GTA San Andreas and Vice City AI NPC Mod: Smart NPC Dialogue

What would the barber in Ganton say if you could actually talk to him? In the 3D-era GTA games, still some of the most modded on PC, the answer is a handful of shouted lines. A GTA San Andreas AI NPC mod gives those characters real dialogue: they answer questions, remember you and react to your stats, your gang and your driving. Neocortex adds AI characters with voices, actions and emotions, Conversation Flows, quizzes and on-device voice commands, and the same approach works for Vice City and GTA III.

Screenshot: Grand Theft Auto: San Andreas © Rockstar Games

Which classic GTA are you modding?

Classic GTA mods load as native code inside the game process. Which tools you reach for depends on the game and the version you own:

The pieces behind that table:

• Ultimate ASI Loader is a proxy DLL that loads .asi plugins from the game folder or a scripts folder.
• plugin-sdk is the C++ SDK for writing ASI and CLEO plugins for San Andreas, Vice City and GTA III. It exposes the reversed game classes, so your plugin can read peds, vehicles and player stats, and draw text through the game's own message and font functions.
• CLEO 5 ships plugins for audio playback, text, INI files and input.
• CLEO Redux runs JavaScript and TypeScript scripts on GTA III, Vice City and San Andreas (with CLEO 4.4 or CLEO 5), plus other titles.

The 2021 Trilogy remasters are a different engine: plugin-sdk and CLEO 5 do not apply, and CLEO Redux is the main scripting option. If you want AI NPCs, start from the classic PC versions.

ASI plugin or CLEO script?

You will probably use both, for different jobs.

The ASI plugin talks to the web. In C++ it can make HTTPS requests with WinHTTP or libcurl on a background thread, show the reply as subtitles with the game's message functions, and play the voice audio. That is everything Neocortex needs from the game side.

CLEO scripts handle gameplay glue. Spawning the character, marking where they stand, quick triggers: CLEO is faster to iterate on for that kind of work, and it does not need to know anything about the network.

Ideas for a GTA San Andreas AI NPC mod

Locals who notice who you are. San Andreas tracks a lot about CJ: fat, muscle, respect, wanted level, the clothes he is wearing, which gang owns the block. Send that to an original character, say a barber in Ganton or a burger stand owner in Los Santos, as events with each message. Turn up with low respect and a terrible haircut and they say so. Come back after taking three territories and they have heard about it. Every reply carries an emotion tag you can map to a facial animation or a voice tone, and actions like { "name": "GIVE_DISCOUNT" } let the character affect your game.

Voice commands for your crew. San Andreas lets you recruit gang members, and voice is the natural way to boss them around. The player says "recruit two guys and follow me", "wait here" or "everyone get in the car", and your plugin receives the matched commands, quantity included. In Vice City the same command set can call a cab, switch the radio or tell your passenger to wait by the car, all without a menu.

A radio-style trivia host. Both games are famous for their radio. Build an original late-night host for a fictional station who runs a trivia quiz while you drive from Los Santos to Las Venturas, or an 80s pop culture quiz on Ocean Drive. The quiz engine (Team plan) handles questions, scoring and the leaderboard, speech-to-text lets the player answer out loud, and the host's voice streams back as audio.

Screenshot: Grand Theft Auto: San Andreas © Rockstar Games

The Neocortex side

Characters are built in a visual node editor: personality, emotion, knowledge files about the neighbourhood, world details, voice. You can test them in the browser before touching the game. From the plugin, four features do the work:

• Dialogue: the plugin reads game state (stats, location, nearby peds, recent events), sends it with the player's line to a Neocortex character (/v3/chat), shows the reply as subtitles, plays the voice from /v3/audio/generate or /v3/audio/stream, and runs the actions the character returns.
• Conversation Flows: for a longer chat, a flow steers the character through beats you design and returns checkpoint keywords (flowState), such as TRUSTS_PLAYER, that your plugin reacts to.
• Quizzes: the quiz engine runs the trivia host through /v3/quiz: start with a question set, send the player's answers, read back the score.
• Voice commands: on-device voice commands turn speech into game actions without a cloud round trip. Neocortex Voice Commands runs on the player's machine, and you design the command set in the dashboard as actors ("crew"), actions ("follow", "wait", "recruit") and objects ("me", "car"). Push-to-talk or always listening, in multiple languages.

Voice Commands is a licensed SDK: contact us for a Voice Commands license.

Rockstar's rules for classic GTA mods

Rockstar's PC single-player mods policy covers its PC games: Take-Two generally will not act against single-player, non-commercial projects that respect third-party IP, and new stories, missions and maps are excluded. Rockstar's newer Mod Guidelines apply to every Rockstar game, classic ones included, and spell out more:

• Do not expand or modify Rockstar's storylines, missions or characters, so CJ, Sweet and Tommy Vercetti get no new AI dialogue.
• Do not modify or reuse Rockstar's voiceover performances. Give your characters original Neocortex voices or voices you have the rights to, never clones of the original cast.
• Do not bring maps, characters or other assets from one Rockstar game into another, such as Vice City inside San Andreas.
• Multiplayer modding is limited to Rockstar's Creator Platform, and everything outside it must stay strictly non-commercial.

The guidelines also state that they are not a license. So build talking locals, crew commands and quizzes with original characters, keep the mod free and single-player, and have each player use their own Neocortex API key.

Start with one character

Set up a classic PC copy with Ultimate ASI Loader, plus CLEO 5 for San Andreas or CLEO for III and Vice City if you want scripts. Create a plugin-sdk project and build an empty .asi that loads in game. Then design one character, flow, quiz or voice command set in the Neocortex dashboard and test it in the browser. Connect from the plugin with HTTPS on a background thread, show subtitles and play audio on the game side, and read the API key from an .ini file that each player fills in with their own key. Test in single-player on a save you do not mind breaking.

One barber who remembers your haircut is enough to prove the idea. For the newer games, see our GTA 5 AI NPC mod and GTA 4 AI NPC mod guides, and for the voice side, read about on-device voice commands for game mods. Neocortex is free to start, so the first character costs nothing but an evening.

Tool versions and links checked October 2026. Modding tools change often; check each project's page for the latest release.

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