Turn the NPCs in a GTA III remake into AI agents
Claude Opus 5.5 built a System 1 / System 2 AI layer into re3, the reverse-engineered GTA III. Type a cheat and nearby NPCs become agents: a fast model picks actions like walk, run, fight, talk or drive while GPT-4.1 mini writes what they say and think.
Source
@vladrezdev on X · 2026-10-20
Written in our own words. Credit to the original author. Link checked 2026-10-20.
What they did
Claude Opus 5.5 built a System 1 / System 2 AI layer into re3, the reverse-engineered GTA III. Type a cheat and nearby NPCs become agents: a fast model picks actions like walk, run, fight, talk or drive while GPT-4.1 mini writes what they say and think.
Result (as claimed)
Demo video in the post.
Tools they used
Cost: Claude Opus 5.5: from $4 in / $20 out per 1M tokens.
Set it up
Write a one-page brief
Describe the app in plain words: who it is for, the 3 core screens or actions, and what "done" looks like.
Start the project with your agent
Open Claude Opus 5.5 and paste the brief. Ask it to propose a stack and a file plan before writing code.
Build one slice at a time
Ship the smallest working flow first, run it, then add features one by one. Commit after each working step.
Test it like a user
Click through on desktop and phone. Ask the agent to add basic tests and fix anything that breaks.
Check security and ship
Keep keys in environment variables, check auth and database rules, then deploy and share the link.
Copy the full setup prompt
Paste into your agent and it will walk you through the setup, asking before anything that sends, posts or spends.
You are helping me set up this AI use case end to end in Claude Code. Goal: Turn the NPCs in a GTA III remake into AI agents What the original author did: Claude Opus 5.5 built a System 1 / System 2 AI layer into re3, the reverse-engineered GTA III. Type a cheat and nearby NPCs become agents: a fast model picks actions like walk, run, fight, talk or drive while GPT-4.1 mini writes what they say and think. Reported result (as claimed by the author): Demo video in the post. Source: https://x.com/vladrezdev/status/2112437552183701557 Tools they used: Claude Opus 5.5, GPT-4.1 mini Category: Vibe coding & apps Please: 1. Ask me 3 short questions about my situation (accounts I have, budget, what I want the output to look like). 2. Propose a step-by-step plan using these tools or cheaper alternatives, with the time and cost of each step. Use official pricing pages; say "check pricing" if unsure. 3. Then do the setup with me one step at a time, waiting for my OK before anything that sends messages, posts publicly, spends money or deletes data. 4. Finish with a checklist to run it again next time.
You are helping me set up this AI use case end to end in Codex. Goal: Turn the NPCs in a GTA III remake into AI agents What the original author did: Claude Opus 5.5 built a System 1 / System 2 AI layer into re3, the reverse-engineered GTA III. Type a cheat and nearby NPCs become agents: a fast model picks actions like walk, run, fight, talk or drive while GPT-4.1 mini writes what they say and think. Reported result (as claimed by the author): Demo video in the post. Source: https://x.com/vladrezdev/status/2112437552183701557 Tools they used: Claude Opus 5.5, GPT-4.1 mini Category: Vibe coding & apps Please: 1. Ask me 3 short questions about my situation (accounts I have, budget, what I want the output to look like). 2. Propose a step-by-step plan using these tools or cheaper alternatives, with the time and cost of each step. Use official pricing pages; say "check pricing" if unsure. 3. Then do the setup with me one step at a time, waiting for my OK before anything that sends messages, posts publicly, spends money or deletes data. 4. Finish with a checklist to run it again next time.
You are helping me set up this AI use case end to end in Grok Bot. Goal: Turn the NPCs in a GTA III remake into AI agents What the original author did: Claude Opus 5.5 built a System 1 / System 2 AI layer into re3, the reverse-engineered GTA III. Type a cheat and nearby NPCs become agents: a fast model picks actions like walk, run, fight, talk or drive while GPT-4.1 mini writes what they say and think. Reported result (as claimed by the author): Demo video in the post. Source: https://x.com/vladrezdev/status/2112437552183701557 Tools they used: Claude Opus 5.5, GPT-4.1 mini Category: Vibe coding & apps Please: 1. Ask me 3 short questions about my situation (accounts I have, budget, what I want the output to look like). 2. Propose a step-by-step plan using these tools or cheaper alternatives, with the time and cost of each step. Use official pricing pages; say "check pricing" if unsure. 3. Then do the setup with me one step at a time, waiting for my OK before anything that sends messages, posts publicly, spends money or deletes data. 4. Finish with a checklist to run it again next time.
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Guides for this use case
How to reverse-engineer and revive old devices with AI · How to run multiple coding agents together · How to automate work with n8n and AI
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