Sample R Shiny app to run local models with an Ollama server. Coded mostly by various LLMs including Posit's Shiny Assistant

app_ollama.R

# This is a sample R Shiny app chatbot that runs local models with an Ollama server.
# You also need Ollama installed and a ollama server running, plus at least one local model pulled.
# I hard-coded a few local models,
# If you use this, you'll want to hard code yours (including descriptions, or take those out)

# Coded with lots of LLM help + Posit's Shiny Assistant.

library(shiny)
library(shinychat)
library(bslib)

ui <- page_sidebar(
  title = "Chat with LLMs",
  sidebar = sidebar(
    selectInput("model_choice", 
                "Select Model:", 
                choices = c("gemma3:12b", "mistral-small:latest", "phi4:latest"),
                selected = "phi4:latest"),
    
    # Add some helpful info about the models
    card(
      title = "About Models (from Ollama page descriptions)",
      tags$div(
        style = "line-height: 1.2;",
        p(tags$b("gemma3:"), "'Most capable model that runs on a single GPU.' From Google.", style = "margin-bottom: 8px;"),
        p(tags$b("mistral-small:"), "Mistral Small 3 'sets a new benchmark in the 'small' LLM category below 70B'.", style = "margin-bottom: 8px;"),
        p(tags$b("phi4:"), "14B parameter, state-of-the-art open model from Microsoft.", style = "margin-bottom: 0;")
      )
    ),
    
    # Add a button to download the chat
    actionButton("downloadChat", "Download Chat")
  ),
  chat_ui("chat")
)

# Attach a JavaScript snippet to handle the download.
# When the download button is clicked, the script extracts the text inside
# the chat's <shiny-chat-messages> element, creates a Blob from it, and triggers a download.
ui <- tagList(
  ui,
  tags$script(HTML("
    document.addEventListener('DOMContentLoaded', function() {
      document.getElementById('downloadChat').addEventListener('click', function() {
        // Find the chat container by the id you provided to chat_ui()
        var chatContainer = document.getElementById('chat');
        if (!chatContainer) return;
        // The chat messages are rendered inside the <shiny-chat-messages> element
        var chatMessages = chatContainer.querySelector('shiny-chat-messages');
        if (!chatMessages) return;
        // Get the visible text (this will strip extra formatting)
        var text = chatMessages.innerText;
        // Create a blob and a temporary anchor to trigger download
        var blob = new Blob([text], { type: 'text/plain' });
        var url = URL.createObjectURL(blob);
        var a = document.createElement('a');
        a.href = url;
        a.download = 'chat.txt';
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        URL.revokeObjectURL(url);
      });
    });
  "))
)

server <- function(input, output, session) {
  # Create reactive value to store current chat instance
  chat_rv <- reactiveVal()
  
  # Initialize and update chat when model changes
  observeEvent(input$model_choice, {
    chat_rv(ellmer::chat_ollama(
      system_prompt = "You're a helpful assistant",
      model = input$model_choice
    ))
  }, ignoreInit = FALSE)  # Don't ignore initial value
  
  observeEvent(input$chat_user_input, {
    stream <- chat_rv()$stream_async(input$chat_user_input)
    chat_append("chat", stream)
  })
  
}

shinyApp(ui, server)