A production-quality iOS AI chat app with branching sub-thread conversations.
Powered by OpenAI — use your own API key.
Most AI chat apps are linear. ThreadAI is not.
You can fork any message into a sub-thread, where the parent conversation is carried forward as context. Sub-threads can be nested arbitrarily deep. This lets you explore multiple directions from a single message without losing any history.
- Start a top-level conversation with any supported model
- Fork any message into a sub-thread — parent context is automatically included
- Sub-threads are displayed as inline cards inside the parent chat
- Unlimited nesting depth with full context chain built recursively
- Browse all sub-threads of a conversation from the thread list sheet
| Provider | Models | Context Window |
|---|---|---|
| OpenAI | GPT-4o, GPT-4o mini | 128k tokens |
- Switch model mid-conversation from the chat toolbar
- Streaming responses with a live blinking cursor
- Stop generation at any time with the stop button
- API key validated before saving (live test request)
- Responses stream token-by-token with smooth buffered rendering
- Typing indicator while waiting for the first token
- Animated blinking cursor during generation
- Cancel streaming at any time — partial response is preserved
- Full markdown support: headers, bold, italic, bullet lists, ordered lists, blockquotes
- Syntax-highlighted code blocks with language label and one-tap copy
- Inline code formatting
- Text selection enabled on all message content
- Bookmark any message with a long-press context menu
- Bookmarks are given an auto-generated short title
- Dedicated Bookmarks tab shows all saved messages across conversations
- Tap a bookmark to navigate directly back to its conversation
- Pin conversations to keep them at the top of the list
- Search conversations by title
- Swipe to delete individual conversations or sub-threads
- Create conversations with an optional custom system prompt
- Sub-threads displayed inline under their parent in the conversation list
- Enter and validate your OpenAI API key
- Key stored in the iOS Keychain — never in UserDefaults or logs
- API key status: Not Set / Validating / Valid / Invalid
- Validation makes a real 1-token test request before saving
ThreadAI follows MVVM + Clean Architecture with strict layer separation.
Presentation → Domain ← Data
(Views / VMs) (Entities, UseCases, Protocols) (CoreData, URLSession, Keychain)
| Layer | Responsibility |
|---|---|
| Presentation | SwiftUI Views + @Observable ViewModels. No business logic. |
| Domain | Pure Swift. Entities, UseCases, Repository protocols. Zero framework imports. |
| Data | Implements Domain protocols. Owns CoreData, URLSession, Keychain. |
| AI Harness | Provider abstraction (AIProvider protocol) used by UseCases via injection. |
SendMessageUseCase— sends a message and handles the streaming responseBuildContextChainUseCase— recursively walks thread ancestry to assemble the full contextCreateSubThreadUseCase— forks a sub-thread from a message, carrying parent contextBookmarkMessageUseCase— bookmarks a message with a generated title
- Create
Core/AIHarness/Providers/YourProvider.swift - Conform to
AIProvider - Register in
AppDependencies.swift
Nothing else changes.
| Component | Technology |
|---|---|
| Language | Swift 5.9+ |
| UI | SwiftUI (no UIKit) |
| iOS Target | iOS 17+ |
| State | @Observable macro |
| Persistence | CoreData |
| Concurrency | Async/Await + AsyncThrowingStream |
| Security | Keychain Services |
| Networking | URLSession with SSE streaming |
- Xcode 15+
- iOS 17+ device or simulator
- An OpenAI API key
git clone git@github.com:dsngeu/ThreadAI.git
cd ThreadAI
open ThreadAI.xcodeprojBuild and run on your device or simulator. No package manager setup needed — there are no third-party dependencies.
- Open the app and go to the Settings tab
- Tap OpenAI API Key
- Paste your key and tap Validate & Save
- A live test confirms the key works before it is stored
Keys are stored in the iOS Keychain and are never logged or transmitted anywhere other than OpenAI's API.
ThreadAI/
├── App/ # Entry point and dependency wiring
├── Core/
│ ├── AIHarness/ # AIProvider protocol + OpenAI implementation
│ ├── Domain/ # Entities, UseCases, Repository protocols
│ └── Data/ # CoreData stack, repository implementations, Keychain
├── Features/
│ ├── ConversationList/ # Conversation list with search, pin, sub-thread preview
│ ├── Chat/ # Streaming chat, markdown, code blocks, thread forking
│ ├── Bookmarks/ # Saved messages browser
│ └── Settings/ # API key management
└── Shared/
└── UI/
├── Components/ # MarkdownContentView, CodeBlockView
└── Theme/ # AppColors, AppTypography, AppSpacing
- No force unwraps in production code
- No
print()statements — OSLog only - No silent error swallowing — all async functions surface errors
- No hardcoded strings —
LocalizedStringKeythroughout - View files capped at 400 lines — components are extracted when views grow
- ViewModels never import SwiftUI — they expose only primitives and domain types
MIT — see LICENSE.
Built with Swift + SwiftUI · No third-party dependencies · Your keys, your data