feat(bidi): support request_state stop_event_loop flag

[agent-of-mkmeral]

Summary

Replace the hard-coded stop_conversation tool name check with a generic request_state["stop_event_loop"] mechanism, while keeping stop_conversation with a deprecation warning for backward compatibility.

Motivation

The previous approach hard-coded a stop_conversation tool name check in the bidi agent loop. This was:

• Inflexible: Only one specific tool could stop the conversation
• Tightly coupled: The loop checked tool names instead of a generic signal
• Redundant: strands_tools already has a stop tool that uses request_state

Changes

Deprecated (kept for backward compatibility)

• stop_conversation tool now emits DeprecationWarning when called
• Tool name check in loop also emits DeprecationWarning as a fallback
• Both the tool and its export in bidi/__init__.py are preserved

Changed

• agent/loop.py:
  • Initialize request_state in _invocation_state before tool execution
  • Primary: Check request_state.get("stop_event_loop", False) flag
  • Fallback: Check tool_use["name"] == "stop_conversation" with deprecation warning
• tools/stop_conversation.py: Added DeprecationWarning pointing users to strands_tools.stop
• tools/__init__.py: Updated docstring with deprecation notice
• io/text.py: Updated log message

Added

• test_bidi_agent_loop_stop_conversation_deprecated_but_works — verifies backward compatibility with deprecation
• test_bidi_agent_loop_stop_event_loop_flag — verifies new flag mechanism
• test_bidi_agent_loop_request_state_initialized_for_tools — verifies request_state availability
• test_bidi_agent_loop_request_state_preserved_with_invocation_state — verifies existing state preserved

Migration Path

Before (deprecated):

from strands.experimental.bidi import stop_conversation, BidiAgent
agent = BidiAgent(tools=[stop_conversation, ...])

After (recommended):

from strands_tools import stop
from strands.experimental.bidi import BidiAgent
agent = BidiAgent(tools=[stop, ...])

Or any custom tool:

@tool
def my_stop_tool(request_state: dict) -> str:
    request_state["stop_event_loop"] = True
    return "Goodbye!"

Based on: 657ddcd

[mkmeral]

also check the docs, if we need to update anything there, create a related PR. check if stop event loop is documented somewhere. also check if stop conversation tool is used, etc.

[mkmeral]

@agent-of-mkmeral we should probably keep it for now, but add a warning that we will remove in next versions. So we support both, and we can remove the tool later.

It gives users who depend on it some time

[agent-of-mkmeral]

Done! Commit 1381ba1 keeps stop_conversation with backward compatibility:

What	How
stop_conversation tool	Restored — emits DeprecationWarning when called
bidi/__init__.py export	Restored — from strands.experimental.bidi import stop_conversation works
Loop check	Primary: request_state["stop_event_loop"] flag. Fallback: tool_use["name"] == "stop_conversation" with deprecation warning
Tests	New test_bidi_agent_loop_stop_conversation_deprecated_but_works verifies both the tool works AND the warning is emitted

Users who depend on stop_conversation get a clear deprecation message pointing them to strands_tools.stop or request_state["stop_event_loop"].