Fall back to Chat Completions for provider/proxy Responses endpoint failures before any output is emitted.
Preserve streamed Chat Completions tool-call deltas as structured LLMResult function-call items, so fallback providers can still drive tools.
Document Docker host-gateway addressing for local model servers, where container localhost does not reach host loopback.
Verified with: PYTHONPATH="/home/eclypso/a0/agent-zero" conda run -n a0 pytest tests/test_stream_tool_early_stop.py tests/test_responses_architecture.py -q; PYTHONPATH="/home/eclypso/a0/agent-zero" conda run -n a0 python -m py_compile helpers/litellm_transport.py helpers/llm_result.py; git diff --check.
Route Agent Zero turns through a LiteLLM transport layer that prefers the Responses API while preserving chat-completions fallback for providers without compatible endpoints.
Persist Responses metadata in history and agent state so provider-state continuation, local replay, native function-call execution, and stored-response cleanup survive normal chat workflows.
Normalize prompt caching by provider: OpenAI and Azure use prompt_cache_key and prompt_cache_retention, while Anthropic, Gemini, Bedrock, OpenRouter, and compatible chat providers keep block-level cache_control breakpoints and cached tool definitions.
