Agent Context Trail

See how one agent conversation's context evolves, prompt by prompt: tokens, cache reuse, and cost — for Claude Code, Codex, and GitHub Copilot.

Your coding agent reads far more than you type. Every prompt re-sends the conversation context, caches parts of it, and burns tokens you never see. Agent Context Trail reads the session files your agent CLIs already write on your machine and turns them into a readable trail: what each prompt actually cost, how much context it carried, and how much the cache saved.

Features

• Status bar cost — the last request's cost and the conversation's running total, in USD, always visible. Click it to open the panel.
• Conversation panel — one scrollable page, opened on demand (no permanent sidebar icon):
  • per-conversation stacked token bars showing each conversation's token composition at a glance;
  • a sortable conversations table for the current workspace, grouped by provider, with request count, first/last message, total tokens, and cost;
  • a thread chart with one bar per request — token composition and cost, scaled to the conversation itself;
  • a request detail card: model, input / output / cache-read / cache-write tokens, tool calls with per-call latency, prompt text, wall time, and more when the provider exposes it.
• Cache reuse made visible — cache reads and writes are first-class everywhere, so you can see when a long conversation is paying off and when a cache break made it expensive again.
• Honest numbers — every cost is labeled provider-reported or estimated; fields a provider does not expose are shown as unavailable, never as a fake zero.

Supported providers

Getting started

1. Install the extension and open a workspace where you use Claude Code or Codex.
2. The status bar item appears automatically with the latest conversation's cost.
3. Click it — or run Agent Context Trail: Open Conversation Panel from the Command Palette (Ctrl+Shift+P) — to explore the trail.

Other commands: Agent Context Trail: Refresh and Agent Context Trail: Show Conversation Summary (Text) (plain-text summary in the output channel).

Privacy

Local-first, by contract:

• Everything is read from the local session files the agent CLIs already write. No server process, no account, no sign-in.
• No telemetry, no analytics, no upload of prompts, transcripts, or file contents — under any configuration.

Cost estimation

When a provider reports cost directly, that value is used and labeled provider-reported. Otherwise cost is estimated from token counts against a hand-maintained rate table that cites the official pricing page and the date it was last checked. Subscription-billed providers still get an estimate: the dollar-equivalent of the same tokens at the vendor's public API rates, so opaque rate-limit plans become legible too.

Development

Build, packaging, and contribution notes live in DEVELOPMENT.md.