[rfan-debug]

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: run_live: change instruction/tools or transfer agents on the open Live connection (send_context_update, in-session transfer) #7692
• Related: N/A

Proposed change

• google-genai==2.32 added AsyncSession.send_context_update, but the live runner offered no way to use it: callers reached into the private _gemini_session, which left the new tools unknown to ADK's function-call dispatch and reverted the update on every reconnect.

This change adds LiveContextUpdate and LiveRequestQueue.send_context_update. The flow rewrites the LlmRequest first, registering the tools in tools_dict and storing the instruction where Gemini.connect reads it, so function calls execute and reconnects replay the latest context, then forwards the update through BaseLlmConnection.send_context_update.

    live_request_queue.send_context_update(
        system_instruction=CHECKOUT_INSTRUCTION,
        tools=[FunctionTool(lookup_order)],
    )

Both fields are part of the model preamble, so an update invalidates the Live prefix cache; the docstrings say so and point per-turn context to send_content(partial=True) or tool responses instead.

Testing Plan

Unit tests (all under tests/unittests/):

• live/test_live_request_queue.py: queueing, [] vs None, missing-field ValueError, extra='forbid'.
• live/test_live_llm_flow.py: tools replaced in tools_dict / config.tools / live_connect_config.tools and sent; [] clears; instruction stored where Gemini.connect reads it and sent as role='system' Content; send_to_model applies the update before content in the same request.
• models/test_gemini_llm_connection.py: SDK forwarding (incl. empty list), unset fields stay None, SDK-floor error.

pytest tests/unittests/live tests/unittests/models/test_gemini_llm_connection.py \
       tests/unittests/test_import_loading.py tests/unittests/agents
pre-commit run --files <touched files>   # all hooks pass
mypy <touched src files>                  # Success: no issues found
tox                                        # py311 OK, py312 OK, py313 OK, py314 OK

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Please include a summary of passed pytest results.

Manual End-to-End (E2E) Tests:

Manual E2E (to do before opening the PR): adk web with a live agent, send a context update from a tool callback, confirm (a) the model follows the new instruction, (b) a call to a swapped-in tool is executed by ADK, (c) after a forced reconnect the new tools are still declared.

Doc change: google/adk-docs#2545

Checklist

• I have read the CONTRIBUTING.md document.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have manually tested my changes end-to-end.
• Any dependent changes have been merged and published in downstream modules.