Run efficiency for coding agents: share of paid tokens that became output, not context re-reading.
contextburn reads the transcripts Claude Code already writes on your machine and tells you what share of the tokens you paid for became model output — and how much was the agent re-reading context it had already sent.
Token counters answer "how much did I spend?". This answers "how much of it was work?" — a normalised share, so it can be compared across sessions, models and ways of working.
cp bin/contextburn ~/bin/contextburn && chmod +x ~/bin/contextburn # python3 only, no dependencies
contextburn detail 24
Real output over the session logs of the 36 runs behind the U-curve report — nothing else on the machine. Video with DOI: 10.5281/zenodo.22713920. The runs themselves are open: Hugging Face (DOI 10.57967/hf/10366) · Kaggle · OSF (DOI 10.17605/OSF.IO/5QTWY).
The comparison above comes from a controlled experiment with its dataset and analysis scripts: Clear Every Third Task: A Measured U-Curve in the Context Economy of Coding Agents.
~/.claude/projects/**/*.jsonl). Nothing leaves the
machine — no network calls at all.bin/contextburn. Update them
there when they change.| command | what it shows |
|---|---|
contextburn | what is burning tokens right now |
contextburn detail [hours] | run efficiency, sessions, and what specifically inflated the context |
contextburn window | the current 5-hour subscription window |
contextburn --json | machine-readable state (used by the menu-bar app) |
contextburn --probe <hours> | raw JSON dump of the parsed sessions |
contextburn --efficiency [hours] | run efficiency as JSON |
contextburn mcp | start the MCP server |
| setting | default | meaning |
|---|---|---|
CONTEXTBURN_LANG or ~/.config/contextburn/lang | en | interface language: en or ru |
CONTEXTBURN_DAY_START | 6 | hour your day starts — the daily total resets here |
CONTEXTBURN_WARN | 30000000 | tokens/hour that turns the menu-bar counter yellow |
CONTEXTBURN_ALARM | 90000000 | tokens/hour that turns it red |
The language file exists because the menu-bar app is launched from Finder, where environment
variables never reach it: echo ru > ~/.config/contextburn/lang switches both the app and the CLI.
Let the agent read its own run efficiency mid-session. The package ships a dependency-free MCP
server (stdio) with two tools: run_efficiency returns the shares as structured data, and
spend_breakdown returns the full report.
claude mcp add contextburn -- uvx contextburn mcp
Or install it as a Claude Code plugin, which registers the same server:
/plugin marketplace add arsentev-ai/contextburn
/plugin install contextburn@contextburn
editors/vscode.editors/raycast, Store submission pending.app/main.swift is a small status-bar app. It polls contextburn --json once a minute and shows the
current burn rate with an hourly graph; click a bar to see that hour's breakdown.
swiftc -O -o ContextBurn app/main.swift
Set CONTEXTBURN_BIN=/path/to/contextburn if the CLI is not in ~/bin or the usual Homebrew paths.
bin/contextburn.Software DOI (all versions): 10.5281/zenodo.22712985. GitHub's "Cite this repository" button gives the
reference; metadata is in CITATION.cff.
Evgenii Arsentev — arsentev.ai · ORCID 0000-0002-9120-7298
This project was published as tokmon on its first day and renamed to avoid confusion with
unrelated tools of that name; TOKMON_* environment variables still work.
MIT — see LICENSE.
Source-derived launch command. Check the maintainer’s required arguments and credentials before running:
uvx contextburnMerge this template into ~/Library/Application Support/Claude/claude_desktop_config.json. Keep existing servers. Add any arguments, credentials, and permissions required by the maintainer; this template has not been install-tested.
{
"mcpServers": {
"ai-arsentev-contextburn": {
"command": "uvx",
"args": [
"contextburn"
]
}
}
}Restart Claude Desktop completely for changes to take effect. Confirm the server appears connected in the client’s tool list, then try a read-only example from its documentation.
Claude Desktop setup referencecontextburn works with any MCP-compatible client. Copy the config snippet from the Configuration section above and add it to the file shown for your client, then restart the application.
~/Library/Application Support/Claude/claude_desktop_config.jsonRestart Claude Desktop completely for changes to take effect.~/.cursor/mcp.jsonRestart Cursor for changes to take effect..vscode/mcp.jsonReload VS Code window for changes to take effect.~/.codeium/windsurf/mcp_config.jsonRestart Windsurf for changes to take effect..mcp.jsonSave at the project root, then start Claude Code in that project and review the MCP server approval prompt. Keep real credentials out of shared files.