AI SDK 5.0.0: what breaks when you upgrade ai from 4.x

AI SDK 5 redesigned the message model, and most of what it breaks follows from that. The ai package dropped its React and RSC entrypoints, replaced the data stream API, and renamed or reshaped the types that describe a message. It also renamed the key that holds a tool’s schema and the fields on the parts streamText streams. Upgrade from 4.x and the typecheck fails on the first file that touches any of them.

What changed

• Two entrypoints left the package. ai/react is now @ai-sdk/react and ai/rsc is now @ai-sdk/rsc, same names, new dependency.
• Model message types were renamed, with aliases kept. CoreMessage is ModelMessage, the four role types gained the ModelMessage suffix, and convertToCoreMessages is convertToModelMessages. The old names still compile as deprecated aliases until AI SDK 6.0 removes CoreMessage and convertToCoreMessages.
• Two renames are breaks. IDGenerator is IdGenerator, and experimental_wrapLanguageModel is exported only as wrapLanguageModel.
• UI message types changed shape. Message is UIMessage, and it has no content string: text, files and tool calls are entries in a parts array. ToolInvocation, Attachment and the CoreTool type family went with the fields they described.
• A tool’s schema key is inputSchema. parameters is a type error in v5, on the object handed to tool() and on each entry of tools handed to generateText or streamText. It is still wrong at every release up to ai@7.0.99.
• Stream parts renamed their fields. On what streamText streams, textDelta is text, args is input and result is output. tool-call-delta became tool-input-delta carrying delta, step-finish became finish-step with providerMetadata, and logprobs is gone with no replacement.
• The data stream API was replaced. StreamData and the createDataStream* helpers are gone; custom data travels as typed parts on a UI message stream. The LangChain and LlamaIndex adapters moved to their own packages. The assistant API was removed with no replacement.

Before and after

Renames with no shape change are what Emendant rewrites. This file passes one of them on without calling it, which is why the entry anchors on the import:

import { experimental_wrapLanguageModel, type IDGenerator } from 'ai';

export const wrapped = (model: never, middleware: never) =>
  experimental_wrapLanguageModel({ model, middleware });

export function label(generate: IDGenerator): string {
  return `msg_${generate()}`;
}

export const wrap = experimental_wrapLanguageModel;

After npx emendant fix:

import { wrapLanguageModel, type IdGenerator } from 'ai';

export const wrapped = (model: never, middleware: never) =>
  wrapLanguageModel({ model, middleware });

export function label(generate: IdGenerator): string {
  return `msg_${generate()}`;
}

export const wrap = wrapLanguageModel;

The tool rename is one key at each site, and the schema value stays put:

export const weather = tool({
  description: 'Look up the weather',
  parameters: schema,
  execute: async () => ({ temperature: 12 }),
});

export const weather = tool({
  description: 'Look up the weather',
  inputSchema: schema,
  execute: async () => ({ temperature: 12 }),
});

The entrypoint moves are the same edit on the specifier: 'ai/react' becomes '@ai-sdk/react' and 'ai/rsc' becomes '@ai-sdk/rsc'. Three reads off a fullStream part are one word each: part.textDelta becomes part.text, part.args becomes part.input and part.result becomes part.output. The shape changes have no mechanical form: a StreamData route becomes a writer inside createUIMessageStream, and message.content becomes the text parts of message.parts.

Migration guidance and its limits

The ten deterministic patches are safe as offered. The two entrypoint rewrites do not add @ai-sdk/react or @ai-sdk/rsc to your manifest, so install them, or the verification run reports those patches as failing until you do.

The nine assisted changes are the reshapes. Emendant writes them only when you name a model provider, because the right edit depends on how your code reads a message or builds a stream. Two of them turn on the type tag too: argsTextDelta sits in a branch v5 never enters, and experimental_providerMetadata is a rename under step-finish and a removal under finish. Without a provider they are reported with guidance. The assistant API removal and a logprobs read are report only, because nothing in v5 replaces either.

A repository on 6.x or 7.x still writing parameters is reported without the --adopted flag, under a heading saying it is affected today.

Two limits: createIdGenerator now takes its size at creation, which the IdGenerator rename does not touch, and useChat itself changed in 5.0.0 in ways this entry does not describe. A clean scan says a file uses none of the constructs below, nothing more.

A repository still on 3.x has the AI SDK 4.0 stream helper removals to make first. After 5.0, read what breaks when you upgrade ai from 5.x to 6.0.

What Emendant detects, fixes and verifies

22 changes in ai 5.0.0. 10 automatic fixes, 10 fixes requiring a model provider you choose, 2 report only. Each patch states which checks passed. Understand patch evidence.

error TS2724: '"ai"' has no exported member named 'CreateMessage'. Did you mean 'CreateUIMessage'?

error TS2724: '"ai"' has no exported member named 'Message'. Did you mean 'UIMessage'?

error TS2724: '"ai"' has no exported member named 'IDGenerator'. Did you mean 'IdGenerator'?

error TS2305: Module '"ai"' has no exported member 'experimental_wrapLanguageModel'.

error TS2305: Module '"ai"' has no exported member 'createDataStream'.

error TS2305: Module '"ai"' has no exported member 'StreamData'.

error TS2305: Module '"ai"' has no exported member 'DataStreamWriter'.

error TS2305: Module '"ai"' has no exported member 'LangChainAdapter'.

error TS2305: Module '"ai"' has no exported member 'LlamaIndexAdapter'.

error TS2305: Module '"ai"' has no exported member 'CoreTool'.

error TS2724: '"ai"' has no exported member named 'CoreToolChoice'. Did you mean 'ToolChoice'?

error TS2305: Module '"ai"' has no exported member 'AssistantResponse'.

error TS2305: Module '"ai"' has no exported member 'UseAssistantOptions'.

error TS2305: Module '"ai"' has no exported member 'ToolInvocation'.

error TS2305: Module '"ai"' has no exported member 'Attachment'.

error TS2339: Property 'textDelta' does not exist on type '{ type: "text-delta"; id: string; providerMetadata?: SharedV2ProviderMetadata | undefined; text: string; }'.

error TS2339: Property 'args' does not exist on type '({ type: "tool-call"; } & DynamicToolCall) | ({ type: "tool-call"; } & { type: "tool-call"; toolCallId: string; toolName: string; input: any; providerExecuted?: boolean | undefined; dynamic?: false | undefined; providerMetadata?: SharedV2ProviderMetadata | undefined; })'.
  Property 'args' does not exist on type '{ type: "tool-call"; } & DynamicToolCall'.

error TS2339: Property 'experimental_providerMetadata' does not exist on type 'never'.

error TS2339: Property 'logprobs' does not exist on type 'never'.

error TS2339: Property 'argsTextDelta' does not exist on type 'never'.

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 4.3.19 was compiled against 5.0.0. A row without one is a change the compiler does not report, such as a deprecation or a change in behaviour.

Coverage

Requires emendant@0.1.4 or later. Run emendant feed update to get the latest coverage.

Primary sources

• Migration guidevercel/ai at ai@5.0.0
• package.jsonvercel/ai at ai@5.0.0
• ai@5.0.0npm registry, the published package
• ai@4.0.0npm registry, the published package
• ai@7.0.99npm registry, the published package

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 release: AI SDK 4.0: what breaks when the 2.x stream helpers go
• Later ai release: AI SDK 6.0.0: what breaks when you upgrade ai from 5.x

The AI SDK migration guide lists every release page and says which to read for your upgrade.