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Build a Greenfield Prototype with a Single Prompt Using Claude Opus 4.8

Turn a detailed greenfield prompt into a runnable prototype and judge the result through real interactions.

Build a Greenfield Prototype with a Single Prompt Using Claude Opus 4.8

01:35 to 04:02: Claire tests Opus 4.8 on a greenfield feature and compares its strong first pass with weaker follow-up behavior at codebase boundaries.

Before you start

What you need

  • A product problem and intended user
  • Functional and visual requirements
  • A coding workspace with preview access

What you’ll make

A runnable first version that covers the primary interaction and its most important states.

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

Select Model and Environment

Navigate to the Claude Code environment and select the Claude Opus 4.8 model. This model is well suited for complex, single prompt coding tasks.

Example prompt
Choose the model and open a clean greenfield workspace with a browser preview.
Step02

Craft a Detailed Prompt

Draft a single, detailed prompt that describes the entire feature you want to build. Specify the core functionality, target user actions, and key architectural constraints, such as the programming languages, frameworks, or libraries to use.

Example prompt
Specify the user, job, interaction states, data rules, visual direction, and acceptance checks in one prompt.
Step03

Generate the Code

Submit your prompt. Claude will first create a plan and then generate the code. For a complex feature, this autonomous process can take around 20 minutes, so expect to wait for the complete output.

Example prompt
Build the prototype, run it, and report the files, routes, and checks completed.
Step04

Review and Test

Review the generated code for correctness and ensure it follows your architectural specifications. Deploy the code to a preview branch or a local environment to perform a functional test and confirm the feature works as requested.

Example prompt
Test the primary path, empty and error states, and one mobile viewport; return reproducible failures.

What good looks like

  • The core task can be completed in the preview
  • The output follows the stated stack and design constraints
  • Failures are reported with reproducible steps

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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 first result is polished but incomplete
Add explicit states, data rules, and completion checks to the prompt.
The agent invents a product decision
Mark unresolved decisions and provide the missing choice before rerunning.
The prototype cannot be evaluated
Require a preview, seed data, and exact test path.

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