pi-speedometer

A per-turn speedometer for pi: TTFT (time to first token), prefill tok/s, decode tok/s, and total wall time.

Pi's built-in footer already shows tokens, cache, cost, context, and model. This extension surfaces the timing numbers it doesn't show.

Status line

After each turn, pi's status area shows:

ttft 1967ms  prefill 412 tok/s  decode 63.8 tok/s  total 14.2s

Commands

• /speed — show recent turns and per-model session averages
• /speed clear — reset history
• /speed csv — dump full history to ~/.pi/pi-speedometer-<timestamp>.csv

Install

pi install npm:pi-speedometer

Or try it without installing:

pi -e npm:pi-speedometer

How it's measured

• TTFT — performance.now() from turn_start to the first text_delta or toolcall_delta (thinking deltas are skipped so TTFT reflects perceived latency on reasoning models).
• Prefill tok/s — (input + cacheWrite) / ttft. cacheRead is excluded because those tokens didn't require real prefill work this turn. cacheWrite is included because those tokens were processed and persisted to cache.
• Decode tok/s — output / (turn_end - first_token).
• Total — wall-clock from turn_start to turn_end, including any tool round-trips inside the turn.

Numbers come from AssistantMessage.usage (provider-agnostic) plus pi's own event timings, so any provider pi supports will report.

Development

./dev drops you into a nono-sandboxed shell with the toolchain (node 24, matching CI) provided by the nix flake:

./dev                    # interactive sandboxed shell — run pi, npm, etc. inside
./dev npm ci             # or run a one-off command sandboxed
./dev npm run typecheck

The only host prerequisite is nix. One-time setup — install the base sandbox profile pack (using the flake's own nono):

nix --extra-experimental-features 'nix-command flakes' develop -c nono pull always-further/pi

The sandbox profile lives in .nono/pi-speedometer.json and extends always-further/pi; project-specific grants go there.

License

MIT