--- title: "transformers Breaking Changes on PyPI | Since.dev" description: "What each transformers release removed, renamed or changed: 1,394 breaking changes in 8 versions on PyPI, each with its source." canonical_url: https://since.dev/packages/pypi/transformers last_updated: 2026-05-20 --- # transformers breaking changes Every breaking API change we have recorded in transformers on PyPI: 1,394 breaking changes in 8 versions. Below are its newest 6 versions, removals and renames first, each with its source. Newest change May 20, 2026 ## 5.9.0 62 breaking changes, first published May 20, 2026. - **Removed** OpenTelemetry integration was removed from the continuous batching (CB) feature. Code that relies on it will no longer get that telemetry. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.9.0) - **Removed** `masking_utils.py` The mask visualization tool was removed from masking_utils.py. Code that calls it must be changed. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.9.0) - **Behavior changed** Repetition penalty now requires input_ids to be passed. Callers that omit it must now provide it. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.9.0) - **Behavior changed** `text_embeds` The text_embeds input for these models now takes full text embeddings instead of pooler outputs. Users must update their inputs to match. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.9.0) - **Signature changed** `transformers.cli.serve.Serve.__init__` Was def \_\_init\_\_(self, force_model: Annotated\[str | None, typer.Argument(help='Model to preload and use for all requests.')\] = None, continuous_batching: Annotated\[bool, typer.Option(help='Enable continuous batching with paged attention... [pypi.org](https://pypi.org/project/transformers/5.9.0/) - **Signature changed** `transformers.cli.serving.chat_completion.BaseGenerateManager.generate_streaming` Was def generate_streaming(self, model: PreTrainedModel, processor: ProcessorMixin | PreTrainedTokenizerFast, inputs: dict, gen_config: GenerationConfig, request_id: str, tool_config: dict | None = None) -> tuple\[asyncio.Queue... [pypi.org](https://pypi.org/project/transformers/5.9.0/) - **Signature changed** `transformers.cli.serving.chat_completion.BaseHandler.__init__` Was def \_\_init\_\_(self, model_manager: ModelManager, generation_state: GenerationState); now def \_\_init\_\_(self, model_manager: ModelManager, generation_state: GenerationState, chat_template_kwargs: dict | None = None). [pypi.org](https://pypi.org/project/transformers/5.9.0/) - **Signature changed** `transformers.cli.serving.transcription.DirectStreamer.__init__` Was def \_\_init\_\_(self, tokenizer: tokenizers.Tokenizer, loop: asyncio.AbstractEventLoop, queue: asyncio.Queue, skip_special_tokens: bool = True, tool_config: dict | None = None); now def \_\_init\_\_(self, tokenizer: tokenizers.Tokenizer... [pypi.org](https://pypi.org/project/transformers/5.9.0/) - **Signature changed** `transformers.cli.serving.transcription.GenerateManager.generate_streaming` Was def generate_streaming(self, model: PreTrainedModel, processor: ProcessorMixin | PreTrainedTokenizerFast, inputs: dict, gen_config: GenerationConfig, request_id: str, tool_config: dict | None = None) -> tuple\[asyncio.Queue... [pypi.org](https://pypi.org/project/transformers/5.9.0/) - **Signature changed** `transformers.cli.serving.utils.CBGenerateManager.generate_streaming` Was def generate_streaming(self, model: PreTrainedModel, processor: ProcessorMixin | PreTrainedTokenizerFast, inputs: dict, gen_config: GenerationConfig, request_id: str, tool_config: dict | None = None) -> tuple\[asyncio.Queue... [pypi.org](https://pypi.org/project/transformers/5.9.0/) And 52 more in this version. ## 5.8.0 11 breaking changes, first published May 5, 2026. - **Removed** Apex integration, including RMSNorm usage in T5 and related models, has been removed. Users relying on Apex for mixed precision or fused ops should migrate to PyTorch's native equivalents. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.8.0) - **Signature changed** `transformers.cache_utils.DynamicSlidingWindowLayer.__init__` Was def \_\_init\_\_(self, sliding_window: int); now def \_\_init\_\_(self, config: PreTrainedConfig | None = None, sliding_window: int | None = None). [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.cli.serving.build_server` Was def build_server(model_manager: ModelManager, chat_handler: ChatCompletionHandler, completion_handler: CompletionHandler, response_handler: ResponseHandler, transcription_handler: TranscriptionHandler, enable_cors: bool = False) ->... [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.ContinuousBatchingConfig.__init__` Was def \_\_init\_\_(self, block_size: int = 256, num_blocks: int | None = None, max_batch_tokens: int | None = None, max_memory_percent: float | None = None, max_blocks_per_request: int | None = 0, allow_block_sharing: bool = True... [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.ContinuousMixin.continuous_batching_context_manager` Was def continuous_batching_context_manager(self, generation_config: GenerationConfig | None = None, block: bool = True, timeout: float | None = None, continuous_batching_config: ContinuousBatchingConfig | None = None, persistent_manager... [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.ContinuousMixin.init_continuous_batching` Was def init_continuous_batching(self, generation_config: GenerationConfig | None = None, continuous_batching_config: ContinuousBatchingConfig | None = None, \*\*deprecated_kwargs) -> ContinuousBatchingManager; now def... [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.DynamicLayer.__init__` Was def \_\_init\_\_(self); now def \_\_init\_\_(self, config: PreTrainedConfig | None = None). [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.generation.CandidateGenerator.get_candidates` Was def get_candidates(self, input_ids: torch.LongTensor) -> tuple\[torch.LongTensor, torch.FloatTensor\]; now def get_candidates(self, input_ids: torch.LongTensor, \*\*kwargs) -> tuple\[torch.LongTensor, torch.FloatTensor\]. [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.integrations.finegrained_fp8.Fp8Dequantize.convert` Was def convert(self, input_dict: dict\[str, torch.Tensor\], full_layer_name: str | None = None, \*\*kwargs) -> dict\[str, torch.Tensor\]; now def convert(self, input_dict: dict\[str, list\[torch.Tensor\] | torch.Tensor\], full_layer_name: str |... [pypi.org](https://pypi.org/project/transformers/5.8.0/) - **Signature changed** `transformers.masking_utils.create_bidirectional_sliding_window_mask` Was def create_bidirectional_sliding_window_mask(config: PreTrainedConfig, inputs_embeds: torch.Tensor, attention_mask: torch.Tensor | None, past_key_values: Cache | None = None, or_mask_function: Callable | None = None, and_mask_function... [pypi.org](https://pypi.org/project/transformers/5.8.0/) And 1 more in this version. ## 5.7.0 24 breaking changes, first published April 28, 2026. - **Behavior changed** Configurations with problem_type set to single_label_classification and num_labels=1 now raise a clear error instead of proceeding. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.7.0) - **Behavior changed** `PreTrainedTokenizerFast` Decoding with BPE tokenizers in PreTrainedTokenizerFast now skips clean_up_tokenization, so decoded text can differ from earlier versions. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.7.0) - **Signature changed** `transformers.ContinuousBatchingConfig.__init__` Was def \_\_init\_\_(self, block_size: int = 256, num_blocks: int | None = None, max_batch_tokens: int | None = None, max_memory_percent: float = 0.8, max_blocks_per_request: int | None = 0, allow_block_sharing: bool = True... [pypi.org](https://pypi.org/project/transformers/5.7.0/) - **Signature changed** `transformers.ContinuousBatchingConfig.max_memory_percent` Was max_memory_percent: float; now max_memory_percent: float | None. [pypi.org](https://pypi.org/project/transformers/5.7.0/) - **Signature changed** `transformers.ContinuousBatchingManager.warmup` Was def warmup(self, num_query_tokens: int = 0, num_cache_tokens: int = 0) -> None; now def warmup(self) -> None. [pypi.org](https://pypi.org/project/transformers/5.7.0/) - **Signature changed** `transformers.ContinuousMixin.continuous_batching_context_manager` Was def continuous_batching_context_manager(self, generation_config: GenerationConfig | None = None, block: bool = True, timeout: float | None = None, continuous_batching_config: ContinuousBatchingConfig | None = None, persistent_manager... [pypi.org](https://pypi.org/project/transformers/5.7.0/) - **Signature changed** `transformers.core_model_loading.LoadStateDictConfig.__init__` Was def \_\_init\_\_(self, pretrained_model_name_or_path: str | None = None, download_kwargs: DownloadKwargs | None = DownloadKwargs(), use_safetensors: bool | None = None, ignore_mismatched_sizes: bool = False, sharded_metadata: dict | None =... [pypi.org](https://pypi.org/project/transformers/5.7.0/) - **Signature changed** `transformers.core_model_loading.LoadStateDictConfig.device_mesh` Was device_mesh: Optional\[torch.distributed.device_mesh.DeviceMesh\]; now device_mesh: DeviceMeshLike | None. [pypi.org](https://pypi.org/project/transformers/5.7.0/) - **Signature changed** `transformers.generation.continuous_batching.cache.PagedAttentionMemoryHandler.__init__` Was def \_\_init\_\_(self, block_size: int, page_size: int, num_groups: int, group_size: int, peak_activation_per_token: int, num_attention_masks: int, continuous_batching_config: ContinuousBatchingConfig) -> None; now def \_\_init\_\_(self... [pypi.org](https://pypi.org/project/transformers/5.7.0/) - **Signature changed** `transformers.generation.continuous_batching.cache.PagedAttentionMemoryHandler.infer_num_blocks_and_max_batch_tokens` Was def infer_num_blocks_and_max_batch_tokens(self, num_blocks: int | None = None, max_batch_tokens: int | None = None, max_memory_percent: float = 0.8, cache_dtype: torch.dtype = torch.float16) -> tuple\[int, int\]; now def... [pypi.org](https://pypi.org/project/transformers/5.7.0/) And 14 more in this version. ## 5.6.0 74 breaking changes, first published April 22, 2026. - **Removed** `rotary_fn` Code that calls self.rotary_fn(...) inside an Attention module will break and must call the function directly instead. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.6.0) - **Signature changed** `transformers.audio_utils.load_audio_torchcodec` Was def load_audio_torchcodec(audio: str | np.ndarray, sampling_rate=16000) -> np.ndarray; now def load_audio_torchcodec(audio: str | np.ndarray, sampling_rate=16000, timeout=None) -> np.ndarray. [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.BatchEncoding` Was class BatchEncoding(UserDict); now class BatchEncoding(UserDict, Generic\[\_V\]). [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.BatchEncoding.__getitem__` Was def \_\_getitem\_\_(self, item: int | str) -> Any | EncodingFast; now def \_\_getitem\_\_(self, item: int | str | slice) -> \_V | EncodingFast | dict\[str, \_V\]. [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.BatchEncoding.to` Was def to(self, device: str | torch.device, \*, non_blocking: bool = False) -> BatchEncoding; now def to(self, device: str | torch.device, \*, non_blocking: bool = False) -> BatchEncoding\[torch.Tensor\]. [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.cli.add_new_model_like.find_modular_structure` Was def find_modular_structure(module_name: str, old_model_infos: ModelInfos, new_cased_name: str) -> tuple\[str, str, list\]; now def find_modular_structure(module_name: Path, old_model_infos: ModelInfos, new_cased_name: str) -> tuple\[str... [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.cli.chat.RichInterface.stream_output` Was async def stream_output(self, stream: AsyncIterator\[ChatCompletionStreamOutput\]) -> tuple\[str, str | Any | None\]; now async def stream_output(self, stream: Awaitable\[AsyncIterator\[ChatCompletionStreamOutput\]\]) -> tuple\[str, str | Any |... [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.cli.serving.build_server` Was def build_server(model_manager: ModelManager, chat_handler: ChatCompletionHandler, response_handler: ResponseHandler, transcription_handler: TranscriptionHandler, enable_cors: bool = False) -> FastAPI; now def... [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.cli.serving.chat_completion.BaseGenerateManager.generate_non_streaming` Was def generate_non_streaming(self, model: PreTrainedModel, processor: ProcessorMixin | PreTrainedTokenizerFast, inputs: dict, gen_config: GenerationConfig, request_id: str) -> tuple\[str, int, list\[int\]\]; now async def... [pypi.org](https://pypi.org/project/transformers/5.6.0/) - **Signature changed** `transformers.cli.serving.chat_completion.BaseGenerateManager.generate_streaming` Was def generate_streaming(self, model: PreTrainedModel, processor: ProcessorMixin | PreTrainedTokenizerFast, inputs: dict, gen_config: GenerationConfig, request_id: str) -> tuple\[asyncio.Queue, DirectStreamer | CBStreamer\]; now def... [pypi.org](https://pypi.org/project/transformers/5.6.0/) And 64 more in this version. ## 5.5.2 1 breaking change, first published April 9, 2026. - **Behavior changed** Gemma4 no longer stores shared weights, and loading silently skips them instead of erroring. Code that reads or expects those weight names may need to change. [github.com](https://github.com/huggingface/transformers/releases/tag/v5.5.2) ## 5.5.1 2 breaking changes, first published April 9, 2026. - **Signature changed** `transformers.Cache.early_initialization` Was def early_initialization(self, batch_size: int, num_heads: int, head_dim: int, dtype: torch.dtype, device: torch.device); now def early_initialization(self, batch_size: int, num_heads: int | list\[int\], head_dim: int | list\[int\], dtype... [pypi.org](https://pypi.org/project/transformers/5.5.1/) - **Signature changed** `transformers.RopeParameters.rope_theta` Was rope_theta: float; now rope_theta: float | None. [pypi.org](https://pypi.org/project/transformers/5.5.1/) ## Check your code These are the changes. To see which of them reach your code, [scan a public repository](https://since.dev/scan.md), or have your coding agent call `check_code` with your manifest or lockfile over [MCP](https://since.dev/docs.md#mcp). [The API](https://since.dev/docs.md#api) reads every change in every version, not only the newest. On Team and up, a fix pull request opens for the changes that reach a connected repository. Nothing merges or deploys. ## Put your code on continuous management. Scan a public repository now, or give your agent one line. ### See how out of date your code is. [Scan a repository](https://since.dev/scan.md). Any public GitHub repository. No sign-in. ### Tell your agent what changed since it was trained. `claude mcp add --transport http since https://api.since.dev/mcp` --- Every page on this site as Markdown: https://since.dev/sitemap.md. For agents: https://since.dev/llms.txt.