CLAUDE_CODE_FRAME_TIMING_LOG

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_FRAME_TIMING_LOG is a Claude Code environment variable: Enable per-frame render timing logs in the terminal UI. A diagnostic variable — when set, it likely writes timing data for each UI frame render cycle, useful for identifying performance bottlenecks in the CLI's rendering path. Useful when profiling slow terminal refresh under heavy output loads. Removed between v2.1.269 and v2.1.283, so current releases ignore it. It is not in the official reference.

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_FRAME_TIMING_LOG=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_FRAME_TIMING_LOG": "<value>"
  }
}

Release notes that mention it

• Claude Code v2.1.74 — 2 New Environment Variables: Frame Timing & Session End Hooks

Related variables

• ANTHROPIC_LOG: SDK internal logging level.
• CLAUDE_CODE_COMMIT_LOG: Likely controls whether or where Claude Code logs commit operations.
• CLAUDE_CODE_DEBUG_LOG_LEVEL: Set debug logging verbosity level.
• CLAUDE_GATEWAY_LOG_LEVEL
• CLAUDE_RUNNER_DEBUG_LOG_PATH
• ANTHROPIC_PROFILE
• CLAUDE_CODE_DEBUG_LOGS_DIR: Custom directory for debug logs.
• CLAUDE_CODE_DEBUG_REPAINTS: Enables debug logging for terminal repaint operations.

Frequently asked questions

All variables, searchable: Claude Code environment variables.