changelog added

Author: igorbenav

docs/changelog.md

@@ -0,0 +1,62 @@
+# FastroAI Changelog
+
+## Introduction
+
+The Changelog documents all notable changes made to FastroAI. This includes new features, bug fixes, and improvements. It's organized by version and date, providing a clear history of the library's development.
+
+---
+
+## [0.3.0] - Dec 17, 2025
+
+#### Added
+- **LogfireTracer** by [@igorbenav](https://github.com/igorbenav)
+  - Built-in tracer implementation for Pydantic's Logfire observability platform
+  - Implements the `Tracer` protocol - drop-in replacement for `SimpleTracer`
+  - Automatic span creation with `_tags=["fastroai"]` for easy filtering in Logfire dashboard
+  - Metric logging via `logfire.info()` with trace correlation
+  - Error logging with full exception info via `logfire.error()`
+  - Clear `ImportError` when logfire package is not installed
+
+- **Optional Dependency** by [@igorbenav](https://github.com/igorbenav)
+  - Install with `pip install fastroai[logfire]` to enable Logfire support
+  - Logfire remains optional - core functionality works without it
+
+#### Documentation
+- Added LogfireTracer to built-in tracers section in tracing guide
+- Added LogfireTracer to API reference
+- Updated README with Logfire installation instructions
+
+#### What's Changed
+- LogfireTracer implementation by [@igorbenav](https://github.com/igorbenav)
+
+**Full Changelog**: https://github.com/benavlabs/fastroai/compare/v0.2.0...v0.3.0
+
+---
+
+## [0.2.0] - Dec 15, 2025
+
+#### Added
+- **FastroAgent** - PydanticAI wrapper with automatic cost calculation and tracing
+- **Pipeline** - DAG-based workflow orchestration with automatic parallelization
+- **@step decorator** - Concise function-based pipeline step definitions
+- **@safe_tool** - Production-safe tool decorator with timeout and retry
+- **CostCalculator** - Precise cost tracking using microcents (integer arithmetic)
+- **Tracer Protocol** - Protocol-based tracing interface for observability integration
+- **SimpleTracer** - Logging-based tracer for development
+- **NoOpTracer** - No-op tracer for testing or disabled tracing
+
+#### Documentation
+- Complete documentation site with guides, API reference, and recipes
+- MkDocs Material theme with dark/light mode support
+
+**Full Changelog**: https://github.com/benavlabs/fastroai/compare/v0.1.0...v0.2.0
+
+---
+
+## [0.1.0] - Dec 10, 2025
+
+Initial release.
+
+- Core FastroAgent functionality
+- Basic pipeline support
+- Cost calculation primitives

mkdocs.yml

@@ -76,6 +76,7 @@ nav:
       - Tools: api/tools.md
       - Usage: api/usage.md
       - Tracing: api/tracing.md
+  - Changelog: changelog.md
 
 markdown_extensions:
   - admonition