anthropometer  ·  amtr

A btop-style, real-time diagnostic instrument for Claude Code sessions.

amtr attaches to a Claude Code session's transcript and renders — live — exactly what is happening inside the model's context window: how the token budget is being spent, which files and tools are resident, when compactions fire, what subagents are doing, and the true cost of every turn. Press R and it compiles a ground-truth PDF report of the whole session.

_{↑ replaying a session turn-by-turn: the context map fills, the composition shifts, the trend climbs.}

 ·   ·  Rust + ratatui TUI · Python engine · terminal-only

AI usage

 hand-written ▕█████████████████████████████████████████████████████████ ▏  vibe coded  
              └── none ──── copilot ──── pair-programmed ──── VIBE CODED ──┘

Why

/context gives you one number. amtr gives you the whole picture, continuously: the context window as a live memory map, file access as a traffic seismograph, cache economics as a per-turn ledger, compactions as forensic events, and subagents as an economics table — every quantity labeled authoritative (read straight from the API usage records) or estimated, never blurred together.

It works on any Claude Code session — interactive or headless (claude -p) — because every session already writes a complete transcript. amtr just reads it in real time.

The live TUI

A fast, keyboard-driven terminal UI. Tabs 1–6, f for the session picker, i to inspect, R to build a report, ? for help, q to quit.

Context map — where your budget actually goes

The resident context as a fixed-scale grid: the whole box is the budget, and every cell is colored by what occupies it — system overhead, file content, hidden reasoning, shell output, tool results, and more. At a glance you see how full you are and what's filling you up. m cycles four lenses (category · access-heat · turn-age · cache billing); i walks the segments like a memory debugger and reads back the actual text occupying any region.

Files & subagents

Live file traffic (2)	Subagent fan-out (4)

FILES shows every file's read/write/edit history and a "now" view of what's being touched this instant (fading on a heat law), with a waste column that prices re-reads. AGENTS is a concurrency load-strip over a ledger of each subagent's own-tokens, return-tokens, amplification, and live duration.

Session picker — find any session by name or path

Press f for a searchable, scrollable list of every session on your machine (live ones first). Type to filter by name or project; paste a .jsonl path or a session id to jump straight to it.

Other tabs: TURNS (per-turn stacked cache/input columns with the 5m/1h billing split), SHELL (the command console Claude never shows you + the external-retrieval feed), and EVENTS (compactions, API errors, model fallbacks — with a compaction post-mortem on Enter). A timeline scrubber holds the whole session; ←/→ rewinds every view to any past turn.

The report — press R

amtr turns a session's transcript into a compiled, ground-truth PDF report: a self-contained directory with report.pdf, animated GIFs + static figures, and a per-turn capture (turns.jsonl / turns.md). Everything is rendered locally.

The figures reconstruct the session faithfully:

Context map	File traffic roll

Subagent branch tree	Agent fan-out timeline

Plus a cost-ranked phase table and a stage-by-stage, turn-by-turn account of what the session actually did.

Install

Quick install (prebuilt binary)

No Rust, no Homebrew — one line downloads the binary + engine for your platform (macOS arm64/x86_64, Linux x86_64/arm64) and installs it under ~/.local:

curl -fsSL https://raw.githubusercontent.com/arian-shamaei/anthropometer/main/install.sh | sh

If ~/.local/bin isn't on your PATH, the installer tells you how to add it. Override the install prefix with AMTR_PREFIX or pin a version with AMTR_VERSION. The live TUI needs only python3 (≥3.9, stdlib); the report extras (R) still need pip install matplotlib pillow plus brew install tectonic.

Homebrew (recommended)

brew tap arian-shamaei/anthropometer
brew trust arian-shamaei/anthropometer   # newer Homebrew asks you to trust third-party taps
brew install amtr

This installs the live TUI (a small Rust binary + a stdlib Python engine — no heavy dependencies). To enable the report feature (R / amtr-paper):

pip install matplotlib pillow      # figures
brew install tectonic              # LaTeX → PDF

From source

Needs Rust and Python 3.9+.

git clone https://github.com/arian-shamaei/anthropometer
cd anthropometer/rust
cargo install --path .             # → ~/.cargo/bin/amtr

The engine path is baked in at build time (overridable with $AMTR_ENGINE), so amtr runs from any directory.

Usage

amtr                       # newest/active session, from anywhere
amtr --session S.jsonl     # a specific transcript
amtr --project ~/my/repo   # newest session for that project
amtr --demo                # a self-contained demo (no live session needed)

Arm it beside a headless run to get a report the moment it finishes:

claude -p "do the thing" &
amtr-report --watch        # tails the live session; prints the report when it ends

Keys: 1–6 tabs · f sessions · i inspect · m map mode · ←/→ scrub · R report · ? help · q quit.

Authoritative vs. estimated

amtr is careful about what it knows versus what it estimates:

• R (resident context) — exact: input + cache_read + cache_creation of the newest assistant usage record (the same quantity /context reports).
• The cache waterline — exact: cache_read_input_tokens; backward jumps are real prefix invalidations (thrash).
• Per-item allocations — estimated (chars/3.8), laid out in true prompt order and force-fit to sum exactly to R, with the invisible server-side context (system prompt, tool schemas) carried as an honest overhead segment and a displayed calibration factor α.
• Compaction attribution — from compact_boundary set-difference, cross-checked against pre/post token counts.

How it works

Two processes over newline-delimited JSON: a Rust/ratatui UI that owns only the terminal, and a Python engine that owns all the data (transcript discovery, tailing, accounting, checkpoints, replay). SPEC.md is the normative contract; both sides are implemented against it alone, and cross-process contract tests spawn the real engine and require every emitted line to parse.

┌───────────────────────────┐   JSON lines over stdin/stdout   ┌───────────────────────────┐
│  amtr  (Rust ratatui bin) │ ── Control (UI → Engine) ──▶      │  amtr_engine.py           │
│  owns ONLY the terminal   │                                  │  (python3 ≥3.9, stdlib)   │
└───────────────────────────┘ ◀── Update (Engine → UI) ──       │  owns ALL data            │
                                                                └───────────────────────────┘

Repository layout

SPEC.md            the normative protocol + view contract
amtr_engine.py     the engine: discovery, tailing, accounting, checkpoints, replay
amtr_paper.py      the PDF report builder (amtr_figures/_turns/_phases support it)
rust/              the TUI (cargo test runs a headless screenshot suite)
tests/             engine test suite + synthetic fixtures
packaging/homebrew the Homebrew formula + tap runbook
docs/assets/       screenshots and figures for this README

License

MIT © Arian Shamaei