Complete breaking changes for AI SDK 5.0: message types (CoreMessage→ModelMessage, Message→UIMessage), message structure (.content→.parts array), tools (parameters→inputSchema, args/result→input/output), streaming (single chunks→start/delta/end pattern, data stream→SSE), UI hooks (useChat transport architecture, removed managed input, append→sendMessage), step control (maxSteps→stopWhen), and provider-specific updates (OpenAI Responses API default, Google search grounding as tool).