chat-core 0.2.2

# chat-core

Core traits, types, and engine for [chat-rs](https://github.com/EggerMarc/chat-rs) — the foundation every provider crate builds on. Exposes the `Chat` engine, `ChatBuilder`, the `CompletionProvider` / `StreamProvider` / `EmbeddingsProvider` traits, the `Transport` trait (with built-in HTTP/SSE and WebSocket impls), and the core message/tool/response types.

You usually don't depend on this crate directly — instead, depend on a provider crate (e.g. [`chat-openai`](https://crates.io/crates/chat-openai), [`chat-gemini`](https://crates.io/crates/chat-gemini), [`chat-completions`](https://crates.io/crates/chat-completions)) which brings `chat-core` in transitively. Bring `chat-core` in explicitly when you want the engine types in your code without pulling the umbrella `chat-rs` crate.

## Install

```toml
[dependencies]
chat-core = "0.2.2"
```

## What's in here

- **`builder::ChatBuilder`** — the type-state builder that wires a provider into a `Chat` engine
- **`chat::Chat`** — the engine; orchestrates the call loop, tool calls, retries, HITL, structured output
- **`traits`** — `CompletionProvider`, `StreamProvider`, `EmbeddingsProvider`, `ChatProvider`
- **`transport`** — `Transport` trait + three built-in impls (feature-gated): `ReqwestTransport` (HTTP/SSE, default), `AsyncWsTransport` (tokio-tungstenite), `WsTransport` (tungstenite)
- **`types`** — `Messages`, `Content`, `Parts`, `Tool`, `ChatOptions`, `ChatResponse`, `StreamEvent`, `Metadata`, etc.
- **`error`** — `ChatError`, `ChatFailure`

## Feature Flags

| Feature | What it enables |
|---|---|
| `reqwest-transport` | HTTP/SSE transport via reqwest (default for most providers) |
| `tokio-tungstenite` | Async WebSocket transport |
| `tungstenite` | Sync WebSocket transport bridged via `spawn_blocking` |
| `stream` | `StreamProvider` trait + streaming machinery |
| `testing` | Test helpers for provider crates |

## Writing a Custom Provider

Implement `CompletionProvider` (and optionally `StreamProvider`, `EmbeddingsProvider`) on your client struct. Use the `Transport` abstraction so users can swap reqwest for their own HTTP/WS client. See [`providers/AGENTS.md`](https://github.com/EggerMarc/chat-rs/blob/main/providers/AGENTS.md) for the conventions every existing provider follows.