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How to Build a Custom AI Model Benchmark Using Claude Code

Create a repeatable, automated benchmark to evaluate AI models on tasks relevant to your work. This workflow uses Claude Code to brainstorm, refine, and generate a complete evaluation system, including a test runner and scoring backend.

How to Build a Custom AI Model Benchmark Using Claude Code

05:05 to 13:58: Claire uses Claude Code to turn her real product tasks into a benchmark harness with automated judges and manual taste scoring.

Before you start

What you need

  • A representative set of real tasks and inputs
  • The models and configurations to compare
  • Scoring dimensions with examples of strong and weak outputs

What you’ll make

A runnable benchmark that sends the same task set to each model and records comparable automated and human scores.

Tools used

Step by step

The workflow

Follow the sequence once, then adapt the prompts, checks, and handoffs to your own setup.

4 steps

Step01

Brainstorm the Benchmark with AI

Use an AI tool with session history, like Claude Code, to brainstorm the structure of your benchmark. Provide context about your audience and goals so the AI can use your past work to generate relevant tasks and design principles.

Example prompt
Based on our work together, can you help me brainstorm how I AI benchmark and eval set we can test every time a new model comes out to consistently score different tasks That would be relevant to our podcast audience.
Step02

Refine the Scope of Your Benchmark

Refine the benchmark's scope to a manageable set of tasks. Instruct the AI to focus on specific areas relevant to your work, such as generating PRDs, creating prototypes, and performing multi-step agentic tasks.

Example prompt
Let's actually focus on task for builders, PRDs prototypes, agentic, multi-step and agentic voice basically does a pass the vibe check in my open claw.
Step03

Generate the Evaluation Harness

Prompt the AI to generate the complete evaluation system based on your refined scope. The output should be a full test harness, including a test runner script, an LLM-as-judge scorer, and a local HTML page for manual human evaluation.

Example prompt
Now, build the complete evaluation harness for the tasks we've defined. Generate the following components:
1. A test runner script that can execute the same prompts across multiple models, like [Opus 4.8, GPT-5.5, and Sonnet 5].
2. A backend scorer that uses an LLM-as-judge to evaluate the outputs based on a clear rubric.
3. A local HTML page that displays the outputs from all models side-by-side for a blind human review, allowing me to enter a 1-5 score and notes for each.
Step04

Implement a Hybrid Scoring System

Confirm the generated harness includes both an automated LLM-as-judge scorer and an interface for manual human scoring, or a 'vibe check'. This hybrid system allows you to combine objective performance metrics with your own subjective, taste-based feedback.

Example prompt
Confirm the generated harness includes both an automated LLM-as-judge scorer and an interface for manual human scoring, or a 'vibe check'. This hybrid system allows you to combine objective performance metrics with your own subjective, taste-based feedback.

My actual values:
[insert the files, settings, accounts, or constraints for this step]

Give me the exact commands, settings, or output to use. Finish with a pass or fail check for implement a hybrid scoring system.

What good looks like

  • Every model receives the same prompt, context, and tool access
  • Automated scores are reproducible and manual scores remain blinded
  • A new model can be added without rewriting the test suite

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After the steps

Runbook notes

How to recover when the loop fails and where human judgment helps.

Recover

If it goes sideways

The benchmark rewards easy formatting instead of useful work
Replace shallow tests with task outcomes and rubric examples drawn from real product decisions.
Repeated runs produce materially different rankings
Fix model settings, record versions, run multiple trials, and report score spread beside the average.

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