EchoMimics

EchoMimics makes the Masked enemies in Lethal Company sound like the people in your crew.

The mod listens to opted-in players during a round, remembers useful parts of the conversation, and gives nearby Masked enemies short contextual replies. The reply is written locally by Qwen3.5 2B and spoken locally with a clone of the copied crewmate's voice using Audio8 TTS 0.1B.

Everything runs on the host computer. There are no API keys, subscriptions, or cloud AI services.

What the mod does

When your crew talks during a round, EchoMimics can:

• Detect when someone is speaking without requiring a special push-to-talk key.
• Transcribe that speech locally with Whisper.
• Remember recent conversation from the current round.
• Give a nearby Masked enemy the identity of the crewmate it copied.
• Generate a short lie, warning, plea, or lure that fits the current situation.
• Speak from the Masked enemy's position using the copied crewmate's voice.
• Play the same generated voice for every modded player in the lobby.

EchoMimics does not replace the normal enemy AI. Masked enemies remain hostile and continue to move, chase, hide, and attack normally. The language model cannot control the enemy, run commands, access files, or use game tools.

Important privacy warning

This mod performs voice cloning.

Every player must understand what the mod does and agree before enabling voice capture. Voice capture is disabled by default on every installation. A player must set AllowVoiceCapture to true before their microphone is recorded.

The host computer receives short voice clips from participating players because the host performs the local transcription and voice generation. The data is not uploaded to an AI service.

During a round, the host stores:

• A bounded list of recent transcripts.
• The newest usable reference clip for each participating player.
• The exact transcript that belongs to that reference clip.

Round data is deleted when the round ends. If the game or runtime closes unexpectedly, the host can delete the data folder inside BepInEx/plugins/EchoMimics to remove all remaining voice references and transcripts.

Do not use this mod to clone someone who has not consented.

Requirements

Every player needs

• Lethal Company v81 on Windows.
• The same EchoMimics version.
• BepInExPack 5.4.2100, normally installed by the mod manager.
• A working in-game microphone.

The host also needs

• Windows 10 or Windows 11.
• Python 3.11.
• Ollama.
• Around 8 GB of free disk space for packages and model files.
• An NVIDIA CUDA GPU is strongly recommended.
• 8 GB or more VRAM is recommended.

Audio8 can run on a CPU, but replies will usually be too slow for natural gameplay. Only the host needs to install and run the local AI runtime.

Easy installation with a mod manager

Use these steps with r2modman or the Thunderstore Mod Manager.

1. Create or select your Lethal Company profile.
2. Search for EchoMimics and install it.
3. Make sure every person joining the lobby installs the exact same version.
4. Start the game once with the modded profile.
5. Close the game after reaching the main menu.

The mod files should now be located at:

BepInEx/plugins/EchoMimics/

Manual installation

1. Install BepInExPack 5.4.2100.
2. Download the EchoMimics ZIP.
3. Open the ZIP.
4. Copy its BepInEx folder into the Lethal Company profile or game folder that already contains your BepInEx installation.
5. Allow Windows to merge the folders.
6. Confirm that this file exists:

BepInEx/plugins/EchoMimics/EchoMimics.dll

Do not copy EchoMimics.dll into the game root.

Host setup

Only the person hosting the lobby performs this section.

Step 1: Open the EchoMimics folder

In r2modman:

1. Select your Lethal Company profile.
2. Open Settings.
3. Select Browse profile folder.
4. Open BepInEx, then plugins, then EchoMimics.

Step 2: Run the setup script

Right-click inside the EchoMimics folder and choose Open in Terminal, then run:

powershell -ExecutionPolicy Bypass -File .\setup-runtime.ps1

The setup script will:

1. Install Python 3.11 through Windows Package Manager if it is missing.
2. Install Ollama if it is missing.
3. Create an isolated Python environment inside the mod folder.
4. Install the local EchoMimics runtime.
5. Download Qwen3.5 2B.
6. Download and verify the Whisper and Audio8 model files.

The first setup can take several minutes. Model downloads are much larger than the mod ZIP.

If winget is unavailable, install Python 3.11 from python.org and Ollama from ollama.com, then run the setup command again.

Step 3: Start the runtime

Before starting Lethal Company, open a terminal in the same folder and run:

powershell -ExecutionPolicy Bypass -File .\start-runtime.ps1

Keep this terminal window open while playing. A successful start prints:

EchoMimics runtime listening on http://127.0.0.1:17841

The runtime listens only on the host computer. It is not exposed to the internet.

Enable voice capture

Every participating player must do this for their own installation.

1. Start Lethal Company with the modded profile once.
2. Close the game.
3. In the mod manager, open Config editor.
4. Find com.testyee.echomimics.cfg.
5. Change the following setting:

[Privacy]
AllowVoiceCapture = true

1. Save the config.

Players who leave this setting as false are not recorded by EchoMimics. They can still hear generated mimic speech.

Starting a game

Use this order for the smoothest start:

1. The host runs start-runtime.ps1 and leaves it open.
2. Every player launches the same modded profile.
3. The host creates the lobby.
4. Players join and confirm they have the same EchoMimics version.
5. Start a round and speak normally.

The mod only captures opted-in speech while the local player is alive, player-controlled, and connected to an active game session. It does not capture speech from the main menu.

A Masked enemy needs a clean sample from the crewmate it copied before it can use that voice. Talking naturally near the beginning of a round gives the mod better reference audio.

How replies are chosen

A Masked enemy does not answer every sentence. It can speak when:

• It is alive.
• It is within the configured hearing distance.
• Its reply cooldown has finished.
• The random reply check succeeds.
• The runtime has a usable voice reference for the copied crewmate.
• Qwen decides that speaking helps the deception.

The model can also choose silence. This prevents Masked enemies from talking constantly and makes their timing less predictable.

The context supplied to Qwen includes:

• The current moon.
• Whether the speaker and Masked enemy are inside or outside.
• Nearby player names.
• Whether nearby players are alive or dead.
• Approximate distances from the Masked enemy.
• Recent dialogue from the current round.

Replies are limited to 24 words. Qwen is instructed not to invent items, deaths, locations, or door states that were not supplied by the game.

Configuration guide

The config file is named com.testyee.echomimics.cfg.

General

Enabled turns the whole mod on or off. Default: true.

Privacy

AllowVoiceCapture allows this player's microphone speech to be processed. Default: false.

Mimics

HearingRange is the maximum distance in game units at which a Masked enemy can hear a player. Default: 32.

ReplyChance is the probability that an eligible Masked enemy answers. 0 means never. 1 means every eligible utterance. Default: 0.58.

ReplyCooldownSeconds is the minimum delay between replies from the same Masked enemy. Default: 8 seconds.

Voice

ActivityThreshold controls microphone speech detection. Raise it if background noise triggers the mod. Lower it slightly if normal speech is ignored. Default: 0.018.

InputDevice is the microphone name. Leave it blank to follow the microphone selected by Lethal Company where possible.

MimicVolume controls generated spatial voice volume. Default: 1.2.

Language is the Whisper language code. Default: en. Leave it blank to allow automatic language detection.

Local runtime

Url is the local runtime address. Default: http://127.0.0.1:17841.

Token is an optional local bearer token. Most users should leave it blank. Advanced users must set the same value in the ECHOMIMICS_TOKEN environment variable before starting the runtime.

Troubleshooting

The game says connection refused

The host runtime is not running. Open BepInEx/plugins/EchoMimics, run start-runtime.ps1 from PowerShell, and keep the window open. Check that it says the runtime is listening on port 17841.

PowerShell blocks the setup script

Run it from a terminal with:

powershell -ExecutionPolicy Bypass -File .\setup-runtime.ps1

The setup script cannot find Python

Install the 64-bit version of Python 3.11 from python.org. Enable the installer option that adds Python to PATH, reopen PowerShell, then run setup again.

The setup script cannot find Ollama

Install Ollama for Windows, restart PowerShell, and run:

ollama pull qwen3.5:2b

Then run the setup script again.

My microphone is not detected

1. Confirm AllowVoiceCapture is true.
2. Confirm the correct microphone works in Lethal Company's voice settings.
3. Set InputDevice to the exact microphone name.
4. Check the BepInEx console or log for Local voice capture started.
5. Lower ActivityThreshold in small steps, such as 0.018 to 0.014.

Background noise keeps triggering it

Raise ActivityThreshold in small steps, such as 0.018 to 0.025. Headphones are strongly recommended so generated mimic speech does not feed back into the microphone.

A Masked enemy never speaks

Check all of the following:

• The host runtime is running.
• The copied player spoke long enough to create a clean reference.
• The Masked enemy is within HearingRange.
• ReplyChance is above 0.
• The reply cooldown has elapsed.
• The Audio8 model finished loading.

The first generated line after starting the runtime can be slower because models are being moved into GPU memory.

Replies are very slow

Audio8 works best with an NVIDIA CUDA GPU. CPU generation is supported as a fallback but may be too slow for live conversation.

Close other GPU-heavy programs. If the GPU runs out of memory, you can force Audio8 to the CPU before starting the runtime:

$env:ECHOMIMICS_AUDIO8_DEVICE = "cpu"
.\start-runtime.ps1

Different players hear different results

Every player must install the same EchoMimics version. Return to the main menu, confirm versions in the mod manager, and recreate the lobby.

Data removal

To remove stored EchoMimics data manually:

1. Close Lethal Company.
2. Close the EchoMimics runtime window.
3. Open BepInEx/plugins/EchoMimics.
4. Delete the data folder.

Models downloaded by Hugging Face and Ollama are stored in their normal user caches. Removing the EchoMimics data folder deletes voice references and transcripts, but it does not uninstall the models.

Uninstall

With a mod manager, disable or uninstall EchoMimics from the profile.

For a manual installation, remove:

BepInEx/plugins/EchoMimics
BepInEx/config/com.testyee.echomimics.cfg

You can uninstall the downloaded Qwen model with:

ollama rm qwen3.5:2b

Python and Ollama are normal applications and are not removed automatically.

Models and licenses

• Qwen3.5 2B uses the Apache 2.0 license.
• Audio8 TTS Preview 0.1B uses the Audio8 Community License v1.0.
• faster-whisper uses the MIT license.

Audio8 permits free non-commercial use and commercial use below the revenue limit stated in its license. Larger commercial users need a separate license from Audio8.

See THIRD_PARTY_NOTICES.md for attribution and additional details.

Building from source

The mod targets .NET Standard 2.1 and builds against pinned Lethal Company v81 game references.

dotnet build mod/EchoMimics.csproj -c Release

Run the runtime tests with Python 3.11:

python -m pip install -e "runtime[dev]"
pytest runtime/tests -q

Create the release package with:

python tools/release_checks.py

Current verification

• Runtime unit and live HTTP tests pass.
• The mod builds against Lethal Company v81 references with zero warnings and zero errors.
• The pinned Audio8 processor and model load successfully.
• Release checks validate package structure, versions, required files, privacy defaults, and common secret patterns.

The final gameplay check must be performed in a Windows Lethal Company multiplayer lobby because the automated build environment cannot run the game.

Credits

EchoMimics is a separate project. Wendigos-Mod was used as a gameplay reference only and its source was not copied.

The multiplayer framing, microphone selection, PCM conversion, and host-authority approach were informed by the MIT-licensed Buddy project.