fix: avoid blocking Reactor scheduler thread during AutoContext compression

agentscope-extensions/agentscope-extensions-autocontext-memory/src/main/java/io/agentscope/core/memory/autocontext/AutoContextHook.java

@@ -33,6 +33,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import reactor.core.publisher.Mono;
+import reactor.core.scheduler.Schedulers;
 
 /**
  * Hook for automatically registering AutoContextMemory integration with ReActAgent.
@@ -208,6 +209,12 @@ private Mono<PreCallEvent> handlePreCall(PreCallEvent event) {
      * <p>This ensures compression happens at a deterministic point (before reasoning)
      * and the LLM receives the compressed context.
      *
+     * <p>Compression is executed on {@link Schedulers#boundedElastic()} to avoid blocking
+     * the Reactor scheduler thread. Without this, the internal {@code .block()} calls inside
+     * {@link AutoContextMemory#compressIfNeeded()} would occupy the scheduler thread, preventing
+     * downstream streaming chunks from being dispatched until the entire Mono chain completes,
+     * causing all chunks to be flushed at once instead of incrementally.
+     *
      * @param event the PreReasoningEvent
      * @return Mono containing the potentially modified event
      */
@@ -225,9 +232,24 @@ private Mono<PreReasoningEvent> handlePreReasoning(PreReasoningEvent event) {
             return Mono.just(event);
         }
 
-        // Trigger compression if needed (this modifies workingMemoryStorage in place)
-        autoContextMemory.compressIfNeeded();
+        // Trigger compression on a boundedElastic thread to avoid blocking the Reactor scheduler.
+        // compressIfNeeded() internally calls .block() for LLM-based compression, which must not
+        // run on a Reactor scheduler thread as it would stall downstream streaming chunk dispatch.
+        return Mono.fromCallable(autoContextMemory::compressIfNeeded)
+                .subscribeOn(Schedulers.boundedElastic())
+                .then(Mono.defer(() -> buildUpdatedEvent(event, autoContextMemory)));
+    }
 
+    /**
+     * Builds an updated PreReasoningEvent with compressed memory messages and system prompt
+     * instructions about compressed context offload tags.
+     *
+     * @param event the original PreReasoningEvent
+     * @param autoContextMemory the AutoContextMemory instance
+     * @return Mono containing the updated event
+     */
+    private Mono<PreReasoningEvent> buildUpdatedEvent(
+            PreReasoningEvent event, AutoContextMemory autoContextMemory) {
         // Always append system prompt instruction about compressed messages
         List<Msg> originalInputMessages = event.getInputMessages();
         List<Msg> newInputMessages = new ArrayList<>();