Runner.runAsync applies stateDelta too late, causing missing(outdated) context in onUserMessageCallback

[anastasiiapeleshok-festcloud]

Description

In the current implementation of Runner.java, the stateDelta provided to runAsync is merged into the session only after the pluginManager.onUserMessageCallback has been executed.

Because the stateDelta is merged into the session only after the pluginManager.onUserMessageCallback has been executed, the data available to plugins is inconsistent with the current execution call. Furthermore, because the session is a copy, any attempt to manually update the state from the outside before the callback is ineffective, as the InvocationContext is built from a stale snapshot.

Steps to Reproduce

1. Call runner.runAsync(userId, sessionId, message, config, stateDelta).
2. sessionService.getSession(sessionId) returns a copy of the session.
3. pluginManager.onUserMessageCallback(initialContext, newMessage) is triggered using this copy.
4. Any stateDelta passed in the runAsync call is missing from the initialContext.
5. The stateDelta is only applied inside appendNewMessageToSession after the plugin execution, leading to inconsistent behavior during the plugin lifecycle.

Expected Behavior

The stateDelta must be integrated into the session state before the InvocationContext is created and before any plugins are notified. This ensures that plugins operate on a consistent and up-to-date representation of the user session.

[hemasekhar-p]

Hi @anastasiiapeleshok-festcloud, Thank you for reporting this issue. I have tried reproducing this on my end but unable to trigger the exact behavior you described. To help us investigate further, could you please provide a Minimal Reproducible Example along with the error logs and specific version details. and also please share the configurations details like RunConfig settings and initialized plugins. This information will help investigate rapidly and provide a solution.

[anastasiiapeleshok-festcloud]

Hi there, thank you for looking into this!

Here are the specific environment and configuration details you requested:

ADK Version: 1.0.0
RunConfig Settings: Default RunConfig.builder().build()
Plugins Initialized: A single custom Plugin overriding onUserMessageCallback.

Below is a standalone minimal reproducible example. To make debugging as easy as possible, I have silenced the agent's output and reduced the prompt to a single word.

The code simply passes a stateDelta containing a messageId into runAsync, and the plugin immediately attempts to read this state.

public class Main {
  public static void main(String[] args) {
    try {
      BaseAgent minimalAgent = LlmAgent.builder().name("Test Agent").model("gemini-2.5-flash")
          .instruction("Reply with exactly one word: OK.").build();

      Plugin stateCheckPlugin = new Plugin() {
        @Override
        public String getName() {
          return "State Check Plugin";
        }

        @Override
        public Maybe<Content> onUserMessageCallback(InvocationContext invocationContext,
                                                    Content userMessage) {
          Map<String, Object> currentState = invocationContext.session().state();
          Object messageIdObj = currentState.get("messageId");

          if (messageIdObj == null) {
            System.err.println(
                ">>> [BUG REPRODUCED] 'messageId' is null! stateDelta was not applied before the callback.");
          } else {
            System.out.println(">>> [SUCCESS] messageId found: " + messageIdObj);
          }

          return Maybe.just(userMessage);
        }
      };

      Runner runner = new InMemoryRunner(minimalAgent, "StateDeltaTest", List.of(stateCheckPlugin));
      Session session = runner.sessionService().createSession("StateDeltaTest", "user-1")
          .blockingGet();

      Content content = Content.fromParts(Part.fromText("Test"));

      Map<String, Object> stateDelta = new HashMap<>();
      String expectedMessageId = UUID.randomUUID().toString();
      stateDelta.put("messageId", expectedMessageId);
      System.out.println(">>> [RUNNER] Passing stateDelta with messageId: " + expectedMessageId);

      Flowable<Event> responseStream = runner.runAsync(session.userId(), session.id(), content,
                                                       RunConfig.builder().build(), stateDelta);

      responseStream.blockingSubscribe();
      System.out.println(">>> [RUNNER] Execution finished.");

    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

Actual Output
When you run the code above, the console output instantly proves the issue. The plugin reads an empty state, meaning the stateDelta has not been merged into the session's InvocationContext at the time onUserMessageCallback is fired:

>>> [RUNNER] Passing stateDelta with messageId: 8a1b2c3d-4e5f...
>>> [BUG REPRODUCED] 'messageId' is null! stateDelta was not applied before the callback.
>>> [RUNNER] Execution finished.

Expected Output
If the stateDelta was correctly merged into the session prior to the plugin execution, the output should look like this:

>>> [RUNNER] Passing stateDelta with messageId: 8a1b2c3d-4e5f...
>>> [SUCCESS] messageId found: 8a1b2c3d-4e5f...
>>> [RUNNER] Execution finished.

Let me know if this helps you trigger the exact behavior on your end or if you need any additional logs.

[hemasekhar-p]

Hi @anastasiiapeleshok-festcloud, thank you for providing the minimal reproducible code and environment details. I am able to reproduce the behavior with your sample code. The PR #1117 will address this issue.

@YuqiGuo105, thank you for your contribution. The PR is under review by our team, and we will keep you updated if any additional information is required.

[hemasekhar-p]

@sherryfox, Could you please have a look into it.