> ## Documentation Index
> Fetch the complete documentation index at: https://docs.instructorphp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# V1.8.0

## Major Changes

### Immutable ToolUse System

* `ToolUseState` and `ToolUseStep` are now immutable readonly classes
* State transitions create new instances instead of modifying existing ones
* Functional composition replaces method chaining

### Enhanced Chat Events

* Added `ChatResponseRequested` event for tracking participant responses
* Improved event dispatching with dedicated methods per event type
* Better participant selection and state update event handling

### Improved Message Compilation

* Chat participants now handle their own message compilation
* `CanCompileMessages` interface used consistently across participants
* Default compiler (`AllSections`) applied where not specified

## Internal Improvements

### Processing Pipeline

* `StepProcessors` rewritten using middleware pattern
* State processors use functional composition for better predictability
* Continuation criteria refactored as immutable collections

### Code Organization

* Event emission extracted to private methods for better maintainability (selected locations so far)
* Consistent error handling across participant implementations
* Reduced coupling between chat state and compilation logic

### Performance

* Immutable structures reduce side effects and improve memory safety
* Functional approach enables better optimization opportunities
* Cleaner separation of concerns reduces object graph complexity

## Breaking Changes

* **Removed**: `ToolUseOptions` class - configuration now handled directly in `ToolUse` constructor
* **Changed**: `CanUseTools::useTools()` signature now requires `Tools` parameter
* **Removed**: Observer interfaces (`ToolUseObserver`, `ToolsObserver`) - replaced with event system
* `CanProcessToolStep::processStep()` → `CanProcessToolState::process()`
* `ToolUse` methods (`withOptions()`, `withTools()`, `withMessages()`) removed
* `ChatState::compiledMessages()` removed - compilation moved to participants