Show Lean's measured impact as a compact scoreboard: less code, more speed, from the benchmark medians. One-shot display, not a persistent mode, and not a per-repo number. Trigger: /lean-gain, "lean gain", "what does lean save", "show lean impact", "lean scoreboard".
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---
name: lean-gain
description: >
Show Lean's measured impact as a compact scoreboard: less code, more speed,
from the benchmark medians. One-shot display, not a persistent mode, and not
a per-repo number. Trigger: /lean-gain, "lean gain", "what does lean save",
"show lean impact", "lean scoreboard".
license: Apache-2.0
---
# Lean Gain
Display this scoreboard when invoked. One-shot: do NOT change mode, write flag
files, or persist anything.
The figures are Prompt-Studio's own benchmark medians, measured — not computed
from the current repo. Source: `benchmarks/results/latest.json` and
`benchmarks/results/2026-08-12-lean-vs-ponytail.md`.
## Scoreboard
Render plain ASCII bars. The bar length shows the measured range; the label
carries the exact figure:
```
lean gain measured · gpt-4o-mini · n=3 · 7 tasks
Lines of code baseline ████████████████████ 100%
lean ██████·············· 25–35% ▼ 65–75%
Speed lean ▸ ~4× faster (3.5–4.3×, full = 4.25×)
Cost not shown by design — see Honesty boundary.
This repo: /prompt-studio:lean-stats (real tokens, this session)
/prompt-studio:lean-debt (counted shortcut ledger)
/prompt-studio:lean-audit (what's still cuttable)
```
## Honesty boundary
These are benchmark medians, not this repo. NEVER print a per-repo savings
number ("you saved X lines/tokens here"): the unbuilt version was never
written, so there is no real baseline to subtract from in a live repo.
No cost bar is shown **by design, not omission**: on single-shot tasks Lean's
cost is roughly flat (~100–108% of baseline in `latest.json`) because the Lean
system-prompt input tokens offset the output-token savings. Claiming a cost win
would contradict the measured data. For real per-session cost use
`/prompt-studio:lean-stats` (actual token counts) and `/prompt-studio:lean-debt`
(counted ledger); for what's still cuttable, `/prompt-studio:lean-audit`.
Basis is a single model (gpt-4o-mini, n=3) — the footer says so. Do not present
it as multi-model.
## Boundaries
One-shot display. Edits nothing, changes no mode.
"stop lean" or "normal mode": revert.
