feat (ui): introduce message parts for useChat

[lgrammel]

Background

Text fields on Message for content and reasoning do not support multi-step invocations. A mechanism for support many message parts is needed to properly represent complex user messages and assistant responses.

Tasks

• implementation
  • update in addToolResult
    • react
    • svelte
    • solid
    • vue
  • function that fills in parts for existing ui messages
    • react
    • svelte
    • solid
    • vue
    • fill should have msg at end if it's a single message
  • auto-fill in parts when processing response
  • appendResponseMessages function needs to fill in parts
  • map to core messages based on parts
    • support anthropic-like ordering
  • support parts in text protocol responses
  • update in automatic client side tool execution
  • start new reasoning / new text part on new step
  • update re-submit check to work with anthropic
    • react
    • svelte
    • solid
    • vue
  • useAssistant compatibility fixes
    • react
    • svelte
    • solid
    • vue
  • deprecate message, reasoning, toolInvocations
  • useChat append must have optional parts; fill them in
    • react
    • svelte
    • solid
    • vue
  • send parts to server
    • react
    • svelte
    • solid
    • vue
• examples & manual testing
  • anthropic
  • resuming old conversation
  • storing single message
  • vue
  • solid
  • react
  • svelte
• documentation
  • message reference
  • chatbot with tools guide
  • chatbot guide
  • jsdoc for parts
• changeset

Stored old conversation for reference

[
  {
    "id": "msgc-HsgNJ3TURcE5lGkm",
    "createdAt": "2025-01-30T11:33:23.885Z",
    "role": "user",
    "content": "what is the weather  at my current location "
  },
  {
    "id": "msgs-2ySYamF9UyKoeUmm",
    "createdAt": "2025-01-30T11:33:23.978Z",
    "role": "assistant",
    "content": "The current weather in Los Angeles is rainy.",
    "annotations": [
      {
        "start": "start",
        "count": 1
      }
    ],
    "toolInvocations": [
      {
        "state": "result",
        "step": 0,
        "toolCallId": "call_cMbBQGbGCvHZDy5AQKqpIekC",
        "toolName": "askForConfirmation",
        "args": {
          "message": "Can I access your current location to provide the weather information?"
        },
        "result": "Yes, confirmed."
      },
      {
        "state": "result",
        "step": 1,
        "toolCallId": "call_mQ0IevsD0PTpv17iRyOogDsd",
        "toolName": "getLocation",
        "args": {},
        "result": "Los Angeles"
      },
      {
        "state": "result",
        "step": 2,
        "args": {
          "city": "Los Angeles"
        },
        "toolCallId": "call_8DfGRUjtVVoYWumEL19skTQV",
        "toolName": "getWeatherInformation",
        "result": "rainy"
      }
    ],
    "revisionId": "msgc-1mM8ABtpPTzAM1pL"
  }
]

[jeremyphilemon]

stray comment

[lgrammel]

wanted to leave it in for future testing