fix: close off dangling steps by properly tracking open ones

Author: ranst91

typescript-sdk/integrations/langgraph/python/ag_ui_langgraph/agent.py

@@ -1,6 +1,8 @@
 import uuid
 import json
 from typing import Optional, List, Any, Union, AsyncGenerator, Generator
+from dataclasses import is_dataclass, asdict
+from datetime import date, datetime
 
 from langgraph.graph.state import CompiledStateGraph
 from langchain.schema import BaseMessage, SystemMessage
@@ -85,6 +87,7 @@ def __init__(self, *, name: str, graph: CompiledStateGraph, description: Optiona
         self.messages_in_process: MessagesInProgressRecord = {}
         self.active_run: Optional[RunMetadata] = None
         self.constant_schema_keys = ['messages', 'tools']
+        self.active_step = None
 
     def _dispatch_event(self, event: ProcessedEvents) -> str:
         return event  # Fallback if no encoder
@@ -135,9 +138,8 @@ async def _handle_stream_events(self, input: RunAgentInput) -> AsyncGenerator[st
 
         # In case of resume (interrupt), re-start resumed step
         if resume_input and self.active_run.get("node_name"):
-            yield self._dispatch_event(
-                StepStartedEvent(type=EventType.STEP_STARTED, step_name=self.active_run.get("node_name"))
-            )
+            for ev in self.start_step(self.active_run.get("node_name")):
+                yield ev
 
         state = prepared_stream_response["state"]
         stream = prepared_stream_response["stream"]
@@ -151,6 +153,7 @@ async def _handle_stream_events(self, input: RunAgentInput) -> AsyncGenerator[st
 
         should_exit = False
         current_graph_state = state
+        
         async for event in stream:
             if event["event"] == "error":
                 yield self._dispatch_event(
@@ -175,16 +178,8 @@ async def _handle_stream_events(self, input: RunAgentInput) -> AsyncGenerator[st
                 )
 
             if current_node_name and current_node_name != self.active_run.get("node_name"):
-                if self.active_run["node_name"] and self.active_run["node_name"] != node_name_input:
-                    yield self._dispatch_event(
-                        StepFinishedEvent(type=EventType.STEP_FINISHED, step_name=self.active_run["node_name"])
-                    )
-                    self.active_run["node_name"] = None
-
-                yield self._dispatch_event(
-                    StepStartedEvent(type=EventType.STEP_STARTED, step_name=current_node_name)
-                )
-                self.active_run["node_name"] = current_node_name
+                for ev in self.start_step(current_node_name):
+                    yield ev
 
             updated_state = self.active_run.get("manually_emitted_state") or current_graph_state
             has_state_diff = updated_state != state
@@ -224,19 +219,14 @@ async def _handle_stream_events(self, input: RunAgentInput) -> AsyncGenerator[st
                 CustomEvent(
                     type=EventType.CUSTOM,
                     name=LangGraphEventTypes.OnInterrupt.value,
-                    value=json.dumps(interrupt.value) if not isinstance(interrupt.value, str) else interrupt.value,
+                    value=json.dumps(interrupt.value, default=make_json_safe) if not isinstance(interrupt.value, str) else interrupt.value,
                     raw_event=interrupt,
                 )
             )
 
         if self.active_run.get("node_name") != node_name:
-            yield self._dispatch_event(
-                StepFinishedEvent(type=EventType.STEP_FINISHED, step_name=self.active_run["node_name"])
-            )
-            self.active_run["node_name"] = node_name
-            yield self._dispatch_event(
-                StepStartedEvent(type=EventType.STEP_STARTED, step_name=self.active_run["node_name"])
-            )
+            for ev in self.start_step(node_name):
+                yield ev
 
         state_values = state.values if state.values else state
         yield self._dispatch_event(
@@ -250,10 +240,7 @@ async def _handle_stream_events(self, input: RunAgentInput) -> AsyncGenerator[st
             )
         )
 
-        yield self._dispatch_event(
-            StepFinishedEvent(type=EventType.STEP_FINISHED, step_name=self.active_run["node_name"])
-        )
-        self.active_run["node_name"] = None
+        yield self.end_step()
 
         yield self._dispatch_event(
             RunFinishedEvent(type=EventType.RUN_FINISHED, thread_id=thread_id, run_id=self.active_run["id"])
@@ -700,3 +687,43 @@ async def get_checkpoint_before_message(self, message_id: str, thread_id: str):
 
         raise ValueError("Message ID not found in history")
 
+    def start_step(self, step_name: str):
+        if self.active_step:
+            yield self.end_step()
+
+        yield self._dispatch_event(
+            StepStartedEvent(
+                type=EventType.STEP_STARTED,
+                step_name=step_name
+            )
+        )
+        self.active_run["node_name"] = step_name
+        self.active_step = step_name
+
+    def end_step(self):
+        if self.active_step is None:
+            raise ValueError("No active step to end")
+
+        dispatch = self._dispatch_event(
+            StepFinishedEvent(
+                type=EventType.STEP_FINISHED,
+                step_name=self.active_run["node_name"]
+            )
+        )
+
+        self.active_run["node_name"] = None
+        self.active_step = None
+        return dispatch
+
+def make_json_safe(o):
+    if is_dataclass(o):          # dataclasses like Flight(...)
+        return asdict(o)
+    if hasattr(o, "model_dump"): # pydantic v2
+        return o.model_dump()
+    if hasattr(o, "dict"):       # pydantic v1
+        return o.dict()
+    if hasattr(o, "__dict__"):   # plain objects
+        return vars(o)
+    if isinstance(o, (datetime, date)):
+        return o.isoformat()
+    return str(o)                # last resort

typescript-sdk/integrations/langgraph/src/agent.ts

@@ -123,6 +123,7 @@ export class LangGraphAgent extends AbstractAgent {
   // @ts-expect-error no need to initialize subscriber right now
   subscriber: Subscriber<ProcessedEvents>;
   constantSchemaKeys: string[] = DEFAULT_SCHEMA_KEYS;
+  activeStep?: string;
 
   constructor(config: LangGraphAgentConfig) {
     super(config);
@@ -383,7 +384,9 @@ export class LangGraphAgent extends AbstractAgent {
           break;
         }
 
-        if (streamResponseChunk.event === "updates") continue;
+        if (streamResponseChunk.event === "updates") {
+          continue;
+        }
 
         if (streamResponseChunk.event === "values") {
           latestStateValues = chunk.data;
@@ -467,7 +470,6 @@ export class LangGraphAgent extends AbstractAgent {
         newNodeName = isEndNode ? '__end__' : (state.next[0] ?? Object.keys(writes)[0]);
       }
 
-
       interrupts.forEach((interrupt) => {
         this.dispatchEvent({
           type: EventType.CUSTOM,
@@ -944,22 +946,27 @@ export class LangGraphAgent extends AbstractAgent {
   }
 
   startStep(nodeName: string) {
+    if (this.activeStep) {
+      this.endStep()
+    }
     this.dispatchEvent({
       type: EventType.STEP_STARTED,
       stepName: nodeName,
     });
     this.activeRun!.nodeName = nodeName;
+    this.activeStep = nodeName;
   }
 
   endStep() {
-    if (!this.activeRun!.nodeName) {
+    if (!this.activeStep) {
       throw new Error("No active step to end");
     }
     this.dispatchEvent({
       type: EventType.STEP_FINISHED,
       stepName: this.activeRun!.nodeName!,
     });
     this.activeRun!.nodeName = undefined;
+    this.activeStep = undefined;
   }
 
   async getCheckpointByMessage(