Building with Claude Code is fast until you open your usage dashboard and wonder where $4 went on a session you barely remember running.
Last weekend, a developer shipped Argus, a free VS Code extension that turns Claude Code’s raw JSONL session logs into an actual cost timeline. The twist: it runs entirely locally. No account, no upload, no telemetry. Just reads the files Claude Code already writes to ~/.claude/projects/ and makes them legible.
Every tool call laid out in order. Every Read, Write, and Edit. Token cost per step. Cache hit ratio. Subagent attribution. Plus a set of rules that flag the expensive patterns: duplicate reads, retry loops, context pressure before compaction kicks in. The stuff you suspect is happening but can never prove after the fact.
Here’s how to try it:
- 🔍 Clone the repo at github.com/yessGlory17/argus
- 📦 Install the extension in VS Code (setup steps in the repo README)
- Run any Claude Code session as normal
- Open Argus and load that session. You’ll see cost breakdown, file operation dependency graph, and context window usage in separate tabs
- Find the exact step where the agent started looping or re-reading the same files
Pro tip: Check the cache hit ratio first. If you’re not hitting cache consistently, your context structure is costing you real money on every run. Argus makes that visible instead of buried in JSONL noise.
The developer is actively collecting feedback on what failure patterns to surface next. If you run heavier agent workflows, this is the right time to test it and share what you find. 🛠️
Free and open source: github.com/yessGlory17/argus
I built in real time Claude Code monitor for VSCode
by u/fIak88 in PromptEngineering