Trace Claude Code to Braintrust

Automatically send Claude Code conversations to Braintrust for tracing and observability. Get full visibility into your AI coding sessions with hierarchical traces showing sessions, turns, and every tool call.

What you get

Claude Code Session (root trace)
├── Turn 1: "Add error handling"
│   ├── Read: src/app.ts
│   ├── Edit: src/app.ts
│   └── Response: "I've added try-catch..."
├── Turn 2: "Now run the tests"
│   ├── Terminal: npm test
│   └── Response: "All tests pass..."
└── Turn 3: "Great, commit this"
    ├── Terminal: git add .
    ├── Terminal: git commit -m "..."
    └── Response: "Changes committed..."

How it works

Four hooks capture the complete workflow:

Hook	What it captures
SessionStart	Creates root trace when you start Claude Code
PostToolUse	Captures every tool call (file reads, edits, terminal commands)
Stop	Captures conversation turns (your message + Claude's response)
SessionEnd	Logs session summary when you exit

Quick setup

Run the setup script in any project directory where you want tracing:

bash /path/to/skills/trace-claude-code/setup.sh

The script prompts for your API key and project name, then configures all hooks automatically.

Manual setup

Prerequisites

• Claude Code CLI installed
• Braintrust API key
• jq command-line tool (brew install jq on macOS)

Configuration

Create .claude/settings.local.json in your project directory:

{
  "hooks": {
    "SessionStart": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "bash /path/to/hooks/session_start.sh"
          }
        ]
      }
    ],
    "PostToolUse": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "command",
            "command": "bash /path/to/hooks/post_tool_use.sh"
          }
        ]
      }
    ],
    "Stop": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "bash /path/to/hooks/stop_hook.sh"
          }
        ]
      }
    ],
    "SessionEnd": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "bash /path/to/hooks/session_end.sh"
          }
        ]
      }
    ]
  },
  "env": {
    "TRACE_TO_BRAINTRUST": "true",
    "BRAINTRUST_API_KEY": "sk-...",
    "BRAINTRUST_CC_PROJECT": "my-project"
  }
}

Replace /path/to/hooks/ with the actual path to this skill's hooks directory.

Environment variables

Variable	Required	Description
TRACE_TO_BRAINTRUST	Yes	Set to "true" to enable tracing
BRAINTRUST_API_KEY	Yes	Your Braintrust API key
BRAINTRUST_CC_PROJECT	No	Project name (default: claude-code)
BRAINTRUST_CC_DEBUG	No	Set to "true" for verbose logging

Viewing traces

After running Claude Code with tracing enabled:

1. Go to braintrust.dev
2. Navigate to your project (e.g., claude-code)
3. Click Logs to see all traced sessions

Each trace shows:

• Session root: The overall Claude Code session
• Turns: Each conversation exchange (user input → assistant response)
• Tool calls: Individual operations (file reads, edits, terminal commands)

Trace structure

Traces are hierarchical:

• Session (root span)

  • span_attributes.type: "task"
  • metadata.session_id: Unique session identifier
  • metadata.workspace: Project directory

• Turn (child of session)

  • span_attributes.type: "llm"
  • input: User message
  • output: Assistant response
  • metadata.turn_number: Sequential turn number

• Tool call (child of turn or session)

  • span_attributes.type: "tool"
  • input: Tool input (file path, command, etc.)
  • output: Tool result
  • metadata.tool_name: Name of the tool used

Troubleshooting

No traces appearing

1. Check hooks are running:

   tail -f ~/.claude/state/braintrust_hook.log
   

2. Verify environment variables in .claude/settings.local.json:

   • TRACE_TO_BRAINTRUST must be "true"
   • BRAINTRUST_API_KEY must be valid

3. Enable debug mode:

   {
     "env": {
       "BRAINTRUST_CC_DEBUG": "true"
     }
   }
   

Permission errors

Make hook scripts executable:

chmod +x /path/to/hooks/*.sh

Missing jq command

Install jq:

• macOS: brew install jq
• Ubuntu/Debian: sudo apt-get install jq

State issues

Reset the tracing state:

rm ~/.claude/state/braintrust_state.json

Hook logs

View detailed hook execution logs:

# Follow logs in real-time
tail -f ~/.claude/state/braintrust_hook.log

# View last 50 lines
tail -50 ~/.claude/state/braintrust_hook.log

# Clear logs
> ~/.claude/state/braintrust_hook.log

File structure

hooks/
├── common.sh          # Shared utilities (logging, API, state)
├── session_start.sh   # Creates root trace span
├── post_tool_use.sh   # Captures tool calls
├── stop_hook.sh       # Captures conversation turns
└── session_end.sh     # Finalizes trace

Alternative: SDK integration

For programmatic use with the Claude Agent SDK, use the native Braintrust integration:

import { initLogger, wrapClaudeAgentSDK } from "braintrust";
import * as claudeSDK from "@anthropic-ai/claude-agent-sdk";

initLogger({
  projectName: "my-project",
  apiKey: process.env.BRAINTRUST_API_KEY,
});

const { query, tool } = wrapClaudeAgentSDK(claudeSDK);

See Braintrust Claude Agent SDK docs for details.