.
Existing route.tags is preserved unless you pass --tag or set BRAINTRUST_TAGS.
route.flush_mode resets to fire_and_forget. Restore its previous value if you customized it.
Restore any other custom tracing settings you recorded before updating.

Restart and verify Claude Code

Restart Claude Code, run a short local session in the CLI or desktop app, and confirm that its trace appears on the Logs page in the intended Braintrust project.

Remove obsolete environment settings

Complete this step only if you started with a tracing-plugin version earlier than v2.0.1 and verified that traces reach the intended project in the previous step.

Environment settings used before trace-claude-code v2.0.1

The tracing plugin now reads its settings from a dedicated configuration file. Environment variables you previously configured for tracing may no longer be needed.Check these locations for leftover settings:

The env object in ~/.claude/settings.json
The env object in your project’s .claude/settings.local.json
Your shell configuration

Remove the variables below if they were used only for tracing. Keep any that other bt commands, MCP connections, or integrations still need:

TRACE_TO_BRAINTRUST
BRAINTRUST_CC_PROJECT
BRAINTRUST_API_KEY
BRAINTRUST_API_URL and BRAINTRUST_APP_URL
BRAINTRUST_ORG_NAME
CC_PARENT_SPAN_ID, CC_ROOT_SPAN_ID, and CC_EXPERIMENT_ID
BRAINTRUST_CC_DEBUG, BRAINTRUST_ENVIRONMENT_TYPE, and BRAINTRUST_ENVIRONMENT_NAME

Troubleshooting tracing

First, run bt trace doctor claude. Then, review the following:

The tracing plugin is missing or disabled

Run claude plugin list and confirm that trace-claude-code@braintrust-claude-plugin is installed and enabled. If it is missing or broken, run:

bt trace enable claude --project <your-project>

Restart Claude Code afterward.

Traces do not appear after setup

Opening Claude Code alone does not create a trace. Submit a prompt to verify tracing.If Claude Code was running when its plugin or configuration changed, restart it.Confirm that bt is on the PATH of the environment that launches Claude Code.Run bt trace doctor claude and confirm that tracing is enabled and routed to the intended project.If authentication succeeds but traces do not appear, confirm that your account has permission to write logs to the selected project.For authentication, tracing destination, or endpoint problems, see bt trace troubleshooting and the CLI migration troubleshooting guide.Tracing failures do not interrupt the Claude Code session.

Claude Code uses an unexpected configuration directory

Check whether CLAUDE_CONFIG_DIR is set in the environment that launches Claude Code. When it’s set, bt trace enable claude and the tracing integration use $CLAUDE_CONFIG_DIR/braintrust.json instead of ~/.claude/braintrust.json.An explicit BRAINTRUST_DAEMON_CONFIG (BT_DAEMON_CONFIG in bt v0.25.0 and earlier) override changes the tracing file path. If you use it, supply the same path when enabling tracing and launching Claude Code.

Traces use unexpected settings

Invocation settings supplied by bt trace run take precedence over the saved tracing configuration. For normal sessions, the integration does not use TRACE_TO_BRAINTRUST, BRAINTRUST_CC_PROJECT, or BRAINTRUST_ADDITIONAL_METADATA from the agent’s environment to override the saved tracing settings.For environment variables accepted by the bt commands themselves, see bt trace.

bt reports obsolete tracing environment settings

bt trace enable claude warns when Claude settings contain environment variables used by an earlier tracing plugin.

Follow step 6, “Remove obsolete environment settings,” under Migrate from an older plugin version to clean up these variables.

Trace with OpenTelemetry

Claude Code can export OpenTelemetry traces and events directly to Braintrust’s OTLP endpoint, without the tracing plugin or bt.

Set up tracing

Configure the OTLP exporter

Set these environment variables before starting Claude Code:

export CLAUDE_CODE_ENABLE_TELEMETRY=1
export CLAUDE_CODE_ENHANCED_TELEMETRY_BETA=1

export OTEL_TRACES_EXPORTER=otlp
export OTEL_EXPORTER_OTLP_PROTOCOL=http/protobuf
export OTEL_EXPORTER_OTLP_ENDPOINT="https://api.braintrust.dev/otel"
export OTEL_EXPORTER_OTLP_HEADERS="Authorization=Bearer <BRAINTRUST_API_KEY>,x-bt-parent=project_id:<PROJECT_ID>"

The x-bt-parent header sets the Braintrust project that receives the traces. It also accepts project_name:<PROJECT_NAME>. Organizations on the EU data plane use https://api-eu.braintrust.dev/otel, and self-hosted deployments use their data plane’s API URL followed by /otel.

Capture prompts and tool content (optional)

By default, Claude Code redacts prompts and omits tool details. To include them in traces, also set:

export OTEL_LOG_USER_PROMPTS=1
export OTEL_LOG_TOOL_DETAILS=1
export OTEL_LOG_TOOL_CONTENT=1

These options send prompts, commands, file paths, and tool output to Braintrust. Review your organization’s data handling policies before enabling them.

Export Claude Code events (optional)

To also send Claude Code events, such as API requests, errors, and tool results, as log records, set:

export OTEL_LOGS_EXPORTER=otlp

Start Claude Code

Start Claude Code and submit a prompt. Confirm that the trace appears on the Logs page of the project you set in x-bt-parent.

What Braintrust traces

Braintrust maps Claude Code spans to typed spans:

Claude Code span	Braintrust span
`claude_code.interaction`	Task span. The user prompt becomes the input when `OTEL_LOG_USER_PROMPTS=1`.
`claude_code.llm_request`	LLM span with the model, token metrics, and time to first token, so Braintrust can estimate cost. Cache read and cache creation tokens are included in prompt tokens.
`claude_code.tool`	Tool span named after the tool, such as `Bash` or `Read`. Tool input requires `OTEL_LOG_TOOL_DETAILS=1`, and tool output requires `OTEL_LOG_TOOL_CONTENT=1`.
`claude_code.hook`	Task span named after the hook, such as `PreToolUse:Read`.
Other spans, such as `claude_code.tool.execution`	Task span.

With Claude Code’s detailed beta tracing active, LLM spans also show the conversation as input messages and the model response as output. Values that Claude Code redacts as <REDACTED> are never used as input or output. When you export events, each event becomes a log row. Braintrust sets the prompt as input, the assistant response as output, and populates error for API errors, failed tool results, and internal errors. API request events carry token metrics only when they have no trace ID, so tokens aren’t counted twice when you export both traces and events.

Connect to Braintrust MCP

The Braintrust MCP server lets Claude Code query and update Braintrust data. MCP is configured independently from the tracing plugin.

Remove the retired Braintrust MCP plugin (if installed)

Braintrust retired its braintrust MCP plugin for Claude Code in favor of Claude Code’s native MCP configuration. If you installed the plugin, remove it before configuring the direct connection.Check whether the plugin is still installed:

claude plugin list --json

If braintrust@braintrust-claude-plugin appears in the list, use its scope value to remove it:

claude plugin uninstall braintrust@braintrust-claude-plugin \
  --scope <scope>

If it appears at more than one scope, repeat the command for each scope. Keep the marketplace if you use the trace-claude-code tracing plugin.

Choose authentication

OAuth (recommended)
API key

Use OAuth when your client supports it. Your client opens a Braintrust authorization page where you sign in and approve access. The server acts with the permissions of the account you sign in with.

No Braintrust API key required
No OAuth client ID or client secret to configure

The server implements OAuth 2.0 with dynamic client registration and publishes its metadata at /.well-known/oauth-authorization-server on the same host as your MCP endpoint (see next step), so a client can register itself.

Use an API key for clients without OAuth support or for programmatic connections. The server acts with the permissions of the account the key belongs to.

Create a key in Settings > API keys.
Configure your client to send this header on every request, replacing YOUR_BRAINTRUST_API_KEY with your key:
Authorization: Bearer YOUR_BRAINTRUST_API_KEY

Your bt login doesn’t authenticate the MCP server.

Choose your endpoint

Use the endpoint for your organization’s data plane region:

Region	MCP endpoint
US	`https://api.braintrust.dev/mcp`
EU	`https://api-eu.braintrust.dev/mcp`

Other connection details:

Self-hosted: Copy the MCP URL from Settings > Data plane. This is your Braintrust API URL with /mcp appended.
Transport: If your client asks you to choose a transport, choose HTTP (also called streamable HTTP). SSE-only clients can’t connect.

Add the server to Claude Code

Follow the Claude Code guide to add the remote server.

Verify the connection

To verify the connection, ask Claude Code to list your recent Braintrust projects. If it can’t connect, see Braintrust MCP troubleshooting.

Start using Braintrust tools

Claude Code can query logs, compare experiments, work with datasets, and use other Braintrust tools. For example:

“Show me my recent Braintrust experiments.”
“Query the last 10 logged requests with errors.”
“Compare accuracy scores between my two latest experiments.”

See what the Braintrust MCP can do for more workflows and example prompts.

Next steps

Learn the CLI: See the full bt trace reference.
Run evaluations: Follow the evaluation guide.
Explore MCP tools: See the Braintrust MCP tool reference.
Browse the source: View the coding-agent plugins repository.

AI providers

SDKs

Developer tools

Runtime environments

Trace Claude Code sessions

Set up tracing

What Braintrust traces

Common workflows

Update the tracing plugin

Migrate from an older plugin version

Troubleshooting tracing

Trace with OpenTelemetry

Set up tracing

What Braintrust traces

Connect to Braintrust MCP

Next steps

​Trace Claude Code sessions

​Set up tracing

​What Braintrust traces

​Common workflows

​Update the tracing plugin

​Migrate from an older plugin version

​Troubleshooting tracing

​Trace with OpenTelemetry

​Set up tracing

​What Braintrust traces

​Connect to Braintrust MCP

​Next steps

Trace Claude Code sessions

Set up tracing

What Braintrust traces

Common workflows

Update the tracing plugin

Migrate from an older plugin version

Troubleshooting tracing

Trace with OpenTelemetry

Set up tracing

What Braintrust traces

Connect to Braintrust MCP

Next steps