Sydney Runkle c99773b652 feat(langchain_v1): refactoring HITL API (#33397)
Easiest to review side by side (not inline)

* Adding `dict` type requests + responses so that we can ship config w/
interrupts. Also more extensible.
* Keeping things generic in terms of `interrupt_on` rather than
`tool_config`
* Renaming allowed decisions -- approve, edit, reject
* Draws differentiation between actions (requested + performed by the
agent), in this case tool calls, though we generalize beyond that and
decisions - human feedback for said actions

New request structure

```py
class Action(TypedDict):
    """Represents an action with a name and arguments."""

    name: str
    """The type or name of action being requested (e.g., "add_numbers")."""

    arguments: dict[str, Any]
    """Key-value pairs of arguments needed for the action (e.g., {"a": 1, "b": 2})."""


DecisionType = Literal["approve", "edit", "reject"]


class ReviewConfig(TypedDict):
    """Policy for reviewing a HITL request."""

    action_name: str
    """Name of the action associated with this review configuration."""

    allowed_decisions: list[DecisionType]
    """The decisions that are allowed for this request."""

    description: NotRequired[str]
    """The description of the action to be reviewed."""

    arguments_schema: NotRequired[dict[str, Any]]
    """JSON schema for the arguments associated with the action, if edits are allowed."""

class HITLRequest(TypedDict):
    """Request for human feedback on a sequence of actions requested by a model."""

    action_requests: list[Action]
    """A list of agent actions for human review."""

    review_configs: list[ReviewConfig]
    """Review configuration for all possible actions."""
```

New response structure

```py
class ApproveDecision(TypedDict):
    """Response when a human approves the action."""

    type: Literal["approve"]
    """The type of response when a human approves the action."""


class EditDecision(TypedDict):
    """Response when a human edits the action."""

    type: Literal["edit"]
    """The type of response when a human edits the action."""

    edited_action: Action
    """Edited action for the agent to perform.

    Ex: for a tool call, a human reviewer can edit the tool name and args.
    """


class RejectDecision(TypedDict):
    """Response when a human rejects the action."""

    type: Literal["reject"]
    """The type of response when a human rejects the action."""

    message: NotRequired[str]
    """The message sent to the model explaining why the action was rejected."""


Decision = ApproveDecision | EditDecision | RejectDecision


class HITLResponse(TypedDict):
    """Response payload for a HITLRequest."""

    decisions: list[Decision]
    """The decisions made by the human."""
```

User facing API:

NEW

```py
HumanInTheLoopMiddleware(interrupt_on={
    'send_email': True,
    # can also use a callable for description that takes tool call, state, and runtime
    'execute_sql': {
        'allowed_decisions': ['approve', 'edit', 'reject'], 
        'description': 'please review sensitive tool execution'},
    }
})

Command(resume={"decisions": [{"type": "approve"}, {"type": "reject": "message": "db down"}]})
```

OLD

```py
HumanInTheLoopMiddleware(interrupt_on={
    'send_email': True,
    'execute_sql': {
        'allow_accept': True, 
        'allow_edit': True, 
        'allow_respond': True, 
        description='please review sensitive tool execution'
    },
})

Command(resume=[{"type": "approve"}, {"type": "reject": "message": "db down"}])
```
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LangChain is a framework for building LLM-powered applications. It helps you chain together interoperable components and third-party integrations to simplify AI application development — all while future-proofing decisions as the underlying technology evolves.

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