Ace Sidecar

ACE Sidecar

Local developer observability for AI coding agents — see what your Claude Code, Antigravity, and OpenAI Codex sessions actually cost.

[](https://github.com/ACE-Engineering/ace-sidecar/actions/workflows/ci.yml) [](https://pypi.org/project/ace-sidecar/) [](https://pypi.org/project/ace-sidecar/) [](LICENSE)


**[What it does](#what-it-does)** · **[Requirements](#requirements)** · **[Install](#install)** · **[Check Version](#check-version)** · **[Upgrade](#upgrade)** · **[Quickstart](#quickstart)** · **[Features](#features)** · **[Who builds this](#who-builds-this)** · **[Configuration](#configuration)** · **[Endpoints](#endpoints)** · **[Development](#development)** · **[License](#license)**

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What it does

ACE Sidecar runs a proxy on your machine in front of model providers, recording what each turn costs — tokens in and out, what came from cache, how long you waited. It automatically reads your existing local transcripts (`~/.claude/projects`, `~/.gemini/antigravity/brain`, `~/.codex/sessions`), providing unified history and cost tracking from the first run.

Nothing leaves your machine: no account, no upload. Metrics live in a local SQLite file you can delete anytime.

Built by [ACE Fleet](https://acefleet.dev) — see [Who builds this](#who-builds-this).

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Requirements

• Python 3.12+ — the one hard requirement. Check with python3 --version.
• macOS, Linux, or Windows. No admin rights needed.
• A coding agent you already use. Claude Code, Google Antigravity, and OpenAI Codex are supported. However you pay for it — subscription or API key — is how it stays paid; the sidecar adds no account of its own.