fix: guard init-time stdio writes

run_agent.py

@@ -110,18 +110,17 @@ HONCHO_TOOL_NAMES = {
 
 
 class _SafeWriter:
-    """Transparent stdout wrapper that catches OSError from broken pipes.
+    """Transparent stdio wrapper that catches OSError from broken pipes.
 
     When hermes-agent runs as a systemd service, Docker container, or headless
-    daemon, the stdout pipe can become unavailable (idle timeout, buffer
+    daemon, the stdout/stderr pipe can become unavailable (idle timeout, buffer
     exhaustion, socket reset). Any print() call then raises
-    ``OSError: [Errno 5] Input/output error``, which can crash
+    ``OSError: [Errno 5] Input/output error``, which can crash agent setup or
-    run_conversation() — especially via double-fault when the except handler
+    run_conversation() — especially via double-fault when an except handler
     also tries to print.
 
     This wrapper delegates all writes to the underlying stream and silently
-    catches OSError.  It is installed once at the start of run_conversation()
+    catches OSError. It is transparent when the wrapped stream is healthy.
-    and is transparent when stdout is healthy (zero overhead on the happy path).
     """
 
     __slots__ = ("_inner",)
@@ -154,6 +153,14 @@ class _SafeWriter:
         return getattr(self._inner, name)
 
 
+def _install_safe_stdio() -> None:
+    """Wrap stdout/stderr so best-effort console output cannot crash the agent."""
+    for stream_name in ("stdout", "stderr"):
+        stream = getattr(sys, stream_name, None)
+        if stream is not None and not isinstance(stream, _SafeWriter):
+            setattr(sys, stream_name, _SafeWriter(stream))
+
+
 class IterationBudget:
     """Thread-safe shared iteration counter for parent and child agents.
 
@@ -324,6 +331,8 @@ class AIAgent:
             honcho_manager: Optional shared HonchoSessionManager owned by the caller.
             honcho_config: Optional HonchoClientConfig corresponding to honcho_manager.
         """
+        _install_safe_stdio()
+
         self.model = model
         self.max_iterations = max_iterations
         # Shared iteration budget — parent creates, children inherit.
@@ -3868,10 +3877,9 @@ class AIAgent:
         Returns:
             Dict: Complete conversation result with final response and message history
         """
-        # Guard stdout against OSError from broken pipes (systemd/headless/daemon).
+        # Guard stdio against OSError from broken pipes (systemd/headless/daemon).
-        # Installed once, transparent when stdout is healthy, prevents crash on write.
+        # Installed once, transparent when streams are healthy, prevents crash on write.
-        if not isinstance(sys.stdout, _SafeWriter):
+        _install_safe_stdio()
-            sys.stdout = _SafeWriter(sys.stdout)
 
         # Generate unique task_id if not provided to isolate VMs between concurrent tasks
         effective_task_id = task_id or str(uuid.uuid4())

tests/test_run_agent.py

@@ -1800,12 +1800,13 @@ class TestSafeWriter:
             sys.stdout = original
 
     def test_installed_in_run_conversation(self, agent):
-        """run_conversation installs _SafeWriter on sys.stdout."""
+        """run_conversation installs _SafeWriter on stdio."""
         import sys
         from run_agent import _SafeWriter
         resp = _mock_response(content="Done", finish_reason="stop")
         agent.client.chat.completions.create.return_value = resp
-        original = sys.stdout
+        original_stdout = sys.stdout
+        original_stderr = sys.stderr
         try:
             with (
                 patch.object(agent, "_persist_session"),
@@ -1814,6 +1815,41 @@ class TestSafeWriter:
             ):
                 agent.run_conversation("test")
             assert isinstance(sys.stdout, _SafeWriter)
+            assert isinstance(sys.stderr, _SafeWriter)
+        finally:
+            sys.stdout = original_stdout
+            sys.stderr = original_stderr
+
+    def test_installed_before_init_time_honcho_error_prints(self):
+        """AIAgent.__init__ wraps stdout before Honcho fallback prints can fire."""
+        import sys
+        from run_agent import _SafeWriter
+
+        broken = MagicMock()
+        broken.write.side_effect = OSError(5, "Input/output error")
+        broken.flush.side_effect = OSError(5, "Input/output error")
+
+        original = sys.stdout
+        sys.stdout = broken
+        try:
+            hcfg = HonchoClientConfig(enabled=True, api_key="test-honcho-key")
+            with (
+                patch("run_agent.get_tool_definitions", return_value=_make_tool_defs("web_search")),
+                patch("run_agent.check_toolset_requirements", return_value={}),
+                patch("run_agent.OpenAI"),
+                patch("hermes_cli.config.load_config", return_value={"memory": {}}),
+                patch("honcho_integration.client.HonchoClientConfig.from_global_config", return_value=hcfg),
+                patch("honcho_integration.client.get_honcho_client", side_effect=RuntimeError("boom")),
+            ):
+                agent = AIAgent(
+                    api_key="test-k...7890",
+                    quiet_mode=True,
+                    skip_context_files=True,
+                    skip_memory=False,
+                )
+
+            assert isinstance(sys.stdout, _SafeWriter)
+            assert agent._honcho is None
         finally:
             sys.stdout = original