Telemetry: Plugins observe incorrect current span

[r4inee]

Describe the Bug:
ADK Java plugin callbacks are not consistently invoked with the semantically correct OpenTelemetry span as Span.current(). This affects plugin authors who enrich ADK-created spans using:

Span.current().setAttribute(...);

Steps to Reproduce:

1. Use ADK Java with OpenTelemetry tracing enabled, and with either manual context propagation or via a library.
2. Add the following plugin that logs Span.current() inside model and tool callbacks.
3. Run a tool-calling agent with a prompt such as: “What is the weather in Sydney?”
4. Compare callback Span.current() span IDs to exported span IDs.

public final class CurrentSpanDebugPlugin extends BasePlugin {
  public CurrentSpanDebugPlugin() {
    super("CurrentSpanDebugPlugin");
  }

  @Override
  public Maybe<LlmResponse> beforeModelCallback(
      CallbackContext callbackContext, LlmRequest.Builder llmRequest) {
    recordModel("beforeModelCallback", callbackContext);
    return Maybe.empty();
  }

  @Override
  public Maybe<LlmResponse> afterModelCallback(
      CallbackContext callbackContext, LlmResponse llmResponse) {
    recordModel(
        "afterModelCallback partial=" + llmResponse.partial().orElse(null),
        callbackContext);
    return Maybe.empty();
  }

  @Override
  public Maybe<LlmResponse> onModelErrorCallback(
      CallbackContext callbackContext,
      LlmRequest.Builder llmRequest,
      Throwable error) {
    recordModel("onModelErrorCallback error=" + error.getMessage(), callbackContext);
    return Maybe.empty();
  }

  @Override
  public Maybe<Map<String, Object>> beforeToolCallback(
      BaseTool tool, Map<String, Object> toolArgs, ToolContext toolContext) {
    recordTool("beforeToolCallback:" + tool.name(), toolContext);
    return Maybe.empty();
  }

  @Override
  public Maybe<Map<String, Object>> afterToolCallback(
      BaseTool tool,
      Map<String, Object> toolArgs,
      ToolContext toolContext,
      Map<String, Object> result) {
    recordTool("afterToolCallback:" + tool.name(), toolContext);
    return Maybe.empty();
  }

  @Override
  public Maybe<Map<String, Object>> onToolErrorCallback(
      BaseTool tool,
      Map<String, Object> toolArgs,
      ToolContext toolContext,
      Throwable error) {
    recordTool("onToolErrorCallback:" + tool.name() + " error=" + error.getMessage(), toolContext);
    return Maybe.empty();
  }

  private static void recordModel(String callback, CallbackContext callbackContext) {
    Span span = Span.current();
    SpanContext spanContext = span.getSpanContext();

    // Marker attributes show which exported span this callback mutated.
    span.setAttribute("debug.callback", callback);
    span.setAttribute("debug.callback.span_id", spanContext.getSpanId());
    span.setAttribute("debug.callback.trace_id", spanContext.getTraceId());
    span.setAttribute("debug.callback.valid", spanContext.isValid());
    span.setAttribute("debug.callback.invocation_id", callbackContext.invocationId());
    span.setAttribute("debug.callback.event_id", callbackContext.eventId());

    System.out.printf(
        "PLUGIN %s invocationId=%s eventId=%s currentSpanId=%s currentTraceId=%s valid=%s%n",
        callback,
        callbackContext.invocationId(),
        callbackContext.eventId(),
        spanContext.getSpanId(),
        spanContext.getTraceId(),
        spanContext.isValid());
  }

  private static void recordTool(String callback, ToolContext toolContext) {
    Span span = Span.current();
    SpanContext spanContext = span.getSpanContext();

    // Marker attributes show which exported span this callback mutated.
    span.setAttribute("debug.callback", callback);
    span.setAttribute("debug.callback.span_id", spanContext.getSpanId());
    span.setAttribute("debug.callback.trace_id", spanContext.getTraceId());
    span.setAttribute("debug.callback.valid", spanContext.isValid());
    span.setAttribute("debug.callback.agent_name", toolContext.agentName());
    span.setAttribute(
        "debug.callback.function_call_id",
        toolContext.functionCallId().orElse("<none>"));

    System.out.printf(
        "PLUGIN %s functionCallId=%s agentName=%s currentSpanId=%s currentTraceId=%s valid=%s%n",
        callback,
        toolContext.functionCallId().orElse("<none>"),
        toolContext.agentName(),
        spanContext.getSpanId(),
        spanContext.getTraceId(),
        spanContext.isValid());
  }
}

Expected Behavior:
Plugin callbacks should observe the span corresponding to their semantic operation.

beforeModelCallback #1 -> first call_llm
afterModelCallback  #1 -> first call_llm

beforeToolCallback      -> execute_tool [getWeather]
afterToolCallback       -> execute_tool [getWeather]

beforeModelCallback #2 -> second call_llm
afterModelCallback  #2 -> second call_llm

Observed Behavior:

Without context propagation

beforeModelCallback M1 -> invoke_agent weather-agent
afterModelCallback  M1 -> first call_llm

beforeToolCallback  T1 -> execute_tool [getWeather]
afterToolCallback   T1 -> first call_llm

beforeModelCallback M2 -> execute_tool [getWeather]
afterModelCallback  M2 -> second call_llm

With context propgation

beforeModelCallback M1 -> invoke_agent weather-agent
afterModelCallback  M1 -> first call_llm

beforeToolCallback  T1 -> execute_tool [getWeather]
afterToolCallback   T1 -> execute_tool [getWeather] // fixes this

beforeModelCallback M2 -> previous call_llm or leaked downstream context
afterModelCallback  M2 -> second call_llm

Environment Details:

• ADK Library Version (see maven dependency): 1.3.0
• macOs

Model Information:

• gemini-2.5-pro

---

🟡 Optional Information

How often has this issue occurred?:
Always (100%)

[hemasekhar-p]

Hi @r4inee, Thanks for reporting this issue and and We appreciate you taking the time to submit this pull request. am able to reproduce this behavior which you described. Currently this Issue and PR are under review by our team, we will keep you update if any additional information is required. thank you.

[hemasekhar-p]

@tilgalas, Please take a look into it.