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Amazon AI BlogPublished: Jul 31, 2026, 01:00 JST

Amazon Bedrock launches prompt optimizer for multiple models at once

Amazon Bedrock launches prompt optimizer for multiple models at once

3 Key Points

  1. What happened

    Amazon Bedrock introduced Advanced Prompt Optimization, a tool that automatically optimizes prompts for up to 5 models simultaneously and compares their original and optimized performance. The system uses a reinforcement learning-style feedback loop—evaluating responses against a metric, rewriting the prompt, and repeating—without changing model weights. Results include evaluation scores, time-to-first-token (TTFT) per sample, and inference cost estimates at on-demand pricing for each model.

  2. Why it matters

    Manual prompt migration and optimization currently forces teams to spend days to weeks rewriting prompts, running test cases, comparing results, and tweaking iteratively—work that multiplies across every prompt template and model candidate. This bottleneck creates model lock-in (avoiding migration even when newer models are faster and cheaper), underperformance on capable models, regression blindness (shipping degraded outputs unknowingly), and slow iteration cycles. The tool replaces that manual cycle with a guided, metrics-driven workflow in a single job, unblocking faster model migration and optimization decisions.

  3. What to watch

    The tool supports three evaluation modes—AWS Lambda functions (for concrete metrics like accuracy or F1), LLM-as-a-Judge (for open-ended tasks like summarization), and steering criteria (for brand voice, format, or safety constraints)—plus multimodal inputs (PNG, JPG, JPEG, GIF, WebP, PDF via Amazon S3) for document analysis and visual tasks. Jobs can be created and submitted via the Amazon Bedrock console, API, or boto3 SDK. Example runs showed accuracy improving from 0.267 to 0.647 (NESTFUL function-calling task on Amazon Nova 2 Lite) and quality score rising from 0.550 to 0.743 while output tokens dropped from 51 to 28 (XSum summarization on Claude Haiku 4.5).

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Context & Analysis

Prompt optimization sits at a critical bottleneck in the generative AI development lifecycle. When companies deploy a generative AI application and a faster, cheaper, or more capable model becomes available on Amazon Bedrock, teams face a difficult decision: migrate and retune, or stay locked in to the current model to avoid weeks of manual optimization work. The manual cycle—rewrite prompt, test against cases, compare results, tweak, repeat—compounds across every prompt template in production and every model candidate, creating a problem that scales with business ambition.

Amazon Bedrock Advanced Prompt Optimization breaks this cycle by automating the feedback loop. Rather than heuristic prompt rewrites, the system operates backward from the evaluation metric you define: it sends your prompt template and inputs to your chosen models, evaluates responses against your metric, rewrites the prompt, and repeats. This approach lets teams test up to five models in one job, eliminating days of manual iteration. The tool is model-agnostic and supports three evaluation methods—AWS Lambda functions for concrete metrics, LLM-as-a-Judge for open-ended tasks, and natural language steering criteria—letting teams align optimization with their actual use case. By providing side-by-side comparisons of quality scores, latency, and cost, the tool removes the guesswork from model migration decisions and unblocks faster iteration.

FAQ
What evaluation methods can I use with Advanced Prompt Optimization?
You can choose one of three: an AWS Lambda function (for concrete metrics like accuracy, F1, or ROUGE), an LLM-as-a-Judge with a rubric prompt (for open-ended tasks), or steering criteria (up to 5 natural language criteria for brand voice, format, or safety). If you omit all evaluation fields, the system uses a built-in default combining accuracy, answer completeness, and writing style.
How many models can I compare in a single job?
You can target up to 5 models at once. You can select your current model as a baseline plus up to 4 additional candidates, or optimize only your current model for same-model improvement.
What file format and inputs do I need to submit?
Your input file uses JSONL format (one JSON object per line), with each line containing a prompt template, variable placeholders, evaluation samples with optional ground-truth answers, and your chosen evaluation metric specification. Advanced Prompt Optimization also supports multimodal inputs (PNG, JPG, JPEG, GIF, WebP, PDF) referenced via Amazon S3 URIs for document analysis and visual tasks.
What does the tool output?
For each model, you receive the original and optimized prompts ready to copy and deploy, evaluation scores before and after optimization, time-to-first-token (TTFT) per sample, and inference cost estimates at on-demand pricing—all allowing direct comparison of quality, latency, and cost across candidates.
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