contextrot measures Claude Code degradation using session logs

The contextrot utility analyzes the exact context fill level at which an agent begins to fail. It reads local JSONL transcripts that Claude Code already writes to disk, requiring no API keys or network requests.
The tool extracts five failure signals at each step: failed code edits, repeated calls after errors, re-reading already processed files, self-corrections, and tool errors. It then correlates these with context fill levels, calculating statistics using 95% Wilson score intervals.
The report provides one of four verdicts: degradation detected, edge degradation at the window limit, no degradation, or insufficient data. You can run it via uvx contextrot or pip3 install contextrot. Support for Codex CLI, OpenCode, and Gemini CLI is planned. The project is under the MIT license.
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