Fallout 4 AI NPC Mod: Talking Companions and Voice Commands

Fallout 4 companions are great company until you want to talk about something the writers did not plan for. A Fallout 4 AI NPC mod built on Neocortex lets companions answer the player in their own words, turns settlement management into voice commands and adds a Vault-Tec quiz terminal to your favorite settlement. Here is what you could build and how it fits on top of F4SE and Papyrus.

Screenshot: Fallout 4 © Bethesda Softworks

What you could build with Neocortex in Fallout 4

Companions with real conversations

Rebuild a companion's voice as a Neocortex character, or add a new one: a Personality type, an Emotion profile and a Knowledge base from a TXT file about their past and the factions they distrust. Your mod sends each player line with recent events ("the player sided with the Brotherhood", "radstorm incoming") and nearby objects such as a locked door or a power armor station. The companion answers in voice, every line carries an emotion tag like ANGRY or CURIOUS for expressions, and actions like { "name": "OPEN_DOOR", "targetId": "door_02" } tell your mod what to do. On Pro and Team plans, group chat lets up to six characters share one conversation, so a road trip with two companions and a caravan trader turns into an actual argument.

A Conversation Flow can steer a personal quest: the companion opens up, asks for help, and each beat returns a checkpoint keyword your Papyrus quest script turns into the next stage.

Settlement voice commands

Settlement building is menu-heavy, which makes it the best place for voice. Design a command set with actors ("settlers", "Preston", "Dogmeat"), actions ("build", "go", "guard", "follow") and objects ("turret", "workshop", "the gate"). Players say "build a turret here" or "everyone to the workshop", and your mod receives clean commands, including several actions in one sentence and quantities like "post two guards at the gate". It works push-to-talk or always-listening, offline, in multiple languages, using the Neocortex Voice Commands library on the player's machine. Learn more in our guide to on-device voice commands for game mods. Voice Commands is a licensed SDK: contact us for a Voice Commands license.

A Vault-Tec aptitude quiz terminal

Place a terminal in Sanctuary that runs a Vault-Tec style aptitude test with a cheerful host voice. The question set lives in the Neocortex dashboard and the quiz engine (Team plan) handles questions, scoring and a leaderboard. The player answers out loud through speech-to-text, and your mod hands out caps or a perk magazine for a high score.

How Fallout 4 modding works

• F4SE is the Fallout 4 Script Extender. It supports the latest Steam and GOG versions, which are not always the same build, and it cannot support the Microsoft Store release. Alongside the current 1.11 runtime that arrived with the Anniversary Edition update, F4SE still publishes builds for the Next-Gen runtime (1.10.984) and the older 1.10.163, because many players keep an earlier version for mod compatibility.
• Address Library for F4SE Plugins provides version-independent IDs so a plugin can find game functions at runtime. Players need the file that matches their game version.
• Papyrus is the game's scripting language, written and compiled with the free Creation Kit on Steam. It drives quests, dialogue, terminals and settlements, but it has no network access.

So the network code goes into a native F4SE plugin in C++. The plugin calls the Neocortex API with WinHTTP or libcurl on a worker thread, then hands results to Papyrus through new native functions your scripts call. Papyrus handles the game side: Debug.Notification for simple subtitles, SetStage for quest beats, and the workshop and actor functions for settlement commands. Voice lines in Fallout 4 are .fuz files that pair audio with lip-sync data, so a mod either generates lip data for each reply or plays the audio without mouth movement.

Mantella is an existing community AI mod that also runs on F4SE.

Screenshot: Fallout 4 © Bethesda Softworks

How Neocortex fits in

• Dialogue. The mod reads game state and sends it to a Neocortex character through /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.
• Story beats. Conversation Flows steer branching scenes and return checkpoint keywords (flowState) the mod reacts to.
• Quizzes. The quiz engine runs question-and-answer games through /v3/quiz.
• Voice commands. On-device voice commands turn spoken phrases into game actions without a cloud round trip.

This is how a plugin could handle a /v3/chat reply with nlohmann::json:

// raw = response body from POST https://api.neocortex.link/v3/chat
void HandleReply(const std::string& raw) {
    auto reply = nlohmann::json::parse(raw);
    sessionId = reply["sessionId"].get<std::string>();  // reuse on the next call
    for (auto& msg : reply["messages"]) {
        for (auto& line : msg["lines"])                  // text + emotion tag
            QueueSubtitle(msg["name"].get<std::string>(), line["text"].get<std::string>(),
                          line["emotion"].get<std::string>());
        for (auto& action : msg["actions"])              // e.g. OPEN_DOOR on door_02
            QueuePapyrusAction(action["name"].get<std::string>(),
                               action.value("targetId", std::string{}));
        std::string flow = msg.value("flowState", std::string{});
        if (!flow.empty()) QueueQuestCheckpoint(flow);   // e.g. advance a quest stage
    }
}

The Queue... functions are your own code that hands work back to the game thread.

Getting started with your Fallout 4 AI NPC mod

1. Pick a target runtime. Install the matching F4SE build and Address Library file, and decide which game versions your mod supports.
2. Design the character in the Neocortex node editor: Personality, Emotion, Knowledge, Voice and the Actions your mod understands. Test it in the browser for free.
3. Add the extras: a Conversation Flow for a companion quest, a quiz question set for the terminal, or a settlement command set.
4. Connect from your F4SE plugin and pass replies to Papyrus on the game thread.
5. Keep the API key in a config file each player fills in. Never hard-code a key in a shared mod.
6. Test in single-player on a separate save before touching your main playthrough.

Mod policy and fair play

Fallout 4 is a single-player game, so an AI companion mod only changes the player's own world. Keep your mod free and non-commercial, follow Bethesda's terms for player-made content, and use a designed voice or one you own the rights to instead of cloning the game's cast. Players should use their own Neocortex API key so usage stays on their account.

Start with our foundation post on on-device voice commands for game mods, then see the Fallout: New Vegas AI NPC mod and Skyrim AI NPC mod guides for the same ideas on other Bethesda games.

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

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