929 lines
34 KiB
Python

from __future__ import annotations
import logging
from typing import TYPE_CHECKING, Any, Literal, cast
from langchain_core.language_models._compat_bridge import message_to_events
from langchain_core.language_models.chat_model_stream import (
AsyncChatModelStream,
ChatModelStream,
)
from langchain_core.messages import AIMessageChunk, BaseMessage
from langchain_protocol.protocol import MessagesData
from typing_extensions import NotRequired, TypedDict
from langgraph.errors import GraphDrained, GraphInterrupt
from langgraph.stream._types import ProtocolEvent, StreamTransformer
from langgraph.stream.run_stream import AsyncSubgraphRunStream, SubgraphRunStream
from langgraph.stream.stream_channel import StreamChannel
if TYPE_CHECKING:
from collections.abc import Awaitable, Callable
from langgraph.stream._mux import StreamMux
_logger = logging.getLogger(__name__)
class ValuesTransformer(StreamTransformer):
"""Capture values events as a drainable stream of state snapshots.
Provides the `run.values` projection. `run.output`,
`run.interrupted` and `run.interrupts` are tracked directly
by the run stream and do not depend on this transformer.
Native transformer — projection keys are exposed as direct
attributes on the run stream (e.g. `run.values`).
Only values events at the run's own level are captured; snapshots
from deeper subgraphs are left in the main event log but excluded
from the projection. "Own level" is defined by `scope`, which
`stream_events(version="v3")` / `astream_events(version="v3")` populate from the caller's
checkpoint namespace so that a nested `stream_events(version="v3")` call still
sees its own root snapshots.
"""
_native = True
required_stream_modes = ("values",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[dict[str, Any]] = StreamChannel()
self._latest: dict[str, Any] | None = None
self._interrupted = False
self._interrupts: list[Any] = []
# Cached as a list once for cheap equality with the protocol
# event's `namespace` field, which is `list[str]`.
self._scope_list: list[str] = list(scope)
def init(self) -> dict[str, Any]:
return {"values": self._log}
@property
def error(self) -> BaseException | None:
"""The error that ended the run, or `None` if it succeeded.
Set by the mux when it auto-fails the projection log.
"""
return self._log._error
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "values":
return True
params = event["params"]
if params["namespace"] != self._scope_list:
return True
self._latest = params["data"]
interrupts = params.get("interrupts", ())
if interrupts:
self._interrupted = True
self._interrupts.extend(interrupts)
self._log.push(params["data"])
return True
class CustomTransformer(StreamTransformer):
"""Capture custom events as a drainable stream of arbitrary payloads.
Nodes emit custom data via `get_stream_writer()`. This transformer
surfaces those events on `run.custom` as a `StreamChannel[Any]`,
preserving payloads in arrival order.
Only events at the run's own scope are captured; custom data from
deeper subgraphs is available on the respective subgraph handle's
`.custom` projection.
Native transformer — `run.custom` is a direct attribute.
"""
_native = True
required_stream_modes = ("custom",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[Any] = StreamChannel()
self._scope_list: list[str] = list(scope)
def init(self) -> dict[str, Any]:
return {"custom": self._log}
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "custom":
return True
params = event["params"]
if params["namespace"] != self._scope_list:
return True
self._log.push(params["data"])
return True
class UpdatesTransformer(StreamTransformer):
"""Capture updates events as a drainable stream of node outputs.
Surfaces `stream_mode="updates"` data on `run.updates` as a
`StreamChannel[dict[str, Any]]`. Each item is a dict mapping a node
(or task) name to the update it returned after a step.
Only events at the run's own scope are captured; updates from deeper
subgraphs are available on the respective subgraph handle's
`.updates` projection.
Native transformer — `run.updates` is a direct attribute.
"""
_native = True
required_stream_modes = ("updates",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[dict[str, Any]] = StreamChannel()
self._scope_list: list[str] = list(scope)
def init(self) -> dict[str, Any]:
return {"updates": self._log}
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "updates":
return True
params = event["params"]
if params["namespace"] != self._scope_list:
return True
self._log.push(params["data"])
return True
class MessagesTransformer(StreamTransformer):
"""Capture messages events as ChatModelStream objects.
The messages projection yields one `ChatModelStream` (or
`AsyncChatModelStream`) per LLM call. Consumers iterate
`run.messages` to get stream handles, then use each handle's typed
projections (`.text`, `.reasoning`, `.tool_calls`, `.usage`,
`.output`) for per-message content.
Two input shapes are handled (via `params["data"] = (payload,
metadata)` from `StreamMessagesHandler`):
1. Protocol event (dict with `"event"` key) — emitted by
`stream_events(version="v3")` / `astream_events(version="v3")` via the `on_stream_event`
callback. Routed to an existing `ChatModelStream` by
`metadata["run_id"]`. A `message-start` event creates a new
stream; `message-finish` closes it.
2. Whole `AIMessage` — emitted from `on_chain_end` when a node
returns a finalized message. Replayed as a synthetic protocol
event lifecycle via `message_to_events`, then the
already-complete stream is pushed to the log.
V1 `AIMessageChunk` tuples (from `on_llm_new_token`) are not
streamed into this projection: chat models that want to populate
`run.messages` with content-block streaming must use
`stream_events(version="v3")` / `astream_events(version="v3")`. Models called via the legacy
`stream()` method still surface their final `AIMessage` via
`on_chain_end` when a node returns it as state.
Only events at the run's own level are projected; tokens from
deeper subgraphs are left in the main event log but excluded from
`.messages`. "Own level" is defined by `scope`, which
`stream_events(version="v3")` / `astream_events(version="v3")` populate from the caller's checkpoint
namespace so that a `stream_events(version="v3")` call inside a node still sees its
own root chat model streams on `.messages`. Consumers that need
subgraph tokens should iterate the raw event stream or register a
custom transformer.
Native transformer — the `messages` projection is exposed as a
direct attribute on the run stream.
"""
_native = True
required_stream_modes = ("messages",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[ChatModelStream] = StreamChannel()
# Correlate protocol events back to a ChatModelStream by run_id
# (attached to the event's metadata by StreamMessagesHandler).
self._by_run: dict[str, ChatModelStream] = {}
self._pump_fn: Callable[[], bool] | None = None
self._apump_fn: Callable[[], Awaitable[bool]] | None = None
# Cached as a list once for cheap equality with the protocol
# event's `namespace` field, which is `list[str]`.
self._scope_list: list[str] = list(scope)
def init(self) -> dict[str, Any]:
return {"messages": self._log}
def _bind_pump(self, fn: Callable[[], bool]) -> None:
"""Wire the sync pull callback. Called by GraphRunStream._wire_request_more."""
self._pump_fn = fn
def _bind_apump(self, fn: Callable[[], Awaitable[bool]]) -> None:
"""Wire the async pull callback.
Called by `AsyncGraphRunStream._wire_arequest_more` so each
`AsyncChatModelStream` this transformer creates can drive the
shared graph pump from its projection cursors.
"""
self._apump_fn = fn
def _make_stream(
self,
*,
namespace: list[str],
node: str | None,
message_id: str | None,
) -> ChatModelStream:
"""Create a ChatModelStream (sync) or AsyncChatModelStream (async).
Wires whichever pump is bound. Prefers the async pump so nested
iteration under `AsyncGraphRunStream` drives the graph forward
without a background task. The unwired fallback (no pump bound)
is used by unit tests that dispatch events manually.
"""
if self._apump_fn is not None:
astream = AsyncChatModelStream(
namespace=namespace,
node=node,
message_id=message_id,
)
astream.set_arequest_more(self._apump_fn)
return astream
if self._pump_fn is not None:
stream: ChatModelStream = ChatModelStream(
namespace=namespace,
node=node,
message_id=message_id,
)
stream.set_request_more(self._pump_fn)
return stream
return AsyncChatModelStream(
namespace=namespace,
node=node,
message_id=message_id,
)
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "messages":
return True
params = event["params"]
if params["namespace"] != self._scope_list:
return True
payload, metadata = params["data"]
node: str | None = metadata.get("langgraph_node")
run_id = str(metadata.get("run_id", "")) if metadata else ""
if isinstance(payload, dict) and "event" in payload:
self._route_protocol_event(
cast("MessagesData", payload), run_id=run_id, node=node
)
elif isinstance(payload, BaseMessage) and not isinstance(
payload, AIMessageChunk
):
self._route_whole_message(payload, node=node)
# Legacy AIMessageChunk tuples (from on_llm_new_token) are ignored;
# v1 streaming callers must switch to stream_events(version="v3") to populate this
# projection.
return True
def _route_protocol_event(
self,
event: MessagesData,
*,
run_id: str,
node: str | None,
) -> None:
event_type = event.get("event")
if event_type == "message-start":
message_id = event.get("message_id")
stream = self._make_stream(
namespace=[],
node=node,
message_id=str(message_id) if message_id is not None else None,
)
self._by_run[run_id] = stream
self._log.push(stream)
stream.dispatch(event)
elif run_id in self._by_run:
stream = self._by_run[run_id]
stream.dispatch(event)
if event_type == "message-finish":
del self._by_run[run_id]
def _route_whole_message(self, message: BaseMessage, *, node: str | None) -> None:
stream = self._make_stream(namespace=[], node=node, message_id=message.id)
for evt in message_to_events(message, message_id=message.id):
stream.dispatch(evt)
self._log.push(stream)
def finalize(self) -> None:
"""Clear any routing state — streams close themselves via `message-finish`."""
self._by_run.clear()
def fail(self, err: BaseException) -> None:
"""Propagate run error to any streams still open when the graph fails."""
for stream in list(self._by_run.values()):
stream.fail(err)
self._by_run.clear()
SubgraphStatus = Literal["started", "completed", "failed", "interrupted", "drained"]
def _parse_ns_segment(segment: str) -> tuple[str, str | None]:
"""Split a namespace segment into `(graph_name, trigger_call_id)`.
Segments are formatted `node_name:task_id` by `prepare_next_tasks`.
Returns `(segment, None)` if no `:` is present.
"""
name, sep, task_id = segment.partition(":")
return name, task_id if sep else None
class LifecyclePayload(TypedDict, total=False):
"""Payload of a lifecycle event surfaced on the `lifecycle` channel.
Auto-forwarded as `lifecycle` protocol events (no `custom:` prefix
because `LifecycleTransformer` is a native transformer) so remote
SDK clients receive the same data in-process consumers see via
`run.lifecycle`.
"""
event: SubgraphStatus
namespace: list[str]
graph_name: NotRequired[str]
trigger_call_id: NotRequired[str]
error: NotRequired[str]
class _TasksLifecycleBase(StreamTransformer):
"""Shared bookkeeping for `tasks`-event-driven lifecycle inference.
Both `LifecycleTransformer` (wire-serializable channel) and
`SubgraphTransformer` (in-process navigation handles) discover
subgraphs by watching the same `tasks` stream — `started` on the
first event at a tracked namespace, terminal status when the
parent's `TaskResultPayload` arrives. Centralizing the dispatch
+ open-set bookkeeping here keeps the inference rules from
drifting between the two surfaces.
Subclasses provide three template-method hooks:
- `_should_track(ns)` — scope filter (e.g. multi-depth vs
direct-children-only).
- `_on_started(ns, graph_name, trigger_call_id)` — first sighting
action (push payload / build handle / etc.). Called once per
discovered namespace.
- `_on_terminal(ns, status, error)` — terminal action (push
terminal payload / mark handle status). Called once per
tracked namespace at result time, or via `finalize` / `fail`
sweeps if no parent result arrived.
Tasks events are suppressed from the main event log (`process`
returns False) — they're folded into whichever projection the
subclass populates; consumers iterating the raw protocol stream
see the higher-level view.
"""
required_stream_modes = ("tasks",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._seen: set[tuple[str, ...]] = set()
# Maps tracked namespace -> task_id of the parent task whose
# `TaskResultPayload` will close it.
self._open: dict[tuple[str, ...], str] = {}
# --- Template-method hooks (subclass overrides) ---
def _should_track(self, ns: tuple[str, ...]) -> bool:
"""Scope filter — return True iff `ns` is in this transformer's region."""
raise NotImplementedError
def _on_started(
self,
ns: tuple[str, ...],
graph_name: str | None,
trigger_call_id: str | None,
) -> None:
"""Fired once per discovered namespace (first observed task event)."""
raise NotImplementedError
def _on_terminal(
self,
ns: tuple[str, ...],
status: SubgraphStatus,
error: str | None,
) -> None:
"""Fired once per tracked namespace when its parent's result arrives,
or via finalize/fail safety-net sweeps.
"""
raise NotImplementedError
# --- Dispatch + bookkeeping (shared) ---
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "tasks":
return True
ns = tuple(event["params"]["namespace"])
data = event["params"]["data"]
if "result" in data:
self._handle_task_result(ns, data)
else:
self._handle_task_start(ns)
# Tasks events are folded into the synthesized projections;
# suppress from the main event log so iterators don't double-see
# the same information in two shapes.
return False
def _handle_task_start(self, ns: tuple[str, ...]) -> None:
if not self._should_track(ns) or ns in self._seen:
return
self._seen.add(ns)
graph_name, trigger_call_id = _parse_ns_segment(ns[-1])
self._on_started(ns, graph_name or None, trigger_call_id)
if trigger_call_id is not None:
self._open[ns] = trigger_call_id
def _pop_terminal_transitions(
self, ns: tuple[str, ...], data: dict[str, Any]
) -> list[tuple[tuple[str, ...], SubgraphStatus, str | None]]:
"""Return and remove tracked children closed by this task result."""
result_id = data.get("id")
if not result_id:
return []
transitions: list[tuple[tuple[str, ...], SubgraphStatus, str | None]] = []
for child_ns, parent_task_id in list(self._open.items()):
if child_ns[:-1] != ns or parent_task_id != result_id:
continue
status, error = _terminal_from_result(data)
transitions.append((child_ns, status, error))
del self._open[child_ns]
return transitions
def _handle_task_result(self, ns: tuple[str, ...], data: dict[str, Any]) -> None:
for child_ns, status, error in self._pop_terminal_transitions(ns, data):
self._on_terminal(child_ns, status, error)
def finalize(self) -> None:
"""Emit `completed` for any tracked namespace still open at run end."""
for ns in list(self._open):
self._on_terminal(ns, "completed", None)
self._open.clear()
def fail(self, err: BaseException) -> None:
"""Emit terminal status for any tracked namespace still open."""
status, error_str = _status_from_exception(err)
for ns in list(self._open):
self._on_terminal(ns, status, error_str)
self._open.clear()
def _status_from_exception(err: BaseException) -> tuple[SubgraphStatus, str | None]:
"""Map a run exception to a subgraph terminal status and error string."""
if isinstance(err, GraphDrained):
return "drained", None
if isinstance(err, GraphInterrupt):
return "interrupted", None
return "failed", str(err)
def _terminal_from_result(
payload: dict[str, Any],
) -> tuple[SubgraphStatus, str | None]:
"""Map a `TaskResultPayload` to a `(status, error)` pair.
Order matters: a result with both `error` and `interrupts` prefers
the interrupt classification, since `GraphInterrupt` manifests as
a populated `interrupts` list, not as `error`.
"""
if payload.get("interrupts"):
return "interrupted", None
error = payload.get("error")
if error:
return "failed", str(error)
return "completed", None
class LifecycleTransformer(_TasksLifecycleBase):
"""Surface subgraph lifecycle as `lifecycle` protocol events.
Pushes `LifecyclePayload` to a `StreamChannel` named `lifecycle`.
The channel is auto-forwarded by the mux so payloads land in the
main event log under `method = "lifecycle"` (native transformer —
no `custom:` prefix) — visible to remote SDK clients over the
wire and to in-process consumers via `run.lifecycle`.
Tracks subgraphs at every depth strictly below the transformer's
scope, so a graph → subgraph → subgraph chain produces lifecycle
events for both nested levels in a flat stream.
Native transformer — projection key `lifecycle` is exposed as
`run.lifecycle`.
"""
_native = True
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._channel: StreamChannel[LifecyclePayload] = StreamChannel("lifecycle")
def init(self) -> dict[str, Any]:
return {"lifecycle": self._channel}
def _should_track(self, ns: tuple[str, ...]) -> bool:
depth = len(self.scope)
return len(ns) > depth and ns[:depth] == self.scope
def _on_started(
self,
ns: tuple[str, ...],
graph_name: str | None,
trigger_call_id: str | None,
) -> None:
if trigger_call_id is None:
# Without a task id we can't correlate a parent-result
# event back to this namespace — skip the started payload
# and rely on finalize/fail to close.
return
payload: LifecyclePayload = {"event": "started", "namespace": list(ns)}
if graph_name:
payload["graph_name"] = graph_name
payload["trigger_call_id"] = trigger_call_id
self._channel.push(payload)
def _on_terminal(
self,
ns: tuple[str, ...],
status: SubgraphStatus,
error: str | None,
) -> None:
payload: LifecyclePayload = {"event": status, "namespace": list(ns)}
if error is not None:
payload["error"] = error
self._channel.push(payload)
class SubgraphTransformer(_TasksLifecycleBase):
"""Discover subgraph invocations as in-process navigation handles.
Per discovered direct-child subgraph, builds a `SubgraphRunStream`
(or `AsyncSubgraphRunStream`) wrapping a child mini-mux scoped to
the subgraph's namespace. Consumers iterate `run.subgraphs` to
receive handles, then drill into `handle.values` / `handle.messages`
/ `handle.subgraphs` (recursive grandchildren) / `handle.lifecycle`.
Each mini-mux owns its own scope and uses its own
`SubgraphTransformer` to discover its direct children, so
grandchildren live on the child handle — never on the root's
`subgraphs` log. Forwarding events into the matching child mini-mux
is what keeps the child's projections populated.
Native transformer — `subgraphs` is exposed as `run.subgraphs`.
"""
_native = True
supports_sync = True
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[SubgraphRunStream | AsyncSubgraphRunStream] = (
StreamChannel()
)
self._handles: dict[
tuple[str, ...], SubgraphRunStream | AsyncSubgraphRunStream
] = {}
self._mux: StreamMux | None = None
def init(self) -> dict[str, Any]:
return {"subgraphs": self._log}
def _on_register(self, mux: Any) -> None:
self._mux = mux
def _should_track(self, ns: tuple[str, ...]) -> bool:
# Direct children only — grandchildren are picked up by the
# child mini-mux's own SubgraphTransformer.
depth = len(self.scope)
return len(ns) == depth + 1 and ns[:depth] == self.scope
def _on_started(
self,
ns: tuple[str, ...],
graph_name: str | None,
trigger_call_id: str | None,
) -> None:
if self._mux is None:
return
try:
child_mux = self._mux._make_child(ns)
except RuntimeError:
return
handle_cls = AsyncSubgraphRunStream if child_mux.is_async else SubgraphRunStream
handle = handle_cls(
mux=child_mux,
path=ns,
graph_name=graph_name,
trigger_call_id=trigger_call_id,
)
self._handles[ns] = handle
self._log.push(handle)
def _on_terminal(
self,
ns: tuple[str, ...],
status: SubgraphStatus,
error: str | None,
) -> None:
handle = self._handles.get(ns)
if handle is None or not self._mark_terminal(handle, status, error):
return
self._close_or_fail_handle(handle, status, error)
async def _aon_terminal(
self,
ns: tuple[str, ...],
status: SubgraphStatus,
error: str | None,
) -> None:
handle = self._handles.get(ns)
if handle is None or not self._mark_terminal(handle, status, error):
return
await self._aclose_or_fail_handle(handle, status, error)
def _mark_terminal(
self,
handle: SubgraphRunStream | AsyncSubgraphRunStream,
status: SubgraphStatus,
error: str | None,
) -> bool:
"""Mark a handle terminal once. Returns True on first transition."""
if handle._seen_terminal:
return False
handle.status = status
if error is not None and handle.error is None:
handle.error = error
handle._seen_terminal = True
return True
def _close_or_fail_handle(
self,
handle: SubgraphRunStream | AsyncSubgraphRunStream,
status: SubgraphStatus,
error: str | None,
) -> None:
if handle._mux is None or handle._mux._events._closed:
return
if status == "failed":
handle._mux.fail(RuntimeError(error or "Subgraph failed"))
else:
handle._mux.close()
async def _aclose_or_fail_handle(
self,
handle: SubgraphRunStream | AsyncSubgraphRunStream,
status: SubgraphStatus,
error: str | None,
) -> None:
if handle._mux is None or handle._mux._events._closed:
return
if status == "failed":
await handle._mux.afail(RuntimeError(error or "Subgraph failed"))
else:
await handle._mux.aclose()
def _handle_for_event(
self, event: ProtocolEvent
) -> SubgraphRunStream | AsyncSubgraphRunStream | None:
ns = tuple(event["params"]["namespace"])
depth = len(self.scope)
if len(ns) < depth + 1:
return None
handle = self._handles.get(ns[: depth + 1])
if handle is None or handle._mux is None or handle._mux._events._closed:
return None
return handle
def process(self, event: ProtocolEvent) -> bool:
# Run tasks bookkeeping first so a `started` handle exists
# by the time we forward the event to the child mini-mux.
keep = super().process(event)
handle = self._handle_for_event(event)
if handle is not None:
handle._observe_event(event)
handle._mux.push(event)
return keep
async def aprocess(self, event: ProtocolEvent) -> bool:
# Async counterpart: repeats the tasks bookkeeping here so
# child mini-muxes receive events through their async lane.
if event["method"] == "tasks":
ns = tuple(event["params"]["namespace"])
data = event["params"]["data"]
if "result" in data:
for child_ns, status, error in self._pop_terminal_transitions(ns, data):
await self._aon_terminal(child_ns, status, error)
else:
self._handle_task_start(ns)
keep = False
else:
keep = True
handle = self._handle_for_event(event)
if handle is not None:
handle._observe_event(event)
await handle._mux.apush(event)
return keep
def _complete_open_handles(self) -> BaseException | None:
first_error: BaseException | None = None
for ns in list(self._open):
try:
self._on_terminal(ns, "completed", None)
except BaseException as e:
if first_error is None:
first_error = e
self._open.clear()
for handle in self._handles.values():
if self._mark_terminal(handle, "completed", None):
try:
self._close_or_fail_handle(handle, "completed", None)
except BaseException as e:
if first_error is None:
first_error = e
return first_error
async def _acomplete_open_handles(self) -> BaseException | None:
first_error: BaseException | None = None
for ns in list(self._open):
try:
await self._aon_terminal(ns, "completed", None)
except BaseException as e:
if first_error is None:
first_error = e
self._open.clear()
for handle in self._handles.values():
if self._mark_terminal(handle, "completed", None):
try:
await self._aclose_or_fail_handle(handle, "completed", None)
except BaseException as e:
if first_error is None:
first_error = e
return first_error
def finalize(self) -> None:
first_error = self._complete_open_handles()
if first_error is not None:
raise first_error
async def afinalize(self) -> None:
first_error = await self._acomplete_open_handles()
if first_error is not None:
raise first_error
def fail(self, err: BaseException) -> None:
status, error_str = _status_from_exception(err)
self._open.clear()
for handle in self._handles.values():
self._mark_terminal(handle, status, error_str)
if handle._mux is not None and not handle._mux._events._closed:
try:
handle._mux.fail(err)
except Exception:
_logger.warning(
"Error failing subgraph mini-mux at %s; "
"subscribers may not see the terminal error.",
handle.path,
exc_info=True,
)
async def afail(self, err: BaseException) -> None:
status, error_str = _status_from_exception(err)
self._open.clear()
for handle in self._handles.values():
self._mark_terminal(handle, status, error_str)
if handle._mux is not None and not handle._mux._events._closed:
try:
await handle._mux.afail(err)
except Exception:
_logger.warning(
"Error failing subgraph mini-mux at %s; "
"subscribers may not see the terminal error.",
handle.path,
exc_info=True,
)
class CheckpointsTransformer(StreamTransformer):
"""Capture checkpoint events as a drainable stream.
Surfaces `stream_mode="checkpoints"` data on `run.checkpoints` as
a `StreamChannel[dict[str, Any]]`. Each item is in the same format
as returned by `get_state()`.
Checkpoint events are only emitted when a checkpointer is configured
on the graph. When no checkpointer is present, the projection exists
but receives no events.
Only events at the run's own scope are captured; checkpoint data from
deeper subgraphs is available on the respective subgraph handle's
`.checkpoints` projection.
Native transformer — `run.checkpoints` is a direct attribute.
"""
_native = True
required_stream_modes = ("checkpoints",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[dict[str, Any]] = StreamChannel()
self._scope_list: list[str] = list(scope)
def init(self) -> dict[str, Any]:
return {"checkpoints": self._log}
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "checkpoints":
return True
params = event["params"]
if params["namespace"] != self._scope_list:
return True
self._log.push(params["data"])
return True
class DebugTransformer(StreamTransformer):
"""Capture debug events as a drainable stream.
Surfaces `stream_mode="debug"` data on `run.debug` as a
`StreamChannel[dict[str, Any]]`. Each item is a debug event with
step-level detail (checkpoint snapshots, task payloads, and
task results wrapped with step number and timestamp).
Only events at the run's own scope are captured; debug data from
deeper subgraphs is available on the respective subgraph handle's
`.debug` projection.
Native transformer — `run.debug` is a direct attribute.
"""
_native = True
required_stream_modes = ("debug",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[dict[str, Any]] = StreamChannel()
self._scope_list: list[str] = list(scope)
def init(self) -> dict[str, Any]:
return {"debug": self._log}
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "debug":
return True
params = event["params"]
if params["namespace"] != self._scope_list:
return True
self._log.push(params["data"])
return True
class TasksTransformer(StreamTransformer):
"""Capture raw task events as a drainable stream.
Surfaces `stream_mode="tasks"` data on `run.tasks` as a
`StreamChannel[dict[str, Any]]`. Each item is a task payload
(start or result).
`LifecycleTransformer` and `SubgraphTransformer` also consume
`tasks` events for subgraph discovery and lifecycle tracking.
This transformer captures the raw payloads independently for
consumers who need task-level detail.
Only events at the run's own scope are captured; task data from
deeper subgraphs is available on the respective subgraph handle's
`.tasks` projection.
Native transformer — `run.tasks` is a direct attribute.
"""
_native = True
required_stream_modes = ("tasks",)
def __init__(self, scope: tuple[str, ...] = ()) -> None:
super().__init__(scope)
self._log: StreamChannel[dict[str, Any]] = StreamChannel()
self._scope_list: list[str] = list(scope)
def init(self) -> dict[str, Any]:
return {"tasks": self._log}
def process(self, event: ProtocolEvent) -> bool:
if event["method"] != "tasks":
return True
params = event["params"]
if params["namespace"] != self._scope_list:
return True
self._log.push(params["data"])
return True