AI Companion NPCs: Party Members Who Notice, Talk and Act

A typical party member has a bark for low health and a bark for opening a chest, and players hear each one two hundred times. Neocortex lets you build AI companion NPCs who comment on what the player actually just did, notice what is lying around them, and return actions like follow, pick up or heal that your game carries out.

What it looks like

An original pulp adventure game: the player is leading an expedition through the Verdant Hollow, a jungle valley that supposedly hides a lost city. Two companions travel with them. Juno Reyes is a field medic who sketches every plant she sees. Calloway is a former mail pilot whose plane is somewhere behind them in a tree, and he has opinions about everything.

Pursuers are closing in. The player crosses a rope bridge and shoots through the ropes behind them. The game sends that as an event, along with metadata for what is near the party: a supply crate, a carved stone idol, and a patch of bloodroot by a rock.

Calloway: That was our only way back, you realise. Brilliant. Truly inspired. Juno: It was also their only way across. And there's bloodroot by that rock. I'm taking it before your sulking scares it off.

Juno's reply carries a PICK_UP action aimed at the bloodroot's ID, and the game plays her walking over to collect it. Ten minutes later, after a fall, the game sends an event that the player's health is low. Juno's next line comes with HEAL targeting the player. When the player says "stay close, both of you", the reply holds two FOLLOW actions, one per companion, and your pathfinding takes it from there.

Nobody wrote a line about the bridge. The writer described two people and what they can do, and the expedition gave them something to talk about.

How Neocortex makes it work

• Events. Your game sends what just happened as short sentences, like "the player cut the rope bridge" or "the player spared the poacher". The companions react to this playthrough, not a generic script.
• Metadata. Send the entities near the party, each with an ID, a name, a position and properties. Companions can name the idol, warn about the snake, and use those IDs as action targets. See our spatial awareness page.
• Actions. You author FOLLOW, PICK_UP and HEAL as Action nodes. A reply can return several at once, each with a target, and your navigation and animation code runs them.
• Group chat. Put both companions in one conversation so they can bicker, back each other up or interrupt (Pro and Team plans, up to six characters). An AI director picks who speaks, or you force a speaker with speakerCharacterId when a moment belongs to one of them.
• A single companion on any plan. One sidekick talking to the player works on every plan, including Free.
• Session memory. Store the sessionId with the save file and send it when the player loads in. Resume the player's session and the companions carry on from the last conversation.
• Voices and emotions. Each line streams in the companion's own voice with an emotion tag, so Calloway can sound appalled and Juno amused. In Unity, lip sync drives their faces from the reply.

Ideas to build

A ship's drone with commentary. In a space salvage game, a small repair drone floats at the player's shoulder. It reacts to events like "hull integrity at 40 percent", spots valuable scrap in the metadata, and returns SCAN or REPAIR on the part it is talking about.

Two apprentices who want the same job. In a wizard academy game, two classmates follow the player through the dungeon. Their personalities say they are competing for the top grade, so in group chat (Pro and Team) each one points out the other's mistakes, and both rush to answer when the player asks for help.

A nervous companion in a horror game. A night guard follows the player through an abandoned hospital. When the game sends "the lights in the east wing just went out", his emotion tags turn to fear, his voice wavers, and he returns HOLD_LIGHT on the torch the player handed him.

A pack mule with opinions. In a survival crafting game, the companion carries the overflow. They PICK_UP what the player asks for, complain when the player hoards a twelfth stack of rocks, and point out the berries the player walked straight past.

Building it

Companions work with the Unity SDK, the Unreal Engine plugin, the Godot addon (beta) or the Web API from any engine. Your game keeps doing what it already does well, moving characters and playing animations; Neocortex decides what each companion says and does next.

1. Design each companion in the visual editor: personality, backstory, how they feel about the player, a voice and the actions they may return.
2. Author the actions your game can already perform, like FOLLOW, PICK_UP, HEAL or WAIT, so every action that comes back maps to real behaviour.
3. Choose what counts as nearby. Pick a radius or a rule in your own code, and send only those entities as metadata.
4. Send events for moments worth a comment: fights won, choices made, the player getting hurt.
5. Test the party in the dashboard, alone or in the group preview, before any game code exists.
6. Wire the reply: play each line with its voice and emotion, then run the actions in order.

Keep the metadata small. Five or six relevant things within reach make a companion sound observant; the entire level makes them comment on a crate three rooms away.

Party companions are one of our AI NPC, ambient AI and voice command use cases. For party chatter while the player is busy, read ambient NPC conversations, and for companions who notice the big moments, see NPCs that react to world events. The AI companions page and the interactables docs cover the rest. Start with one companion, three actions and a bridge to argue about.

Checked October 2026.

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