v1.20.0

## New Features ✨

* **Remote Execution**:
  * Implement remote Python WasmExecutor by @albertvillanova in https://github.com/huggingface/smolagents/pull/1261

* **Callbacks**:
  * Support callbacks after planning step by @albertvillanova in https://github.com/huggingface/smolagents/pull/1445
  * Support multiple callbacks per step type in step_callbacks dict by @albertvillanova in https://github.com/huggingface/smolagents/pull/1517

## Enhancements 🛠️

* **Models**:
  * Implement rate limiting in all API models by @albertvillanova in https://github.com/huggingface/smolagents/pull/1516

* **Tools**:
  * Implement exception mechanism for final answer in remote executors by @tobiasofsn in https://github.com/huggingface/smolagents/pull/1429
  * Set default api_key_name in ApiWebSearchTool by @albertvillanova in https://github.com/huggingface/smolagents/pull/1507
  * Implement rate limit mechanism in ApiWebSearchTool by @albertvillanova in https://github.com/huggingface/smolagents/pull/1508
  * Implement rate limit mechanism in DuckDuckGoSearchTool by @albertvillanova in https://github.com/huggingface/smolagents/pull/1515
  * Enable image output for Tool.from_space by @aymeric-roucher in https://github.com/huggingface/smolagents/pull/1510
  * Add adapter_kwargs parameter to MCPClient by @LucasDltg in https://github.com/huggingface/smolagents/pull/1528

* **Validation of Tool Arguments**:
  * Support multiple types in tool arguments validation by @duguyue100 in https://github.com/huggingface/smolagents/pull/1505
  * Fix input type validation when input schema has multiple types by @duguyue100 in https://github.com/huggingface/smolagents/pull/1530
  * Fix optional args toolcalling by @aymeric-roucher in https://github.com/huggingface/smolagents/pull/1538

* **Agent Output Formatting**:
  * Implement CodeOutput as analog to ToolOutput by @albertvillanova in https://github.com/huggingface/smolagents/pull/1496
  * Allow markdown or custom formatting for code blocks by @aymeric-roucher in https://github.com/huggingface/smolagents/pull/1493

* **Other**:
  * Add ApiWebSearchTool to __all__ list by @albertvillanova in https://github.com/huggingface/smolagents/pull/1492
  * Enforced type annotations in `ChatMessage` via `MessageRole` enum by @daavoo in https://github.com/huggingface/smolagents/pull/1479
  * Check authorized imports in LocalPythonExecutor constructor by @jank in https://github.com/huggingface/smolagents/pull/265

## Bug Fixes 🐛
* Fix `KeyError` when agent reaches max steps with image input by @robin-ede in https://github.com/huggingface/smolagents/pull/1525
* Fix when `response.usage` is `None` for some OpenRouter models by @sentienthouseplant in https://github.com/huggingface/smolagents/pull/1402
* Fix incorrect token counting in streaming TransformersModel by @albertvillanova in https://github.com/huggingface/smolagents/pull/1503
* Minor fix nested quotes that prevent execution by @vinoo-ganesh-keru in https://github.com/huggingface/smolagents/pull/1497
* Fix ChatMessage attribute access after replacing dict with dataclass by @albertvillanova in https://github.com/huggingface/smolagents/pull/1534
* Fix access of `content` field in `ChatMessage` by @mdr223 in https://github.com/huggingface/smolagents/pull/1533
* Fix parallel final answers handling by @aymeric-roucher in https://github.com/huggingface/smolagents/pull/1482

## Documentation Improvements 📚

* **Examples & Tutorials**:
  * Add complete Plan Customization example by @albertvillanova in https://github.com/huggingface/smolagents/pull/1506
  * Add Async App with Agent example by @albertvillanova in https://github.com/huggingface/smolagents/pull/1509
  * Improve Plan Customization example with Human-in-the-Loop by @albertvillanova in https://github.com/huggingface/smolagents/pull/1513

* **API References**:
  * Fix docstring of WikipediaSearchTool by @albertvillanova in https://github.com/huggingface/smolagents/pull/1521
  * Explain rate_limit in tools docstrings by @albertvillanova in https://github.com/huggingface/smolagents/pull/1519
  * Fix Examples in AmazonBedrockServerModel docstring by @albertvillanova in https://github.com/huggingface/smolagents/pull/1522
  * Split Built-in Tools from Tools in Reference docs by @albertvillanova in https://github.com/huggingface/smolagents/pull/1520

* **Other**:
  * Update Langfuse tracing documentation to SDK v3 by @jannikmaierhoefer in https://github.com/huggingface/smolagents/pull/1447
  * Fix use of context manager agent in docs by @albertvillanova in https://github.com/huggingface/smolagents/pull/1502

## Maintenance 🏗️
* Fix CI LiteLLM test_call_different_providers_without_key by @albertvillanova in https://github.com/huggingface/smolagents/pull/1527
* Fix test_send_tools_with_default_wikipedia_search_tool by @albertvillanova in https://github.com/huggingface/smolagents/pull/1494
* Fix DockerExecutor tests with final_answer by calling send_tools by @albertvillanova in https://github.com/huggingface/smolagents/pull/1495
* Bump dev version: v1.20.0.dev0 by @albertvillanova in https://github.com/huggingface/smolagents/pull/1477

## New Contributors
* @sentienthouseplant made their first contribution in https://github.com/huggingface/smolagents/pull/1402
* @daavoo made their first contribution in https://github.com/huggingface/smolagents/pull/1479
* @duguyue100 made their first contribution in https://github.com/huggingface/smolagents/pull/1505
* @vinoo-ganesh-keru made their first contribution in https://github.com/huggingface/smolagents/pull/1497
* @robin-ede made their first contribution in https://github.com/huggingface/smolagents/pull/1525
* @LucasDltg made their first contribution in https://github.com/huggingface/smolagents/pull/1528
* @mdr223 made their first contribution in https://github.com/huggingface/smolagents/pull/1533

**Full Changelog**: https://github.com/huggingface/smolagents/compare/v1.19.0...v1.20.0