fix: Wait for input guardrails before executing model requests

Fixes #889

When an input guardrail triggers a tripwire, tools (especially hosted
tools like FileSearchTool) should not execute. Previously, input
guardrails ran in parallel with model requests, creating a race
condition where tools could execute before guardrails completed.

This change makes input guardrail execution sequential:
1. Run input guardrails first and wait for completion
2. If any guardrail triggers, raise InputGuardrailTripwireTriggered
3. Only proceed with model request if all guardrails pass

This ensures that:
- No model requests are sent if guardrails trigger
- Hosted tools (FileSearchTool) don't execute unnecessarily
- Token consumption is prevented when input is blocked
- Slow guardrails (e.g., calling external services) work correctly

Author: gn00295120

src/agents/run.py

@@ -599,26 +599,28 @@ async def run(
                     )
 
                     if current_turn == 1:
-                        input_guardrail_results, turn_result = await asyncio.gather(
-                            self._run_input_guardrails(
-                                starting_agent,
-                                starting_agent.input_guardrails
-                                + (run_config.input_guardrails or []),
-                                _copy_str_or_list(prepared_input),
-                                context_wrapper,
-                            ),
-                            self._run_single_turn(
-                                agent=current_agent,
-                                all_tools=all_tools,
-                                original_input=original_input,
-                                generated_items=generated_items,
-                                hooks=hooks,
-                                context_wrapper=context_wrapper,
-                                run_config=run_config,
-                                should_run_agent_start_hooks=should_run_agent_start_hooks,
-                                tool_use_tracker=tool_use_tracker,
-                                server_conversation_tracker=server_conversation_tracker,
-                            ),
+                        # Run input guardrails first, before sending any model requests.
+                        # This ensures that if a guardrail triggers a tripwire, no tools
+                        # (especially hosted tools like FileSearchTool) execute.
+                        # See Issue #889: https://github.com/openai/openai-agents-python/issues/889
+                        input_guardrail_results = await self._run_input_guardrails(
+                            starting_agent,
+                            starting_agent.input_guardrails + (run_config.input_guardrails or []),
+                            _copy_str_or_list(prepared_input),
+                            context_wrapper,
+                        )
+                        # Only proceed with agent execution if guardrails passed
+                        turn_result = await self._run_single_turn(
+                            agent=current_agent,
+                            all_tools=all_tools,
+                            original_input=original_input,
+                            generated_items=generated_items,
+                            hooks=hooks,
+                            context_wrapper=context_wrapper,
+                            run_config=run_config,
+                            should_run_agent_start_hooks=should_run_agent_start_hooks,
+                            tool_use_tracker=tool_use_tracker,
+                            server_conversation_tracker=server_conversation_tracker,
                         )
                     else:
                         turn_result = await self._run_single_turn(