mirror of
https://github.com/CopilotKit/CopilotKit.git
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Tyler Slaton
7f2a9ae176
## Summary
Adds **factory mode** to `BuiltInAgent`, enabling backend-agnostic LLM
integration without introducing a new class. Users provide a factory
function that creates the LLM stream — CopilotKit handles lifecycle
events, stream-to-AG-UI conversion, error handling, and
abort/cancellation.
### What's included
- **Three backend types**: `aisdk` (Vercel AI SDK), `tanstack` (TanStack
AI), and `custom` (raw AG-UI events)
- **Stream converters**: `convertAISDKStream` and
`convertTanStackStream` extract AG-UI events from backend-native streams
- **Input helpers**: `convertInputToTanStackAI` and
`convertMessagesToVercelAISDKMessages` for message/prompt conversion
- **State management**: Automatic `STATE_SNAPSHOT`/`STATE_DELTA` event
extraction from tool results
- **Reasoning support**: Auto-close logic for providers that never emit
`reasoning-end` (e.g. `@ai-sdk/anthropic`)
- **273 tests** across 16 test files covering all backend types,
converters, state tools, multimodal, and edge cases
- **Docs**: Comprehensive factory mode guide with 16 examples covering
tools, reasoning, state, forwardedProps, structured output
- **Example app**: React Router example migrated to factory mode
### Architecture
Factory mode is a discriminated union on `BuiltInAgentConfiguration`:
```typescript
const agent = new BuiltInAgent({
type: "aisdk", // or "tanstack" | "custom"
factory: ({ input, abortSignal }) =>
streamText({ model: openai("gpt-4o"), messages: ..., abortSignal }),
});
```
No new public classes — `BuiltInAgent` handles both simple mode (model
string) and factory mode (user-owned LLM call).
## PR feedback addressed
### Critical fixes
- **C1/M3**: Fixed TOCTOU window — `abortController` now set
synchronously before Observable creation in classic `run()`, with
concurrent run guard
- **C2/M2**: Classic `tool-result` now checks both `output` and `result`
property names, with `try/catch` on `JSON.stringify`
- **C3**: Error case safely handles `undefined` `p.error` with proper
fallback chain
### Important fixes
- **I2**: `RUN_ERROR` events now include `threadId` and `runId` in
classic mode (matching factory mode)
- **I3**: State tool events guarded against `undefined` snapshot/delta
before emitting
- **I4**: `JSON.stringify` wrapped in try/catch with descriptive
fallback message
- **M1**: `assignToolsToAgents` now skips factory-mode agents (prevents
config corruption)
- **M5**: TanStack converter's dropped event types documented with clear
limitation note
### Suggestions addressed
- **S1**: `@ts-expect-error` on `clone()` middlewares documented with
rationale
- **M4**: `AgentFactoryContext.abortController` kept (needed by TanStack
AI) but JSDoc added discouraging direct `.abort()` calls
## Test plan
- [x] 273 unit tests pass across all 3 backend types
- [x] Build succeeds
- [x] React Router example compiles
- [x] Docs render correctly (Vercel preview)
CopilotKit <> strands Starter
This is a starter template for building AI agents using strands and CopilotKit. It provides a modern Next.js application with an integrated investment analyst agent that can research stocks, analyze market data, and provide investment insights.
Prerequisites
- Node.js 20+
- Python 3.12+
- OpenAI API Key (for the strands agent)
- Any of the following package managers:
- pnpm (recommended)
- npm
- yarn
- bun
Note: This repository ignores lock files (package-lock.json, yarn.lock, pnpm-lock.yaml, bun.lockb) to avoid conflicts between different package managers. Each developer should generate their own lock file using their preferred package manager. After that, make sure to delete it from the .gitignore.
Getting Started
- Install dependencies using your preferred package manager:
# Using pnpm (recommended)
pnpm install
# Using npm
npm install
# Using yarn
yarn install
# Using bun
bun install
Note: Installing the package dependencies will also install the agent's python dependencies via the
install:agentscript.
- Set up your OpenAI API key:
export OPENAI_API_KEY="your-openai-api-key-here"
or create a .env file.
echo "OPENAI_API_KEY=your-openai-api-key-here" > agent/.env
- Start the development server:
# Using pnpm
pnpm dev
# Using npm
npm run dev
# Using yarn
yarn dev
# Using bun
bun run dev
This will start both the UI and agent servers concurrently.
Available Scripts
The following scripts can also be run using your preferred package manager:
dev- Starts both UI and agent servers in development modedev:debug- Starts development servers with debug logging enableddev:ui- Starts only the Next.js UI serverdev:agent- Starts only the strands agent serverbuild- Builds the Next.js application for productionstart- Starts the production serverlint- Runs ESLint for code lintinginstall:agent- Installs Python dependencies for the agent
📚 Documentation
The main UI component is in src/app/page.tsx. You can:
- Modify the theme colors and styling
- Add new frontend actions
- Customize the CopilotKit sidebar appearance
Otherwise, check out the documentation relevant to your task:
- Strands Documentation - Learn more about Strands and its features
- CopilotKit Documentation - Explore CopilotKit's capabilities
- Next.js Documentation - Learn about Next.js features and API
Contributing
Feel free to submit issues and enhancement requests! This starter is designed to be easily extensible.
License
This project is licensed under the MIT License - see the LICENSE file for details.
Troubleshooting
Agent Connection Issues
If you see "I'm having trouble connecting to my tools", make sure:
- The strands agent is running on port 8000
- Your OpenAI API key is set correctly
- Both servers started successfully
Python Dependencies
If you encounter Python import errors:
cd agent
uv sync