Auto prompt optimization

Evaluate & Benchmark

Auto prompt optimization

Closed-loop system: an optimizer LLM writes prompts and reads failure summaries, a target LLM runs batches against synthetic data, and a JSON ledger tracks every iteration until scores converge.

The problem

Prompt optimization lacks systematic validation. Teams can't tell whether a prompt change actually improves performance or just looks different.

  • You tweak a prompt, it feels better, but you can't prove it's actually better.
  • Two people on the team ship contradictory prompt changes because neither can measure impact.
  • Regressions from a "small" prompt edit show up in production, not in review.

What NEO built

NEO built a dual-LLM loop: an optimizer model writes and revises prompts while a separate target model evaluates them against synthetic data, with every iteration logged to a JSON ledger.

Dual-LLM loopPrompt optimizationJSON ledger

The result

Dual-LLM optimization loop

Delivers a closed-loop, dual-LLM optimization system that converges on measurably better prompts with a full audit trail of every iteration.

AutoPrompter: Closed-Loop Autonomous Prompt Optimization

From the blog · 8 min

AutoPrompter: Closed-Loop Autonomous Prompt Optimization

NEO built a closed-loop system that automatically refines LLM prompts through iterative testing, failure analysis, and measurable performance improvement.

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Build a closed-loop prompt optimizer for my prompt: have one LLM propose revisions while a second LLM scores them against my test set, and log every iteration to a ledger until the score converges.

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