# Hugging Face Transformers v4.34.0 — Release & Upgrade Intelligence
- **Product:** Hugging Face Transformers (https://huggingface.co)
- **Version:** v4.34.0
- **Released:** Oct 03, 2023
- **Impact Score:** 7/10
- **Breaking Changes:** Source flagged
- **Canonical Analysis:** https://changelogs.us/transformers/updates/v4.34.0/

## Executive Summary (TL;DR)
Hugging Face Transformers v4.34.0. Source highlight: Mistral-7B-v0.1 is a decoder-based LM with the following architectural choices:

## Breaking Changes & Deprecations
- These are not breaking changes per se but rather bugfixes. However, we understand that this may result in some workflow changes so we highlight them below.
- - the length of a tokenizer is now max(set(self.get_vocab().keys())) accounting for holes in the vocab. The vocab_size no longer takes into account the added vocab for most of the tokenizers (as it should not). Mostly breaking for T5

## New Features
- [`Persimmon`] Add support for persimmon  by @ArthurZucker in #26042
- Add BROS  by @jinhopark8345 in #23190
- Add ViTMatte  by @NielsRogge in #25843
- Add Nougat  by @NielsRogge and @molbap in #25942
- loading a slow from a fast or a fast from a slow will no longer raise and error if the tokens added don't have the correct index. This is because they will always be added following the order of the added_tokens but will correct mistakes in the saved vocabulary if there are any. (And there are a lot in old format tokenizers)
- the length of a tokenizer is now max(set(self.get_vocab().keys())) accounting for holes in the vocab. The vocab_size no longer takes into account the added vocab for most of the tokenizers (as it should not). Mostly breaking for T5

## Improvements
- 🌐 [i18n-KO] Translated `perf_train_gpu_many.md` to Korean (#26244)

## Bug Fixes
- Sliding Window Attention - Trained with 8k context length and fixed cache size, with a theoretical attention span of 128K tokens
- [`Tokenizer`] attemp to fix add_token issues by @ArthurZucker in #23909
- Nit-added-tokens  by @ArthurZucker in #26538 adds some fix to #23909 .
- Fix typo  by @susnato in #25966
- Fix Detr CI  by @ydshieh in #25972
- Fix `test_load_img_url_timeout`  by @ydshieh in #25976

## Upgrade Command
```bash
python -m pip install 'transformers==4.34.0'
```