# DeltaChannelHistory

> **Class** in `langgraph.checkpoint`

📖 [View in docs](https://reference.langchain.com/python/langgraph.checkpoint/base/DeltaChannelHistory)

Per-channel result entry from `BaseCheckpointSaver.get_delta_channel_history`.

!!! warning "Beta"

    Part of the `DeltaChannel` support surface; in beta. Field names and
    semantics may change.

Storage-level view of what one channel contributed across the ancestor
chain of a target checkpoint:

* `writes` — on-path deltas oldest→newest as `PendingWrite` tuples.
  Always present; possibly empty. Already filtered to one channel.
  Writes stored at the target checkpoint itself are pending for the
  next super-step and are excluded.
* `seed` — the stored value at the nearest ancestor whose
  `channel_values[ch]` is populated. Omitted if the walk reached the
  root without finding any stored value (consumer treats absence as
  "start empty"). Typically a `_DeltaSnapshot` for delta channels with
  finite snapshot frequency, or a plain value for threads migrated
  from a pre-delta channel type.

## Signature

```python
DeltaChannelHistory()
```

## Extends

- `TypedDict`

## Constructors

```python
__init__(
    writes: list[PendingWrite],
    seed: NotRequired[Any],
)
```

| Name | Type |
|------|------|
| `writes` | `list[PendingWrite]` |
| `seed` | `NotRequired[Any]` |


## Properties

- `writes`
- `seed`

---

[View source on GitHub](https://github.com/langchain-ai/langgraph/blob/aa322c13cd5f16a3f6254a931a4104e412cd687c/libs/checkpoint/langgraph/checkpoint/base/__init__.py#L149)