# Ray 2.56.1 — Ray-2.56.1

- Product: Ray (https://whatsnew.fyi/product/ray)
- Vendor: Anyscale
- Date: 2026-07-17
- Version: 2.56.1
- Original notes: https://github.com/ray-project/ray/releases/tag/ray-2.56.1
- Permalink: https://whatsnew.fyi/product/ray/releases/2.56.1

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **fixed** — Fixed Arrow-backed to_pandas regressions by adding DataContext.enable_arrow_backed_pandas_conversion as an opt-out and reconciling divergent numeric column types before concatenation to avoid int64/double[pyarrow] overflow crashes
- **fixed** — Fixed TensorDtype.__from_arrow__ crash on zero-size tensor elements by using an explicit row count instead of numpy's -1 dimension inference
- **fixed** — Fixed a crash in hash partition caused by read-only hash arrays
- **fixed** — Nullified _input_dependencies in _get_args so exporting operator args no longer triggers an exponential sanitize_for_struct call chain over fused operators
- **changed** — Added protobuf >=7 compatibility to _proto_to_dict by binding to FieldDescriptor.is_repeated when the deprecated label attribute is absent
- **fixed** — Fixed direct-streaming routing for body-aware routers by parsing the raw request body into a SimpleNamespace over routing-key fields so choose_replica receives the message body instead of raw bytes
- **changed** — Upgraded the ONNX example from MobileNet v1 to MobileNet v3 via torchvision and pinned onnxscript in GPU/ml-build CI dep locks
- **changed** — The threshold memory monitor now snapshots both the user and system cgroup slices and logs an error when system-slice usage exceeds the reserved system memory
- **fixed** — Disabled NCCL cuMem host buffer registration in CI pytests to stabilize GPU test runs

#### Highlights

- **Ray Data**: We added fixes for several `to_pandas` regressions introduced in 2.56: an opt-out flag (`RAY_DATA_ENABLE_ARROW_BACKED_PANDAS_CONVERSION`) for Arrow-backed conversion, an int64/`double[pyarrow]` overflow crash on concatenation, and a `TensorDtype.__from_arrow__` crash on empty tensor columns (#64793, #64794).
- **Ray Core**: We added early detection for system-slice memory pressure: the memory monitor now snapshots the user and system cgroup slices together and logs an error when the system slice exceeds reserved system memory, warning users to raise `--system-reserved-memory` before it causes node deaths (#64492).
- **Ray Serve**: We added protobuf 7 compatibility and a routing fix for LLM direct streaming, so body-aware routers like `PrefixCacheAffinityRouter` no longer hang when `RAY_SERVE_LLM_ENABLE_DIRECT_STREAMING=1` (#64592, #64488).

#### Ray Data

##### 🔨 Fixes
- Fixed two Arrow-backed `to_pandas` regressions: added `DataContext.enable_arrow_backed_pandas_conversion` as an opt-out, and reconciled divergent numeric column types before concatenation to avoid int64/`double[pyarrow]` overflow crashes (#64793, #64768).
- Fixed a `TensorDtype.__from_arrow__` crash on zero-size tensor elements by using an explicit row count instead of numpy's `-1` dimension inference (#64794, #64767).
- Fixed a crash in hash partition caused by read-only hash arrays (#64584, #64552, #64559).
- Nullified `_input_dependencies` in `_get_args` so exporting operator args no longer triggers an exponential `sanitize_for_struct` call chain over fused operators (#64412, #64316).

#### Ray Serve

##### 🔨 Fixes
- Added protobuf `>=7` compatibility to `_proto_to_dict` by binding to `FieldDescriptor.is_repeated` when the deprecated `label` attribute is absent (#64592, #64362).

#### Ray LLM

##### 🔨 Fixes
- Fixed direct-streaming routing for body-aware routers: the ingress now parses the raw request body into a `SimpleNamespace` over routing-key fields (`messages`, `prompt`) so `choose_replica` receives the message body instead of raw bytes (#64488, #64328, #64326).

#### Ray RLlib

##### 🔨 Fixes
- Upgraded the ONNX example from the retired MobileNet v1 to MobileNet v3 via `torchvision` and pinned `onnxscript` in the GPU/ml-build CI dep locks, fixing ONNX export failures (#64591, #64028, #64031, #64590, #64033).

#### Ray Core

##### 💫 Enhancements
- The threshold memory monitor now snapshots both the user and system cgroup slices and logs an error when system-slice usage exceeds the reserved system memory, prompting users to raise `--system-reserved-memory` (#64492).

##### 🔨 Fixes
- Disabled NCCL `cuMem` host buffer registration in CI pytests to stabilize GPU test runs (#64580, #64146).

#### Documentation

##### 📖 Documentation
- Repointed the ASHA Tune example links to the renamed `README` document, fixing the `fail_on_warning` ReadTheDocs build on the release line (#64761, #64630).
- Updated the Python 3.10 CPU `pip freeze` dependency list for the Ray 2.56.0 release (#64447, #64357).