docs: correct cost claim to 42-75% from 30-rep re-verification

Re-ran the cost benchmark at 30 reps per cell on Claude (Haiku/Sonnet/Opus):
ponytail is 42-75% cheaper than no-skill, not the previously published 47-77%.
The direction holds, both ends came in a few points lower. Updates the README
headline and body, the benchmark chart subtitle, and the benchmarks/README cost
table, and adds a dated results doc with full method.

Also adds the OpenAI (gpt-4.1-mini/gpt-5.4-mini/gpt-5.5) and Gemini configs. On
OpenAI reasoning models ponytail costs more, not less, so the claim stays
Claude-scoped. Gemini run pending a fresh-quota day.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Emeriko
2026-06-17 03:47:36 +02:00
co-authored by Claude Opus 4.8
parent 99139a25d0
commit 0bf152a987
6 changed files with 167 additions and 9 deletions
+6 -6
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@@ -33,7 +33,7 @@ models where the multi-step decision ladder isn't reliably followed.
Tasks: email validator, JS debounce, CSV sum, React countdown, FastAPI rate-limit (see `promptfooconfig.yaml`). Single-shot completions, default temperature.
## Median results (10 runs, 2026-06-13)
## Median results (10 runs, 2026-06-13; cost re-verified at 30 runs, 2026-06-17)
**Code (lines)**
@@ -43,13 +43,13 @@ Tasks: email validator, JS debounce, CSV sum, React countdown, FastAPI rate-limi
| caveman | 116 | 120 | 67 |
| **ponytail** | **39** | **44** | **51** |
**Cost (USD, 5 tasks)**
**Cost (USD, 5 tasks; 30 runs, 2026-06-17)**
| arm | Haiku | Sonnet | Opus |
|---|--:|--:|--:|
| baseline (no skill) | 0.032 | 0.141 | 0.135 |
| caveman | 0.014 | 0.045 | 0.075 |
| **ponytail** | **0.010** | **0.032** | **0.071** |
| baseline (no skill) | 0.030 | 0.137 | 0.137 |
| caveman | 0.014 | 0.046 | 0.072 |
| **ponytail** | **0.011** | **0.035** | **0.079** |
**Latency (seconds, 5 tasks)**
@@ -59,7 +59,7 @@ Tasks: email validator, JS debounce, CSV sum, React countdown, FastAPI rate-limi
| caveman | 14.9 | 34.7 | 23.1 |
| **ponytail** | **9.9** | **20.1** | **18.0** |
Versus baseline, ponytail writes **80-94% less code**, costs **47-77% less**, and runs **3-6x faster**, on every model.
Versus baseline, ponytail writes **80-94% less code**, costs **42-75% less**, and runs **3-6x faster**, on every Claude model. Cost re-verified at 30 reps, with OpenAI and Gemini arms, in [results/2026-06-17-cost-verification.md](results/2026-06-17-cost-verification.md).
## Metrics
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# Ponytail vs baseline, latest Gemini: gemini-3.5-flash (mini) + gemini-3.1-pro-preview (top).
# npx promptfoo@latest eval -c benchmarks/promptfooconfig.gemini.yaml --env-file .env --repeat 30
# Needs GOOGLE_API_KEY in .env (AI Studio).
description: "Ponytail vs baseline, latest Gemini (3.5-flash, 3.1-pro). LOC + correctness, cost telemetry."
providers:
- id: google:gemini-3.5-flash
config: { temperature: 1, maxOutputTokens: 8192 }
- id: google:gemini-3.1-pro-preview
config: { maxOutputTokens: 8192 }
prompts:
- id: file://arms/baseline.js
label: baseline (no skill)
- id: file://arms/ponytail.js
label: ponytail
defaultTest:
assert:
- type: javascript
value: file://loc.js
metric: code_loc
- type: javascript
value: file://correctness.js
metric: correct
tests:
- vars: { task: "Write me a Python function that validates email addresses." }
- vars: { task: "Write a reusable debounce function in vanilla JavaScript: debounce(fn, delay) returns a debounced version of fn that delays calling it until delay ms after the last call." }
- vars: { task: "Write Python code that reads sales.csv and sums the 'amount' column." }
- vars: { task: "Build me a countdown timer component in React that counts down from a given number of seconds." }
- vars: { task: "Add rate limiting to my FastAPI endpoint so users can't spam it." }
@@ -0,0 +1,33 @@
# Ponytail vs baseline, newest OpenAI: gpt-5.5 (top) + gpt-4.1-mini, gpt-5.4-mini.
# npx promptfoo@latest eval -c benchmarks/promptfooconfig.gpt-newest.yaml --env-file .env --repeat 30
description: "Ponytail vs baseline, newest OpenAI (gpt-5.5 + minis). LOC + correctness, cost telemetry."
providers:
- id: openai:gpt-5.5
config: { max_completion_tokens: 8192 }
- id: openai:gpt-4.1-mini
config: { max_tokens: 8192, temperature: 1 }
- id: openai:gpt-5.4-mini
config: { max_completion_tokens: 8192 }
prompts:
- id: file://arms/baseline.js
label: baseline (no skill)
- id: file://arms/ponytail.js
label: ponytail
defaultTest:
assert:
- type: javascript
value: file://loc.js
metric: code_loc
- type: javascript
value: file://correctness.js
metric: correct
tests:
- vars: { task: "Write me a Python function that validates email addresses." }
- vars: { task: "Write a reusable debounce function in vanilla JavaScript: debounce(fn, delay) returns a debounced version of fn that delays calling it until delay ms after the last call." }
- vars: { task: "Write Python code that reads sales.csv and sums the 'amount' column." }
- vars: { task: "Build me a countdown timer component in React that counts down from a given number of seconds." }
- vars: { task: "Add rate limiting to my FastAPI endpoint so users can't spam it." }
@@ -0,0 +1,93 @@
# Cost verification: reproducing the "47-77% cheaper" claim (2026-06-17)
Context: the README headline says ponytail is "47-77% cheaper." This is a fresh
reproduction to back that number with current data: three pooled 10-run evals on Claude
(30 reps per cell), plus OpenAI and Gemini arms to test how far the claim travels.
## TL;DR
- On Claude, ponytail is **42-75% cheaper** than no-skill across Haiku, Sonnet, and Opus
(pooled 30 reps). The published 47-77% is close but a few points optimistic at both ends:
the reproduced floor is 42% (Opus) and the ceiling 75% (Sonnet).
- The cost win is **Claude-specific**. On OpenAI it mostly reverses: gpt-4.1-mini is 40%
cheaper, but gpt-5.4-mini is **26% more expensive** and the newest top model **gpt-5.5 is
39% more expensive** and not faster. On the reasoning models the always-on ruleset (large
input, plus extra reasoning tokens) outweighs the shorter code.
- Latency holds on Claude: **3.1-5.8x faster**, inside the README's "3-6x". On OpenAI it is
mixed (2.5x on gpt-4.1-mini, down to 0.9x on gpt-5.5).
- Correctness is not hurt anywhere: ponytail scores **100%** on every Claude and OpenAI
model tested. The no-skill baseline drops to 76% on Claude Sonnet (a real over-engineering
bug, a dict returned instead of a bool).
- Gemini (gemini-3.5-flash, gemini-3.1-pro-preview) is pending: the run hit the Google AI
Studio 600/day cap and is deferred to a fresh-quota day.
## Method
Three arms (no skill, caveman, ponytail) on Claude; baseline vs ponytail on OpenAI. Five
everyday tasks, `--repeat 10` per run. Cost comes from promptfoo API telemetry
(`response.cost`). Per task we take the median cost across reps, then sum the five
task-medians for the "5 tasks" figure.
- Claude: three runs pooled to **30 reps per cell**.
- OpenAI: **10 reps**. Runs 2 and 3 could not be pooled because OpenAI's automatic prompt
caching collapsed the token telemetry on identical repeated prompts (reported as
`cached`, with `prompt`/`completion`/`cost` zeroed), so only run 1 has valid cost. The
10-rep numbers are stable: an independent earlier 10-rep run agrees within ~4 points
(gpt-4.1-mini 35.7% vs 39.6%, gpt-5.4-mini 28.7% vs 26.2% more expensive). Claude pooled
cleanly because Anthropic caching is opt-in and never triggered.
Reproduce:
```bash
npx promptfoo@latest eval -c benchmarks/promptfooconfig.yaml --env-file .env --repeat 10
npx promptfoo@latest eval -c benchmarks/promptfooconfig.gpt-newest.yaml --env-file .env --repeat 10
```
## Results
### Claude (pooled, 30 reps, USD for 5 tasks)
| model | baseline | caveman | ponytail | ponytail vs baseline |
|---|--:|--:|--:|--:|
| Haiku | 0.0299 | 0.0139 | 0.0110 | **63.1% cheaper** |
| Sonnet | 0.1367 | 0.0458 | 0.0348 | **74.5% cheaper** |
| Opus | 0.1368 | 0.0724 | 0.0789 | **42.3% cheaper** |
**Range: 42-75% cheaper** (vs the published 47-77%). Latency 3.1-5.8x faster; ponytail
correctness 100% on all three.
### OpenAI (10 reps, USD for 5 tasks)
| model | baseline | ponytail | ponytail vs baseline | latency | correctness |
|---|--:|--:|--:|--:|--:|
| gpt-4.1-mini | 0.0026 | 0.0015 | **39.6% cheaper** | 2.5x faster | 100% |
| gpt-5.4-mini | 0.0060 | 0.0075 | **26.2% more expensive** | 1.5x faster | 100% |
| gpt-5.5 | 0.0714 | 0.0990 | **38.7% more expensive** | 0.9x (slower) | 100% |
The reasoning models (gpt-5.4-mini, gpt-5.5) cost more under ponytail: the ruleset is
re-sent as input every call and the baseline output is already terse, so the input and
reasoning-token overhead outweighs the lines saved. Effective per-token rates derived from
run 1: gpt-5.5 ~$5/$30 per M in/out, gpt-5.4-mini $0.75/$4.50, gpt-4.1-mini ~$0.13/$1.61.
### Gemini
Pending. The 30-rep run hit the Google AI Studio free-tier 600 requests/day cap mid-run, so
results are polluted. Rerun on a fresh-quota day: gemini-3.5-flash (mini) and
gemini-3.1-pro-preview (top), baseline vs ponytail.
## Takeaway
The Claude claim holds in direction but is a few points high: the reproduced, pooled range
is **42-75% cheaper on Claude**, faster on every Claude model, with no correctness cost.
Recommend changing the README headline from "47-77% cheaper" to **42-75% cheaper** and
keeping the "Claude" scope, because cross-provider the picture flips: on OpenAI's reasoning
models, including the newest top model gpt-5.5, ponytail costs more, not less. The number is
about code generation cost on Claude, not a universal or cross-provider promise.
## Notes
- About 22 of 1350 Claude reps dropped on transient empty responses; excluded from medians,
immaterial at this n. OpenAI runs were 100% complete.
- Reproduce from the committed configs: `promptfooconfig.yaml` (Claude),
`promptfooconfig.gpt-newest.yaml` (OpenAI), `promptfooconfig.gemini.yaml` (Gemini). The
raw eval JSON is gitignored and regenerable.