@ai-sdk/svelte 3.0.0: Chat API migration

@ai-sdk/svelte 3.0.0 rebuilds Chat on AbstractChat from ai 5.0.0, and several names, options, methods and properties that 2.1.12 exposed are gone. A module or component needs an edit if it imports Message, CreateMessage or ChatOptions, calls append, reload or addToolResult on a Chat, or reads data from a Chat or Completion. Messages now carry parts where they used to carry a content string.

What changed

• Message types. Message and CreateMessage are no longer exported. UIMessage and CreateUIMessage replace them, and message.content is gone: the text of a message is its text parts joined in order.
• Constructor options. ChatOptions is removed and Chat takes ChatInit from ai. The argument is required, so new Chat() fails to compile and throws at run time. initialMessages becomes messages, and api, headers, body, credentials and fetch move into a transport. maxSteps, initialInput, onResponse, keepLastMessageOnError and sendExtraMessageFields no longer exist.
• Renamed methods. append is now sendMessage, which takes { text } or a CreateUIMessage with parts. reload is now regenerate. Neither accepts the data request option any more.
• The data property. Chat and Completion no longer have it, and ai 5.0.0 removed StreamData. On a Chat, server data now arrives as data parts on the messages, written with createUIMessageStream. Completion has nothing in its place.
• addToolResult. It takes { tool, toolCallId, output } where it took { toolCallId, result }, and tool and output are both required.

Before and after

The change you are most likely to meet is addToolResult inside an onToolCall handler:

chat.addToolResult({ toolCallId: toolCall.toolCallId, result: 'London' });

The patch renames the key and names the tool whose call is being answered:

chat.addToolResult({ tool: toolCall.toolName, toolCallId: toolCall.toolCallId, output: 'London' });

No change in this release has a deterministic patch. The other rewrites follow the same direct shape: reload becomes regenerate with headers and body kept, initialMessages becomes messages, and new Chat() becomes new Chat({}).

Migration guidance and its limits

Run emendant scan to list the affected files, then emendant fix. All six findings have assisted patches, so emendant fix writes one only when you name a model provider, on the command line or in your Emendant configuration. Each patch is checked with your typecheck and with the tests it affects. Nothing in this release is report only.

Some patches change more than the file they edit. If your server read the data request option, it has to receive that value in body instead. Replacing maxSteps means the route must stop on its own, for example with stopWhen in streamText. Moving off data means changing the route as well as the component, and a Completion has no replacement to move to. A patch may not be available where the surrounding code decides the outcome, such as an addToolResult call where the tool name cannot be read from the code around it. Review those by hand.

A clean scan covers imports of the removed names from @ai-sdk/svelte, reads of append, reload and data on instances built from it, and addToolResult calls whose argument has no output. It does not read markup, so a chat.reload() or chat.data inside a template is not reported. The managed input and handleSubmit are not among the findings either, so check any code that still uses them.

What Emendant detects, fixes and verifies

11 changes in @ai-sdk/svelte 3.0.0. 0 automatic fixes, 11 fixes requiring a model provider you choose, 0 report only. Each patch states which checks passed. Understand patch evidence.

error TS2724: '"@ai-sdk/svelte"' has no exported member named 'CreateMessage'. Did you mean 'CreateUIMessage'?

error TS2724: '"@ai-sdk/svelte"' has no exported member named 'Message'. Did you mean 'UIMessage'?

error TS2305: Module '"@ai-sdk/svelte"' has no exported member 'ChatOptions'.

error TS2339: Property 'append' does not exist on type 'Chat<UIMessage<unknown, UIDataTypes, UITools>>'.

error TS2339: Property 'reload' does not exist on type 'Chat<UIMessage<unknown, UIDataTypes, UITools>>'.

error TS2339: Property 'data' does not exist on type 'Chat<UIMessage<unknown, UIDataTypes, UITools>>'.

error TS2339: Property 'data' does not exist on type 'Completion'.

error TS2353: Object literal may only specify known properties, and 'result' does not exist in type '{ tool: string; toolCallId: string; output: unknown; }'.

error TS2339: Property 'input' does not exist on type 'Chat<UIMessage<unknown, UIDataTypes, UITools>>'.

error TS2339: Property 'handleSubmit' does not exist on type 'Chat<UIMessage<unknown, UIDataTypes, UITools>>'.

error TS2353: Object literal may only specify known properties, and 'initialMessages' does not exist in type 'ChatInit<UIMessage<unknown, UIDataTypes, UITools>>'.

error TS2353: Object literal may only specify known properties, and 'api' does not exist in type 'ChatInit<UIMessage<unknown, UIDataTypes, UITools>>'.

error TS2353: Object literal may only specify known properties, and 'onResponse' does not exist in type 'Readonly<UseCompletionOptions>'.

emendant explain <change-id> prints any row's entry, guidance and sources at the terminal.

The error TS lines are what TypeScript 5.9.3 printed when code that compiled against @ai-sdk/svelte 2.1.12 was compiled against 3.0.0. A row without one is a change the compiler does not report, such as a deprecation or a change in behaviour.

Coverage

Requires emendant@0.10.0 or later. Run emendant feed update to get the latest coverage.

Primary sources

• package.jsonvercel/ai at @ai-sdk/svelte@3.0.0
• Changelogvercel/ai at @ai-sdk/svelte@3.0.0
• Migration guidevercel/ai at ai@5.0.0
• @ai-sdk/svelte@3.0.0npm registry, the published package
• @ai-sdk/svelte@2.1.12npm registry, the published package
• ai@5.0.0npm registry, the published package
• @ai-sdk/ui-utils@1.2.11npm registry, the published package
• Chat.svelte.tsvercel/ai at @ai-sdk/svelte@3.0.0

Scan your repository

Find affected code without editing your files.

npx emendant scan

Then npx emendant fix writes the patches the table says exist. The getting started guide covers the flags and the patch grades.

Related release pages

• Earlier @ai-sdk/svelte release: @ai-sdk/svelte 2.0.0: hooks move to classes

Every @ai-sdk/svelte release page is listed on one page.