server/index.js

It's a good practice to use a static file for robots.txt instead of generating it dynamically for each request. This will reduce the load on the server.
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    app.use(express.static(path.join(__dirname, 'public')));

server/utils/AiProviders/anthropic/index.js

It's a good practice to define default values at the top of the file or in a configuration file. This makes it easier to find and change these values.
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    const DEFAULT_MODEL = "claude-2";
    this.model = process.env.ANTHROPIC_MODEL_PREF || DEFAULT_MODEL;

server/utils/AiProviders/lmStudio/index.js

The variable 'model' is not defined in the current scope. It seems like you wanted to reference 'this.model' instead.
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    throw new Error(`LMStudio chat: ${this.model} is not valid or defined for chat completion!`);

server/utils/AiProviders/openAi/index.js

It's a good practice to define default values at the top of the file or in a configuration file. This makes it easier to find and change these values.
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    const DEFAULT_MODEL = "gpt-3.5-turbo";
    this.model = process.env.OPEN_MODEL_PREF || DEFAULT_MODEL;

There's no need to check if the model is valid for chat completion twice. You can store the result in a variable and use it in the if statement and the error message.
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    const isValidModel = await this.isValidChatCompletionModel(this.model);
    if (!isValidModel)
      throw new Error(`OpenAI chat: ${this.model} is not valid for chat completion!`);