fix: skip signal handler registration in non-main thread

When CrewAI is initialized from a non-main thread (e.g., in Streamlit,
Flask, Django, Jupyter), the telemetry module was printing multiple
ValueError tracebacks for each signal handler registration attempt.

This fix adds a proactive main thread check in _register_shutdown_handlers()
before attempting signal registration. If not in the main thread, a debug
message is logged and signal handler registration is skipped.

Fixes #4289

Co-Authored-By: João <joao@crewai.com>

docs/en/changelog.mdx

@@ -4,6 +4,74 @@ description: "Product updates, improvements, and bug fixes for CrewAI"
 icon: "clock"
 mode: "wide"
 ---
+<Update label="Jan 26, 2026">
+  ## v1.9.0
+
+  [View release on GitHub](https://github.com/crewAIInc/crewAI/releases/tag/1.9.0)
+
+  ## What's Changed
+
+  ### Features
+  - Add structured outputs and response_format support across providers
+  - Add response ID to streaming responses
+  - Add event ordering with parent-child hierarchies
+  - Add Keycloak SSO authentication support
+  - Add multimodal file handling capabilities
+  - Add native OpenAI responses API support
+  - Add A2A task execution utilities
+  - Add A2A server configuration and agent card generation
+  - Enhance event system and expand transport options
+  - Improve tool calling mechanisms
+
+  ### Bug Fixes
+  - Enhance file store with fallback memory cache when aiocache is not available
+  - Ensure document list is not empty
+  - Handle Bedrock stop sequences properly
+  - Add Google Vertex API key support
+  - Enhance Azure model stop word detection
+  - Improve error handling for HumanFeedbackPending in flow execution
+  - Fix execution span task unlinking
+
+  ### Documentation
+  - Add native file handling documentation
+  - Add OpenAI responses API documentation
+  - Add agent card implementation guidance
+  - Refine A2A documentation
+  - Update changelog for v1.8.0
+
+  ### Contributors
+  @Anaisdg, @GininDenis, @Vidit-Ostwal, @greysonlalonde, @heitorado, @joaomdmoura, @koushiv777, @lorenzejay, @nicoferdi96, @vinibrsl
+
+</Update>
+
+<Update label="Jan 15, 2026">
+  ## v1.8.1
+
+  [View release on GitHub](https://github.com/crewAIInc/crewAI/releases/tag/1.8.1)
+
+  ## What's Changed
+
+  ### Features
+  - Add A2A task execution utilities
+  - Add A2A server configuration and agent card generation
+  - Add additional transport mechanisms
+  - Add Galileo integration support
+
+  ### Bug Fixes
+  - Improve Azure model compatibility
+  - Expand frame inspection depth to detect parent_flow
+  - Resolve task execution span management issues
+  - Enhance error handling for human feedback scenarios during flow execution
+
+  ### Documentation
+  - Add A2A agent card documentation
+  - Add PII redaction feature documentation
+
+  ### Contributors
+  @Anaisdg, @GininDenis, @greysonlalonde, @joaomdmoura, @koushiv777, @lorenzejay, @vinibrsl
+
+</Update>
+
 <Update label="Jan 08, 2026">
   ## v1.8.0
 

docs/ko/changelog.mdx

@@ -4,6 +4,74 @@ description: "CrewAI의 제품 업데이트, 개선 사항 및 버그 수정"
 icon: "clock"
 mode: "wide"
 ---
+<Update label="2026년 1월 26일">
+  ## v1.9.0
+
+  [GitHub 릴리스 보기](https://github.com/crewAIInc/crewAI/releases/tag/1.9.0)
+
+  ## 변경 사항
+
+  ### 기능
+  - 프로바이더 전반에 걸친 구조화된 출력 및 response_format 지원 추가
+  - 스트리밍 응답에 응답 ID 추가
+  - 부모-자식 계층 구조를 가진 이벤트 순서 추가
+  - Keycloak SSO 인증 지원 추가
+  - 멀티모달 파일 처리 기능 추가
+  - 네이티브 OpenAI responses API 지원 추가
+  - A2A 작업 실행 유틸리티 추가
+  - A2A 서버 구성 및 에이전트 카드 생성 추가
+  - 이벤트 시스템 향상 및 전송 옵션 확장
+  - 도구 호출 메커니즘 개선
+
+  ### 버그 수정
+  - aiocache를 사용할 수 없을 때 폴백 메모리 캐시로 파일 저장소 향상
+  - 문서 목록이 비어 있지 않도록 보장
+  - Bedrock 중지 시퀀스 적절히 처리
+  - Google Vertex API 키 지원 추가
+  - Azure 모델 중지 단어 감지 향상
+  - 흐름 실행 시 HumanFeedbackPending 오류 처리 개선
+  - 실행 스팬 작업 연결 해제 수정
+
+  ### 문서
+  - 네이티브 파일 처리 문서 추가
+  - OpenAI responses API 문서 추가
+  - 에이전트 카드 구현 가이드 추가
+  - A2A 문서 개선
+  - v1.8.0 변경 로그 업데이트
+
+  ### 기여자
+  @Anaisdg, @GininDenis, @Vidit-Ostwal, @greysonlalonde, @heitorado, @joaomdmoura, @koushiv777, @lorenzejay, @nicoferdi96, @vinibrsl
+
+</Update>
+
+<Update label="2026년 1월 15일">
+  ## v1.8.1
+
+  [GitHub 릴리스 보기](https://github.com/crewAIInc/crewAI/releases/tag/1.8.1)
+
+  ## 변경 사항
+
+  ### 기능
+  - A2A 작업 실행 유틸리티 추가
+  - A2A 서버 구성 및 에이전트 카드 생성 추가
+  - 추가 전송 메커니즘 추가
+  - Galileo 통합 지원 추가
+
+  ### 버그 수정
+  - Azure 모델 호환성 개선
+  - parent_flow 감지를 위한 프레임 검사 깊이 확장
+  - 작업 실행 스팬 관리 문제 해결
+  - 흐름 실행 중 휴먼 피드백 시나리오에 대한 오류 처리 향상
+
+  ### 문서
+  - A2A 에이전트 카드 문서 추가
+  - PII 삭제 기능 문서 추가
+
+  ### 기여자
+  @Anaisdg, @GininDenis, @greysonlalonde, @joaomdmoura, @koushiv777, @lorenzejay, @vinibrsl
+
+</Update>
+
 <Update label="2026년 1월 8일">
   ## v1.8.0
 

docs/pt-BR/changelog.mdx

@@ -4,6 +4,74 @@ description: "Atualizações de produto, melhorias e correções do CrewAI"
 icon: "clock"
 mode: "wide"
 ---
+<Update label="26 jan 2026">
+  ## v1.9.0
+
+  [Ver release no GitHub](https://github.com/crewAIInc/crewAI/releases/tag/1.9.0)
+
+  ## O que Mudou
+
+  ### Funcionalidades
+  - Adicionar suporte a saídas estruturadas e response_format em vários provedores
+  - Adicionar ID de resposta às respostas de streaming
+  - Adicionar ordenação de eventos com hierarquias pai-filho
+  - Adicionar suporte à autenticação SSO Keycloak
+  - Adicionar capacidades de manipulação de arquivos multimodais
+  - Adicionar suporte nativo à API de respostas OpenAI
+  - Adicionar utilitários de execução de tarefas A2A
+  - Adicionar configuração de servidor A2A e geração de cartão de agente
+  - Aprimorar sistema de eventos e expandir opções de transporte
+  - Melhorar mecanismos de chamada de ferramentas
+
+  ### Correções de Bugs
+  - Aprimorar armazenamento de arquivos com cache de memória de fallback quando aiocache não está disponível
+  - Garantir que lista de documentos não esteja vazia
+  - Tratar sequências de parada do Bedrock adequadamente
+  - Adicionar suporte à chave de API do Google Vertex
+  - Aprimorar detecção de palavras de parada do modelo Azure
+  - Melhorar tratamento de erros para HumanFeedbackPending na execução de fluxo
+  - Corrigir desvinculação de tarefa do span de execução
+
+  ### Documentação
+  - Adicionar documentação de manipulação nativa de arquivos
+  - Adicionar documentação da API de respostas OpenAI
+  - Adicionar orientação de implementação de cartão de agente
+  - Refinar documentação A2A
+  - Atualizar changelog para v1.8.0
+
+  ### Contribuidores
+  @Anaisdg, @GininDenis, @Vidit-Ostwal, @greysonlalonde, @heitorado, @joaomdmoura, @koushiv777, @lorenzejay, @nicoferdi96, @vinibrsl
+
+</Update>
+
+<Update label="15 jan 2026">
+  ## v1.8.1
+
+  [Ver release no GitHub](https://github.com/crewAIInc/crewAI/releases/tag/1.8.1)
+
+  ## O que Mudou
+
+  ### Funcionalidades
+  - Adicionar utilitários de execução de tarefas A2A
+  - Adicionar configuração de servidor A2A e geração de cartão de agente
+  - Adicionar mecanismos de transporte adicionais
+  - Adicionar suporte à integração Galileo
+
+  ### Correções de Bugs
+  - Melhorar compatibilidade do modelo Azure
+  - Expandir profundidade de inspeção de frame para detectar parent_flow
+  - Resolver problemas de gerenciamento de span de execução de tarefas
+  - Aprimorar tratamento de erros para cenários de feedback humano durante execução de fluxo
+
+  ### Documentação
+  - Adicionar documentação de cartão de agente A2A
+  - Adicionar documentação de recurso de redação de PII
+
+  ### Contribuidores
+  @Anaisdg, @GininDenis, @greysonlalonde, @joaomdmoura, @koushiv777, @lorenzejay, @vinibrsl
+
+</Update>
+
 <Update label="08 jan 2026">
   ## v1.8.0
 

lib/crewai/src/crewai/telemetry/telemetry.py

@@ -173,6 +173,13 @@ class Telemetry:
 
         self._original_handlers: dict[int, Any] = {}
 
+        if threading.current_thread() is not threading.main_thread():
+            logger.debug(
+                "CrewAI telemetry: Skipping signal handler registration "
+                "(not running in main thread)."
+            )
+            return
+
         self._register_signal_handler(signal.SIGTERM, SigTermEvent, shutdown=True)
         self._register_signal_handler(signal.SIGINT, SigIntEvent, shutdown=True)
         if hasattr(signal, "SIGHUP"):

lib/crewai/tests/telemetry/test_telemetry.py

@@ -1,6 +1,6 @@
 import os
 import threading
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 from crewai import Agent, Crew, Task
@@ -121,3 +121,90 @@ def test_telemetry_singleton_pattern():
         thread.join()
 
     assert all(instance is telemetry1 for instance in instances)
+
+
+def test_signal_handler_registration_skipped_in_non_main_thread():
+    """Test that signal handler registration is skipped when running from a non-main thread.
+
+    This test verifies that when Telemetry is initialized from a non-main thread,
+    the signal handler registration is skipped without raising noisy ValueError tracebacks.
+    See: https://github.com/crewAIInc/crewAI/issues/4289
+    """
+    Telemetry._instance = None
+
+    result = {"register_signal_handler_called": False, "error": None}
+
+    def init_telemetry_in_thread():
+        try:
+            with patch("crewai.telemetry.telemetry.TracerProvider"):
+                with patch.object(
+                    Telemetry,
+                    "_register_signal_handler",
+                    wraps=lambda *args, **kwargs: None,
+                ) as mock_register:
+                    telemetry = Telemetry()
+                    result["register_signal_handler_called"] = mock_register.called
+                    result["telemetry"] = telemetry
+        except Exception as e:
+            result["error"] = e
+
+    thread = threading.Thread(target=init_telemetry_in_thread)
+    thread.start()
+    thread.join()
+
+    assert result["error"] is None, f"Unexpected error: {result['error']}"
+    assert (
+        result["register_signal_handler_called"] is False
+    ), "Signal handler should not be registered in non-main thread"
+
+
+def test_signal_handler_registration_skipped_logs_debug_message():
+    """Test that a debug message is logged when signal handler registration is skipped.
+
+    This test verifies that when Telemetry is initialized from a non-main thread,
+    a debug message is logged indicating that signal handler registration was skipped.
+    """
+    Telemetry._instance = None
+
+    result = {"telemetry": None, "error": None, "debug_calls": []}
+
+    mock_logger_debug = MagicMock()
+
+    def init_telemetry_in_thread():
+        try:
+            with patch("crewai.telemetry.telemetry.TracerProvider"):
+                with patch(
+                    "crewai.telemetry.telemetry.logger.debug", mock_logger_debug
+                ):
+                    result["telemetry"] = Telemetry()
+                    result["debug_calls"] = [
+                        str(call) for call in mock_logger_debug.call_args_list
+                    ]
+        except Exception as e:
+            result["error"] = e
+
+    thread = threading.Thread(target=init_telemetry_in_thread)
+    thread.start()
+    thread.join()
+
+    assert result["error"] is None, f"Unexpected error: {result['error']}"
+    assert result["telemetry"] is not None
+
+    debug_calls = result["debug_calls"]
+    assert any(
+        "Skipping signal handler registration" in call for call in debug_calls
+    ), f"Expected debug message about skipping signal handler registration, got: {debug_calls}"
+
+
+def test_signal_handlers_registered_in_main_thread():
+    """Test that signal handlers are registered when running from the main thread."""
+    Telemetry._instance = None
+
+    with patch("crewai.telemetry.telemetry.TracerProvider"):
+        with patch(
+            "crewai.telemetry.telemetry.Telemetry._register_signal_handler"
+        ) as mock_register:
+            telemetry = Telemetry()
+
+            assert telemetry.ready is True
+            assert mock_register.call_count >= 2