Argus: A VS Code Extension to Debug Claude Code Session Costs and Behavior

Claude Code session costs can spike without obvious reasons—retry loops, repeated file reads, or context filling up before compaction. The JSONL files at ~/.claude/projects/ contain all the data, but raw inspection is painful. A developer built Argus, a VS Code extension that parses those transcripts and lays the session out as a timeline with granular metrics.

Key Features

• Timeline view of every tool call: Read, Write, Edit, and subagent calls.
• Per-step token and USD cost breakdown.
• Cache hit ratio for each step.
• Subagent attribution—see which subagent did what.
• Rule-based flagging for duplicate reads, retry loops, and context pressure.
• Cost breakdown tab and dependency graph of file operations.
• Context window usage visualization.

How It Works

Argus runs entirely locally—no login, no upload. It reads the JSONL files that Claude Code already writes, so no extra setup is needed. The developer built it originally for personal use after noticing unpredictable cost spikes across sessions.

Who It's For

Developers using Claude Code in agent mode who want to understand exactly what their agent did and why costs vary across sessions.