Bylder
AI fitness coaching chat
Bylder is a Flutter fitness app for a client in the Netherlands, built around a chat coach rather than static workout plans. Users pick a topic, start chatting, and the app sends the conversation to OpenAI to get back coaching-style answers.
- 2023
- Netherlands
- Flutter (FlutterFlow)
- Firebase Auth
- OpenAI chat API
The challenge
Bylder's users wanted fitness guidance they could ask questions of directly, on training schedules, nutrition, motivation, and sleep, without booking a human trainer or digging through a generic article library. We built a Flutter app that signs users in, lets them start a topic-based chat, and sends their messages to OpenAI's chat API so they get a conversational, tailored-sounding reply instead of a static FAQ.
Who uses it
- App user
- Signs in, picks a coaching topic, and chats with the AI coach about that topic.
What we built
We built a Flutter app with Firebase authentication (Google, Apple, GitHub, email, anonymous) and topic-based chat screens for training, nutrition, motivation, and sleep, each sending the conversation to OpenAI's chat API and streaming the coach's reply back into the thread.
Topic-based chat
Four entry points on the home screen (training schedule, nutrition, motivation, better sleep) each open a chat scoped to that topic.
OpenAI-powered replies
Each chat sends the conversation to OpenAI's chat completions endpoint and shows the reply in the thread.
Multiple sign-in options
Users can sign in with Google, Apple, GitHub, email, or anonymously via Firebase Authentication.
Profile and settings
A profile screen lets users change language, send feedback, and log out.
Information screen
An in-app info page points users to the Bylder website and explains what they can ask about.
Branded chat header
The chat screen shows the active topic name in the header, set when the user taps a topic on the home screen.
How it works
- User signs in with Google, Apple, GitHub, email, or anonymously.
- User lands on the home screen and picks a topic: training schedule, nutrition, motivation, or better sleep.
- The app opens a chat screen for that topic and the user types a question.
- The question is sent to OpenAI's chat completions API and the reply streams back into the thread.
- The user continues the conversation, or returns to the home screen to pick a different topic.
Where the AI fits
Each chat screen sends the user's message to OpenAI's chat completions endpoint, with the selected topic (training schedule, nutrition, motivation, or better sleep) setting the context for the conversation. The reply comes back as plain chat text and is appended to the thread, so the coaching tone comes entirely from the prompt and model rather than from any canned response library.
- OpenAI chat completions endpoint called directly from the Flutter app
- Topic selected on the home screen frames the chat context
- Firebase Authentication gates access to the chat screens
Every part of the product
Flutter mobile app
Flutter (FlutterFlow), Firebase Auth, OpenAI API
The single client surface: handles sign-in, topic selection, and the AI chat itself.
How it’s built
Bylder was built in FlutterFlow, which gave the client a working cross-platform app quickly while still leaving room for custom code where FlutterFlow's visual builder falls short, like the direct OpenAI API integration behind the chat screens. Firebase handles authentication across five sign-in methods, keeping the onboarding friction low for a consumer fitness app. The topic-based chat structure keeps each conversation focused instead of exposing one open-ended chatbot, so a user asking about sleep gets a coach that's primed for sleep advice rather than a generic assistant.
- Flutter
- FlutterFlow
- Firebase Authentication
- OpenAI API
Related services: LLM integration AI app development
What clients say about working with us
Verified Fiverr reviews from our clients, quoted word for word.
As always my go-to team for multiple years now.
danielpaaijbaxNetherlands · Client on this projectGreat experience working with this developer. The app was delivered clean, bug-free, and exactly as requested. Super quick to respond and very detail-oriented, highly recommend!
jamillesodreRepeat buyerBrazil · AI Mobile Apps
Venkey is a true professional. Before starting work, he spends a lot of time understanding the organization's dynamics and trying to understand the true function of development. Thanks again for the work done and for having met not just a developer but a wonderful, understanding and always available person!
vladpereverzyevRepeat buyerItaly · AI Mobile Apps
"The team knows the craft and are expert in it. I'm impressed with the kind of knowledge they have in this industry and its remarkable to work with them. I highly recommend this team to everyone who is serious about their AI Startups"
sivakumarc45Repeat buyerIndia · AI Technology Consulting
Questions about Bylder
What does Bylder do?
Bylder is a Flutter fitness coaching app Venzpire built for a client in the Netherlands. Users chat with an AI coach about training schedules, nutrition, motivation, and better sleep, instead of reading static articles or booking a human trainer for every question.
How does Bylder use AI?
Bylder sends each user's chat message to OpenAI's chat completions API, with the topic the user picked (training, nutrition, motivation, or sleep) framing the conversation, and shows the reply directly in the chat thread. Venzpire built this integration directly into the Flutter app.
What platform is Bylder built on?
Bylder is a single cross-platform Flutter app, built with FlutterFlow and Firebase Authentication, that Venzpire extended with a custom OpenAI chat integration where the visual builder wasn't enough.
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